Two experiments were conducted to compare ruminal, physiological, and performance responses of forage-fed cattle consuming grain-based supplements without (NF) or with the inclusion (10%; DM basis) of a rumen-protected PUFA (PF) or SFA source (SF). Supplements were offered and consumed at 0.6% of BW/animal daily (DM basis). In Exp. 1, DMI and ruminal in situ forage degradability were evaluated in 3 Angus × Hereford cows fitted with ruminal cannulas and allocated to a 3 × 3 Latin square design. Within each experimental period, hay was offered in amounts to ensure ad libitum access from d 1 to 13, DMI was recorded from d 8 to 13, and cows were limited to receive 90% of their average hay DMI (d 1 to 13) from d 14 to 21. On d 16, polyester bags containing 4 g of ground hay (DM basis) were incubated within the rumen of each cow for 0, 4, 8, 12, 24, 36, 48, 72, and 96 h. Hay and total DMI were reduced (P < 0.05) in cows receiving PF compared with cows receiving SF and NF. No treatment effects were detected (P > 0.48) for ruminal disappearance rate and effective ruminal degradability of hay DM and NDF. In Exp. 2, preconditioning DMI, ADG, carcass traits, and plasma concentrations of cortisol, fatty acids, acute-phase proteins, and proinflammatory cytokines were assessed in 72 Angus × Hereford steers receiving supplement treatments during a 28-d preconditioning period. All steers were transported to a commercial growing lot after preconditioning (d 1) and were later moved to an adjacent commercial finishing yard (d 144), where they remained until slaughter. No treatment effects were detected (P ≥ 0.52) for preconditioning ADG and G:F, but DMI tended (P = 0.09) to be reduced in steers receiving PF compared with those receiving NF and SF. Plasma PUFA concentrations were greater in steers receiving PF compared with those receiving NF and SF (P = 0.01). After transportation, concentration of tumor necrosis factor-α increased for steers receiving NF, did not change for steers receiving SF, but decreased for steers receiving PF (treatment × day interaction, P < 0.01). Steers fed PF had greater (P = 0.02) ADG compared with those fed NF during the growing phase. Carcass yield grade and marbling were greater (P < 0.05) for steers fed PF compared with those fed NF. In conclusion, PUFA supplementation did not affect ruminal forage degradability but did impair DMI in beef cows. Further, PUFA supplementation to steers during preconditioning reduced plasma concentrations of tumor necrosis factor-α after transportation, and benefited growing lot ADG and carcass marbling.
Production expenses associated with harvesting and feeding hay account for a large proportion of annual production costs for ruminant livestock systems. A 2‐yr experiment compared windrow grazing, as a potential method to reduce winter cost, with feeding baled hay to beef cows. Two irrigated meadows (16.2 and 10.1 ha) consisting of a mixture of ‘Garrison’ creeping foxtail ( Alopecurus arundinaceus Poir.) and other introduced and native forage species were either baled and removed or windrowed and left in place 26 Aug. 1999 and 27 July 2000. Forage samples were collected from windrows and baled hay at harvest and then monthly until January. Beginning in November 1999 and 2000, 64 and 54 pregnant cows, respectively, were assigned to windrowed or baled forage for 42 d. Forage acid detergent fiber (ADF) was greater ( P < 0.01) in 1999 and neutral detergent fiber (NDF) tended to be greater ( P = 0.09) in 2000 for windrowed than baled forage. Crude protein (CP) tended to be greater in windrowed (100 g kg −1 ) than baled (93 g kg −1 ) forage in 2000 ( P = 0.08), but was similar (windrows, 89 g kg −1 ; bales, 90 g kg −1 ) in 1999 ( P = 0.11). In 1999, cows offered windrowed forage had greater average daily gain (ADG = 1 kg d −1 ; P = 0.04) and body condition score (BCS = 5.5; P = 0.02) than cows fed baled forage [ADG = 0.66 kg −d ; BCS = 5.3]. In 2000, cattle offered windrows (−0.42 kg −d ) had lower ( P = 0.03) ADG compared with cattle fed baled forage (0.1 kg −d ). Windrow grazing was less economical under the study and management conditions than bale feeding due to high cost of watering livestock and forage wastage.
