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Evaluation of protein flow to the duodenum in dairy cattle by the in sacco method
Abstract
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.
... In vivo feeding studies e.g. with markers and digestive tract collections may be more accurate but are costly, labor intensive and time consuming. Evaluations of in vivo measurements and other methods, primarily the in sacco method by Ørskov and McDonald (1979), have been performed (Norman et al., 2010;Hedqvist & Udén, 2006;Sehgal & Makkar, 1994;Arieli et al., 1993). The in sacco method is based on the incubation of feed containing small porous bags in the rumen of a fistulated animal. ...
... This is particularly relevant in grazing studies with the differences between ruminal environment of grazing and nongrazing cows (Jones-Endsley et al., 1997; Holden et al., 1994b; Rearte and Santini, 1993; Van Vuuren et al., 1986). The in situ technique also allows for prediction of the amount of protein flowing to the duodenum, comparable to that found with in vivo methods (Arieli et al., 1993). Intake of RDP and RUP was calculated with the EDCP of pasture (Table 6) and concentrates (Table 7) estimated in experiment 1, and the concentrates and pasture CP intake measured in experiment 2 (Table 8). ...
Six Holstein cows fitted with ruminal cannulae were used in two simultaneous 3 x 3 Latin squares to study the effects of protein supplements on ruminal fermentation and in situ crude protein degradability. Cows rotationally grazed a winter oats (Avena sativa L.) pasture and were supplemented with one of three concentrate supplements: 1) low protein sunflower meal (L-SM); 2) high protein sunflower meal (H-SM); or 3) high protein feather meal (H-FM). Concentrates (6.5 kg/d) were offered in equal portions twice daily during milking. Ruminal pH and total volatile fatty acids concentration were unaffected by treatments. Supplementation with L-SM and H-FM decreased ruminal NH3-N concentration compared with H-SM. The concentrate with feather meal had lower effective rumen degradability of crude protein than concentrates containing sunflower meal. Effective rumen degradability of crude protein of pasture averaged 82.7%. Thirty-six multiparous Holstein cows (71 d in milk) were used in a complementary experiment to study the effect of treatments on intake, milk yield, and milk composition. Pasture (13.2 kg/d) and total (19.6 kg/d) dry matter intake (estimated using Cr2O3 as fecal marker) and milk yield (20.5 kg/d) were unaffected by level or source of protein supplemented. Intake of rumen undegradable protein in grazing dairy cows was higher when the amount of sunflower meal was increased or when feather meal was used in the supplement. However, higher rumen undegradable protein intake did not increase milk production, suggesting that rumen undegradable protein was not limiting for cows on pasture producing less than 22 kg of milk.
... The approach employed in the current study was to facilitate capture of surplus ruminal ammonia via an adequate supply of RDOM. The ratio of RDOM to RDP of about 5:1 used in the LP diets (Table 3) is considered adequate for satisfying energy requirements for microbial protein production (Arieli et al., 1993). That yield of milk and milk protein were unaffected by CP concentration whereas milk protein efficiency was higher in the LP diets, is consistent with the assumption that the supply of CP for LP groups was adequate, implying that cows fed the HP diet were fed a relative surplus of protein. ...
