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Prediction of Duodenal Nitrogen Supply from Degradation or Organic and Nitrogenous Matter In Situ
Abstract
The contribution of different feedstuffs to nitrogen reaching the duodenum was evaluated in situ. Dacron bags containing barley grain, corn grain, wheat silage, corn silage, alfalfa hay, rye grass, whole cottonseeds, or soybean meal were suspended in the rumens of three dairy cows fed roughage and concentrate diets. The effective degradability of the nitrogenous and organic matter of feedstuffs was calculated from their residues after incubation in the rumen for 3, 6, 9, 12, 24, 36, or 48 h. The duodenal nitrogen content at ruminal outflows of 2, 5, or 8%/h was calculated as the sum of undegradable dietary nitrogen and potential microbial nitrogen (assuming 32 g N/kg ruminally degradable organic matter). Comparison of the in situ estimates with previously reported in vivo measurements of duodenal nitrogen in cattle fed diets with similar ingredients to the tested feedstuffs yielded a linear relationship (r2 = .887). The dacron bag technique appears to hold promise for the prediction of nitrogen flow to the duodenum.
... NE L values for feedstuffs that were used in the formulated diets were calculated using the NRC values (2001), except for the added supplements. The rumen undegradable protein (RUP) values of most of the feedstuffs that used were derived from Arieli et al. (1989). For feedstuffs that were not examined previously (Arieli et al., 1989), published RUP values (NRC, 2001 were used. ...
... The rumen undegradable protein (RUP) values of most of the feedstuffs that used were derived from Arieli et al. (1989). For feedstuffs that were not examined previously (Arieli et al., 1989), published RUP values (NRC, 2001 were used. ...
Several processes have been suggested to protect lipids from bioactivity of the rumen microorganisms. The majority of experiments with conjugated linoleic acid (CLA) were conducted using calcium salts of CLA. The objectives of this study were to determine the effects of encapsulated CLA (E-CLA) that was supplemented during days 21 to 100 post partum (PP), on milk fat depression, recovery rate and performance parameters. Forty-two multiparous Israeli-Holstein cows were divided at day 21 PP into two treatment groups: (i) control - supplemented with 43 g/day per cow of calcium salts of fatty acids (FAs). (ii) E-CLA - supplemented with 50 g/day per cow of encapsulated lipid supplement providing 4.7 g/day per cow of trans-10, cis-12 CLA. Post-treatment cows were followed for recovery rate until 140 days PP. Dry matter intake (DMI) during the treatment period was reduced by 2.5%, and milk yield was enhanced by 4.5% in the E-CLA cows. Milk fat percentage and yield were reduced by 13% and 9%, respectively, in the E-CLA treatment as compared with the control. The energy-corrected milk output was 3.6% higher in the control group than in the E-CLA group. Yields of trans-10, cis-12 CLA isomer in milk was 2.13-fold higher in the E-CLA cows than in the controls. Full recovery to milk fat percentage of the control group occurred 4 to 5 weeks after cessation of the E-CLA supplementation. No differences between groups were observed in any fertility parameter that was tested. In conclusion, the E-CLA supplement decreased DMI, enhanced milk yield, and decreased energy output in milk, and was effective in depressing milk fat. Full recovery to the milk fat content, but not yield, of the control group in the E-CLA group was relatively slow and occurred 4 to 5 weeks after termination of the supplementation.
... To calculate the daily MPI and the casein infusate, a spreadsheet was created with the diet ingredients (pellets, corn and barely grains and hay) and their corresponding chemical composition of CP, RUP, RDP, and rumen-degradable OM. These parameters were measured in situ, and MP was calculated in accordance to AFRC model (1992) and the model suggested previously (Arieli et al., 1989). The pellets were considered the major supplement of MP and, according to daily corrected feed intake, the amount was changed in order not to exceed the total calculated MPI. ...
... To prevent severe alterations in microbial CP flow, rumen-degradable OM was calculated for the diet and kept at the semioptimal concentration by manipulating the amount of barley and corn grain in the diet. A ratio of 5:1 of rumendegradable OM:RDP was considered ideal for keeping optimal microbial CP synthesis in the rumen (Arieli et al., 1989). ...
This study examined the localization and the effect of circulating peptides on the expression of aminopeptidase N (EC 3.4.11.2) in caprine mammary gland. Four lactating goats in mid to late lactation were used in a crossover design and were subjected to 2 dietary treatments. Abomasal infusion of casein hydrolysate was used to increase the concentration of peptide-bound amino acid in the circulation. Samples of mammary gland tissue from each goat were taken by biopsy at the end of each treatment period to measure gene and protein expression of aminopeptidase N in the tissue. There were no measurable effects on feed intake and milk production for any of the treatments. Western blot analysis showed that aminopeptidase N is located on the basolateral side of parenchymal cells and not on the apical membranes. Abomasal infusion of casein hydrolysate caused a marked change in the profile of arterial blood free amino acids and peptide-bound amino acids smaller than 1500 Da. Abundance of aminopeptidase N mRNA and protein increased by 51 and 58%, respectively, in casein hydrolysate-infused goats compared with the control treatment. It was concluded that aminopeptidase N is one candidate actively involved in the mammary gland to support protein synthesis and milk production. In accordance with the nutritional conditions in the current experiment, it is suggested that aminopeptidase N expression is partly controlled by the metabolic requirements of the gland and postabsorptive forms of amino acids in the circulation.
... Net energy for lactation (NE L ) values was calculated using the NRC (2001) values except for the fat supplements. The rumen undegradable protein (RUP) values of most of the feedstuffs were from Arieli et al. (1989). The NRC (2001) RUP values were used for feedstuffs that were not examined in Arieli et al. (1989). ...
... The rumen undegradable protein (RUP) values of most of the feedstuffs were from Arieli et al. (1989). The NRC (2001) RUP values were used for feedstuffs that were not examined in Arieli et al. (1989). Concentrations of P 4 and E 2 in FF, and plasma P 4 were determined by RIA (Diagnostic Products, Los Angeles, CA, USA) as well as FF A 4 concentrations (Diagnostic Systems Laboratories, Webster, TX, USA). ...
Dietary unsaturated fatty acids (UFAs) have been implicated in several reproductive processes in dairy cows through a variety of mechanisms. This study examined the effects of periparturient supplementation of rumen bypass fats low or high in proportion of UFAs (oleic and linoleic) on preovulatory follicle characteristics. Forty-two 256-day pregnant dairy cows were divided into three groups and were fed a control diet (n=14) or supplemented with fats either low (LUFA; n=14) or high (HUFA; n=14) in UFAs. At 14-15 days following behavior estrus, the cows received a prostaglandin F(2)(alpha) injection and 48 h later >7 mm follicles were aspirated. Progesterone (P(4)), androstenedione (A(4)), and estradiol (E(2)) were determined in the follicular fluid. Out of 75 follicles, 37 follicles that were aspirated between 55 and 70 days post partum were regarded as E(2)-active follicles (E(2)/P(4) ratio >1) and subjected for further analysis. The diameter of preovulatory follicles was greater in cows fed HUFA than in those fed control or LUFA. The concentrations and content of A(4) and E(2) in follicles and E(2)/P(4) ratio were higher in the HUFA group than in the other two groups. The P450 aromatase mRNA expression in granulosa cells that were collected from the aspirated preovulatory follicles was also higher in the HUFA cows than in the other groups. A significant correlation was observed between E(2) concentrations in preovulatory follicles and E(2) concentrations in plasma at aspiration. In conclusion, dietary UFA increased the size of and elevated steroid hormones in preovulatory follicles, which may be beneficial to consequent ovarian function.
... Samples were dried at 550 •C for 3 h for ash determination. The NRC values (NRC, 2001) were used for metabolizable energy (NEL) and the rumen-undegradable protein (RUP) values were calculated according to Arieli et al. (1989). ...
Metabolizable energy requirements rise dramatically at late gestation in ewes bearing multiple-fetuses; consequently, prolific ewes may suffer pregnancy toxemia and fetal intrauterine growth restriction. The present objectives of this study were to examine in ewes bearing ≥ 2 fetuses, the effects of dietary supplementation with a molasses-based product from 90 d of pregnancy until lambing on dams' metabolic status and perinatal lambs' performance. Fifty Afec-Assaf ewes, genetically bred to achieve multiple-fetus pregnancies, and bearing at least 2 fetuses were included in the study. The ewes were divided into two groups according to predicted number of fetuses, lambing time, parity number, and body weight (BW). The control group (CTL) was fed solely a basal diet; the treatment group (MLS) was fed the same diet supplemented with the molasses-based product ENERGILASS Sheep 15, in free-choice tubs. Blood samples were collected weekly. Average litter sizes were 3.06 and 3.19 for CTL and MLS groups, respectively. Fetal survival rates at birth differed insignificantly (P > 0.05) at 0.82 and 0.84 in the CTL and MLS group, respectively, and the survival rate of lambs until weaning was insignificantly 6.8% higher in the MLS than in the CTL group (P > 0.05). The CTL ewes lost 0.40 body condition score units from 90 d of pregnancy until lambing compared with only 0.15 by the MLS ewes (P < 0.05). The average concentration of glucose in plasma during the last 3 wk of pregnancy was 17.3% higher in MLS than in CTL ewes (59.1 vs 50.4 mg/dL, respectively; P < 0.01), whereas the BHBA concentrations were 30.9% lower (0.67 vs 0.97 mmol/L, respectively; P < 0.03) and NEFA concentrations were 30.0% lower in the MLS than in the CTL ewes (P < 0.007). During the last 3 wk of pregnancy glucose concentrations were ≤ 50 mg/dL in 37/70 and 16/72 of the CTL and MLS blood samples, respectively (P < 0.0002). Also, BHBA concentrations ≥ 1.4 mmol/L were found in 19/70 and 6/72, respectively, of the CTL and MLS blood samples (P < 0.003). In conclusion, molasses-based product supplementation to prolific ewes from 90 d in pregnancy until lambing greatly improved the metabolic status of dams but with minor effects on perinatal survival and growth of lambs, suggesting that the extra nutrients consumed were prioritized to dams rather than to the components of the gravid uterus.
... Normalmente, para se estimar o fluxo de compostos nitrogenados microbianos para o intestino in vivo, utilizam-se animais fistulados no rúmen e no abomaso ou duodeno. Esse método baseia-se no fluxo de digesta e no uso de indicadores microbianos, sendo sua acurácia influenciada pelas proporções relativas de bactérias e protozoários no rúmen, bem como pelo indicador utilizado e pela coleta representativa da fase líquida e sólida (ARIELI et al., 1989). ...