Multiparous Angus × Gelbvieh (n = 155) beef cows (initial BW = 604.5 ± 4.2 kg) were used to determine the effect of prepartum fat supplementation on cow BW, BCS, reproduction, and calf birth weight, health, immunity, plasma fatty acid (FA) concentrations, and performance. Starting approximately 80 d prepartum, cows were adapted to a limit-fed (60% rolled corn:40% millet hay) diet. At 60 ± 1.3 d prior to calving, cows were allotted to one of two isocaloric, isonitrogenous diets containing either 2.69% (CON; n = 79) or 4.63% (FSUP; n = 76) dietary fat. Following parturition, all cows received CON diet plus adlibitum grass hay until breeding. Cows were synchronized for estrus on d 61 ± 1.32 postpartum and calves were weaned at 101 ± 1.1 d of age received a s.q. antigen injection at 116 ± 1.08 d of age. Prepartum diet did not affect (P ≥ 0.35) cow BW or BCS change. Calf birth weight, vigor score, and rectal temperature were not influenced (P ≥ 0.52) by cow diet; however, FSUP calves had higher plasma IgG levels (P = 0.05; 15.44 vs 11.00 ± 1.63 mg/ml) at 14 ± 0.5 h after birth. Calves from FSUP dams had higher plasma FA concentrations of 18:1 trans-11 (P < 0.01; 0.89 vs 0.42 ± 0.07 %), and CLA (P < 0.01; 0.22 vs 0.13 ± 0.01 %), than CON calves. Cows detected in estrus (P = 0.56) and first service conception rates (P = 0.87) were not different due to diet. Calf weaning weight (P = 0.26) and BW gain (P ≥ 0.39) were not affected by dams prepartum diet. Calf response to antigen injection was not different (P = 0.90) between treatments. Although cow and calf performance was not influenced by prepartum fat supplementation, calf IgG levels and plasma FA associated with immune function were increased in calves from FSUP dams. Thus, prepartum supplemental fat may have positive effects on calf immune status and overall health.
The mammalian target of rapamycin (mTOR) signaling controls nutrient-stimulated protein synthesis in skeletal muscle, whereas ubiquitin-proteasome systems control the degradation of myofibrillar proteins. The objective of this study was to elucidate the effect of nutrient restriction on the mTOR signaling and ubiquitin-proteasome system in the skeletal muscle of cows and their fetuses. Beginning 30 d after conception, 20 cows were fed either a control diet that provided 100% nutrient requirements or a nutrient-restricted diet at 68.1% of NEm and 86.7% of metabolizable protein requirement. Cows were slaughtered on 125 d of gestation, and the LM of both cows and fetuses was sampled for the measurement of mTOR, ribosomal protein S6, adenosine 5′-monophosphate-activated protein kinase (AMPK), and protein ubiquitylation. When comparing the muscle samples from nutrient-restricted and control cows and their fetuses, no difference was observed for the content of mTOR and ribosomal protein S6, but the phosphorylation of mTOR at Ser2448 and ribosomal protein S6 at Ser235/336 were greater (P < 0.05) in control muscle than in muscle from nutrient-restricted animals. Because the phosphorylation of mTOR and ribosomal protein S6 upregulates translation, these results showed that nutrient restriction inhibits protein synthesis in muscle. The activity of AMPK in the muscle of nutrient-restricted cows was significantly lower (P = 0.05) than that of control cows. The protein ubiquitylation, however, was greater (P < 0.05) in the muscle from nutrient-restricted cows, showing accelerated protein degradation. No difference in the protein ubiquitylation was detected for fetal muscle. Data suggested that the decreased protein synthesis and promoted protein degradation resulted in muscle atrophy of pregnant cows, but not in fetal muscle. Results of this study show that in response to nutrient restriction, protein degradation was differentially regulated between cow and fetal muscle. The atrophy of cow muscle during nutrient deficiency may involve the enhanced degradation of muscle proteins.
