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ABSTRACT: Flaxseed is a potent source of the n-3 fatty acid α-linolenic acid (ALA), yet most ALA is lost during ruminal biohydrogenation when ground flaxseed is fed to ruminants. Heat processing and urea formaldehyde condensation polymer (UFCP) treatment of flaxseed were investigated as possible means of protecting ALA from ruminal degradation. Ground flaxseed (GF), heated ground flaxseed (HGF), or UFCP-treated ground flaxseed (UFCPGF) were incubated for 0, 4, 8, and 12 h in 4 ruminally cannulated multiparous lactating Holstein cows. Compared with GF, HGF and UFCPGF decreased ruminal disappearance of dry matter, crude protein, and ALA. Pepsin-digestible protein remaining after 12 h of ruminal incubation was greater for UFCPGF and HGF than for GF. Twenty-four lactating Holstein cows (207 ± 37 d in milk, 668 ± 66 kg of body weight, and 1.33 ± 0.56 lactations) were then used in a randomized complete block design experiment with a basal feeding period to assess effects of flaxseed treatment on ALA enrichment of plasma and milk as well as lactational performance. No evidence existed that supplementation of HGF and UFCPGF affected dry matter intake, milk fat content, milk protein content, or energy-corrected milk yield, but UFCPGF marginally decreased milk yield compared with HGF. Plasma concentration of ALA was not affected by treatment. Concentrations of n-3 fatty acids and conjugated linoleic acids in milk fat were increased by UFCPGF relative to HGF, but ALA yield was not affected. Taken together, in situ results suggest that heat-treated flaxseed, with or without UFCP treatment, slowed ruminal disappearance of ALA. Feeding UFCP-treated flaxseed failed to alter ALA content of plasma or milk ALA yield relative to heating alone.
Journal of Dairy Science 03/2013; · 2.56 Impact Factor
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ABSTRACT: We evaluated a product containing methionine mixed with soy lecithins and added to a mechanically extracted soybean meal (meSBM-Met). Lactational responses of cows, plasma methionine concentrations, and in vitro degradation of methionine were measured. Twenty-five Holstein cows were used in a replicated 5 × 5 Latin square design and fed a diet designed to be deficient in methionine or the same diet supplemented either with 4.2 or 8.3 g/d of supplemental methionine from a ruminally protected source or with 2.7 or 5.3 g/d of supplemental methionine from meSBM-Met. All diets were formulated to provide adequate amounts of metabolizable lysine. Concentration of milk true protein was greater when methionine was provided by the ruminally protected methionine than by meSBM-Met, but milk protein yield was not affected by treatment. Milk yields and concentrations and yields of fat, lactose, solids-not-fat, and milk urea nitrogen were not affected by supplemental methionine. Body condition scores increased linearly when methionine from meSBM-Met was supplemented, but responses were quadratic when methionine was provided from a ruminally protected source. Nitrogen retention was not affected by supplemental methionine. Plasma methionine increased linearly when methionine was supplemented from a ruminally protected source, but plasma methionine concentrations did not differ from the control when supplemental methionine from meSBM-Met was provided. In vitro degradation of supplemental methionine from meSBM-Met was complete within 3 h. Data suggest that meSBM-Met provides negligible amounts of metabolizable methionine to dairy cows, and this is likely related to extensive ruminal destruction of methionine; however, cow body condition may be improved by ruminally available methionine provided by meSBM-Met.
Journal of Dairy Science 03/2013; · 2.56 Impact Factor
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ABSTRACT: The objective of these studies was to characterize some factors affecting lysine degradation by mixed ruminal bacteria and by ruminal Fusobacterium necrophorum. Mixed ruminal bacteria degraded lysine, and addition of pure cultures of F. necrophorum did not increase lysine degradation. Addition of acetic or propionic acid strikingly reduced NH(3) production from lysine by mixed ruminal bacteria at pH 6, but not at pH 7. Although typical ruminal environments with acidic pH and normal concentrations of volatile fatty acids might inhibit lysine degradation by F. necrophorum, ruminal fluid contained enough bacteria with a lysine-degrading capacity to ferment 50 mM lysine in vitro. Of 7 strains of ruminal F. necrophorum tested, all grew on both lactate and lysine as the primary energy source. Both subspecies of ruminal F. necrophorum (necrophorum and funduliforme) used lysine as a primary C and energy source. Lysine and glutamic acid were effectively fermented by F. necrophorum, but alanine and tryptophan were not, and histidine and methionine were fermented only to a minor extent. The end products of lactate fermentation by F. necrophorum were propionate and acetate, and those of lysine degradation were butyrate and acetate. Fermentation of glutamic acid by F. necrophorum yielded acetate and butyrate in a ratio near to 2:1. The minimum inhibitory concentration of tylosin for F. necrophorum was not dependent on whether bacteria were grown with lactate or lysine, but F. necrophorum was more susceptible to monensin when grown on lysine than on lactate. Although F. necrophorum is generally resistant to monensin, the ionophore may reduce lysine degradation by F. necrophorum in the rumen. The essential oil components limonene, at 20 or 100 μg/mL, and thymol, at 100 μg/mL, inhibited F. necrophorum growth, whereas eugenol, guaiacol, and vanillin had no effect. Our findings may lead to ways to minimize ruminal lysine degradation and thus increase its availability to the animal.