The experiment was carried out to evaluate the effect of different levels of broiler litter (15 and 30%), associated or not to a supplement based on bovine lyophilized ruminal microbiota (0 and 10 g/anim.day), in Holstein/Zebu steers feeding. Four steers fistulated in the rumen and abomasum were allotted to a 4 × 4 latin square in a 2 × 2 factorial arrangement (level of broiler litter x with or without ruminal microbiota), full fed individually. The ruminal microorganisms composition, efficiency of microbial synthesis, ruminal pH and N-NH3 ruminal concentration were evaluated. The level of 30.0% of broiler litter in the steers diets did not affect the composition of ruminal microorganisms, the efficiency of microbial synthesis and ruminal pH. Higher concentration means of ruminal N-NH3 were observed in animals fed diets with 30.0% of broiler litter. The daily intake of 10 g of the supplement based on ruminal microbiota by the animals did not affect the composition of ruminal microorganisms, efficiency of microbial synthesis, ruminal pH and N-NH3.
... Normalmente, para se estimar o fluxo de compostos nitrogenados microbianos para o intestino in vivo, utilizam-se animais fistulados no rúmen e no abomaso ou duodeno. Esse método baseia-se no fluxo de digesta e no uso de indicadores microbianos, sendo sua acurácia influenciada pelas proporções relativas de bactérias e protozoários no rúmen, bem como pelo indicador utilizado e pela coleta representativa da fase líquida e sólida (ARIELI et al., 1989). ...
RESUMO -O experimento foi realizado para avaliar o efeito de dois níveis de cama de frango (15,0 e 30,0%), associada ou não a um suplemento à base de microbiota ruminal liofilizada de bovinos adultos (0 e 10 g/anim.dia), na alimentação de novilhos Holandês/ Zebu. Quatro novilhos fistulados no rúmen e abomaso foram distribuídos em quadrado latino 4 x 4 em arranjo fatorial 2 x 2 (nível de cama de frango x com ou sem micobiota ruminal), alimentados à vontade e individualmente. Composição microbiana, eficiência de síntese microbiana, pH e concentração de nitrogênio amoniacal no rúmen foram avaliados. O nível de 30,0% de cama de frango nas dietas de novilhos não influenciou a composição dos microrganismos ruminais, a eficiência de síntese microbiana e o pH ruminal. Maiores concentrações médias de N-NH 3 ruminal foram observadas em animais submetidos a dietas com 30% de cama de frango. A ingestão diária de 10 g do suplemento à base de microbiota ruminal por animal não influiu na composição dos microrganismos ruminais, na eficiência de síntese, no pH ruminal e na concentração de amônia no rúmen.
... Samples were dried at 550 • C for 3 h for ash determination. The rumen-undegradable protein (RUP) values were calculated according to Arieli et al. (1989). ...
The objectives of this study were to determine the effects of extruded flaxseed supplementation to high-yielding dairy cows on milk yield and fatty acid profile. One-hundred Israeli-Holstein dairy cows averaging 150 days in milk (DIM) were stratified into two treatment groups on the basis of milk production, DIM and parity. The treatments were: (1) control—cows were fed a lactating-cows diet; and (2) extruded flaxseed (EF)—cows were fed a lactating-cows diet which included an extruded supplement at 40g/kg dry matter (DM) that contained flaxseed and wheat bran at 700 and 300g/kg, respectively. The average daily milk yield was 2.7% higher in the EF group than in the control group (45.4 and 44.2kg/d, respectively; P
... Bags were introduced serially into the rumen and incubated for 96, 48, 36, 24, 12, 9, 6, or 3 h in the rumen of a dairy cow in mid-lactation fitted with a ruminal cannula and Table 1 Ingredient composition (kg dry matter, DM) and predicted chemical composition (g/kg DM) of diets formulated to differ in the ratio of rumen degradable dry matter to rumen degradable crude protein (RDOM/RDCP) tained on a standard diet (35:65 roughage:concentrate, 16% CP, 34% NDF, and 1.7 Mcal/kg of NE L ). This was done in four replicates for each incubation time (Arieli et al., 1989 ). Solubility at 0 h was evaluated by immersing the bags for two consecutive 30-min periods in warm water (39 @BULLET C). ...
The current ruminant protein systems aim at synchronizing the provision of rumen degradable organic matter (RDOM) and degradable crude protein (RDCP) but no specific information on their optimal ratio for dairy sheep is available. We studied the effect of the ratio of RDOM to RDCP on milk yield and composition, during a summer lactation, in 34 confined Assaf sheep managed under farm condition. Individual feed intake was assessed by using PEG (MW 4000) as external marker of fecal output, and indigestible INDF as internal marker of digestibility. Four total mixed rations contained two levels of RDCP (108 and 117 g/kg DM) and two levels of RDOM (510 and 570 g/kg DM). This resulted in one diet featuring high (5.3), one diet featuring medium (4.8) ratio, and two diets featuring low (4.5) ratio of RDOM to RDCP. Individual DM intake, digestibility, and the daily yields of milk components were not affected by RDOM, RDCP or RDOM/RDCP. High RDOM/RDCP tended (P < 0.10) to be associated with higher milk yield, and lower (P < 0.05) CP content. The casein/CP ratio and urea-N in milk were lowest when both dietary RDCP and RDOM were low, whereas lactose was highest (P < 0.05) when both RDOM and RDCP concentrations were high. Our data suggest that RDOM and RDCP interact on milk composition in a way that is not fully encompassed by the RDOM/RDCP ratio and that the use of this ratio to formulate diets for pre-determined milk composition is not warranted.
... Effective ruminal degradability of the dietary ingredients was measured by in situ incubation (Arieli et al., 1989). Polyester bags containing about 5 g of heifer TMR, wheat straw, corn grain, barley grain, and soybean meal hulls were suspended in large nets containing weights in the rumen of each heifer. ...
Ruminal wall metabolism was studied in nonlactating heifers by altering the carbohydrate (CHO) digestion site between rumen and intestine. The CHO digestion site was estimated from in situ and total-tract digestibility of control (CONT) diets and diets supplemented with corn (CRN), barley (BARL), or soy hulls (SOYH). Ruminal epithelial metabolism regulating gene expression, morphology, and nutrient delivery was assessed from a combination of rumen volatile fatty acid (VFA) concentration, biopsies for papilla morphology, and expression of putative metabolic regulatory genes encoding enzymes that facilitate VFA utilization. Digestible dry matter and CHO intake were 25 and 45% higher, respectively, in the supplemented diets than in CONT diets. Fiber supplementation increased the intestinal and decreased ruminal CHO digestion. Ruminal nonfiber CHO digestibility was 10% lower in CRN than with the high rumen-degradable supplement. The CONT heifers had lowest total ruminal VFA and highest acetate concentration relative to the other treatments. Total VFA concentration in BARL and CRN diets tended to be higher than in SOYH. The SOYH diet tended to reduce papilla dimension relative to CRN and BARL. The CRN diet tended to increase papilla surface area relative to BARL and SOYH. Gene expression of propionyl-coenzyme A carboxylase was higher in CRN and BARL than in SOYH diets, and tended to be higher in CRN than in BARL and SOYH diets. Lactate dehydrogenase and butyryl coenzyme A synthase gene transcripts tended to be higher in CONT than in the supplemented treatments. Thus, rumen epithelial expression of genes involved in VFA metabolism and ruminal wall-structure development are influenced by other regulatory mechanism that is not directly affected by local signals. The in situ methods used are a useful tool for differentiating ruminal from extraruminal nutrient supply.
... Characteristics of OM and CP degradation of GS, MS and FB in the rumen are presented in Moss et al. (1995) and Moss and Givens (2002) (580 and 558 g kg -1 , respectively). The EDGOM of MS was between the values reported by Arieli et al. (1989) and Kaswari et al. (2007) (504 and 740 g kg -1 , respectively). We were unable to find any data in the literature on EDGOM for FB. ...
This study aimed at determining the efficiency of microbial protein synthesis (EMPS) in diets based on highly wilted grass silage (GS, 539 g dry matter (DM) per kg) with the supplementation of starch or water-soluble carbohydrates (WSC) rich feeds, i.e. maize silage (MS, 391 g kg-1 DM intake [DMI]), fodder beet (FB, 173 g kg-1 DMI) or molasses (M, 137 g kg-1 DMI). All the diets were made isonitrogenous by urea supplementation (14.0, 4.0 and 2.0 g per kg DMI in GS-MS, GS-FB and GS-M diets). In sacco determined crude protein (CP) and organic matter (OM) degradabilities were 756, 800, 778 and 814 (P<0.05) and 563, 577, 593 and 618 g kg-1 (P<0.05) in GS, GS-MS, GS-FB and GS-M diets, respectively. Synchrony indexes that describe the synchrony of CP and OM degradation in the rumen were 0.75, 0.67, 0.67 and 0.79 in GS, GS-MS, GS-FB and GS-M diets, respectively. The EMPS, assessed by means of urinary purine derivative excretion, did not differ significantly (P>0.05) among the diets (36.6, 35.1, 34.7 and 34.0 g microbial nitrogen per kg OM apparently digested in the rumen in GS, GS-MS, GS-FB and GS-M diets, respectively). The estimated metabolizable protein supply from GS, GS-MS, GS-FB and GS-M diets amounted to 97, 91, 93 and 86 g kg-1 DMI, respectively. Apparently, highly wilted GS containing a high concentration of WSC (91 g kg-1 DM) supports high EMPS in the rumen and this cannot be improved by the supplementation with starch or WSC rich feeds.
... For cottonseed, dRUP was greater than expected. The observed estimated dRUP for whole cottonseed averaged 967% of the CP and is higher than the value reported by Arieli et al. (1989;64%) but is similar to that reported by Erasmus et al. (1994). These results also suggest that total tract digestibility of protein is not dependent on the degree of ruminal degradation (Beckers et al., 1996). ...
The objectives of this study were to expand the database and determine the intestinal digestibility of rumen undegradable protein (dRUP) of common dairy feeds and to determine the effects of feeding 37.9% wet corn gluten feed on these estimates. Two ruminally and duodenally fistulated steers were assigned randomly to a crossover design with 4-wk periods. The mobile bag technique was used to determine rumen undegradable protein (RUP), dRUP, total tract digestible protein, and total tract digestible dry matter of alfalfa hay, brome hay, alfalfa haylage, corn silage, whole cottonseed, soybean meal, soyhulls, ground corn, nonenzymatically browned soybean meal, and dried distillers grains. There was no consistent effect of diet on RUP, dRUP, total tract digestible protein, and total tract digestible dry matter. The RUP (% of crude protein) ranged from 5.97% for alfalfa haylage to 75.6% for nonenzymatically browned soybean meal. The dRUP ranged from 15.3% for alfalfa haylage to 96.5% for nonenzymatically browned soybean meal. The dRUP for alfalfa hay (33.9%), brome hay (39.1%), alfalfa haylage (15.5%), and corn silage (19.9%) were lower than National Research Council reported values. The higher dRUP of the nonenzymatically browned soybean meal is reflective of more total protein reaching the small intestine. The large range in dRUP was not reflected in total tract digestible protein (% of crude protein), with corn silage being the lowest at 85.2% and nonenzymatically browned soybean meal the highest at 97.9%. In this study, diet had little effect on intestinal digestibility of protein or dry matter.