Two trials were conducted with cows in commercial herds during midlactation to evaluate the effect of dietary crude protein (CP) concentration on the production, composition, and efficiency of milk production under hot ambient conditions. Cows were group-fed in trial 1, which was conducted in two herds, and were fed individually in trial 2. The respective average ambient temperature, relative humidity, and temperature-humidity index (THI) were 31 degrees C, 45%, and 78 in trial 1 and 27 degrees C, 70%, and 76 in trial 2. Cows were cooled by forced evaporative means six times daily in trial 1 and three times daily in trial 2. Dietary CP was 15.3 or 17.3% of dry matter (DM) in trial 1 and 15.1 or 16.7% of DM in trial 2. The respective ratios of rumen-degradable organic matter (RDOM) to rumen-degradable protein were 5.3 and 4.8 for the low CP (LP) and high CP (HP) diets. Average DM intake, milk yield, and milk fat and protein concentrations were 22 and 23 kg/d, 34 and 35 kg/d, 3.1 and 3.4%, and 3.2 and 3.1% in trials 1 and 2, respectively, and were similar among diets in both trials. The resultant calculated milk protein efficiency ratio and overall CP efficiency were 0.31 and 0.32 for the LP diets and 0.28 and 0.29 for the HP diets. In cows fed the LP diet, diet rumen ammonia was lower in trial 1, and milk urea N was lower in trial 2. The BW change was higher in trial 1, and tended to be higher in trial 2, with the LP diets. Changes in body condition score in trials 1 and 2 tended to be higher with the LP diets. It was concluded that a dietary CP content of 15.3% is adequate to maintain production in heat-exposed dairy cows producing 35 kg of milk/d, provided that the forced evaporative cooling and the ratio of RDOM to rumen-degradable protein is appropriate
One hundred and fifty six Israeli-Holstein cows were randomly allotted to two groups in a continuous design; of these, 59 cows entered the trial within 14 days postpartum. The trial lasted 75 days. Diet 1 (control group) contained 16.5% crude protein (CP), of which 11.0% was rumen-degradable (RDCP). Diet 2 (high-protein; HP) contained 17.8% CP; all the additional protein was planned to be rumen-undegradable. Cows were group-fed. Feed intake and milk yield were recorded daily and milk composition was analyzed every 2 weeks. Dry matter intake, milk, milk fat and protein yields (kg/d) of the control and HP treatments were 21.2 and 20.7 (P≤0.05), 34.3 and 35.5 (P≤0.05), 0.866 and 0.935 (P≤0.05), and 0.963 and 1.002 (P≤0.05), respectively. Average milk, milk fat and protein yields in the control and HP cows that entered the trial within 0-21 d after calving, were 37.0 and 39.6 (P≤0.05), 0.992 and 1.043, and 0.985 and 1.056 (P≤0.05) kg/d, respectively. Supplementation of additional undegradable CP at the beginning of lactation, tended to improve reproductive performance, which was attributed to the earlier recovery of body condition score of those cows.
Crude protein degradability and intestinal digestibility of rumen undegraded protein were predicted for Vitex fodder yeast, soybean meal, meat and bone meal and fish meal. The evaluations were performed in vitro using enzymatic methods. In order to determine crude protein degradability, the enzymatic method with bromelain was used. To determine the intestinal digestibility of rumen undegraded protein, the combined enzymatic method with bromelain and pancreatin was applied. The results were adjusted using regression equations for cereals and protein concentrates. The crude protein degradability was 79% (adjusted by regression equation 72%) for Vitex yeast, 77% (70%) for soybean meal, 65% (59%) for meat and bone meal, and 55% (50%) for fish meal. The intestinal digestibility of rumen undegraded protein was 79% (adjusted by regression equation 87%) for Vitex yeast, 90% (98%) for soybean meal, 61% (70%) for meat and bone meal, and 85% (94%) for fish meal.
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.
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.
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 heat treatment on the nutritive value of rumen undegradable protein (UDP) fraction of whole cottonseed (WCS) was studied in this experiment. Forty two multiparous Israeli Holstein cows were used in a multiple double 3×3 Latin square design. Milk production averaged 38±4.1 kg at the beginning of the experiment. Three different diets were formulated to contain 160 g/kg crude protein (CP), 365 g/kg neutral-detergent fibre (NDF) on a dry matter (DM) basis, 7.24 MJ net energy for lactation (NEL)/kg DM and 170 g/kg WCS. 30% of dietary CP was of cotton origin. Diets were (1) whole cottonseed (WCS), (2) heated whole cottonseed (HWCS) and (3) whole cotton seeds plus 3.1% maize gluten meal (WCS+MG). Diets with HWCS and WCS+MG contained 60 g UDP/kg DM compared with 54 g UDP/kg DM in the WCS treatment. Heat treatment decreased ruminal CP degradability of WCS by 22% and ruminal organic matter (OM) degradability by 5%. Intakes of DM, OM and CP were similar across diets. Higher apparent total tract digestibilities of DM and OM were determined in HWCS and WCS+MG diets (0.62 and 0.64 and 0.63 and 0.65, respectively) compared to WCS diet (0.59 and 0.62, respectively). Higher ruminal propionate proportion was determined in diets containing WCS and WCS+MG over the sampling hours. A higher ruminal ratio of acetate:propionate was measured in the diet containing HWCS. Ammonia N concentration was similar in all treatments, however, blood urea N concentration was the lowest at 3 and 6 h after feeding in the HWCS diet compared to the other diets. Milk yield and composition were similar for all treatments and averaged 34.2±0.45 kg/d with 34.2 g fat/kg, 30.1 g CP/kg and 47 g lactose/kg. It was suggested that inclusion of HWCS in diets for high-yielding dairy cows decreased the endogenous catabolism of amino acids. In this study the effect of heat treatment on WCS on the performance of cows was not apparent because the cows consumed surplus of dietary CP.