Journal of Dairy Science 11/2012; · 2.56 Impact Factor
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ABSTRACT: Urea kinetics were measured in 2 experiments, with treatments designed to change protein deposition by the animal. Our hypothesis was that increased protein deposition by cattle (Bos taurus) would reduce urea production and recycling to the gastrointestinal tract. Urea kinetics were measured by continuous intravenous infusion of (15)N(15)N-urea followed by measurement of enrichment in urinary urea at plateau. In Exp. 1, 6 steers (139 kg) were maintained in a model in which leucine was the most limiting AA. Treatments were arranged as a 2 × 3 factorial and were provided to steers in a 6 × 6 Latin square design. Leucine treatments included 0 or 4 g/d of abomasally supplemented L-leucine, and energy treatments included control, abomasal glucose infusion (382 g DM/d), or ruminal VFA infusion (150 g/d of acetic acid, 150 g/d of propionic acid, and 50 g/d of butyric acid). Leucine supplementation increased (P < 0.01) N retention, and energy supplementation tended to increase (P = 0.09) N retention without differences between glucose and VFA supplements (P = 0.86). Energy supplementation did not strikingly improve the efficiency of leucine utilization. Although both leucine and energy supplementation reduced urinary urea excretion (P ≤ 0.02), treatments did not affect urea production (P ≥ 0.34) or urea recycling to the gut (P ≥ 0.30). The magnitude of change in protein deposition may have been too small to significantly affect urea kinetics. In Exp. 2, 6 steers (168 kg) were maintained in a model wherein methionine was the most limiting AA. Steers were placed in 2 concurrent 3 × 3 Latin squares. Steers in one square were implanted with 24 mg of estradiol and 120 mg trenbolone acetate, and steers in the other square were not implanted. Treatments in each square were 0, 3, or 10 g/d of L-methionine. Implantation numerically improved N retention (P = 0.13) and reduced urea production rate (P = 0.03), urinary urea excretion (P < 0.01), and urea recycling to the gastrointestinal tract (P = 0.14). Effects of methionine were similar to implantation, but smaller in magnitude. When protein deposition by the body is increased markedly, ruminally available N in the diet may need to be increased to offset reductions in urea recycling.
Journal of Animal Science 07/2012; 90(10):3515-26. · 2.10 Impact Factor
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ABSTRACT: Effects of supplemental glucose and degradable intake protein on nutrient digestion and urea kinetics in steers (Bos taurus) given ad libitum access to prairie hay (4.7% CP) were quantified. Six ruminally and duodenally cannulated steers (initial BW 391 kg) were used in a 4 × 4 Latin square with 2 extra steers. Treatments were arranged as a 2 × 2 factorial and included 0 or 1.2 kg of glucose and 240 or 480 g of casein dosed ruminally once daily. Each period included 9 d for adaptation, 4 d for total fecal and urine collections, and 1 d for ruminal and duodenal sampling. Jugular infusion of (15)N(15)N-urea with measurement of enrichment in urine was used to measure urea kinetics. Glucose reduced forage intake by 18% (P < 0.01), but casein did not affect forage intake (P = 0.69). Glucose depressed (P < 0.01) total tract NDF digestion. Glucose supplementation decreased ruminal pH 2 h after dosing, but the effect was negligible by 6 h (treatment × time; P = 0.01). Providing additional casein increased the ruminal concentration of NH(3), but the increase was less when glucose was supplemented (casein × glucose; P < 0.01). Plasma urea-N was increased (P < 0.01) by additional casein but was reduced (P < 0.01) by glucose. Microbial N flow to the duodenum and retained N increased (P ≤ 0.01) as casein increased, but neither was affected by glucose supplementation. Urea-N entry rate increased (P = 0.03) 50% with increasing casein. Urinary urea-N excretion increased (P < 0.01) as casein increased. The proportion of urea production that was recycled to the gut decreased (P < 0.01) as casein increased. Glucose supplementation decreased (P < 0.01) urinary urea excretion but did not change (P ≥ 0.70) urea production or recycling. The amount of urea-N transferred to the gut and captured by ruminal microbes was less for steers receiving 480 g/d casein with no glucose than for the other 3 treatments (casein × glucose interaction, P = 0.05), which can be attributed to an excess of ruminally available N provided directly to the microbes from the supplement. Overall, the provision of supplemental glucose decreased forage intake and digestibility. Increasing supplemental casein from 240 to 480 g/d increased urea production but decreased the proportion of urea-N recycled to the gut.
