Effects of feeding milk replacer once versus twice daily on glucose metabolism in Holstein and Jersey calves.

Eighteen Holstein (experiment 1) and 15 Jersey (experiment 2) heifer calves were fed milk replacer once or twice daily to determine effects of feeding frequency on weight gain, starter intake, and glucose metabolism. Body weights were measured weekly from birth to 8 wk. Blood samples were collected at wk 1 through 6 from all calves before and at 30, 60, 90, 120 and 180 min after the morning feeding. Plasma was analyzed for glucose, insulin, glucagon, and nonesterified fatty acids (NEFA). Urine was collected 90 min postfeeding to measure glucose concentration. Treatment did not affect mean starter intake or body weight. In experiments 1 and 2 mean plasma glucagon, glucose, NEFA, and insulin and urinary glucose concentrations were not affected by treatment. There was an interaction of sampling time and treatment for plasma insulin concentrations but not for glucose concentrations in both experiments. Following feeding, calves fed milk replacer once daily had higher insulin concentrations than those fed twice daily. There was an interaction of sampling time and treatment for plasma NEFA concentrations in Jersey calves only. Jersey calves fed milk replacer once daily had higher plasma NEFA concentrations before the morning milk replacer feeding. At wk 3 and 6, frequently sampled intravenous glucose tolerance tests were performed to assess glucose effectiveness, insulin sensitivity, and acute insulin response. In experiments 1 and 2 glucose effectiveness and insulin sensitivity were similar regardless of milk replacer feeding frequency. In Holstein and Jersey calves fed milk replacer twice daily, acute insulin response was greater than in calves fed once daily. However, insulin sensitivity decreased with age, while acute insulin response increased with age. These data suggest that feeding calves milk replacer once daily did not deleteriously affect performance or glucose metabolism regardless of breed.

Effects of ensiling on the digestibility and utilization of whole oilseeds by wethers.

Two digestion and N metabolism trials were conducted with 35-kg wethers to assess the feeding value of whole cottonseed or soybeans ensiled with corn silage in 3.6-m3 concrete silos (1.8 x 1.4 m). Dietary treatments for the cottonseed trial were ensiled whole cottonseed, untreated whole cottonseed, and 21 or 13% cottonseed meal in a basal diet of corn silage. There were no differences among treatments for DM and ADF intakes. Including ensiled or whole cottonseed in rations decreased digestibility of DM and ADF. Digestibility of CP was similar for the 21% cottonseed meal and whole cottonseed treatments. Nitrogen retention was similar for all treatments. Treatments for the soybean trial were ensiled whole soybeans, untreated whole soybeans, and 4 or 14% soybean meal. Lambs fed 14% soybean meal consumed more DM and ADF than those fed whole soybeans. Dry matter and ADF digestibilities were similar for all diets. Lower CP intakes resulted in less retained N for lambs fed whole soybean diets compared with those fed 14% soybean meal. Ensiling soybeans did not affect digestibilities of DM, CP, or ADF, or N retention. Ensiled whole soybeans or whole cottonseed may be fed to wethers as an alternative to separate feeding of oilseed meals with little effect on intake, CP digestibility, or N retention.

Effect of feeding gossypol in cottonseed meal on growth, semen quality, and spermatogenesis of yearling Holstein bulls.

Yearling Holstein bulls were fed a corn silage ration supplemented with either cottonseed meal with gossypol or soybean meal in two trials to evaluate the effect of feeding gossypol on reproductive characteristics. In Trial 1, roughage to concentrate ratio was 88:12 and was fed for 60 d. In Trial 2, roughage to concentrate ratio was 50:50 and was fed for 42 d. Cottonseed meal concentrate had 3.03 g total gossypol/kg DM. Cottonseed meal concentrate was fed to provide 6 and 30 mg total gossypol/kg BW per d in Trials 1 and 2. Ejaculates were collected twice weekly via artificial vagina and critiqued for quantity and quality before and after thawing and after postthaw incubation. Leptotene spermatocytes to Sertoli cell ratio in stage 1 tubules was used to evaluate spermatogenesis. Growth characteristics and tissue total gossypol concentrations were also evaluated. No gossypol was found in plasma taken before, during, or after Trial 1 or from body organs or plasma taken during or after Trial 2. No signs of gossypol toxicity were observed, and growth characteristics were similar on both rations. Gossypol in cottonseed meal fed at low to moderate concentrations was not deleterious to seminal quantity or quality, and spermatogenesis was unaffected by treatment.

Maintenance nitrogen requirements and intestinal microorganisms in rats.

Nitrogen (N) balance trials with young growing rats fed diets with and without nonabsorbable antibiotics and with various concentrations of crude protein (CP) were conducted to measure maintenance N requirements. In addition, cecal contents were analyzed for ammonia (NH3), urea (U) and free amino acids (AA) to study the reduction in maintenance N requirements due to the action of antibiotics. Results of the N-balance trials verified the reduction in maintenance N requirements with antibiotics as described in the literature. The reduction, however, was not as large as previously demonstrated, possibly because of severe diarrhea and greater liquid accumulation in the cecum of rats fed antibiotics. The concentration of free AA and U in the postabsorptive region of the intestine (cecum) of rats consuming antibiotics was greater than when antibiotics were not consumed. Cecal N concentrations supported the concept that the mode of action of antibiotics in reducing maintenance N requirements was via reduced destruction of AA of body origin in the lower intestine. Cecal levels of NH3 were similar in both antibiotic and nonantibiotic groups. The amount of N needed for body maintenance when conditions favored minimum destruction of body AA by lower intestine microorganisms was small, less than 1% dietary CP. Maintenance N may be limited to the needs for tissues on the exterior of the body, such as hair, which are poorly recycled through the digestive tract.