Four Israeli mix-breed Saanen dairy goats were used in a 2×2 factorial design to evaluate the effect of the level of dietary crude protein (CP) and ruminally degradable OM (RDOM) concentration on the production, composition and efficiency of milk production under hot ambient conditions. Daily ration comprised of 30% hay and 70% concentrates was divided into 12 equal meals. Treatment factors were 18% (HCP) or 15% (LCP) of CP in the diet DM, and 56% (HRDOM) or 50% (LRDOM) of RDOM. Goats were housed in metabolic crates in air-conditioned room. Air temperature ranged between 25 °C and 36 °C, and the thermal humidity index (THI) between 74 and 90 units. Daily amplitude of goat's body temperature was 1.2 °C and was unaffected by treatments. The DM intake, milk yield, and concentrations of protein, fat, and lactose, as well as total tract apparent digestibility of DM and OM were similar among treatments (P>0.1). Digestibility of CP was higher in the HCP diets (P<0.01), and digestibilities of NDF was higher in the LRDOM diets (P<0.01). Digestibility of non-structural carbohydrates was higher in the high RDOM diets and high CP diets (P<0.1). Blood glucose and insulin concentrations were similar among treatments (P>0.1), while NEFA level was higher in LRDOM (P<0.1). Rumen N-ammonia (P<0.05) and milk N-urea (P<0.01) were lower, and plasma N-urea tended to be lower in LCP diets (P<0.15). Overall, these data indicate that N utilization was lowered in goats consuming the high CP diets. It was concluded that diets comprising 15% of CP in DM are adequate for dairy goats exposed to daily high environmental temperatures, and moderate temperatures at night. Though varying dietary RDOM levels did not affect milk N efficiency, the higher NSC digestibility, and the concomitant lower blood NEFA suggest a reduced heat increment in dairy ruminants consuming HRDOM diets.
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.
The potential of the dacron bag technique to assess fluctuations in ruminal metabolites was studied using 40 Israeli-Friesian dairy cows assigned to an experiment with a 2 x 2 factorial design. Diets contained a low (62%) or high (65%) percentage of ruminally degradable CP and a low (55%) or high (59%) percentage of ruminally degradable OM. Metabolites were monitored before feeding and at 3 and 6 h postfeeding. Before feeding, total VFA and propionate were higher, and acetate and pH were lower, in diets containing a high percentage of ruminally degradable OM than in diets containing a low percentage of degradable OM. By 3 H postfeeding, acetate, butyrate and pH were lower, and propionate was higher, in the diets containing a high percentage or ruminally degradable OM than in the diets containing a low percentage of ruminally degradable OM. By 6 h postfeeding, propionate was higher, and acetate was lower, in diets containing a high percentage of ruminally degradable OM than in diets containing a low percentage of ruminally degradable OM. In the diets with a high percentage of ruminally degradable OM, before feeding and by 3 h postfeeding, ammonia concentrations were higher and lower, respectively, relative to the diets containing a low percentage of degradable OM. Milk yield and composition and DMI were similar among treatments. The correlation was good between the degradability data obtained by the dacron bag technique and the meal-induced variations in ruminal metabolites. The lack of a positive yield response to controlled fluctuations in ruminal metabolites may be related to surplus CP intake.