Journal of Animal Science 07/2012; 90(10):3505-14. · 2.10 Impact Factor
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ABSTRACT: Effects of supplemental energy sources on nutrient digestion and urea kinetics at 2 levels of degradable intake protein were evaluated in cattle (Bos taurus). Six ruminally and duodenally cannulated steers (208 ± 17 kg) were used in a 6 × 6 Latin square with treatments arranged as a 3 × 2 factorial. Energy treatments included a control, 600 g glucose dosed ruminally once daily, and 480 g VFA infused ruminally over 8 h daily. Casein (120 or 240 g) was dosed ruminally once daily. Steers had ad libitum access to prairie hay (5.8% CP). Jugular infusion of (15)N(15)N-urea with measurement of enrichment in urine was used to measure urea kinetics. Infusing VFA decreased (P < 0.01) forage intake by 27%. Supplementing glucose decreased (P < 0.01) total tract NDF digestibility and tended to decrease ruminal NDF digestibility; depressions in response to glucose tended to be greater at the lower level of casein. Increasing casein decreased (P < 0.02) ruminal pH. Infusing VFA decreased pH only during infusions, whereas glucose decreased pH 2 h after dosing. Ruminal concentrations of NH(3), acetate, and propionate decreased and butyrate concentration increased when glucose was supplemented. Increasing casein supplementation increased (P < 0.01) ruminal concentrations of NH(3), acetate, and propionate. Supplemental energy decreased (P = 0.03) plasma urea-N concentration, but casein level did not affect it (P = 0.16). Microbial N flow was greater (P < 0.04) for 240 than for 120 g/d casein but was not affected by supplemental energy (P = 0.23). Urea-N entry rate and gut entry of urea-N were not affected (P ≥ 0.12) by supplemental energy or casein, but the proportion of urea production that was recycled to the gut was less (P = 0.01) when 240 g/d rather than 120 g/d casein was provided. Compared with VFA, glucose tended (P = 0.07) to increase the proportion of urea-N entry rate that was recycled to the gut. Supplementation with glucose led to more (P = 0.01) microbial uptake of recycled urea than did supplementation with VFA. Urea recycling did not differ greatly among treatments despite impacts on ruminal pH and NH(3) and on plasma urea-N that were expected to alter urea transport across ruminal epithelium. Lack of treatment effects on urea production indicate that the complete diets did not provide excessive amounts of N and that increases of intestinally available AA were used efficiently by cattle for protein deposition.
Journal of Animal Science 07/2012; 90(10):3492-504. · 2.10 Impact Factor
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ABSTRACT: Experiments were conducted to evaluate the availability to ruminants of lysine from hydroxymethyl lysine, a product potentially resistant to ruminal degradation yet able to release free lysine when subjected to the acidic environment of the abomasum. An in vitro ruminal fermentation assay that led to ammonia production from free lysine was used for initial assessments, but the hydroxymethyl lysine was inhibitory to lysine degradation at the concentrations tested in vitro; therefore, an in vivo assay with sheep, using plasma lysine concentrations as the response criterion, was utilized for assessment. Twelve mature sheep were fed graded levels of lysine from either a commercially available ruminally protected lysine product with known availability or from hydroxymethyl lysine. The protected lysine product provided 3 or 6 g/d of metabolizable lysine, whereas the hydroxymethyl lysine provided 3 or 6 g/d of total lysine. Plasma lysine concentrations increased linearly in response to both the ruminally protected lysine product and hydroxymethyl lysine. By slope ratio analysis, the bioavailability of lysine in hydroxymethyl lysine was estimated to be 94% of that for the commercially available product. We concluded that hydroxymethyl lysine may be used as an effective means of supplementing lysine to ruminants.
Journal of Animal Science 06/2012; · 2.10 Impact Factor
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ABSTRACT: Responses to pharmacological doses of niacin, an agonist for GPR109A (niacin receptor), were different in cattle than in humans and rodents. Thus, the tissue distribution of GPR109A was investigated in cattle. Samples of tail head fat, back fat, perirenal fat, longissimus muscle, and liver were analyzed for abundance of GPR109A mRNA by quantitative real-time reverse transcription-PCR and for abundance of GPR109A protein by Western blotting. Niacin receptor transcript and protein were detected in all tissues analyzed. The mRNA for GPR109A was more abundant in liver than in the other tissues sampled (GPR109A:RPS9 mRNA abundance = 0.56 in liver compared with 0.06 in longissimus muscle, 0.15 in kidney fat, 0.11 in back fat, 0.23 in tail head fat; standard error of the mean = 0.028). Additionally, mRNA for GPR109A was found (GPR109A:RPS9 mRNA abundance ≥ 0.004) in each of the 5 regions of bovine brain that were analyzed: cerebral cortex, cerebellum, thalamus, hypothalamus, and brain stem. Evaluation of liver tissue by immunofluorescence suggested that GPR109A was expressed in parenchymal cells and not localized exclusively to immune-system cells. Finally, analysis of the putative bovine GPR109A sequence verified that AA residues required for binding niacin in human GPR109A are conserved, suggesting that the bovine sequence identified encodes a functional niacin receptor. The identification of GPR109A in bovine liver, muscle, and brain is a novel finding.
