INCREASED MILK-PRODUCTION OF COWS IN EARLY LACTATION FED CHEMICALLY TREATED SOYBEAN-MEAL

Holstein cows in early lactation and producing about 35 kg/d of milk were fed TMR for ad libitum intake and 1 kg/d of long alfalfa hay. Soybean meal and soybean meal treated by a novel technique were compared in diets of 15 and 17% CP in a 2 x 2 factorial design. Digestibilities of DM, CP, and ADF were significantly lower for treated soybean meal diets. Mean DMI was about 21 kg/d and was unaffected by treatment. Milk production was significantly increased during wk 7 to 16 of lactation for cows fed treated soybean meal diets. The production of SCM and milk components was greater for cows fed treated soybean meal than for cows fed soybean meal, but the differences were not significant. By wk 16, compared with wk 3 of lactation, the persistency of production of milk and lactose was markedly increased by treated soybean meal. The persistency of milk protein production was 100.5% for cows fed the diet containing treated soybean meal at 17% CP and about 97% for the other diets. The hypothesis that Met supply was limiting secretion of milk protein in cows fed treated soybean meal is discussed.