Four lactating Israeli Holstein cows that were ruminally and abomasally cannulated were used in an experiment with a 4 x 4 Latin square experimental design to study the effects of different amounts of ruminally degradable crude protein (CP) and ruminally degradable nonstructural carbohydrates on ruminal fermentation and efficiency of bacterial CP synthesis. Four diets were formulated to contain the following percentages (percentage of respective fraction) of ruminally degradable protein (RDP) and ruminally degradable nonstructural carbohydrates, respectively: 1) 73.8 and 85.3%, 2) 72.4 and 75.3%, 3) 67.7 and 86.0%, and 4) 66.3 and 76.0%. The 2 x 2 factorial effects of high and low concentrations of RDP or nonstructural carbohydrates were examined. Intakes of DM and organic matter (OM) were similar among treatments, and apparent and true ruminal digestibilities of OM were also similar. Apparent digestibility of CP in the total tract was higher for diets containing high concentrations of ruminally degradable nonstructural carbohydrates. Efficiency of microbial CP synthesis was higher for diets supplemented with low concentrations of RDP and averaged 196 g of microbial CP/kg of OM truly digested in the rumen. Total and bacterial CP flows were higher for diets containing low concentrations of RDP. Therefore, greater amounts of amino acids (AA) of bacterial origin reached the abomasum. The abomasal flow of AA was higher for diets containing low concentrations of RDP. Most of the profiles for essential AA in the abomasum were influenced and balanced by profiles for bacteria. When diets contained a high concentration of RDP (73% of total dietary CP), the supplementation of a high concentration of ruminally degradable nonstructural carbohydrates had no positive influence on bacterial yield or efficiency of bacterial CP synthesis. Other factors, such as AA and peptides included in the RUP fraction, may be important to maximize the efficiency of bacterial CP synthesis.
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 effects of replacing whole cottonseed by heated whole cottonseed at two levels of crude protein on amino acid (AA) utilization by the bovine mammary gland were investigated. Four Israeli Holstein cows were used in a 4 x 4 Latin square design with 2 x 2 factorial arrangements. Diets were formulated to contain two levels of crude protein (CP), normal (160 g CP/kg dry matter) and low (140 g CP/kg dry matter), and two levels of rumen undegradable protein (UDP), high (380 g UDP/kg CP) and low (350 g UDP/kg CP). Whole cottonseed was quantitatively substituted by heated whole cottonseed to formulate the high UDP diets. Intakes of dry matter and organic matter were similar for all treatments and averaged 15.9 and 14.4 kg/d respectively. Yields of milk and its constituents were similar for all treatments. Milk yield averaged 23.1 kg/d and this contained (per kg) 32.3 g CP, 25.4 g total casein and 47.5 g lactose. The milk fat content was lower in the cows given the high UDP diets, averaging 34.6 g/kg compared with 38.9 g/kg in the cows fed on the diets with low UDP. Plasma AA concentrations were similar for all treatments apart from Leu and Ile, which were higher in the cows given the high CP diets: 152 and 103 microM compared with 183.8 and 131.5 microM for the low CP diets. Net extraction and balance of essential AA across the half udder suggested that essential AA were supplied in amounts sufficient to meet milk protein requirements for all treatments. The surplus AA supplied as a result of feeding the high dietary CP were probably catabolized via an enhanced oxidative pathway, possibly in the liver, presumably as a passive response to their disposal.
Four midlactation, multiparous Holstein cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design to determine the effects of supplementing urea or starch or both to diets containing fish meal on passage of nutrients to the small intestine and performance of lactating cows. The treatments (in a 2 x 2 factorial arrangement) were 1) control and control plus 2) urea, 3) starch, or 4) starch and urea. Supplementing diets with urea did not affect DMI; ruminal, postruminal, or total tract digestibilities of DM, starch, ADF, or NDF; ruminal fluid VFA concentrations or molar percentages; or ruminal fluid or particulate dilution rates. Feeding additional starch depressed DMI but did not alter ruminal or postruminal digestion of OM or VFA concentrations and molar percentages in ruminal fluid. Ruminal fluid ammonia concentration was increased by feeding urea and decreased by feeding additional starch. Passage of nonammonia N, nonammonia nonmicrobial N, or microbial N to the small intestine and efficiency of microbial CP synthesis were not affected significantly by supplying either urea or additional starch. Feeding urea increased passage of methionine to the small intestine, whereas feeding additional starch increased passage of methionine and arginine. Passage of other amino acids to the small intestine was not altered significantly by feeding urea or additional starch. Production of milk and milk protein was increased, but yields of fat and SNF were not altered by feeding diets supplemented with urea. Production of milk and milk fat was not affected, but yields of CP and SNF were decreased when additional starch was fed to cows.
Steam distillation methods of determining ammonium, nitrate, and nitrite in the presence of alkali-labile organic nitrogen compounds are described. They involve the use of magnesium oxide for distillation of ammonium, ball-milled Devarda alloy for reduction of nitrate and nitrite to ammonium, and sulfamic acid for destruction of nitrite. The methods are rapid, accurate, and precise, and they permit nitrogen isotope-ratio analysis of ammonium, nitrate, and nitrite in tracer studies using 15N-enriched compounds. They give quantitative recovery of ammonium, nitrate and nitrite added to soil and plant extracts, and appear suitable for analysis of biological materials.