Journal of Dairy Science 10/2011; 94(10):4962-7. · 2.56 Impact Factor
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ABSTRACT: Nicotinic acid (niacin) can suppress lipolysis, but responses to dietary niacin have been inconsistent in cattle. Our aim was to determine if 24 g/d of encapsulated niacin (EN; providing 9.6g/d of bioavailable nicotinic acid) alters lipid metabolism and productivity of transition cows. Beginning 21 d before expected calving, primiparous (n = 9) and multiparous (n = 13) cows (body condition score of 3.63 ± 0.08) were sequentially assigned within parity to EN (12 g provided with ration twice daily) or control through 21 d postpartum. Liver biopsies were collected on d -21, -4, 1, 7, and 21 relative to parturition. Blood samples were collected on d -21, -14, -7, -4, 1, 4, 7, 14, and 21 relative to parturition. On d 7 postpartum, a caffeine clearance test was performed to assess liver function, and on d 21 to 23 postpartum, blood samples were collected every 8h to monitor posttreatment nonesterified fatty acid (NEFA) responses. Data were analyzed using mixed models with repeated measures over time. A treatment × time × parity effect was observed on prepartum dry matter intake (DMI), which was caused by a 4 kg/d decrease in DMI of EN-treated multiparous cows compared with control multiparous cows during the final 4 d prepartum. A significant increase in plasma nicotinamide concentration occurred in EN-treated cows on d -7 and 21 relative to parturition. Prepartum glucose concentration decreased in treated animals, with no difference in plasma insulin concentration. Treatment × time × parity effects were detected for NEFA and β-hydroxybutyrate concentrations during the postpartum period. Plasma NEFA peaked at 1,467 ± 160 μM for control animals compared with 835 ± 154 μM for EN-treated animals. After treatments ended on d 21, no evidence was found for a plasma NEFA rebound in either parity group. A treatment × parity × time interaction was detected for liver triglyceride content, indicating a tendency for less liver triglyceride in EN-treated primiparous cows, but caffeine clearance rates were not affected by treatment. No treatment effects were observed for body condition score, body weight, energy balance, or milk or milk component production. A high dose of EN can decrease postpartum plasma NEFA concentration, but may also decrease prepartum DMI.
Journal of Dairy Science 10/2011; 94(10):5090-104. · 2.56 Impact Factor
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ABSTRACT: Feeding high-concentrate diets has the potential to cause milk fat depression, but several studies have suggested that dietary sugar can increase milk fat yield. Two experiments were conducted to evaluate the ability of dietary molasses to prevent milk fat depression in the presence of a 65% concentrate diet. In trial 1, molasses replaced corn grain at 0, 2.5, or 5% of diet dry matter in diets fed to 12 second-lactation Holstein cows (134±37 d in milk) in a 3×3 Latin square design. Trial 1 demonstrated that replacing up to 5% of dietary dry matter from corn with molasses had positive effects on de novo fatty acid synthesis, increasing the yield of short- and medium-chain fatty acids during diet-induced milk fat depression. Increasing inclusion rate of molasses increased milk fat concentration, but decreased milk yield and milk protein yield. Trial 2 used 7 ruminally cannulated, multiparous, late-lactation Holstein cows (220±18 d in milk) to evaluate effects of dietary molasses on ruminal parameters and milk composition, and also to assess whether increased metabolizable protein supply would alter these responses. Cows were randomly assigned to a dietary treatment sequence in a crossover split plot design with 0 and 5% molasses diets. Dietary treatments were fed for 28 d, with 16 d for diet adaptation, and the final 12 d for 2 abomasal infusion periods in a crossover arrangement. Abomasal infusions of water or AA (5 g of l-Met/d+15 g of l-Lys-HCl/d+5 g of l-His-HCl-H(2)O/d) were administered 3 times daily for 5 d, with 2 d between infusion periods. Administration of AA had no effect on concentration or yield of any milk components. Addition of molasses increased milk fat concentration (2.71 vs. 2.94±0.21%), but had no effect on yields of milk fat or protein. Dietary molasses decreased total volatile fatty acid concentration (141 vs. 133±4.6mM), decreased the molar proportion of propionate, and increased the molar proportion of butyrate in ruminal fluid. Molasses also increased ruminal pH (5.73 vs. 5.87±0.06), decreased the yield of trans-10 C18:1, and increased the yield of trans-11 C18:1 in milk fat. These data provide evidence that molasses may promote mammary de novo fatty acid synthesis in cows fed high-energy rations by moderating ruminal pH and altering ruminal fatty acid biohydrogenation pathways.
