RESUMEN
Alfalfa-brome hay, haylage, .5% urea-treated corn silage, or .5% urea plus 1% dried whey-treated corn silage was fed as the only forage to one of four groups of 10 lactating cows per group for a lactation trial of 10 wk. Rumen samples were collected via stomach tube 3 to 4 h after the morning feeding. The pH of the rumen samples from cows fed hay was higher than for cows fed haylage, urea-treated corn silage, and urea-whey corn silage, 6.69 versus 6.36, 6.40, and 6.50. Total volatile fatty acids and propionate were highest from cows fed urea-whey corn silage and were higher on all three fermented forages than cows fed hay. Acetate/propionate ratio was highest from cows fed hay and lowest from cows fed corn silages. Butyrate was highest from cows fed haylage or hay. Milk protein composition was not affected by ration although nonprotein nitrogen of milk was highest from cows fed the urea-treated corn silages. Oleic acid and total unsaturated fatty acids were lowest in milk fat from cows fed hay while palmitic acid was highest from cows fed hay and haylage. These results suggest that type of forage fed may cause small changes in rumen fermentation and in milk composition. The importance of these changes is unknown but may affect properties of dairy products produced from this milk.
Asunto(s)
Alimentación Animal , Ácidos Grasos Volátiles/metabolismo , Leche/metabolismo , Rumen/fisiología , Alimentación Animal/análisis , Animales , Bovinos , Femenino , Lactancia , Metabolismo de los Lípidos , Medicago sativa , Proteínas de la Leche/metabolismo , Nitrógeno/análisis , Poaceae , Polisacáridos/análisis , Embarazo , Ensilaje , Urea , Zea maysRESUMEN
Parturition was initiated in 26 Holstein cows given dexamethasone (4.4 mg/100 kg body weight) in combination with 25 mg estradiol benzoate intramuscularly at day 273 of gestation. Parturition occurred at 40.8 +/- 9.6 h after injection. Twenty-six control cows had an average gestation length of 281.5 days. Calving difficulty was not different although birth weight of calves was 2.5 kg less for induced cows compared with control cows. Severity of udder edema did not differ between groups. Average daily milk production for the first 9 wk of lactation was lower (24.2 versus 27.7 kg) from induced than control groups. Incidence of retained placental membranes was 50 and 4% for induced and control cows. Serum estrogens were lower (290 versus 601 pg/ml) in induced than in control cows 2 days prior to parturition. Groups did not differ inserum calcium, phosphorus, magnesium, days to first heat, days to first breeding, days to conception, or in fat, protein, and total solids content of colostrum. Casein in colostrum of induced cows was lower. Results of California Mastitis Tests at 15 and 30 days postpartum were similar.