Structural carbohydrates: acid detergent fiber (ADF) and neutral detergent fiber (NDF) are utilized in dairy ration formulations as negative indicators of energy density. NDF has been identified as a predictor of dry matter intake, and ADF related more to digestibility. However, predictability of intake and digestibility from chemical parameters varies widely with forage type. Nonstructural carbohydrates (NSC) are a major energy source in high- producing-cow diets. Starch comprises the major portion of the total ration NSC fraction. Processing can influence rumen degradability of starch. Enzymatic methods and difference equations have been developed to quantitate NSC. Production studies have shown an optimal level of NSC to maximize milk yield. Rumen degradable carbohydrate/starch are emerging as qualitative measures in formulating dairy rations. Their usefulness in fine-tuning nutrient availability to the dairy cow for production purposes will be enhanced as larger data bases are developed and more production studies are conducted. The synergism between protein and carbohydrate use at the ruminai, pos- truminal, and mammary gland level will ultimately be key in maximizing efficiency of milk yield in dairy cattle.
Samples of milled to 5mm alfalfa (Medicago sativa L.), braquiaria (Brachiaria decumbens Stapf.), coast-cross (Cynodon dactylon X Cynodon nlemfuensis), jaragua (Hyparrehnia rufa Ness.) and braquiaria cut to 15mm were incubated in nylon bags for 6, 24 and 96 hours in rumen of three fistulated steers. The 5g samples in the bags were treated in two ways: not washed as usual and washed for 15 min prior to insertion into the rumen. The objective was to study how the washing procedure could affect the parameters estimates in the in situ dry matter degradability equation, DMD=A-B.e-ct. The potential degradation values (A) for washed alfalfa, coast-cross and jaragua were lower than those corresponding to not washed samples. The same parameter value was greater for washed 5mm braquiaria. When alfalfa, jaragua and coast-cross were washed, degradation rate (C) values increased whereas for 5 and 15mm braquiaria a decrease was observed. The results showed that the initial washing procedure may affect the parameters "A" and "C" according to the characteristics of forage, and therefore should be avoided.
The effect of the number of daily meals on milk yield and composition was studied in a commerial dairy herd. One hundred and eighty Israeli Holstein cows were divided into two groups. One group was given one meal daily and the second group three meals daily. Feeding frequency had no effect on DM intake, milk yield or milk composition. Total VFA and molar proportion of acetate were higher before feeding than 3 h later. The decrease in molar proportion of acetate after feeding was greater in the cows given one meal daily. The propionate molar proportion was higher before feeding and lower 3 h later if cows were given three meals daily. As a result, the acetate to propionate ratio was lower in cows fed three meals daily before feeding and rose after 3 h. Ruminal ammonia-N concentrations, before and after feeding, were lower when cows were fed three meals daily. Plasma urea-N concentrations were higher before feeding, as compared with 3 h later. Plasma urea-N was higher for the one meal treatment, but significantly only 3 h after the morning meal. It is suggested that increasing feeding frequency may improve dietary nitrogen utilization and may shift metabolism towards more gluconeogenesis. Production responses to more frequent feeding are more likely to be revealed in high yielding dairy cows, maintained on high concentrate diets.
The ruminal degradability and intestinal digestibility of dry matter (DM), crude protein (CP) and amino acids (AA) in three total mixed rations with different CP levels were estimated using the modified in vitro three-step procedure (TSP) and mobile nylon bag (MNB) technique on growing lambs. The ruminal effective degradability of DM and CP did not respond with increasing dietary CP level. However, the intestinal digestibility of DM was significantly increased with increasing dietary CP level estimated by TSP (P < 0.05) or MNB method (P < 0.01). Intestinal digestibility coefficients of CP determined by TSP were lower than those of the MNB method. Histidine was extensively degraded by rumen micro-organisms, while tyrosine was the most anti-degradable AA among the samples. The ruminal AA degradability exhibited no significant differences except for threonine, tryptophan, alanine, aspartic acid and proline for the three diets. Similarly, only a few AAs (i.e. histidine, methionine, tryptophan, aspartic acid and cysteine in TSP; histidine, tryptophan, aspartic acid and serine in MNB) had significant differences in their intestinal digestibility; in addition, values of MNB were lower than that of the TSP method, indicating that intestinal digestibility of DM seems to be overestimated in TSP, while that of CP might be overestimated in the MNB method.
The experiment was carried out using fistulated multiparous Holstein Friesian crossbred (75% Holstein Friesian and 25% Red Sindhi) dairy cows in their dry period fed on untreated rice straw to evaluate the nutritive value of local protein feed resources using the in sacco method and in vitro pepsin-pancreatin digestion. Experimental feeds were cottonseed meal (CSM); soybean meal (SBM); dried brewery??s grains (DBG); palm kernel meal (PSM); cassava hay (CH); leucaena leaf meal (LLM). Each feedstuff was weighed into duplicate nylon bags and incubated in each of the two rumen fistulated cows for 0, 2, 4, 8, 16, 24, and 48 h. Rumen feed residues from bags of 16 h incubation were used for estimation of lower gut digestibility by the technique of in vitro pepsin-pancreatin digestion. Ruminal ammonia-nitrogen (NH3-N) concentrations did not differ between treatments or time with a mean of 5.5 mg%. Effective degradability of DM of CSM, SBM, DBG, PSM, CH and LLM were 41.9, 56.1, 30.8, 47.0, 41.1 and 47.5%, respectively. Effective degradabilities of the CP in feedstuffs were 49.6, 59.2, 40.9, 33.5, 47.3 and 65.0% for the respective feedstuffs. The CP in vitro pepsin-pancreatin digestibility as ranked from the highest to the lowest were SBM, CSM, LLM, CH, DBG, PSM, respectively. The intestinal and total tract digestion of feedstuffs in the current study were relatively lower than that obtained from previous literature. The results of this study indicate that SBM and LLM were highly degradable in the rumen, while CH, CSM and DBG were less degradable and, hence resulted in higher rumen undegradable protein. Soybean meal and LLM could be used to improve rumen ecology whilst CH, CSM and DBG could be used as rumen by-pass protein for ruminant feeding in the tropics.
The effect of extrusion or expansion treatment of wheat, barley, corn and sorghum grains on characteristics of rumen degradation was studied. Ruminal disappearance characteristics of dry matter, starch, nitrogen and fat in control and processed grains was determined using the in sacco method.In expanded cereals DM degradation rate was reduced in all grain types. In expanded corn the degradable DM fraction was also reduced. In extruded corn and sorghum rumen DM degradation rate was also reduced. In sorghum, ruminal escape of DM increased by 8% and 5%, in extruded and expanded grains, respectively.The degradation rate of starch was reduced in expanded wheat and barley. Effective degradation of starch in the rumen was considerably lowered in expanded grains by 34%, 27%, 14% and 9% in wheat, barley, sorghum and corn, respectively. Extrusion also resulted in comparable reduction in effective degradation of starch in these grains by 27%, 27%, 17% and 6%, respectively.Expansion decreased the N-degradation rate in all cereal types, and extrusion decreased this in corn and wheat only. Negative fat degradation values were found at zero incubation time. However the data suggest that extensive disappearance of fat from cereals occurs in the rumen.It was concluded that thermal processing of grains alters fermentation characteristics and may facilitate the achievement of optimal ruminal availability of energy: protein for microbial synthesis.
Whole cottonseed (WCS) is an unusual feedstuff for ruminants. Due to its high content of fat and protein, it may be defined as a concentrate. On the other hand, its fiber is similar to that of forages in terms of effectiveness in the rumen. The response of dairy cattle milk production to WCS feeding is variable. A large part of the effect of WCS on milk production is related to ruminal effects, which depend upon the basal diet fermentation balance. The high degradability of crude protein (CP) in the rumen may be associated with high ammonia production. The low heat increment obtained with WCS feeding favors its supplementation at high environmental temperatures, but a possible effect of WCS fat, i.e. reduced microbial activity, and gossypol toxicity may limit the amount of WCS which can be given to high-yielding dairy cattle. Current recommendations are to include WCS at up to 150 g/kg of the diet. Processing, and especially heat treatment of WCS may aid in providing more non-rumen degraded fat and CP from WCS to the small intestine. Heat treatment may also be useful for reducing free gossypol in WCS, and is likely to enable increased supplementation of WCS in dairy cattle rations. Reducing WCS particle size and NaOH treatment may also improve overall WCS digestibility. The advantages of such treatments may be more marked in low-lint WCS.
An in situ study was conducted to investigate the extent and kinetics of microbial colonization of forage particles exposed to the rumen environment of lactating cows and dry camels, not previously reported. Two Holstein cows and three camels, fitted with ruminal cannulas were used at the University of Arizona and United Arab Emirates University, respectively. Besides dairy concentrate, cows received alfalfa hay and camels Rhodes grass hay. The cows received two diets differing in the concentrate by including either dry-rolled (DDR) or steam-flaked (DSF) sorghum grain making up 35% of the diet DM. The concentrate for the camels included 25% barely grain. Corn plants were labeled with 15N as an internal N marker. Amounts of 15N in excess of 0.366 atom% were considered as enrichment. Dilution of enrichment estimated percentage of microbial nitrogen (MN). Labeled whole corn cobs (WCC) were placed in nylon bags and incubated in the rumen of cows for up to 48h and in camels for up to 72h. Labeled corn stalks (CS) were also incubated in camels. Contamination was expressed as the percentage of microbial-N (MN) in the residual N, while colonization was microbial crude protein (MCP) percentile in the residual DM of the WCC or CS exposed to ruminal fermentation. During the initial 2h of rumen incubation in cows, MN was 39% of the residual N in WCC (contamination) and 73% at 48h of incubation. Also at 48h, MCP was 6.0% and 7.5% of DM is WCC residues (colonization) in cows fed DDR and DSF, respectively. In camels, during the first 2h of rumen exposure, MN was 7% of residual N (contamination) and 57% at 72h, while MCP was 5.5% of DM in WCC and 9.8% of DM in CS residues (colonization). In both cows and camels, microbial colonization and microbial contamination increased with incubation time. Microbial contamination greatly affected estimates of in situ ruminal protein degradation of these forges of low N content in both cows and camels. Undegraded feed protein would have been estimated close to or greater than 100% if not corrected for MN contamination, while more consistent values are shown when corrected.