Journal of Dairy Science 08/2011; 94(8):3995-4004. · 2.56 Impact Factor
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ABSTRACT: An experiment was conducted to evaluate the effects of increasing dietary inclusion rates of wet corn gluten feed (WCGF; Sweet Bran; Cargill Inc., Blair, NE) on milk production and rumen parameters. Four primiparous and 4 multiparous ruminally cannulated Holstein cows averaging 90±13 d in milk (mean ± SD) were randomly assigned to 1 of 4 sequences in a replicated 4 × 4 Latin square experiment with 28-d periods. Treatments were diets containing 0, 11, 23, and 34% WCGF on a dry matter basis; alfalfa hay, corn silage, corn grain, soybean meal, expeller soybean meal, and mineral supplements were varied to maintain similar nutrient concentrations across diets. Performance and measures of ruminal fermentation were monitored. Linear and quadratic effects of increasing WCGF inclusion rate were assessed using mixed-model analysis. Increasing dietary WCGF linearly increased dry matter intake (26.7, 25.9, 29.3, and 29.7 kg/d for 0, 11, 23, and 34% WCGF, respectively) and milk production (36.8, 37.0, 40.1, and 38.9 kg/d). Concentrations of milk components did not differ among treatments; however, protein and lactose yields increased linearly and fat yield tended to increase linearly when more WCGF was fed. This led to greater production of energy-corrected milk (38.2, 38.8, 41.7, and 40.4 kg/d) and solids-corrected milk (35.2, 35.7, 38.5, and 37.2 kg/d), but efficiency of production linearly decreased. Increased WCGF in the diet tended to linearly decrease ruminal pH (6.18, 6.12, 6.14, and 5.91), possibly because mean particle size was below typical recommendations for all diets, and diets with greater proportions of WCGF had a smaller mean particle size. Ruminal acetate concentration decreased linearly and propionate increased linearly as WCGF inclusion rate increased. Treatments had a quadratic effect on ammonia concentration, with greater concentrations for the 0 and 34% WCGF diets. In situ digestibility of soybean hulls showed a significant diet-by-time interaction, and increasing dietary levels of WCGF linearly decreased in situ neutral detergent fiber disappearance at 24h. Change in body condition score increased linearly with increasing WCGF inclusion rate. Results indicate that adding WCGF to dairy rations can increase energy-corrected milk yield, and this increase appears to be driven, at least in part, by an increase in dry matter intake.
Journal of Dairy Science 11/2010; 93(11):5329-37. · 2.56 Impact Factor
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ABSTRACT: We used four pregnant Holstein cows to delineate ruminal adaptations as cows transitioned from one lactation to the next. Cows were fed typical diets through far-off and close-up dry periods and lactation. We measured ruminal characteristics on day 72 (late lactation), 51 (far-off dry), 23 and 9 (close-up dry) prepartum and on days 6, 20, 34, 48, 62, 76 and 90 postpartum (early lactation). Measurements included: ruminal fill (weight of actual contents), ruminal capacity (volume of rumen when fully filled), digestibilities and ruminal passage rates. Ruminal capacity tended to increase linearly during early lactation but was stable during dry and transition periods. Both total and liquid fill decreased linearly during the dry period, increased across parturition, and increased linearly through early lactation. Dry matter fill decreased as cows were fed the close-up diet at day 23 prepartum then increased near parturition and continued to increase across early lactation. Solid passage rate was greatest when cows were fed the close-up diet, and decreased throughout the transition period. In lactation, solid passage rate responded quadratically with peak at day 48 followed by decreases through day 90 postpartum. Liquid passage increased linearly across the transition period. Total tract organic matter digestibilities increased linearly over the dry period with significant increases prior to or immediately after parturition, then they remained relatively stable over early lactation until they increased at day 90. Fibre digestibilities demonstrated quadratic responses over early lactation, being higher on day 6 and day 90 than at other times. Starch digestibilities decreased linearly across both the dry and transition periods with decreases in lactation until day 62 followed by increases until day 90. High producing lactating dairy cows go through a multitude of ruminal adaptations, in terms of digestion, passage, capacity and fill, as they transition from one lactation to the next.
J Anim Physiol a Anim Nutr 11/2010; 95(5):571-82. · 0.86 Impact Factor
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ABSTRACT: We studied effects of zilpaterol-HCl on steers consuming corn-based diets with nitrogen (N) supplementation provided by dried distillers grains with solubles (DDGS) or urea. Two sets of six steers (approximately 350 kg) were used in two replicates of similarly designed trials. Within each replicate, three steers were fed 60 mg/day of zilpaterol-HCl throughout the trial and three steers received no zilpaterol-HCl. Within zilpaterol treatment, three corn-based dietary N treatments were offered in Latin square designs: control (9.6% crude protein), urea (UREA; 12.4% crude protein) or DDGS (13.7% crude protein). Total feed intake was unexpectedly greater (p < 0.01) with zilpaterol feeding but was not affected by dietary N (p = 0.76). Nitrogen intake was greater (p < 0.01) when zilpaterol was fed and was greater (p < 0.05) for DDGS and UREA than for control. Despite greater N intake, zilpaterol did not affect urea entry rate (p = 0.80) or urea-N recycled to the gastrointestinal tract (GER; p = 0.94). As a percentage of N intake, urea entry rate (p = 0.19) tended to be less when zilpaterol was fed (91 vs. 123% of N intake), and GER was numerically (p = 0.34) less (72 vs. 92% of N intake). Microbial N flow was greater (p = 0.02) for zilpaterol than for control but did not differ (p = 0.78) among dietary N treatments. As a percentage of N intake, microbial N flow was unaffected by zilpaterol (p = 0.97), but was greater (p < 0.05) for control than DDGS or UREA. The lack of change in urea entry and GER in response to zilpaterol, despite greater N intake, as well as lower urea entry and GER when expressed as proportions of N intake provide some evidence that the amount of N available for urea production and recycling was reduced by zilpaterol.
