Supplemental Niacin and Heat-Treated Whole Soybeans for Jersey Cows During Early Lactation

Fifty-six multiparous Jersey cows were used in a replicated trial to investigate the effect of supplemental niacin and heat-treated whole soybeans on milk production and composition. Dietary treatments included 0 or 6 g/d of supplemental niacin beginning 21 d prior to expected parturition and raw or heat-treated whole soybeans fed at 10% of the dietary DM beginning immediately after parturition. Data were collected for 18 wk following a 2-wk postpartum period during which cows were adjusted to experimental diets and allowed to recover from parturition. Based on index values for protein dispersibility, heat-treated soybeans were marginally heated in yr 1 (12.1) and underheated in yr 2 (17.9). Intake of DM from corn silage plus concentrate, alfalfa hay, or soybeans averaged 15.5, 1.5, and 1.7 kg/d, respectively, and was not different because of niacin supplementation or form of soybean. Percentage of milk fat was highest when raw soybeans plus niacin were fed and lowest for heat-treated soybeans plus niacin. No difference was observed in milk production, milk percentage, or milk protein, lactose, and SNF. No advantage was observed from less than optimally heated whole soybeans or supplemental niacin in diets for Jersey cows during early lactation.