This trial was designed to investigate whether increasing the amount of ruminal undegradable crude protein (CP) content of rations given to high producing dairy cows, affected total non-structural carbohydrate (TNC) digestibility and milk production. A total of 36 Israeli-Holstein multiparous dairy cows were assigned to three treatments according to parity number, calving date, milk yield during the previous lactation and body weight (BW) 2 days after calving. Diets were formulated to contain (on a DM basis) 45% forage, 16.5% CP, 1.7 Mcal/kg net energy lactation (NE), and differed in dietary CP undegradability, as follows: (1) low undegradable CP (LUDCP)-UDCP, 36% of dietary CP; (2) medium UDCP (MUDCP)-UDCP, 41% of dietary CP; and (3) high UDCP (HUDCP)-UDCP, 46% of dietary CP. Dietary UDCP was increased by reducing concentrations of soybean meal and urea and increasing those of fish meal and gluten meal. The cows were maintained in the trial for 3 months. Average dry matter intakes of cows on LUDCP, MUDCP and HUDCP treatments were 25.0, 23.3 and 23.3 kg/day, respectively (P>0.1). Treatment averages of milk yield (kg/day), milk fat, protein and lactose (%) were 43.3, 3.01, 2.97 and 4.48, respectively, and no significant differences between diets were observed. Apparent digestibilities of dietary CP and TNC were increased by UDCP supplementation (P
The protein degradabilities of feedstuffs, roughages and by-products that are commonly used in ruminant rations, were measured by the in situ nylon bag method.Four dry dairy cows were fistulated in the rumen for the in situ nylon bag studies. Twenty-eight different feedstuff samples were placed in 4.5 × 6.5 cm nylon bags, and were then incubated in the rumen for different periods of time (0, 2, 4, 8, 12 and 24 h). Under 8% of rumen solid outflow rate, the percentages of the calculated protein degradability were: corn gluten meal, 8.8; feather meal, 29.1; soya pomace, 79.1; brewers grain, 37.1; distillers grain, 53.9; meat and bone meal, 51.9; wheat bran, 76.8; corn, 34.6, respectively. The size of nylon bag was changed to 10 × 20 cm, and the method of bag suspension was also changed, whilst the incubation period was extended two additional periods of 48 and 72 h in the second trial. The results of the protein degradabilities in 8% ruminal outflow rate were as follows: pangola hay. 38.6; soya pomace, 83.3; corn silage, 75.6; rice bran, 52.5; napier grass, 34.7; distillers grain, 60.1; brewers grain, 54.9; alfalfa hay, 71.8; fish meal, 37.5; soybean meal, 68.0; beancurd pomace, 61.7, respectively. All the degradabilities mentioned were uncorrected for influx microbial nitrogen.From the smaller standard deviation of the crude protein disappearance rate in the large nylon bags (trial 2), it recommended the size of the nylon bags is 10 × 20 cm instead of 4.5 × 6.5 cm.
During two experimental periods, eight non-lactating, rumen fistulated Simmental cows were given 2 kg/day of a cereal based concentrate and fescue hay ad libitum . The hay differed in neutral-detergent fibre concentration (LNDF: low; HNDF: high) and physical form (L: long; C: coarsely chopped). The rumen degradability of the dietary ingredients and of an extracted soya-bean meal was studied using the polyester-bag method.
The estimated effective rumen degradability <DG) of dry matter (DM) was significantly higher for LNDF than for HNDF hay (0·490 v. 0·401; P < 0·01). The DM DG of the extracted soya-bean meal and the dietary concentrate were higher when incubated with LNDF than with HNDF diets (0·630 v. 0·581, P < 0·05, and 0·541 v. 0·514, respectively).
Chopping the hay significantly increased the daily DM intake for HNDF diets (from 9·9 to 11·6 kg; P < 0·05), while no statistical differences were found between the other diets (10·2 and 9·6 kg, respectively for L-LNDF and C-LNDF diets). Cows given HNDF hay drank less water (42·4 v. 51·7 I/day) and total water consumption, expressed per unit of DM intake, was lower for the HNDF diets (4·1 v. 5·3 I/kg DM; P < 0·01).
Dietary treatments did not affect the estimated rumen turn-over rate of hay (0·027 per h on average, k ¹ ), hay post-rumen turn-over rate (0·069 per h on average, k ² ) or the estimated rumen liquid turn-over rate (0·100 per h on average, kj. The calculated outflow from the rumen was lower for the HNDF diets (159·4 v. 198·7 I/day). The daily amount of estimated saliva secreted did not differ between treatments, although saliva expressed per kg DM intake was significantly lower for the HNDF diets (10·8 v. 14·8 I/kg DM; P < 0·05).
The HNDF diets gave a lower post-feeding rumen pH (6·29 v. 6·58; P < 0·01), a higher concentration of n-butyrate (9·58 v. 8·32 mmol/l; P < 0·05) and a lower concentration of ammonia nitrogen (NH ³ -N) (80·5 v. 128·5 mg/l; P < 0·05). Of the C ⁴ and C ⁵ iso-acids, the rumen liquid from cows given HNDF diets had significantly lower concentrations of isobutyrate, isovalerate and n-valerate ( P < 0·01). Hay physical form did not affect rumen pH, NH ³ -N and volatile fatty acid concentrations.
The feeding behaviour of Mamber dairy goats grazing on Mediterranean
woodland in the Upper
Galilee mountains of Israel was studied throughout a year (1991/92).
The percentages of crude
protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF),
acid detergent lignin (ADL)
and condensed tannins (CT) were determined in samples collected by
hand to simulate the plant parts
selected by the goats. Total feed intake was evaluated by using
Cr-sesquioxide as an external marker
to determine the amount of faeces excreted, and 48 h in
sacco
degradability to assess the digestibility
of samples. Overall, more time was spent by goats in feeding on
ligneous material (tree and shrub
foliage) than herbaceous vegetation (60 and 40% of total feeding
time, respectively, P<0·05). The
main ligneous species consumed by the goats were Quercus
calliprinos,
Sarcopoterium
spinosum and
Calicotome
villosa (20, 13 and 7% of total grazing time, respectively).
There was considerable variability in the 48 h dry matter (DM) in
sacco
degradability, and in the concentration of CP, NDF,
ADF, ADL and CT, within and between seasons and plant species. Although
requirements for
nutrients varied according to the physiological stage of the goats,
48 h in
sacco DM degradability and
the concentration of non-ADF linked (available) CP, NDF, ADF, ADL and CT
in the diet did not
vary greatly: respective ranges were 45·0–49·4; 9–12·5;
44–53; 33–39; 12–17 and 3·5–4·7%.
It is
concluded that Mamber goats (i) may not select the best quality diet
available, but may avoid wide
variations in nutrient content of their diets throughout the year;
and (ii) may not select a diet
consistent with maximization of milk yield, but rather with optimization
of body condition at the onset of the mating season.
Dry matter (DM) yields and degradability in situ of two wheat cultivarsan early-maturing, Bet Hashita (BH), and a late-maturing, Ariel (A), harvested and ensiled at four maturity stages, shooting, flowering, milk, and doughwere evaluated. The wheat was ensiled in minisilos for 90 days. The DM yields (t ha-1) of A tended to be higher than those of BH at all maturity stages. Average neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of both cultivars were lowest at the shooting stage and highest at flowering stage. Average NDF and ADF contents of A silages were higher than those of BH: 631 vs 582 g kg-1 DM and 378 vs 338 g kg-1 DM (P < 0.05), respectively. In situ DM degradability of BH was higher than that of A at all stages of maturity (P < 0.05). (average 27.1 vs 20.1%; P < 0.05), and it decreased significantly with maturity. In situ NDF degradability during 24 h of incubation decreased with maturity in both cultivars (P < 0.05) and was higher for BH than for A at the milk stage. Total degradable NDF yields tended to increase with maturity and to be higher in cultivar A. Therefore, A, harvested at a later ripening stage, is preferable to BH as a roughage crop for dairy cattle. Keywords: Wheat silage; maturity; in situ degradability
The effects of the nature of carbohydrate source on in sacco protein degradation of 15 samples of plant protein sources were studied in four mature fistulated rams fed a control diet (C) of meadow hay and soyabean meal (83:15 on dry matter basis) and three diets in which 36, 34 or 40% of diet dry matter was sugar beet pulp, maize or wheat (diets P, M and W respectively). Degradation parameters were estimated from the exponential equation p = a + b[1 − exp(−ct)]. Diet composition significantly affected (P < 0.001) all the degradation parameters, the effect being more pronounced on the degradation rate (c). This parameter was stimulated (P < 0.05) by beet pulp but depressed (P < 0.05) by cereal inclusion in the diets, in particular when animals were fed the W diet (4.46, 5.65, 3.74 and 3.05% h−1 for the C, P, M and W diets respectively). An interaction effect between carbohydrate source and incubated plant protein sources was observed (P < 0.001). The reason(s) for these differential effects were not elucidated. The practical consequences of these findings are discussed. Copyright © 2005 Society of Chemical Industry
In situ evaluation of the duodenal amino acid (AA) profile was attempted in a 4 × 4 Latin square study using four lactating Holstein cows fitted with ruminal and duodenal cannulas. Dietary supplemental crude protein (CP) sources, making up 40% of the dietary CP, were: soybean meal, cottonseed meal, corn gluten meal or urea. Duodenal flow of organic matter (OM) and CP was determined in vivo by means of constant infusion of ytterbium and chromium, and predicted in situ from rumen degradation. Purines were used as microbial markers. In situ calculation of the AA profile, expressed as g AA in 100 g of total AAs, was based on the composition of AA in feed and in isolated bacteria as well as on in situ rumen degradation of OM and CP. The AA profile in the duodenum when assessed in vivo was affected by the nature of the supplemental protein; in situ assessment of the AA profile resulted in comparable profiles. The data are interpreted to suggest that the in situ method enables prediction of the profile of AA (g AA/100 g total AA) flowing to the duodenum, and that the undegraded portion of supplemented protein affects that profile.
The effect of inclusion of poultry litter in the diet on the length of the adaptation period of dry matter intake and levels of rumen and blood N metabolites was studied in heifers. Twenty-four Israeli Friesian heifers were divided into three groups and fed diets containing 0%, 17.5% and 35% poultry litter silage over a period of 7 weeks. The following were determined: dry matter intake, dry matter digestibility (using chromic oxide as a marker), rumen ammonia and blood urea. Disappearance of crude protein and organic matter of poultry litter from dacron bags incubated in situ in the rumen was also measured. Poultry litter feeding was accompanied by a decrease in ruminal ammonia and urea, which was already pronounced in the first week and persisted throughout the experimental period. Digestibility of dry matter dropped for 1 week but returned gradually to the control level. Incubation of poultry litter samples in situ in dacron bags in the rumen revealed that 82% of its crude protein and 37% of its organic matter is rapidly degraded whereas an additional 11% of crude protein and 37% of the organic matter are degraded slowly. Inclusion of poultry litter in the diet was associated with an increase in dry matter intake. Our findings indicate that ruminants require a relatively long adaptation period, of 3 to 4 weeks, in order to reach the maximal dry matter intake when poultry litter is added to their diet. This is in spite of the relatively short time (about 1 week) required for adjustment for ammonia levels in the rumen and urea levels in the blood.
