Comparison of an early and normal weaning management system on cow and calf performance while grazing endophyte-infected tall fescue pastures.

A 3-yr study used 16 cows and their spring-born calves (yr 1) and 48 first-calf heifers (yr 2, n = 24; yr 3, n = 24) and their spring-born calves in a completely randomized design. All cows and heifers were Angus x Beefmaster, and calves were sired by Angus bulls. Cow-calf pairs were assigned randomly to one of two management systems: 1) an early-weaning system, in which steer and heifer calves were weaned at 108 d of age and fed a postweaning growing diet (EW), or 2) a normal weaning system, in which calves were weaned at 205 d without supplementation (NW). Before early weaning and within each management system, calves and their dams were maintained in two 1.4-ha, endophyte-infected tall fescue pastures for 35 d (yr 1) or 14 d (yr 2 and 3). Early-weaned calves and cow-calf pairs were then randomly allotted to 1.4-ha, endophyte-infected tall fescue pastures with two (yr 1) or three (yr 2 and 3) calves or cow-calf pairs per pasture (four pastures per management system). Cow weights and BCS changes and calf gains were measured from early to normal weaning. Dietary intakes and nutrient digestibilities by EW and NW calves were determined during two periods of yr 1 and three periods of yr 2 and 3. Total gains and BCS changes were greater (P < 0.01) for cows that produced EW calves in all years. Calf ADG from early to normal weaning did not differ (P = 0.32). Similar to ADG, BW of calves at normal weaning were not different (P = 0.11). Forage intake was greater (P < 0.01) by NW calves during Periods 2 and 3 of yr 1 and Periods 1 and 2 of yr 2 and 3; however, total DM and CP intakes were greater (P < 0.01) for EW calves in Periods 2 and 3 of each year. Intakes of NDF tended (P = 0.11) to be greater by EW calves across all years. Estimates of CP and NDF digestibilities were higher (P < 0.01) for EW calves during yr 1 and 2; however, all components of the diet consumed by NW calves in yr 3 were more digestible (P < 0.05) than those consumed by EW calves. These results show the condition of cows with EW calves was improved by early weaning and gains by calves weaned at 108 d to pasture plus a commercial grower diet were comparable to those by calves continuing to nurse dams until weaned at 205 d.

Effects of supplementing with calcium salts of palm oil fatty acids or hydrogenated tallow on ewe milk production and twin lamb growth.

Two experiments were conducted with Polypay ewes nursing twin lambs to evaluate the effects of supplementing fat (calcium salts of palm oil fatty acids or hydrogenated tallow) on ewe lactation. In Exp. 1, ewes were fed a 52% concentrate:48% hay-based diet (as-fed basis) consisting of alfalfa hay (n = 4), endophyte-free fescue hay (n = 4), or fescue hay with 3.7% fatty acids (n = 4) from d 4 to 56 of lactation. In Exp. 2, ewes were fed similar diets that had endophyte-free fescue hay (n = 6), fescue hay with 3.7% fatty acids (n = 5), or fescue hay with 3.1% tallow (n = 6) from d 14 before lambing until d 57 of lactation. Diet formulations with supplemental fat were more nutrient dense, and treatments were fed to meet ewe nutrient requirements; this caused diets with added fat to be offered at 10 and 17% lower rates than unsupplemented diets in Exp. 1 and 2, respectively. Lambs were maintained to consume only ewe milk. Ewe milk production and composition were determined using a portable milking machine following a 3-h separation from lambs. In Exp. 1, milk fat content was increased (P < 0.01) when ewes consumed fescue hay with fatty acids vs. the fescue hay diet (11.4 vs. 8.3%). Ewes fed fescue hay with fatty acids lost the most (P < 0.05) weight over lactation (-8.6 kg) compared with ewes fed the alfalfa hay (-2.4 kg) and fescue hay (-3.8 kg) diets. Other milk measures, lamb gain, and production efficiencies were not changed. In Exp. 2, ewes supplemented with fatty acids produced more (P < 0.05) milk fat than those fed tallow (290 vs. 210 g/d). The proportion of synthesized milk fat 14:0 was decreased (P < 0.01), but the percentage of incorporated 16:0 increased (P < 0.05) when fatty acids were fed. Dietary fat digestibility by ewes was increased (P < 0.01) by fatty acid supplementation but decreased (P < 0.01) when tallow was added. Although ewe weight measures were not changed in Exp. 2, twin lamb gain per ewe organic matter intake was most efficient (P < 0.05) when ewes were supplemented with fatty acids. Results suggest that feeding hydrogenated tallow decreased nutrient availability for ewe milk fat production. A complete diet based on endophyte-free fescue hay can replace a traditional alfalfa hay diet, whereas supplementing with the calcium salts of palm oil fatty acids may be more feasible when energy is limiting during ewe lactation.