Preparation of fatty acid methyl esters from forages comparing methanolic boron‐trifluoride (BF 3 ) to methanolic hydrochloric acid (HCl) as a catalyst in single‐step direct transesterification has not been reported. Our objective was to compare 1.09 M methanolic HCl to 1.03 M (7%) methanolic BF 3 as catalysts for direct transesterification of fatty acids in freeze‐dried forage samples. Thin‐layer chromatographic analysis revealed complete conversion of total lipid extracts to fatty acid methyl esters using both catalysts. Additionally, gas–liquid chromatography analysis confirmed similar ( P = 0.95) total fatty acid concentrations for both catalysts. Regression analysis indicated that similar values for total concentration would be obtained ( P < 0.0001; r 2 = 0.96; slope = 0.98 ± 0.03) between the two catalysts. Concentrations of most individual fatty acids were similar ( P = 0.17–0.99) for both catalysts. Summed weight percentages of identified fatty acids, as well as sum of unidentified peaks, were not affected ( P = 0.27) by catalyst (91.8 and 8.7% vs. 90.8 and 9.2% for HCl and BF 3 , respectively). We conclude that 1.09 M methanolic HCl is an appropriate substitute for 1.03 M methanolic BF 3 for preparation of fatty acid methyl esters from freeze‐dried forage samples. This result is of interest because HCL is both less costly and less caustic than BF 3
The objectives were to evaluate effects of maternal nutrient restriction and stage of gestation on maternal and fetal visceral organ mass and indices of jejunal growth and vascularity in beef cows. Thirty multiparous beef cows (BW = 571 +/- 63 kg; BCS = 5.4 +/- 0.7) carrying female fetuses (d 30 of gestation) were allocated to receive a diet of native grass hay (CON; 12.1% CP, 70.7% IVDMD, DM basis) to meet NRC recommendations for BW gain during early gestation or a nutrient-restricted diet of millet straw (NR; 9.9% CP, 54.5% IVDMD, DM basis) to provide 68.1% of NE(m) and 86.7% of MP estimated requirements. On d 125 of gestation, 10 CON and 10 NR cows were killed and necropsied. Five remaining CON cows received the CON diet, and 5 NR cows were realimented with a concentrate supplement (13.2% CP, 77.6% IVDMD, DM basis) and the CON hay to achieve a BCS similar to CON cows by d 220 of gestation. Remaining cows were necropsied on d 245 of gestation. Cow BW and eviscerated BW (EBW) were less (P < 0.01) for NR than CON at d 125 but did not differ (P > 0.63) at d 245. Cows fed the CON diet had greater (P < 0.09) total gastrointestinal (GI) tract, omasal, and pancreatic weights. Stomach complex, ruminal, and liver weights were greater for CON than NR cows (P < 0.09) on d 125. Total GI, stomach complex, and pancreatic weights increased (P < 0.001) with day of gestation. Restricted cows had decreased (P = 0.09) duodenal RNA:DNA compared with CON. Duodenal DNA was less (P = 0.01) and jejunal RNA:DNA (P = 0.09) was greater for cows at d 125 vs. 245. Cow jejunal capillary area density increased with day of gestation (P = 0.02). Fetal BW and EBW were unaffected by dietary treatment (P > or = 0.32). Total GI tract and all components increased in mass with day of gestation (P < 0.001). Fetuses from NR dams had greater (P = 0.003) reticular mass at d 245 than CON fetuses. Fetuses from NR cows had greater (P = 0.02) percent jejunal proliferation at d 125 and greater (P = 0.03) total intestinal vascularity (mL) at d 245. Fetal jejunal DNA decreased (P = 0.09), RNA:DNA increased (P = 0.05), and total jejunal proliferating cells increased (P < 0.001) with day of gestation. Jejunal capillary area density, number density, and surface density were greater (P < 0.008) during late gestation. Results indicate that maternal and fetal intestines undergo changes during gestation, which can be affected by nutrient restriction and may partially explain differences observed in fetal development and postnatal performance.