In situ evaluation of the amount and composition of duodenal crude protein flow was examined in a 4 x 4 Latin square study using four lactating Holstein cows fitted with ruminal and duodenal cannulas. Dietary supplemental CP sources, making up 40% of the dietary CP, were: soybean meal, cottonseed meal, com gluten meal or urea. Duodenal flow of organic matter (OM) and CP was determined in vivo by means of constant infusion of Yb and Cr, and was predicted in situ from rumen degradation. Purines were used as microbial markers. The two methods of estimating ruminally undegraded protein ranked the diets similarly. Microbial CP (1.9 to 2.1 kg/d) was estimated to make up 57% to 68% of the duodenal CP flow in the experimental diets. Efficiency of microbial protein synthesis were 201 (SEM 16) g CP/kg OM truly digested in the rumen, and 224 (SEM 18) g CP/kg OM disappearing in the rumen. Data are interpreted to suggest that the in situ method enables a prediction of total protein flow to the duodenum which is comparable to that obtained using the in vivo method. The added practicality of the former method renders it advantageous.
This trial was designed to investigate effects of the amount of dietary undegradable crude protein (CP) and the ratio of degradable organic matter to degradable CP in the diets of high-yielding dairy cows on milk yield, energy balance and fertility during the first three months postpartum. Forty-five Israeli Holstein cows were assigned to three dietary treatments at 2 d postpartum. Dietary treatments were (1) 16.7% CP, of which 32% was undegradable (control); (2) 16.7% CP, of which 38% was undegradable; and (3) 18.0% CP, of which 35% was undegradable. Corn gluten meal (CGM) was added to diets 2 and 3 in order to increase undegradability. Cows were fed in groups, and diets were offered as a total mixed ration. Intakes of dry matter (DMI) and CP (kg/d) were 23.8 and 3.975, 21.4 and 3.574, and 20.4 and 3.672, for cows on diets 1, 2 and 3, respectively. No significant differences among the three treatments were found for milk yield, milk protein concentration, milk fat, or protein and lactose yields. Control cows lost 35.0 kg of body weight (BW) during the first 27.2 d postpartum, and then started gaining weight. At approximately day 70 the control cows attained their calving weight. Cows on diets 2 and 3 lost 55 kg of BW during 45 d postpartum and, by the end of the trial, these cows still had not attained their calving weight. Change in body condition score (BCS) during the experimental period revealed the same trends. Mean concentrations (mg/100 ml) of ammonia N in ruminal fluids and concentrations of plasma urea N were 14.0 and 20.3, 12.7 and 21.2, and 14.7 and 21.3 for cows on diets 1, 2 and 3, respectively. No significant differences among treatments were detected for any reproduction parameter. It was concluded that the differences between control cows and cows on diets 2 and 3 in DMI, BW and BCS during the first period postpartum cannot be attributed to the level of dietary undegradable CP only but to a more specific effect of CGM.
The objectives were to examine the effect of high dietary crude protein on characteristics of preovulatory follicles in dairy heifers. Eight Israeli-Holstein heifers, 4 fitted with rumen fistula and 4 intact, were assigned to 1 of 3 treatments in a replicated (n=2) 4 × 3 incomplete Latin square design with 39-d periods. Treatments were: low (6.0%; LP), moderate (13.0%; MP), and high (20.0%; HP) crude-protein diets, containing 1.27 Mcal NE(L)/kg dry matter. Diets were based on approximately 66% wheat straw and various proportions of ground corn grain and soybean meal. The estrous cycles of the heifers were synchronized, and 14 d after behavioral estrus, heifers received PGF(2 α) injections. After a further 40 h, at d 39 of each period, follicular fluid (FF) was aspirated from follicles of diameter >7 mm. The intake of the LP diet was 9% lower than that of MP and HP diets. Rumen ammonia and plasma urea nitrogen concentrations were highest in the HP and lowest in the LP, with intermediate levels in MP diets. No differences were found between treatments in plasma and FF concentrations of glucose and nonesterified fatty acids. High-protein diets increased urea concentrations very similarly in preovulatory FF and in plasma. No differences were observed between diets, in preovulatory follicle diameters and concentrations of androstenedione. However, higher estradiol and progesterone concentrations in FF were observed under the HP than under the MP diet, with no difference between diets in estrogen to progesterone ratio. It can be concluded that high concentrations of urea in plasma, caused by high dietary crude protein, penetrated into preovulatory follicles, but did not impair preovulatory characteristics. This lack of detrimental effects might be attributed to the use in this study of nonlactating heifers, which have fewer nutritional and physiological constraints and eliminate negative effects of potential interactions with high urea on dairy cows' reproductive systems.
The current study examined the effects of live yeast (LY) supplementation to dairy cows during the summer season on milk production, feed efficiency and ration digestibility. Forty-two dairy cows (14 primiparous and 28 multiparous) were fed either a control lactating diet or supplemented with 1 g of LY (Saccharomyces cerevisiae, Biosaf, Lesaffre) per 4 kg of dry matter consumed. The LY amounts were adjusted twice a week. Four rumen samples were taken from 30 cows in 2-h periods and ammonia concentrations were determined. Fecal grab samples from 30 cows were collected during 3 consecutive days, to determine the apparent digestibility of diets. The daily dry matter intake in the LY group was 2.5% greater compared with the control group (24.7 and 24.1 kg, respectively). The daily average milk yield of the LY group was greater by 1.5 kg (4.1%) compared with the control group (37.8 vs. 36.3 kg, respectively). There were no significant differences in the milk fat and protein percentages, but fat yield was greater in the LY group than in the control. The fat-corrected milk 4% was 2.0 kg (6.1%) greater in the LY group than in the control group (34.8 vs. 32.8 kg, respectively). The efficiency of using dry matter to produce 4% fat-corrected milk was 3.7% greater in the LY group compared with the control group. The ruminal ammonia concentrations after feeding were greater in the control group than in the LY group (151.9 vs. 126.1 mg/l, respectively). No differences were observed among groups in the total tract apparent digestibility of dry matter and other diet components. The pH values in the rumen that were determined in a companion trial using 4 fistulated cows tended to be higher in cows that were supplemented with LY than in the control (6.67 vs. 6.54, respectively). It may be concluded that LY supplementation to dairy cows during the hot season improved the rumen environment in a way that increased the dry matter intake and in consequence enhanced the productivity and efficiency.
Glucose metabolism was studied in ewes fed 800 g chopped alfalfa hay (H) or 400 g alfalfa hay and 400 g corn grain given in whole (HWC), ground (HGC) or extruded (HEC) form. Daily intake of metabolisable energy and crude protein were: 5.8 MJ, 109 g; 9.0 MJ, 84 g; 9.5 MJ, 84 g and 8.5 MJ, 88 g in H, HWC, HGC and HEC, respectively. In situ ruminal degradability ranked whole, ground, and extruded corn in ascending order. Ruminal pH and concentration of acetic acid were lower and of propionic acid higher (P less than 0.05) in HEC than in HGC and HWC groups. Plasma level of glucose (P less than 0.10), insulin (P less than 0.05), and the ratio of insulin to non-esterified fatty acids (NEFA) (P less than 0.01) were higher in HEC than in other groups. Glucose irreversible loss (GILR) and entry rate (GER), recycling (GRec) and reentry (GRee) were determined by double isotope dilution procedure. GER, but not GILR, was higher in HWC than in H and HGC (6.98 mg/min/kg BW0.75 vs 3.97 and 4.24 mg/min/kg BW0.75, respectively; P less than 0.05) and than in HEC (4.84 mg/min/kg BW0.75; P less than 0.10). GRec and GRee were higher in HWC than in the other treatments. Grinding or extruding the grain increased ruminal degradability and decreased glucose entry rate.
In trial 1, our objectives were to study effects of different substrates (cellulose, red clover, and orchardgrass) on bacterial colonization and degradation of fiber. To quantitate bacterial colonization, we used 15N as a marker. Use of 15N appeared to underestimate bacterial colonization of cellulose, but it was assumed that relative differences among treatments and across times were accurate. The 15N and carboxymethylcellulase activity techniques gave similar patterns for bacterial colonization with time on purified cellulose but not orchardgrass or red clover; this indicated a higher concentration of cellulolytic versus total bacteria colonizing cellulose. Relatively lower detachment from red clover or orchardgrass than cellulose with time may have been due to selection for different types of microbes that were attached more firmly or were less prone to lysis. In trial 2, replacing cellulose with 30% starch or different protein sources (12% CP) decreased NDF digestion of crystalline cellulose but increased adherent bacterial CP concentration (estimated using 15N) and carboxymethylcellulase activity. The addition of starch and preformed protein may have selected for adherent, noncellulolytic microbes and decreased cellulolysis. The addition of 10% unsaturated or saturated fat did not affect colonization or NDF digestion, perhaps because of the larger surface area of the cellulose dispersing fatty acids more than would occur with more typical substrates. The addition of starch probably increased carboxymethylcellulase activity more than when using purines or 15N. Experiments using pure cultures of bacteria or purified substrates are not necessarily related to those using mixed cultures or natural forages.
The effect of variable degradability of both OM and CP, incorporated at a constant ratio in diets of high yielding dairy cows (35 kg/d), was studied under commercial dairy herd conditions. Two diets containing 17% CP were formulated, including high (70%) and low (65%) protein degradability. The ratio of rumen-degradable OM to degradable protein was adjusted to 5:1 in both diets. Cows were assigned to treatments based on equal milk yield prior to trial, parity, and DIM. The trial lasted 7 wk: a reference week (wk 0), in which both groups were fed the high degradability diet, was followed by 6 experimental wk, in which group 1 was fed the high degradability diet and group 2 the low degradability diet. Cows on the low degradability diet consumed 1.2 kg more DM and yielded 1.5 kg/d more milk, .055 kg/d more milk protein, and .196 kg/d more milk fat. Percentages of milk protein (3.06 and 3.03) were similar, but fat (3.67 and 3.28) was higher for cows fed the low degradability diet. The results suggest that, when diets were formulated to balance rumen degradability of both OM and CP, 65% rather than 70% degradability of CP was advantageous for yields of milk and milk components.