J Anim Physiol a Anim Nutr 10/2010; 95(4):409-16. · 0.86 Impact Factor
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ABSTRACT: We studied the effects of supplementing N as distillers dried grains with solubles (DDGS) or urea to steers consuming corn-based diets. Six ruminally and duodenally cannulated steers (244 kg) were used in 2 concurrent 3 x 3 Latin squares and fed 1 of 3 corn-based diets: control (10.2% CP), urea (13.3% CP), or DDGS (14.9% CP). Periods were 14 d, with 9 d for adaptation and 5 d for collection of urine and feces. Urinary (15)N(15)N-urea enrichments, resulting from venous infusions of (15)N(15)N-urea, were used to measure urea kinetics. Dry matter intake (6.0 kg/d) was not affected by treatment, but N intake differed (99, 151, and 123 g/d for the control, DDGS, and urea treatments, respectively). Urea-N synthesis tended to be greater (P = 0.09) for DDGS (118 g/d) than for the control treatment (52 g/d), with the urea treatment (86 g/d) being intermediate. Urea-N excreted in the urine was greater (P < 0.03) for the DDGS (35 g/d) and urea treatments (29 g/d) than for the control treatment (13 g/d). Gastrointestinal entry of urea-N was not statistically different among treatments (P = 0.25), but was numerically greatest for DDGS (83 g/d), intermediate for urea (57 g/d), and least for the control (39 g/d). The amount of urea-N returned to the ornithine cycle tended to be greater (P = 0.09) for the DDGS treatment (47 g/d) than for the urea (27 g/d) or control treatment (16 g/d). The fraction of recycled urea-N that was apparently used for anabolism tended (P = 0.14) to be greater for the control treatment (0.56) than for the DDGS treatment (0.31), with the urea treatment (0.45) being intermediate, but no differences were observed among treatments in the amount of urea-N used for anabolism (P = 0.66). Urea kinetics in cattle fed grain-based diets were largely related to the amount of N consumed. The percentage of urea production that was captured by ruminal bacteria was greater (P < 0.03) for the control treatment (42%) than for the DDGS (25%) or urea treatment (22%), but the percentage of duodenal microbial N flow that was derived from recycled urea-N tended (P = 0.10) to be greater for the DDGS treatment (35%) than for the urea (22%) or control treatment (17%). Thus, ruminal microbes were more dependent on N recycling when the protein supplement was largely resistant to ruminal degradation.
Journal of Animal Science 04/2010; 88(8):2729-40. · 2.10 Impact Factor
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ABSTRACT: We evaluated growth-related responses to ractopamine in steers and heifers. Sixteen Angus steers (512 kg) and 16 Angus heifers (473 kg) housed in individual pens were used in a complete block design. At 90 to 97 d before the experiment, steers were implanted with 120 mg of trenbolone acetate and 24 mg of estradiol-17beta (Component TE-S) and heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17beta (Component TE-H). Treatments were arranged as a 2 x 2 factorial and included sex (steer vs. heifer) and ractopamine-HCl (0 or 200 mg/d). Cattle were fed a diet based on steam-flaked corn once daily. Blood and LM and biceps femoris (BF) biopsy samples were collected on d 0 (before ractopamine feeding) and after 14 and 28 d of ractopamine feeding. Serum insulin concentrations were not affected by ractopamine or sex. Serum IGF-I concentrations were greater in steers than heifers (P < 0.001), and steers demonstrated greater IGF-I mRNA expression in BF than heifers (P = 0.05). Ractopamine decreased serum IGF-I concentrations in heifers on d 14, but increased serum IGF-I concentrations in steers on d 28 (sex x ractopamine x day interaction; P = 0.03). Ractopamine did not affect (P >or= 0.19) mRNA expression of IGF-I, IGFBP-3, or calpastatin in BF or LM. However, ractopamine led to increases in LM expression of IGFBP-5 in heifers, but to decreases in expression in steers (ractopamine x sex interaction; P = 0.04). Ractopamine decreased myosin heavy chain IIA mRNA expression in BF (P = 0.04) but not in LM (P = 0.99). Ractopamine decreased beta(2)-receptor mRNA expression in LM of steers on d 14, but not on d 28; in contrast, expression of beta(2)-receptor mRNA in LM of heifers was not affected by ractopamine (sex x ractopamine x day interaction; P = 0.03). Although there were a few criteria for which ractopamine led to differences in response between steers and heifers, there were no striking disparities to suggest that the effectiveness of ractopamine would markedly differ between sexes.