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
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-
A method is proposed for estimating the percentage of dietary protein that is degraded by microbial action in the rumen when protein supplement is added to a specified ration. The potential degradability, p , is measured by incubating the supplement in artificial-fibre bags in the rumen and is related to incubation time, t , by the equation p = a+b (1 – e -ct ). The rate constant k , measuring the passage of the supplement from the rumen to the abomasum, is obtained in a separate experiment in which the supplement is combined with a chromium marker which renders it completely indigestible. The effective percentage degradation, p , of the supplement, allowing for rate of passage, is shown to be p = a +[ bc/(c+k) ] (1- e -(e+k)t ) by time, t , after feeding. As t increases, this tends to the asymptotic value a+bc /( c+k ), which therefore provides an estimate of the degradability of the protein supplement under the specified feeding conditions.
The method is illustrated by results obtained with soya-bean meal fed as a supplement to a dried-grass diet for sheep. The incubation measurements showed that 89% of the soya-bean protein disappeared within 24 h and indicated that it was all ultimately degradable with this diet.
When the dried grass was given at a restricted level of feeding the allowance for time of retention in the rumen reduced the estimate of final degradability to 71% (69% within 24 h). With ad libitum feeding there was a faster rate of passage and the final degradability was estimated to be 66% (65% within 24 h).
A method for direct purine N isolation and determination was modified from the method of Zinn and Owens for rapid determination of purines. By this method, N derived from purines in digesta was measured and collected for 15N determinations. Measurements of purine N in 33 samples of ruminal contents and duodenal digesta of sheep and goats were compared with purine determinations in the same samples. The results showed that essentially all the N in the purines that could be isolated by the Zinn and Owens procedure also could be detected by N isolation and determination. Determinations of 15N in the NH3 N, NAN, and purine N fractions in a continuous culture in vitro showed significant differences in the 15N enrichment curves between diets based on either roasted or raw soybean meal.
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.
Four Holstein cows fitted with ruminal, duodenal, and ileal cannulae were used in a 4 x 4 Latin square design to measure ruminal protein degradation and small intestinal digestion of diets containing untreated soybean meal or soybean meal treated with heat and either water, xylose, or calcium lignosulfonate. Diets consisting of 40% corn silage, 10% alfalfa cubes, and 50% grain mix, and averaging 16.8% crude protein (DM basis) were fed four times daily. Approximately 50% of the total dietary protein was supplied by the respective soybean meal source. Ruminal protein degradation was 70.6, 69.6, 55.8, and 53.7% for diets containing untreated soybean meal, water-soybean meal, xylose-soybean meal, and calcium lignosulfonate-soybean meal, respectively. Duodenal non-NH3 N flow (g/d) and absorption of non-NH3 N (g/d) in the small intestine were generally not affected by treatment. Duodenal bacterial N flow (g/d) was lower with xylose-soybean meal and lignosulfonate-soybean meal than with untreated soybean meal. Treatment of soybean meal with xylose or calcium lignosulfonate was successful in decreasing ruminal protein degradation. However, it may be necessary to include a source of readily fermentable N in diets that contain protected proteins in order to supply adequate NH3 N for microbial protein synthesis.
Factors influencing microbial protein synthesis in the rumen have been reviewed several times in recent years. Original publications in the past 3 yr have reported microbial and feed protein nitrogen contribution postruminally when feeding a variety of dietary proteins. Ammonia is a satisfactory source of nitrogen for growth of the majority of rumen species, but substitution of intact protein for urea (source of ammonia) usually stimulates microbial protein production. Protein sources such as soybean meal appear to possess properties (perhaps rate of degradability) that optimize microbial growth in vivo. Protein sources more undegradable than soybean meal, when fed as the major nitrogen source, sometimes reduce microbial growth. However, nondegradable proteins may compensate for less microbial protein by supplying intact dietary protein postruminally, so the amino acids potentially available may be equal to or greater than those available when readily degradable protein is fed. Soybean meal may reduce microbial growth in diets containing grass silage at protein exceeding 16.8%. Various measurements of microbial and intact dietary protein postruminally show that the contribution of each can be manipulated. Accuracy of quantitative predictions of postruminal contribution depends on several factors that require more research.
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.
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.