Reducing milk production in ewes at weaning using restricted feeding and methscopolamine bromide.

Restricted feed (RF) and methscopolamine bromide (MB), an anticholinergic agent reported to block growth hormone secretion, were evaluated as potential means for reducing milk production in ewes at weaning. On d 58 +/- 1 postpartum (d 0), 40 fall-lambing ewes were allotted to treatments in a 2 (RF vs full feed [FF]) x 2 (MB vs saline [SAL]) factorial arrangement according to breed, age, and number of lambs born and suckled. On d 0 at 0800, ewes were separated from lambs, injected with 40 IU of oxytocin, and machine milked 30 s later. Ewes remained separated from lambs for 3 h, and at 1100 they were milked and yields were determined. From d 0 through 6, FF ewes received a daily ration of 1.8 kg of alfalfa hay and .9 kg of corn; RF ewes received only 1.8 kg of alfalfa hay. On d 7 at 0800 and 1400, ewes were separated from lambs, milked, treated with a s.c. injection of either 96 mg of MB dissolved in 2 mL of SA or SA alone, and after 3-h separations were milked at 1100 and 1700 and yields determined. Lambs were weaned at 1400. After milking at 1700, all ewes were placed in drylot without feed or water. At 1100 on d 9, residual milk yields were collected. Milk samples were retained for compositional analysis at each collection time. The RF ewes produced less milk than FF ewes (106 vs 137.4 g; P < .01) at 1100 on d 7, but yields of MB and SA ewes were similar. At 1700 on d 7, milk yield was only 15.9 g less (74.3 vs 90.2 g; P < .10) for RF than for FF ewes, but it was 26 g less (69.2 vs 95.2 g; P < .01) for MB than for SA ewes. On d 9, there was no significant difference in yields of RF and FF ewes; however, MB ewes continued to produce less milk than SA ewes (96.6 vs 125.4 g; P < .10). No significant interactions between feeding regimen and MB treatment were found for milk yield. These data provide evidence that MB treatment of ewes is effective in reducing milk production. Furthermore, even greater reduction can be achieved when MB is combined with RF.

Influence of maternal frame size and nutritional restriction on growth and development of the postnatal lamb.

Pregnant ewes (large frame [LF] and small frame [SF]) were nutritionally stressed in early gestation (EGS), late gestation (LGS) or fed 100% of NRC requirements (unstressed, US) throughout gestation. Lambs (128) from these ewes were slaughtered at birth, weaning (18 kg), 41 kg or 55 kg. Sixty-four lambs received a 13% protein diet from weaning to either 41 or 55 kg. Lambs from SF ewes were fatter at 55 kg, had a higher numerical yield grade and a lower percentage of carcass protein. Lambs from US ewes were youngest at slaughter and had the most carcass weight and protein per day of age at 55 kg. The LGS lambs had the lowest percentage of lean and carcass protein at 41 and 55 kg. However, at birth these lambs had the highest concentration of RNA and DNA in muscle. The EGS lambs had the lowest quality grade, carcass weight per day of age and fat percentage. Muscle DNA and RNA at birth was lowest in EGS lambs. However, EGS lambs produced the highest lean percentage and highest percentage carcass protein at 41 and 55 kg. Shortest metacarpals and metatarsals were also found in these lambs at weaning and 41 kg. Although frame size had little effect on carcass characteristics, the effects of nutritional stress in the first 80 d of gestation were apparent in lambs slaughtered at 31 kg. Stress in the last 50 d of gestation had more effect on lambs slaughtered at 55 kg.