Journal of Animal Science 04/2010; 88(4):1349-57. · 2.10 Impact Factor
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ABSTRACT: Twenty-four multiparous Holstein cows (124 +/- 39 d in milk; 682 +/- 72 kg of body weight) were used in 6 simultaneous 4 x 4 Latin squares to evaluate full-fat corn germ as a fat source for lactating dairy cows. Experimental diets were a control (containing 28% ground corn, 23% alfalfa hay, 19% wet corn gluten feed, and 10% corn silage, dry matter basis), and 3 diets with either whole cottonseed (WCS), tallow (TAL), or full-fat corn germ (FFCG) added to provide 1.6% supplemental fat. Cows were fed twice daily for ad libitum intake. Dry matter intake, milk yield, and energy-corrected milk did not differ among diets. Efficiency of milk production (energy-corrected milk/dry matter intake) was greater for cows fed WCS than for cows fed the control, TAL, or FFCG. Milk fat percentage from cows fed FFCG was less than that of cows fed WCS or the control, but was similar to that of cows fed TAL. Milk protein percentage was less for cows fed FFCG than for those fed the control. Total saturated fatty acids were less in milk from cows fed fat sources, and cows fed WCS and TAL had greater saturated fatty acids in milk than did cows fed FFCG. Unsaturated fatty acids were greater in milk from cows fed FFCG than in milk from cows fed the control, WCS, or TAL. The cis-9, trans-11 conjugated linoleic acid content was greater in milk from cows fed WCS, TAL, and FFCG than from cows fed the control, and it was greater in milk from cows fed FFCG than in milk from cows fed WCS or TAL. These results indicate that FFCG can be used effectively as a fat source in diets for lactating dairy cattle.
Journal of Dairy Science 08/2009; 92(7):3386-91. · 2.56 Impact Factor
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ABSTRACT: We measured the incorporation of recycled urea-nitrogen (N) by ruminal microbes, using five ruminally and duodenally fistulated steers (237 kg) fed low-quality grass hay (47 g crude protein/kg dry matter (DM)). Three received 1 kg/day of soybean meal (SBM) and two received no supplemental protein (control). The experiment was 15 days long. Background enrichments of 15N were measured on day 9 and continuous jugular infusion of 0.12 g/day [15N15N]urea began on day 10. Daily samples of urine, feces, ruminal bacteria and duodenal digesta from days 10 through 14 were used to determine plateaus in 15N enrichment. Duodenal and bacterial samples collected on day 15 were used to measure duodenal N flows. Bacterial N flow was calculated as duodenal N flow multiplied by duodenal 15N enrichment divided by bacterial 15N enrichment. Bacterial N from recycled urea-N was calculated as bacterial N flow multiplied by bacterial 15N enrichment divided by urinary urea 15N enrichment. Urinary enrichment of [15N15N]urea plateaued within 24 h, whereas 14N15N urea plateaued within 48 h of [15N15N]urea infusion. Bacteria reached a plateau in 15N enrichment within 24 h and duodenal samples within 48 h. Urea production was 17.6 g of urea-N/day for control and 78.0 g/day for SBM. Gut entry was 0.99 g of urea-N/g of urea-N produced for control and 0.87 g/g for SBM. Incorporation of recycled N into microbial N was 9.0 g of N/day for control and 23.0 g/day for SBM. Recycled urea-N accounted for 0.33 g of N/g of microbial N at the duodenum for control and 0.27 g/g for SBM. Our methods allowed measurement of incorporation of recycled urea-N into ruminal microbial N.
animal 03/2009; 3(3):372-9. · 1.74 Impact Factor
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ABSTRACT: We evaluated the effect of increasing amounts of rumen-degradable intake protein (DIP) on urea kinetics in steers consuming prairie hay. Ruminally and duodenally fistulated steers (278 kg of BW) were used in a 4 x 4 Latin square and provided ad libitum access to low-quality prairie hay (4.9% CP). The DIP was provided as casein dosed ruminally once daily in amounts of 0, 59, 118, and 177 mg of N/kg of BW daily. Periods were 13 d long, with 7 d for adaptation and 6 d for collection. Steers were in metabolism crates for total collection of urine and feces. Jugular infusion of (15)N(15)N-urea, followed by determination of urinary enrichment of (15)N(15)N-urea and (14)N(15)N-urea was used to determine urea kinetics. Forage and N intake increased (linear, P < 0.001) with increasing DIP. Retention of N was negative (-2.7 g/d) for steers receiving no DIP and increased linearly (P < 0.001; 11.7, 23.0, and 35.2 g/d for 59, 118, and 177 mg of N/kg of BW daily) with DIP. Urea synthesis was 19.9, 24.8, 42.9, and 50.9 g of urea-N/d for 0, 59, 118, and 177 mg of N/kg of BW daily (linear, P = 0.004). Entry of urea into the gut was 98.9, 98.8, 98.6, and 95.9% of production for 0, 59, 118, and 177 mg of N/kg of BW daily, respectively (quadratic, P = 0.003). The amount of urea-N entering the gastrointestinal tract was greatest for 177 mg of N/kg of BW daily (48.6 g of urea-N/d) and decreased (linear, P = 0.005) to 42.4, 24.5, and 19.8 g of urea-N/d for 118, 59, and 0 mg of N/kg of BW daily. Microbial incorporation of recycled urea-N increased linearly (P = 0.02) from 12.3 g of N/d for 0 mg of N/kg of BW daily to 28.9 g of N/d for 177 mg of N/kg of BW daily. Provision of DIP produced the desired and previously observed increase in forage intake while also increasing N retention. The large percentage of urea synthesis that was recycled to the gut (95.9% even when steers received the greatest amount of DIP) points to the remarkable ability of cattle to conserve N when fed a low-protein diet.