Eight cannulated wethers (BW = 52.5 +/- 5.7 kg) were used in a replicated 4 x 4 Latin square designed experiment to evaluate the effects of oscillating dietary protein concentrations on ruminal fermentation, site and extent of digestion, and serum metabolite concentrations. Four treatments consisted of a 13, 15, or 17% CP diet fed daily or a regimen in which dietary CP was oscillated between 13 and 17% on a 48-h basis (ACP). All diets consisted of 65% bromegrass hay (10.5% CP, 61.9% NDF, 37.2% ADF) plus 35% corn-based supplement and were formulated to contain the same amount of degradable intake protein (9.6% of DM) plus additional undegradable intake protein (SoyPLUS, West Central Cooperative, Ralston, IA) to accomplish CP levels above 13%. Each of four experimental periods were 16 d in duration with 12 d for diet adaptation followed by 4 d for sample collection. All wethers were fed at 3.0% of initial BW (DM basis) throughout the experiment, resulting in an average organic matter intake of 1.39 kg/d across treatments. When compared to the 15% CP daily treatment, feeding ACP had no effect (P > or = 0.10) on ruminal or lower tract N, NDF, ADF, or OM digestion. True ruminal OM digestion responded quadratically (P = 0.07) to increasing dietary CP, reaching a maximum of 52.0% of OM intake with the 15% CP treatment. Sheep fed ACP tended to have lower (P = 0.08) ruminal NH3 N concentrations and an overall higher (P = 0.0001) molar proportion of acetate compared to those fed 15% CP daily. Total VFA concentrations were not affected (P > or = 0.45) by increasing dietary CP. Microbial efficiency did not differ (P > or = 0.55); thus, bacterial N flow at the duodenum responded quadratically (P = 0.04) to increasing dietary CP. Nonbacterial N (P = 0.001) and total N (P = 0.01) flows at the duodenum and total tract N digestibility (P < or = 0.04) increased linearly as dietary CP increased. Wethers fed ACP maintained a lower (P = 0.002) serum glucose and lower (P = 0.0006) serum urea N compared to those fed 15% CP daily. Because the CP content of the diet was increased at the expense of corn, the response to increased CP observed in this experiment is most likely due to negative associative effects of supplemental starch on ruminal fermentation and microbial growth. Oscillating the CP content of the diet on a 48-h basis has little effect on digestion or N utilization in sheep compared with feeding the same quantity of protein on a daily basis.
Primiparous beef cows (n = 35 Bos taurus, average initial BW of 498 kg) were allotted to treatments in a split-plot designed experiment to determine the effects of supplemental ruminally protected amino acids on cow and calf productivity and metabolic changes in the cows. Cows were fed chopped annual rye hay at 1.5% of BW. The following treatments were used: 1) .8 kg soybean hulls, 1.4 kg ground corn, .6 kg soybean meal (CON); 2) 1.4 kg ground corn, 1.4 kg soybean meal (PRO); 3) PRO plus ruminally protected methionine and lysine (supplied 5 and 10 g, respectively; PRO1); and 4) PRO with twice the level of ruminally protected amino acids in PRO1 (PRO2). Cow weight gain was not different (P > .26) among treatments and averaged 1.2 kg/d for the 45 + 6 d before parturition. After parturition, cow weight gain did not differ (P > .47) between CON and PRO treatments, but it decreased quadratically (P < .01) with increasing level of ruminally protected amino acids. Total milk yield, protein, and fat (4 h) were greater (P < .05) for cows consuming PRO supplements than for CON, whereas CON cattle tended (P = .11) to lose less body condition. Total milk protein showed a quadratic increase (P < .05) in response to level of ruminally protected amino acids that was the inverse of the quadratic response noted for cow weight gain. Serum urea N concentration was greater (P = .07) for cattle consuming additional protein. Metabolic hormones were not affected (P > .18) by dietary treatment, but they responded (P < .05) to changes in physiological state. Supplements with additional protein supported greater (P = .0001) milk urea N concentration and output. Milk urea N concentration increased (P < .05) and milk IGF-I decreased (P < .05) as the lactation period progressed. The measurement of CON and PRO diets revealed that supplements with additional soybean meal had greater (P < .05) DM and N degradation; the extent of forage DM and NDF degradation was similar (P > .05) among treatments. Production shifted away from body weight gain to increased milk protein production when daily supplementation of ruminally protected methionine and lysine increased from 5 and 10 to 10 and 20 g, respectively. This shift in production was not reflective of changes in the metabolic regulators measured.