1. In four feeding experiments with sheep the utilization of proteins contained in lucerne hay and of those in toasted soya-bean meal (SBM), representing a roughage and concentrate feed respectively, were examined. The ration of one group of animals contained lucerne hay as sole source of digestible protein and that of the other SBM.
2. Measurements of the nitrogen balance showed clearly the superiority of lucerne hay as protein source compared with soya-bean meal; this arose from the greater N retention found with the lucerne hay ration.
3. The influence of both rations on the metabolic pathways of the proteins was examined by following the changes of concentration of various metabolites in the rumen contents and of blood urea at different intervals after feeding.
4. Concentrations of urea found in the blood of the sheep given lucerne hay were lower than those of the other group, a finding which is in agreement with the results of the balance experiments.
5. The concentrations of NH 2 -N and of aminoacids in the rumen liquor were higher in sheep given lucerne hay than in those given SBM. These concentrations appeared to be related to the differences between the soluble non-protein N contents of the two feeds.
6. The results agree with the finding from in vitro experiments that rumen liquor from sheep receiving lucerne hay promoted greater synthesis of protein than rumen liquor from sheep receiving SBM.
7. Total bacterial activity as measured by the reduction of triphenyltetrazolium chloride (dehydrogenase activity) was much higher in the rumen liquor of sheep given lucerne hay than when SBM was given.
8. The concentrations of volatile fatty acids (C 2 -C 6 ) were much higher in the rumen liquor in sheep on the lucerne hay diet than in those on the SBM diet. After meals of the lucerne hay diet, the concentrations of acids higher than C 2 , particularly those of valeric acid, exceeded those present in the rumen liquor of the animals kept on the SBM diet.
9. Proline and alanine appeared in relatively higher concentrations in the rumen liquor than the other amino acids determined, and these two acids together with valine disappeared very rapidly. The possible conversion of these amino acids into valeric acid is considered. It is suggested that valeric acid found in relatively high concentrations in rumen liquor of sheep given lucerne hay may be due in part to the deamination of proline, which likewise disappeared very rapidly together with alanine and valine.
Ruminal bypass of cottonseed meal proteins by lactating dairy cows
- A L Goetsch
- F N Owens
- C E Kautz
Goetsch, A.L., Owens, F.N. and Kautz, C.E., 1984. Ruminal bypass of cottonseed meal proteins by lactating dairy cows. Oklahoma Agric. Exp. Statn. Report, pp. 76-78.
Critique and evaluation of markers for use in nutrition of humans and farm and laboratory animals
- Van Soest
- P J Uden
- P Wrick
Van Soest, P.J., Uden, P. and Wrick, K.F., 1983. Critique and evaluation of markers for use in nutrition of humans and farm and laboratory animals. Nutr. Rep. Intern., 27:17-28.
Simultaneous extraction ofYb, Dy and Co from feces with EDTA, DCTA or DTPA
- A R Karime
- F N Owens
- G W Horn
Karime, A.R., Owens, F.N. and Horn, G.W., 1986. Simultaneous extraction ofYb, Dy and Co from feces with EDTA, DCTA or DTPA. J. Anim. Sci., 63 (Suppl. 1 ): 447.
The Nutrient Requirements of Ruminant Livestock. Sup-plement No. 1. Commonwealth Agricultural Bureaux, Farnham Royal Use of nitrogen-15 determination of purine nitrogen fraction of digesta to define nitrogen metabolism traits in the rumen
- Research Agricultural
- Uk Council
- Y Aharoni
- H Tagari
Agricultural Research Council, 1984. The Nutrient Requirements of Ruminant Livestock. Sup-plement No. 1. Commonwealth Agricultural Bureaux, Farnham Royal, Slough, UK. Aharoni, Y. and Tagari, H., 1991. Use of nitrogen-15 determination of purine nitrogen fraction of digesta to define nitrogen metabolism traits in the rumen. J. Dairy Sci., 74: 2540-2547.
Evaluation of calcium lignosulphate-treated soybean meal as a source of rumen protected protein for dairy cattle
- Windschilt
Ruminal bypass of cottonseed meal proteins by lactating dairy cows
- Goetsch
Critique and evaluation of markers for use in nutrition of humans and farm and laboratory animals
- Van Soest
Simultaneous extraction of Yb, Dy and Co from feces with EDTA, DCTA or DTPA
- Karime
Ruminant Nitrogen Usage
- National Research Council