Journal of Animal Science 07/2008; 86(11):3079-88. · 2.10 Impact Factor
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ABSTRACT: We evaluated the effect of frequency and amount of rumen-degradable intake protein (DIP) on urea kinetics in steers consuming prairie hay. Five ruminally and duodenally fistulated steers (366 kg of BW) were used in a 5 x 5 Latin square and provided ad libitum access to low-quality prairie hay (4.7% CP). Casein was provided daily in amounts of 61 and 183 mg of N/kg of BW (61/d and 183/d) and every third day in amounts of 61, 183, and 549 mg of N/kg of BW per supplementation event (61/3d, 183/3d, and 549/3d). Periods were 18-d long with 9 d for adaptation and 9 d for collection. Steers were in metabolism crates for total collection of urine and feces. Jugular infusion of (15)N(15)N-urea followed by determination of urinary enrichment of (15)N(15)N-urea and (14)N(15)N-urea was used to determine urea kinetics. Treatment means were separated to evaluate the effects of increasing DIP supplementation and the effects of frequency at the low (61/d vs. 183/3d) and at the high (183/d vs. 549/3d) amounts of DIP provision. Forage OM and total digestible OM intakes were linearly (P < or = 0.05) increased by increasing DIP provision but were not affected by frequency of supplementation at either the low or high amounts. Production and gut entry of urea linearly (P < or = 0.006) increased with DIP provision and tended to be greater (P < or = 0.07) for 549/3d than 183/d but were not different between 61/d and 183/3d. Microbial N flow to the duodenum was linearly (P < 0.001) increased by increasing DIP provision. Additionally, 183/d resulted in greater (P = 0.05) microbial N flow than 549/3d. Incorporation of recycled urea-N into microbial N linearly (P = 0.04) increased with increasing DIP. Microbial incorporation of recycled urea-N was greater for 549/3d than 183/d, with 42 and 23% of microbial N coming from recycled urea-N, respectively. In contrast, there was no difference due to frequency in the incorporation of recycled urea-N by ruminal microbes at the low level of supplementation (i.e., 61/d vs. 183/3d). This study demonstrates that urea recycling plays a substantial role in the N supply to the rumen and to the animal, particularly in steers supplemented infrequently with high levels of protein.
Journal of Animal Science 07/2008; 86(11):3089-99. · 2.10 Impact Factor
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ABSTRACT: Two experiments were conducted to describe the DE content of tallgrass prairie hay (TPH). In trial 1, steers (n = 13; 277 +/- 15 kg of BW) were used in a 13 x 4 Latin square experiment to measure the DE of 13 samples of TPH fed at 1.5% of BW daily (average feeding level = 0.7 x the maintenance energy requirement). Hays were harvested from a variety of locations in east-central Kansas and represented an array of harvest dates and storage methods. In trial 2, steers (n = 16; 261 + 17 kg of BW) were used in a randomized complete block experiment to assess the effects of TPH intake level on DE. Hay was fed at 1.3, 1.7, 2.1, or 2.5% of BW daily, which corresponded to 0.9, 1.4, 1.6, and 1.9 x the maintenance energy requirement. Steers in both trials were fed soybean meal in amounts calculated to provide ruminally degradable protein (RDP) equal to 11% of digestible OM intake. Hay samples were analyzed for ash, N, NDF, ADF, ADIN, NDIN, acid detergent-insoluble ash, lignin, monosaccharides, and alkali-labile phenolic acids. Chemical components related to DE (P < 0.2) were subjected to iterative regression analysis to predict the DE concentration of the diet. Iterations were ceased when the error mean square of the regression was optimized. At 0.7 x maintenance, the dietary DE concentration (Mcal/kg) was described by: DE = 0.13(CP) - 0.16(ADL) + 2.11 (R(2) = 0.73; S(y*x) = 0.13). Forage OM digestion decreased linearly (P < 0.01) as forage intake increased. Apparent dietary DE concentration decreased by 7.4% when intake was increased from 1 to 2 x maintenance. When RDP was adequate, chemical composition values were useful indicators of forage DE content in our study. Moreover, increased forage intake depressed GE digestion by steers, but ultimately increased total DE intake. Energy digestion varied with forage intake in a predictable manner between 1 and 2 x the maintenance feeding level.
Journal of Animal Science 06/2008; 86(6):1372-81. · 2.10 Impact Factor