Comparative drug depletion in domestic animals and birds.

Decoquinate (Rhone-Poulenc Inc) and Narasin (Eli Lilly and Co) were selected as model drugs for a comparison of metabolism between major (cattle and chickens) and minor (sheep and quail) species. Decoquinate has been studied in all four species. Narasin studies are in progress in chickens and quail. More than 96% of injected 14C-decoquinate (DQ) was eliminated from blood of all species within 1 hr. Disappearance of the remaining 1 to 4% from blood was rapid for all species. Half-times for DQ appearance in excreta were all less than one day. Cumulative excretion of DQ in eggs of chickens and quail was about 1% for both species. Disappearance of DQ from tissues was essentially complete in 14 days. More than 80% of injected 14C-narasin was eliminated from blood within 1/2 hr. Disappearance of the remainder was rapid for both chickens and quail.

Comparative metabolism of 14C-decoquinate in chickens, quail and sheep.

Removal of pulse doses of 14C-decoquinate from blood was studied in chicken hens, quail hens, and ewe lambs. Estimated clearance before the first post-injection sample at 1 1/2 hr was 96% for sheep, 99% for chickens and over 99% for quail. Half-times for removal of the remaining radioactivity from the blood were 26.8 hr for sheep, 144.7 hr for chickens and 27.2 hr for quail. Treating the chicken data as biphasic yielded a 3.4 hr half-time for an initial fast phase and 210 hr for a later slow phase. Radioactivity disappeared from sheep blood between 2 and 7 d, from chicken blood between 7 and 14 d, and from quail blood between 1 and 2 d. Urine accounted for 35% of the radioactivity administered to sheep. It did not contain detectable activity after the third day.

Effect of lipid-coated lysine on digestion and nitrogen metabolism by wethers.

Four mature wethers (70 kg) fitted with permanent abomasal cannulas were assigned to a 4 X 4 Latin square design to study the effect of coating supplemental lysine with coconut oil on nutrient digestion, nitrogen retention and recovery of amino acids in the abomasum and plasma. Dietary treatments were: Control (C) = basal diet; Lysine (LYS) = Control + 1% supplemental lysine; Coconut oil-coated lysine (CN-LYS) = Control + 1% supplemental lysine coated with coconut oil; and Coconut oil + diet (CN-DIET) = Control + 1% supplemental lysine + an equal amount of coconut oil added to the entire diet. Lysine supplementation significantly increased total apparent dry matter, ether extract and energy digestibilities. Total nitrogen and protein nitrogen flows to the abomasum were decreased (p less than .1) in lambs consuming CN-LYS and CN-DIET compared with LYS. Urinary nitrogen excretion (p less than .05), ruminal ammonia nitrogen and plasma urea nitrogen (p less than .05) concentrations were higher for LYS, CN-LYS and CN-DIET compared with C and highest for CN-LYS. There were no differences in nitrogen retention among treatments. Recovery of lysine in the diets after coating (CN-LYS) or lipid addition (CN-DIET) was reduced indicating degradation of supplemental lysine to other nitrogenous compounds during the coating process or storage since total dietary nitrogen content was equivalent to LYS. Flow of abomasal lysine (% of lysine intake) was higher (p = .15) for CN-LYS and CN-DIET than LYS. Flow of total essential amino acids (% of total amino acid flow) was greater (p less than .02) when lysine was added to diets. Essential amino with LYS. Plasma amino acid concentrations did not differ among treatments. Coating lysine with coconut oil did not protect the amino acid from ruminal degradation and was ineffective in improving total nitrogen status of mature wethers.

Effect of breed, slaughter weight and sex on histological properties of ovine muscle.