Four multiparous lactating Holstein cows, fitted with cannulas in the rumen, duodenum, and ileum, were used in a trial with a 4 x 4 Latin square design to examine the effect of source and degradability of dietary CP supplements on AA flow and absorption in the small intestine. The CP supplements consisted of fish meal or meat meal as the animal by-products supplement and soybean meal or heated soybean meal as the plant by-products supplement. Fish meal and heated soybean meal constituted the high RUP diets, and meat meal and soybean meal constituted the low RUP diets. Dry matter intakes were similar among treatments. However, intakes of OM, rumen-degradable OM, total CP, and RDP were affected by the source of the CP supplement and were higher for diets with plant by-products than for those diets with animal by-products. Data were similar for the calculated in situ digestibilities and for true in vivo digestibilities of rumen-degradable OM. Efficiency of bacterial CP synthesis was similar among diets; however, nonbacterial CP flow to the duodenum and OM, CP, and disappearance of AA from the small intestine were affected by the interaction of supplement source and degradability. Heat treatment of soybean meal reduced the availability of most of the essential AA for absorption in the small intestine by 2.3% compared with that of soybean meal; the biggest such reduction (20%) occurred for Met. Availability of AA in the small intestine was affected by source and degradability of the CP dietary supplement. Heat treatment at 140 degrees C for 2.5 h reduced the availability of Met absorption from the small intestine. Although the differences among availabilities of the individual AA in the small intestine ranged from 80 to 84% among treatments, for high yielding cows, these differences may have practical significance.
This study analyzed the relationships among the effective degradabilities of organic matter (OM) in feedstuffs, which were assessed separately by an in situ method and a direct in vivo measurement of the rumen degradation of OM in the diets of Holstein dairy cows. For this comparison, 80 individual data points were used from studies of dairy cows that were in midlactation and that had been cannulated in the rumen and abomasum. In vivo evaluation of the true degradability of OM in the rumen was based on rare earth digesta markers. Purine N served as a microbial marker. Feed samples were incubated in the rumens of dairy cows for 3, 6, 9, 12, 24, 48, and 72 h, and effective rumen degradation was calculated from the percentage of residual OM for rumen outflow rates of 4, 6, and 8%/h. Evaluations of rumen degradability of OM by the in situ method were correlated with actual in vivo measurements of rumen degradability of OM (r2 = 0.31, 0.34, and 0.37; SE of the estimate = 4.1, 4.0, and 3.9%, respectively). We concluded that the in situ method is a useful tool for providing reliable estimates of rumen degradability of OM in dairy cows.
The aim of the study was to determine the effect of 10 sources of lactic acid bacteria (LAB) on dry matter digestibility (DM-D) and neutral detergent fiber digestibility (NDF-D), in various combinations with starch, in vitro. The soluble starch represented a concentrate feed, whereas silage represented feeding only roughage. The DM-D and NDF-D were determined after 24 and 48 h of incubation to represent effective (24 h) and potential (48 h) digestibility. Addition of LAB was both by direct application of the inoculants to rumen fluid (directly fed microbials) and by the use of preinoculated silages. For each feed combination, tubes without added LAB served as controls. The results indicate that, overall, some LAB inoculants applied at ensiling or added directly to the rumen fluid had the potential to increase the DM-D and NDF-D. The major significant inoculant effect on NDF-D was obtained after 24 h of incubation, whereas the effect after 48 h was mainly nonsignificant. The effective inoculants seemed to minimize the inhibitory effect of the starch on NDF-D within 24 h, perhaps by competition with lactate-producing rumen microorganisms.
In vivo and in situ trials were conducted to investigate the utilization of alfalfa protein concentrate as a protein supplement for lactating dairy cows. In the in vivo trial, four Holstein cows fitted with ruminal, duodenal, and ileal cannulae were used in a crossover experiment to measure site and extent of nutrient digestion. Isonitrogenous and isoenergetic diets containing alfalfa protein concentrate or soybean meal were fed four times daily. Sixty percent of dietary total N was provided by the test proteins. Ruminal ammonia and total VFA concentrations were lower in cows fed alfalfa protein concentrate. Fractional digestion coefficient of organic matter (52 vs. 43%) and degradation of dietary protein (57 vs. 47%) in the rumen were slightly lower in cows fed alfalfa protein concentrate. The ratio of amino acid flow to the small intestine to dietary intake of amino acid was higher in cows fed alfalfa protein concentrate. In the in situ trial, rate of N disappearance (2.4 vs. 9.5%.h-1) and potential protein degradability (35 vs. 68%) were lower for alfalfa protein concentrate. Results suggest that alfalfa protein concentrate may be more resistant to ruminal degradation than soybean meal and could be utilized as a relatively undegradable protein source for milk production.
Three ruminal-cannulated Holstein cows in early lactation were fed three diets, each containing different energy and protein supplements in two consecutive 3 X 3 Latin squares. Each supplement contained a combination of three different feedstuffs (ground corn, soybean meal and wheat mids; corn gluten feed, rolled oats and distiller's dried grains; ground barley, brewer's grains and cottonseed meal). Diets consisted of 30% corn silage, 10% alfalfa hay, 10% alfalfa haylage, 17.7% ground corn plus minerals and vitamins, with the remainder as supplemental feedstuffs individually marked for measurement of ruminal turnover and in situ digestion rates. An extra period at the end of each Latin square was used to measure ruminal turnover and in situ digestion of individual forages. Diet had no effect on dry matter intake or milk yield. Mean fractional turnover (per hour) rate, measured by labeling feedstuffs with cerium, samarium or lanthanum was .044, .048, .049, .043, .047, .046, .050, .047, .049, .037, .046 and .045 for corn, soybean meal, wheat mids, corn gluten feed, oats, distiller's dried grains with solubles, barley, brewer's dried grains, cottonseed meal, alfalfa hay, corn silage and alfalfa haylage (P greater than .1), respectively. In situ-predicted ruminal degradation of N weighted for rate of passage was 61.4, 67.0, 81.5, 74.8, 86.3, 71.0, 75.7, 52.1, 54.2, 60.8, 71.7 and 70.9% for respective feedstuffs (P less than .05). In comparison with mean literature values for in vivo-measured N degradability, mean literature value = 1.172 (in situ predicted) -9.73 (P less than .05, R2 = .51). Results are interpreted to indicate a tendency for overestimating ruminal N degradability by in situ methods in feedstuffs of low degradability, while underestimating degradability in more highly degraded feedstuffs. Estimates were 11 to 17 percentage units lower than literature values for alfalfa hay and haylage and 17 units lower than literature values for distiller's dried grains.
Nitrogen metabolism of ruminant animals has been the subject of thousands of research publications. Study of ruminal and intestinal function continues. The quantitative and qualitative importance of ruminal microbes as a source of protein have become apparent in many trials, and factors controlling microbial protein synthesis or growth of microbes as well as ruminal degradation of dietary protein have been explored. Information on the supply side of the protein ledger (ruminal synthesis, bypass or escape of dietary protein; intestinal digestion) exceeds current knowledge of quantitative needs for amino acids. Descriptive models of N metabolism have evolved that amalgamate current concepts. With future amendments, these systems should prove useful in diet formulation to more fully utilize ruminal fermentation and increase productive efficiency of ruminant animals. Expanding knowledge of ruminal N metabolism will permit greater control and manipulation of the processes of ruminal fermentation and postruminal digestion.
Lactating Holstein cows fitted with ruminal and duodenal T-type cannulae were used in two studies to determine the effect of forage: concentrate ratio and forage particle size on site of nutrient digestion and microbial protein synthesis. In exp. 1, cows were fed alfalfa hay at 24, 38, 58 and 80% of total dry matter intake. Organic matter (OM) digestion in the total tract (OMD) increased with increasing concentrate level but apparent ruminal OM digestion (AROMD) was unaffected by diet. Digestion of acid detergent fiber (ADF) was similar among the higher forage diets, but was depressed at the 24% forage level. Efficiency of microbial protein synthesis (MPS) was depressed by high concentrate diets and was positively correlated (P < 0.05) to turnover rate within the rumen. In exp. 2, cows were fed 20% concentrate and 80% alfalfa hay in long, chopped or ground and pelleted form. AROMD was lower with ground hay but OMD was unaffected by diet. Digestibility of ADF in the rumen was lower with ground hay, but was partially compensated for by increased hindgut digestion of ADF. Flow of feed plus endogenous nitrogen (N) at the duodenum was 37% and 47% on N intake with long and ground hay, respectively. Efficiency of MPS increased 15% and postruminal N digestion increased 36% when ground hay replaced long hay. Efficiency of MPS was directly related to ruminal solids turnover rate and inversely related to liquid dilution rate. These results demonstrate improvements in efficiency of MPS with either increasing amounts of forage in the diet or increased ruminal passage of solids. Key words: Digestion, microbial protein, rate of passage, cattle, rumen forage
Samples of fresh alfalfa and alfalfa wilted to dry matter contents of 29, 40, and 66%, collected before and after ensiling, were analyzed for compositional changes resulting from wilting and ensiling. Wilting and ensiling had little effect on total nitrogen content of alfalfa but produced substantial changes in the profile of nitrogen-containing compounds in the forages. Five Holstein cows fitted with rumen cannulae and with T-type cannulae in the proximal duodenum and terminal ileum were employed to study effects on nutrient digestion of feeding the three alfalfa silages and baled hay. Forages supplied approximately 75% of the nitrogen consumed by the cows. Cows fed silage of 66% dry matter had a higher percentage of dietary nitrogen equivalent recovered as nonammonia nitrogen at the duodenum because of less extensive ruminal degradation of dietary crude protein. Treatment did not affect intestinal availability of nitrogen. Intakes (g/day) of amino acids were different because of dietary forage, but profiles of amino acids entering and absorbed from the intestine were similar for all treatments. Availability of amino acids in the small intestine was unaffected by source of forage.
Effects of dietary concentrate level and varying the level of concentrate diurnally on site of digestion and passage rate with high concentrate diets were determined with four mature beef steers. Increasing concentrate level from 65 to 80 and 95% decreased ruminal, duodenal and fecal pH, ruminal dilution rates for fluids and particulates and tended to reduce digestion of acid detergent fiber, especially post-ruminally. Ruminal escape of dietary protein tended to increase with concentrate level although microbial efficiency tended to decrease. Compared with an 80% concentrate diet, feeding 95% concentrate in the morning and 65% concentrate in the evening tended to increase ruminal digestion of acid detergent fiber and starch.
