Effect of the level of concentrate supplementation on the productive response of dairy cows on spring grazing receiving a high herbage allowance

The purpose of this study was to evaluate the effect of different levels of concentrate supplementation on the productive response of dairy cows fed high daily herbage allowance of spring pasture. The study was conducted from September to November of 2005. Twenty eight spring calving Friesian cows were assigned to four treatments: SP, grazing alone; PSC3, pasture Plus 3 kg/d of concentrate; PSC6, pasture plus 6 kg/d and PSC9, pasture plus 9 kg/d of concentrate. The cows were supplemented twice a day and managed under a strip grazing system. Weight and body condition were recorded individually each week. