RESUMEN
Effects of concentrate source (corn or soybean hulls) and amount (40 or 80% of DMI) on plasma hormone concentrations were evaluated for 32 prepubertal Holstein heifers in a 2 x 2 factorial design. Blood samples were collected every other day from d -4 through d 28 of the experiment and were analyzed for growth hormone, prolactin, IGF-1, and glucose. Ruminal samples were collected by esophageal tube on d 0, 7, 14, 21, and 28 and were analyzed for VFA content. Serial blood samples were collected on either d 25 or 26 at 20-min intervals for 8 h and were used for profile analysis of growth hormone and prolactin. Heifers fed 80% concentrate had higher IGF-1 concentrations in serum (158.1 vs. 131.9 ng/ml) than did heifers fed 40% concentrate, and heifers fed corn tended to have higher IGF-1 concentrations than heifers fed soybean hulls. Prolactin concentrations in samples that were collected every other day were higher for heifers fed the 80% soybean hull diet than for those fed 40% concentrate diets or the 80% corn diet. Effects of source and amount of concentrate on plasma prolactin concentrations were not evident in serial samples. Concentrate source or amount had no effect on plasma growth hormone or glucose. At high concentrate intakes, the source (soybean hulls vs. corn) affected intake parameters, ruminal VFA content, and prolactin concentrations.
Asunto(s)
Alimentación Animal , Bovinos/sangre , Dieta , Hormonas/sangre , Acetatos/metabolismo , Animales , Glucemia/metabolismo , Butiratos/metabolismo , Ácido Butírico , Femenino , Hormona del Crecimiento/sangre , Factor I del Crecimiento Similar a la Insulina/metabolismo , Medicago sativa , Progesterona/sangre , Prolactina/sangre , Propionatos/metabolismo , Rumen/metabolismo , Glycine max , Zea maysRESUMEN
Forty-eight Holstein cows were randomly assigned to receive diets containing corn or barley as the primary energy concentrate from wk 4 through 44 postpartum. During wk 14, cows from each grain source group were randomly assigned to receive 0 (control), 10.3, 20.6, and 30.9 mg/cow per d of recombinant bST injected wk 15 through 44 postpartum. Grain source exerted no significant effect on production parameters and efficacy of bST, although milk production tended to be higher with corn diets. Milk production (24.2, 29.2, 31.7, and 29.5 kg/d) and 4% FCM (21.9, 26.2, 28.1, and 28.0 kg/d) were higher for cows injected with bST, and DM intakes (20.9, 22.8, 22.0, and 23.3 kg/d) increased slightly. Percentages of milk fat (3.47, 3.28, 3.39, and 3.52) and protein (3.48, 3.44, 3.44, and 3.38) varied. Lactose, SCC, and body weights were similar for bST and dietary treatments. Diet or bST had no detectable affect on health or reproduction. Injection of bST wk 15 through 44 increased milk production 21 to 31% relative to control animals. Limiting bST use to the latter two-thirds of lactation resulted in an 8 to 17% increase in total yield with only a 0 to 5% increase in lactational DM intake.
Asunto(s)
Bovinos/fisiología , Dieta , Grano Comestible , Hormona del Crecimiento/farmacología , Hordeum , Lactancia/efectos de los fármacos , Zea mays , Animales , Peso Corporal/efectos de los fármacos , Femenino , Fertilización/efectos de los fármacos , Hormona del Crecimiento/administración & dosificación , Inyecciones Subcutáneas/veterinaria , Distribución Aleatoria , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/farmacología , Factores de TiempoRESUMEN
Seventy-six high producing Holstein cows were randomly assigned in a 2 x 2 factorial to evaluate two sources of nonstructural carbohydrates (corn and barley), which supposedly differed in degradability of starch with two sources of CP degradability (soybean meal and urea) in the concentrate mix during wk 4 through 14 postpartum. Total mixed diets, formulated to be isonitrogenous at 16% CP, contained (DM) 40% corn silage, 10% alfalfa hay, and 50% of the respective concentrate mix. Nonstructural carbohydrate degradability was similar for concentrate mixes containing corn or barley. Production of milk (32.2 and 31.8 kg/d) was similar, but production of 4% FCM (29.1 and 27.4 kg/d) and SCM (29.1 and 27.5 kg/d) was decreased for cows fed barley due to lower percentages of fat (3.39 and 3.22) and SNF (8.65 and 8.59). Percentages of protein (3.09 and 3.08) were similar for cows fed corn and barley diets. Degradability of CP did not affect production of milk (31.9 and 32.0 kg/d), 4% FCM (28.5 and 28.0 kg/d), and SCM (28.4 and 28.2 kg/d) for cows fed soybean meal and urea. Dry matter intake was lower for cows fed barley (20.7 and 19.2 kg/d), but intakes (20.1 and 19.8 kg/d) were similar for cows fed soybean meal and urea. Providing an alternative nonstructural carbohydrate source (barley versus corn) did not increase utilization of a more readily degradable CP source (urea versus soybean meal).