The objective of Experiment 1 was to determine protein degradation in the rumen and amino acid supply to and absorption of amino acids from the intestine of lactating dairy cows receiving supplements of soybean meal or a com- bination of dehydrated alfalfa and corn gluten meal. Four lactating Holstein cows, fitted with ruminal, duodenal, and ileal cannulae, were used in a switchback experiment. Two diets consisting of 50% corn silage and 50% concentrate were fed. One diet contained soybean meal and the other contained a mixture of dehydrated alfalfa and corn gluten meal. It was estimated that 76% of the dietary protein was degraded in the rumen with the soybean meal diet compared with 62% with the dehydrated alfalfa:gluten meal diet. Flow of total amino acids to the duodenum was 13% higher for the dehydrated alfalfa:gluten meal than for the soybean meal diet. Experiment 2 consisted of two trials. The objective of Trial 1 was to measure rumen fermentation products in lactating dairy cows fed diets where dehydrated alfalfa, with or without urea, replaced 40% of the concentrate. The objective of Trial 2 was to measure milk production. milk composition, and plasma amino acids of dairy cows in early lactation fed the same diets as in TriaI 1. Milk pro- duction was 34.7, 33.4, and 32.8 kg/d and milk fat was 3.48, 3.58, and 3.63 %
Summary Four lactating Holstein cows fitted with T- type cannulae in the proximal duodenum were used in a 4 4 Latin square experiment to determine degradation in the rumen of protein in corn gluten meal. Cows were fed diets four times daily that contained 50% grain, 35% corn silage and 15% alfalfa hay on a dry matter (DM) basis. Corn gluten meal replaced low protein components of the grain mixture. Chromium- ethylenediaminet etraacetic acid (Cr-EDTA) and La were included in portions of the grain mix- tures to serve as indigestible markers for cal- culating nutrient flow rates and digestibilities. Grain mixtures were fed four times daily. Each experimental period was 14 d in duration and consisted of a 10-d adjustment period followed by a 4-d period for collection of feces and duo- denal digesta. Mean ratios of Cr:La in the feed, duodenal digesta and feces were 5.62, 5.35 and 5.36, respectively. These results indicated that samples taken via the T-type cannula in the duodenum were reasonably representative of digesta flow past the cannula. Lanthanum was subsequently used as the sole digestibility mar- ker for determining digesta flow rates. Appar-
The voluntary intake and digestibility of four hays were measured with eight sheep using two 4 × 4 Latin squares. Measurements were made during the last 8 days of each 3-week period. The degradation characteristics of the hays were measured by incubating samples (in nylon bags) for 12, 24, 48 or 72 h in the rumen of four sheep fitted with rumen cannulae and given a good hay. The exponential p = a + b(1 − e−α) where p = degradation loss, t = time, and a, b and c are constants, was fitted. The potential degradability (defined as a + b) of the dry matter (DM) of the four hays was 0·76, 0·66, 0·54 and 0·46 with corresponding voluntary intakes of 71, 62, 52 and 45 ± 2·9 g DM per kg M075 per day. The in vivo digestibilities were 0·61, 0·59, 0·46 and 0·45 (s.e. 0·013) respectively and corresponded to 23-, 25-, 31- and 67-h degradation. Voluntary intake was better related to potential degradability (and degradability at 12, 24, 48 and 72 h) than to in vivo digestibility. It is concluded that the degradation characteristics of forages may have useful application in predicting voluntary intakes, and that potential degradability could be used to define the rumen (jegradable nitrogen content necessary with any particular forage.
Young steers with rumen and simple duodenal cannulas were given diets of approximately equal amounts of flaked maize and hay (A) or of flaked maize and straw supplemented with decorticated groundnut meal (DCGM) (B), fishmeal (C), heated soya-bean meal (D) or raw soya-bean meal (E) or of dried grass (F). A cow with rumen and re-entrant duodenal cannulas was given diets of hay and dairy cubes.
Some steers received doses of ³² P-labelled inorganic phosphate twice daily with their concentrate feed. This led to small diurnal variations in inorganic P– ³² P specific activity but at similar daily sampling times the ³² P specific activity in rumen bacterial nucleic acids reached a steady state after dosing for about 4 days. Contributions of microbial-N to non-ammonia-N (NA-N) entering the duodenum were then estimated by comparing nucleic acid ³² P/NA-N ratios in related samples of rumen bacteria and duodenal contents. Similar estimates were made in these and other animals using α-, ε-diaminopimelic acid (DAP) and ribonucleic acid (RNA) as bacterial markers.
Estimates for steers given diets A, B, C and F based upon ‘ ³² P-labelled RNA nucleotides’ were, on average, 85% of those based upon total RNA. The differences were attributed mainly to the latter being elevated by the presence of small amounts of dietary RNA. When RNA-based estimates of the proportion of microbial-N in NA-N in duodenal contents for these and other steers which were nearly free of protozoa were multiplied by 0·85 (‘adjusted RNA’) the values were, on average, similar to those based upon DAP. Similar estimates for the cow based upon ‘adjusted RNA’ measurements were, however, about twice those based upon DAP, probably because the cow contained a high protozoal population and the DAP based, method did not account for protozoal N.
For some steers total flows at the duodenum of organic matter (OM), microbial-N (mean based upon ‘adjusted RNA’ and DAP) and residual food N were estimated by reference to chromic oxide. Average values for g microbial-N synthesized/kg OM truly digested in the rumen for the different diets ranged from 15 to 22 (mean 20). Mean degradabilities of food N (residual food N at duodenum/N intake) were 0·57, 0·71, 0·71, 0·70 and 0·84 for diets A, B, C, D and E respectively. No differences between diets were significant at P < 0·05.
SUMMARY The metabolizable protein (MP) feeding standard for lactating cows represents a balance between animal requirements for metabolizable amino acids (MAAs) and their fulfillment by diets composed of a wide variety of feedstuffs. One additional measurement for feedstuffs, the .urea-fermentation-potential (UFP), is utilized when urea is a part of the diet. Although the MP standard is an amiho kei'd (AA) standard, nevertheless, an alte/'fiativd ~if~gle-value MP stan- dard was approximated ~H~out resorting to calculations for each ess~iatlal 'AA. The net protein (NP) of body origin ifi the feces was estimated to be 12 g/kg 0~ dry matter (DM) consumed. This amount Was regarded as a feedstuff expense of digestion reducing the quantity of MP available for productive pur- poses such as lactation. The estimation of rumen microbial protein synthesis as 10.4% of total digestible nutrients (TDN) is based upon three evaluations. The first is that 52% of ration TDN undergoes digestion within the rumen. The second is that 25% of the digested TDN is transformed into microbial crude protein when adequate nitrogen is present. The third evalua- tion is that 80% of the microbial protein is alpha-amino. The 80% true digestibility value for abomasal microbial protein synthesized within the rumen is based upon cattle and sheep metabolism trials. Semi-purified diets
Microbial N produced in the rumen and flowing to the duodenum (Ni) is related to the total amount of OM fermented or apparently digested in the rumen (OMf). This relationship, best expressed as microbial N yield (gNi/kgOMf), is affected mainly by the physical and chemical properties of feed carbohydrates and the amounts ingested. These factors influence yields at three levels of increasing complexity: Bacterial fermentation within one compartment following the continuous culture model. Fermentation pattern as such does not seem to affect yields. High fermentation rates are associated with lactate production, low methane production and transient polysaccharide synthesis. These effects induce acidification and lower yields, partly compensated by faster growth. Protozoal action, determined by the presence of sequestration spaces provided mainly by roughage diets. The presence of protozoa depresses microbial N yield but allows more complete fibre digestion. Compartmentation and differential passage. With roughage diets, optimal microbial N yield seems to require well developed microbial compartmentation, involving a large proportion of microbes in a large-particle pool with a slow turnover, balanced by a small proportion in liquid, small-particle pools with a fast turnover. Such a situation is associated with long roughage feeding. It is hypothesized that microbial N yields in the rumen may vary between two extremes which are associated with the feeding of long roughage on the one hand or with concentrate (starch) feeding on the other.
Six lactating cows were fitted with ruminal and duodenal cannula to measure protein digesta flow to the duodenum during early and midlactation. Diets were composed of corn grain, corn silage, and orchardgrass hay plus supplemental fish meal or soybean meal. Diets contained 15.5% CP and 20.7 ADF. Cobalt-EDTA and Yb were used as liquid and particulate digesta markers and cytosine was used as microbial marker. Corrected organic matter digestibilities in the stomachs were 48.4, 49.8, 44.9, and 53.2% for fish meal and soybean meal diets and early and midlactation, respectively. Preduodenal degradabilities were 47.2, 65.8, 56.7, and 56.2% for fish meal and soybean meal diets and early and midlactation, respectively. Nitrogen recoveries at the duodenum were 93.2 and 84.3% for fish meal and soybean meal diets. Intake of amino acids was greater when cows were fed the soybean meal diet, but total flows of amino acids to the duodenum were similar for both diets. Greater quantity of protein escaping ruminal degradation in cows fed fish meal compared with soybean meal was counterbalanced by less microbial synthesis in the rumen.
Four mature nonlactating Holstein heifers fitted with ruminal and duodenal cannulae were used to investigate in vivo effects of niacin and whole cottonseed. Each heifer was assigned randomly to a treatment in a 2 X 2 factorial arrangement of treatment sequences within a 4 X 4 Latin square design. Heifers were fed isonitrogenous complete mixed rations individually twice daily. Diets contained corn-soybean meal concentrate, corn silage, chopped coastal bermudagrass hay, plus 1) 0% niacin and 0% whole cottonseed, 2) 0% niacin and 15% whole cottonseed, 3) .07% niacin and 0% whole cottonseed, or 4) .07% niacin and 15% whole cottonseed. Dry matter consumption, ruminal pH, ruminal ammonia and VFA concentrations, microbial N production, and DM and ADF digestion were not affected by treatment. Numbers of ruminal protozoa and RNA concentrations were reduced with whole cottonseed feeding and increased by addition of niacin. Whole cottonseed increased molar percentages of acetate while depressing propionate. Niacin supplementation resulted in greater digestion of both CP and NDF. Ether extract digestibility was highest in heifers fed whole cottonseed. Fiber digestion was not affected by whole cottonseed feeding.
Physical constraints on ruminal digestion have received concentrated research attention in the past 10 years. With scanning electron microscopy, microbial attack and digestion of forage components in the rumen have been observed. Limits to passage through the digestive tract have been explored with digesta flow markers and particle-sizing devices. Diet composition analysis has been simplified by near-IR reflectance. NMR procedures, and histological indexing. Rumen microbial function and genetics are being examined by new procedures and genetically altered microbes are being used for production of specific nutrients. Isolated microbial enzymes are being used in feed analysis. The site of digestion in vivo has received detailed attention with new cannula designs, digesta flow markers, and constitutive microbial markers. Ruminants are being maintained by intragastric or i.v. infusion of purified nutrients to quantitate nutrient requirements. Static and dynamic models of digestive function are aiding in the interpretation of research data. Unfortunately, many new procedures have not been critically standardized against traditional methods. The complexity of certain new techniques and models complicates critical review, publication, and comprehension of research results. The most important laboratory tool for increasing research knowledge is still the alert, fertile human imagination.