Thirty-three wether and ewe lambs of two breed groups- Suffolk ram x Suffolk-Rambouillet ewe (Su x R) and Suffolk ram x Finnish Landrace-Southdown ewe (Su x F x So)-and two slaughter weight groups (32 and 41 kg) were studied. Carcass studies, including histological examinations of muscle fiber types, sarcomere lengths and fat cell, were made. The longissimus (LD) muscle at the 13th rib and a sample of the semimembranosus (SM) from the upper proximal location were used. Fibers in both muscles were classified as beta R, alpha R or alpha W. Su x F x So lambs had more alpha W fibers and fewer alphaR fibers in both muscles. Breed type appeared to cause a physiological shift from alpha R to alpha W fiber types. Furthermore, beta R fibers were larger in the SM of the Su x F x So lambs than in that of the Su x R lambs. beta Red fibers in the LD, and all three types fibers in the SM, increased in size with increased weight. Wethers had fewer alpha R fibers in the SM, while ewe lambs had larger alpha R and alpha W fibers in the SM. The more phasic LD muscle had fewer beta R fibers, more alpha W fibers and smaller alpha R and alpha W fibers than the more tonic SM. Su x F x So lambs were fatter, as indicated by larger fat cells in both muscles. In addition, as slaughter weight increased, there was a concurrent increase in fat cell diameters in both muscles. Fat cells were larger in the LD than in the SM. Sarcomere lengths were not affected by breed, slaughter weight or sex. However, sarcomeres were longer in the SM than in the LD. Fat cell size and beta Red cells size for the LD were positively correlated with carcass fat indices, while shear values were negatively correlated with fat cell diameters. There was also a positive relationship between sarcomere length and fat cell size in the SM.

Influence of nitrate and molybdenum on sulfur utilization by rumen microorganisms.

Twenty-four hours in vitro incubations were used to study the effect of nitrate and molybdenum on sulfur utilization by rumen microorganisms. Sulfur was added as sodium sulfate or sulfide at .1, .2, .3, or .4% of the substrate dry matter. Cellulose digestion was an indicator of microbial growth. The addition of .1 to .4% sulfate or sulfide sulfur increased cellulose digestion over the conrol, the two sulfur sources being equal in promoting cellulose digestion. No differences in cellulose digestion were found between .1 and .4% added sulfur. However, the addition of .4 of .8% nitrate-nitrogen depressed cellulose digestion and increased the requirement for both sulfate and sulfide. Depression was greater with .8% nitrate-nitrogen. In the presence of nitrate, sulfide was superior to sulfate in promoting cellulose digestion. When 4 or 8 ppm molybdenum were added to the incubations, increasing concentrations of both sulfate and sulfide were required to obtain maximum cellulose digestion. Molybdenum additions increased both the sulfate and sulfide requirement for maximum cellulose digestion.

Oil coating of dietary protein for the ruminant.

Diets containing expeller-extracted linseed meal treated with corn oil, lard or coconut oil were fed to lambs to determine the effectiveness of coating the protein in reducing its ruminal degradation. Three common indicators of nitrogen metabolism in the ruminant were used in evaluation: ruminal ammonia, blood plasma ammonia and plasma urea. Eight crossbred lambs, averaging 27 kg in weight, were allotted to the four diets which were fed at a rate of 350 g at 12-hour intervals. Ruminal ammonia, plasma ammonia and plasma urea were monitored at 0, 2, 4, 6 and 8 hr after feeding. Lambs consuming coconut oil-treated linseed meal produced less rumen ammonia (average of .5 mg/100 ml across all collection times) than those fed normal linseed meal (10.3 mg/100 ml). Lambs fed corn oil-treated and lard-treated linseed meal had ruminal ammonia levels intermediate to those fed normal and coconut oil-treated linseed meal. Levels of plasma ammonia and plasma urea nitrogen of normal linseed meal were significantly higher than the same measures with the oil-treated linseed meals. Differences in plasma ammonia and urea nitrogen were not significant among the three oil-treated diets.