Seven Holstein steers (340 kg) fitted with ruminal, duodenal and ileal cannulae were used to measure the influence of supplemental N source on digestion of dietary crude protein (CP) and on ruminal rates of protein degradation. Diets used were corn-based (isonitrogenous, 12% CP on a dry matter basis, and isocaloric, 80% total digestible nutrients) with urea, soybean meal (SBM), linseed meal (LSM) or corn gluten meal (CGM) as supplemental N. Ruminal ammonia N concentrations were higher (P less than .05) in steers fed LSM than in those fed CGM, but did not differ from those in steers fed urea or SBM (11.7, 6.7, 9.1 and 9.2 mg/100 ml, respectively). Due to the high degradability of urea, ruminal digestion of dietary CP was greater (P less than .05) in steers fed urea than in those fed CGM, but intermediate in steers fed SBM and LSM (58.4, 48.8, 53.1 and 53.9%, respectively). Flow of bacterial nonammonia N to the duodenum was highest (P less than .05) in steers fed SBM or LSM, intermediate (P less than .05) for urea and lowest (P less than .05) for CGM (86.8, 86.1, 76.3 and 65.9 g/d, respectively). Efficiency of bacterial protein synthesis was lowest in steers fed CGM and differed (P less than .05) from SBM (15.6 vs 21.8 g N/kg organic matter truly digested, respectively). Rate of ruminal digestion for SBM-CP differed (P less than .05) from that of CGM-CP but not from that of LSM-CP (17.70, 5.20 and 10.13%/h, respectively). The slow rate of ruminal degradability of CGM resulted in increased amounts of dietary protein reaching the intestinal tract but lower amounts of bacterial protein, thus intestinal protein supply was not appreciably altered.
Six mature Holstein cows in late lactation and fitted with permanent ruminal, duodenal and ideal cannulae were used in a double 3 X 3 Latin-square design to study the effect of roasting or extruding of cottonseed on protein degradation in the rumen and availability of amino acids in the small intestine. Raw whole cottonseed (CS), extruded whole cottonseed (ECS), and roasted whole cottonseed (RCS) were fed in diets containing 17% crude protein and composed of 42% whole cottonseed, 26% corn grain and 29% hay supplemented with dry molasses, vitamins and minerals. The diets were isocaloric and contained 1.86 Mcal NEL/kg. Acid detergent lignin was used as a digesta marker, and diaminopimelic acid as a bacterial marker. Ruminal ammonia concentration was higher (P less than .05) for CS than for ECS and RCS (15.7, 12.7 and 10.2 mM). Concentrations of isobutyrate (1.3 vs 0.8 and 0.8 mM) and isovalerate (1.8 vs 1.1 and 1.1 mM) were higher (P less than .05) for CS compared with ECS and RCS. Non-ammonia nitrogen flow to the duodenum (g/d) was 248, 300 and 350 for CS, ECS, and RCS, with RCS higher (P less than .05) that in CS. Apparent absorption of total amino acids in the small intestine was .80, 1.01, and 1.24 kg/d, for CS, ECS, and RCS, respectively, with RCS higher (P less than .05) than CS. Apparent absorption of essential and non-essential amino acids was 376, 425; 458, 548;610 and 628 g/d for CS, ECS and RCS respectively, with RCS higher (P less than .05) than CS.
A summary of in vivo estimates of the amount of dietary protein from individual feedstuffs that escapes microbial degradation in the rumen is presented. Values range from approximately 20% for protein in barley, oats, wheat, and alfalfa silage to 65 to 70% for protein in fish meal and animal by-products. In vitro or in situ methods for estimating protein degradation can be used, but at this stage of development, the methodology is more useful in providing a relative ranking of feedstuffs on the basis of protein degradation than in providing absolute estimates of protein degradation. A number of factors influence protein breakdown in the rumen, including extent of crosslinking in the protein (disulfide bonds), retention time in the rumen, protein solubility, and processing and storage effects on protein. It is important to consider the amino acid content of the undegraded dietary protein, particularly lysine and methionine, two amino acids likely to be limiting for milk production. Strategies for using protected proteins in dairy cattle diets are discussed.
Four beef steers (avg wt 300 kg) fitted with duodenal re-entrant cannulae were used to study the effect of dietary concentrate to forage ratio on bacterial and nonbacterial N flow in the duodenum. According to a change-over design, the steers were designated to receive an all forage (83% alfalfa hay and 17% wheat straw) and an 80% sorghum grain diet. Lignin (ADL) and chromium oxide (Cr2O3) ratio techniques were compared with automated total collection (ATC) of digesta for quantitating duodenal protein flow and efficiency of bacterial N yield in the rumen. Estimates of bacterial protein synthesis and ruminal escape of feed protein based on Cr2O3 and lignin tended to be higher by 8 to 16% than those obtained by ATC. Efficiency of ruminal bacterial protein yield estimated by these two markers tended to be greater than that based on ATC (16 vs 12 g of bacterial protein/100 g ruminal true digestion of dry matter corrected for bacterial cell synthesis). Efficiency values did not differ between diets. Crude protein flow into the duodenum was about 33% greater (P less than .01) for the grain than the forage diet, although protein intake was about 10% less on the grain diet. Duodenal bacterial protein, rather than feed protein escaping ruminal degradation, accounted for most of this difference. Average duodenal flow of N, expressed as g/Mcal metabolizable energy (ME) intake, was 11.9 for the forage diet and 10.3 for the grain diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Four lactating Holstein cows fitted with rumen cannulae and T-type cannulae in proximal duodenum and terminal ileum were used to measure protein degradation in the rumen and amino acid flow and absorption in the small intestine. Soybean meal, whole soybeans, and whole soybeans extruded at 132 and 149 degrees C provided 50% of the protein in diets that contained 51% grain, 36% corn silage, and 13% alfalfa hay (dry matter). Spot samples of digesta were collected from duodenum and ileum during 96 h, and lanthanum was an indigestible marker to estimate flow and digestibility of nutrients. With diaminopimelic acid as a microbial marker, apparent degradations of dietary crude protein in the rumen were 73, 80, 66, and 60% for diets containing soybean meal, whole soybeans, and whole soybeans extruded at 132 and 149 degrees C. Because of the extensive degradation of protein with the raw soybean diet, less total amino acids reached the duodenum, and because of decrease of availability, absorption from the small intestine (g/day) was lowest with this diet. Feeding diets containing extruded whole soybeans increased availability of total essential amino acids in the small intestine compared with diets containing soybean meal and whole soybeans. Absorption from the small intestine (g/day and percent entering) of individual amino acids was generally higher for extruded whole soybean diets.
Four lactating cows, each fitted with a rumen cannula and duodenal and ileal t-cannulae, were used to measure flow and digestion of nitrogenous compounds in the digestive tract. Dietary dry matter contained 17% crude protein and 50:50 forage:concentrate. Treatments were: 1) corn silage-soybean meal; 2) corn silage-heated soybean meal; 3) ammonia-treated corn silage-soybean meal; and 4) ammonia-treated corn silage-heated soybean meal. Flow of organic matter to the duodenum was overestimated when lanthanum or chromium ethylene-diaminetetraacetate was used as an indigestible marker. This resulted in low estimates of ruminal digestion of organic matter and high estimates of nitrogen flow to the duodenum. However, calculations using lanthanum or lignin as markers yielded similar organic matter flow to ileum and feces. With acid-detergent lignin as a marker, estimates of dietary nitrogen degraded in the rumen were: corn silage-heated soybean meal, 55.0% ammonia-treated corn silage-heated soybean meal, 58.8%; ammonia-treated corn silage-soybean meal, 63.3%; and corn silage-soybean meal, 66.0%. Digestion in the small intestine of nonammonia nitrogen was equal for all treatments suggesting that availability of heated soybean meal in the intestine was not different, although ruminal degradability tended to be lower. Feeding diets containing nonprotein nitrogen did not decrease available nitrogen at the duodenum.
1. Protozoa-free steers with simple rumen and abomasal cannulas were given basal diets consisting of a concentrate mixture of flaked maize and tapioca with barley straw (BS) or alkali-treated barley straw (BSA). Other diets were supplemented with urea (BSU and BSAU respectively) or with fish meal replacing the tapioca (BSF and BSAF respectively). The diets were isoenergetic and calculated to provide sufficient metabolizable energy (ME) to support a growth rate of 0.5 kg/d. Rumen-degradable nitrogen (RDN): ME values (g/MJ) were estimated to be 0.50, 1.20 and 0.80 for the basal diet, urea- and fish-meal-supplemented diets respectively. RNA and α, ε-diaminopimelic acid (DAP) were used as microbial markers. ¹⁰³ Ruthenium and polyethylene glycol (PEG) were given as flow markers and flows (g/24 h) at the abomasum of organic matter (OM) and nitrogenous constituents were calculated.
2. Samples of mixed bacteria separated from rumen digesta from animals receiving N-supplemented diets contained significantly more N than those from animals receiving basal diets (approximately 74 and 62 mg/g dry matter (DM) respectively) but there were no other significant differences in total-N contents between treatments. RNA-N: total-N values were similar for all diets (approximately 0.13). DAP-N: total-N values were significantly lower in bacteria from animals receiving alkali-treated (AT) rather than untreated (UT) straw (approximately 0.008 and 0.011 respectively).
3. The proportion of OM intake digested in the rumen (ADOM) was significantly higher for animals receiving AT straw rather than UT straw (approximately 0.54 and 0.43 respectively). N supplementation had no effect on OM digestibility.
4. When basal rather than N-supplemented diets or AT-straw- rather than UT-straw-containing diets were given, there were significantly lower flows of ammonia-N, non-ammonia-N (NAN) and microbial-N (based on RNA flow, MN(RNA)) at the abomasum. Mean daily MN(RNA) flows (g) were 21, 30, 31, 16, 27 and 28 for diets BS, BSU, BSF, BSA, BSAU and BSAF respectively. These correspond to estimated efficiencies of microbial protein synthesis, expressed as g MN(RNA) /kg truly-digested OM, at 14, 22, 22, 12, 18 and 19 respectively. Values were significantly lower for basal as compared with corresponding N-supplemented diets and for AT-straw diets as compared with corresponding UT-straw diets.
5. Estimated mean proportions of total feed-N intake degraded in the rumen, based on MN(RNA) as microbial marker, of diets BS, BSU and BSF were 0.60, 0.74 and 0.47 respectively; corresponding values for diets BSA, BSAU and BSAF were 0.72, 0.73 and 0.36 respectively. Making certain assumptions, the mean proportions of fish-meal-N digested in the rumen were calculated to be 0.23 and 0.14 respectively for UT- and AT-straw diets. The values were not significantly different. Values for microbial flows based on DAP as marker were significantly lower, by about 25%, than those based on RNA.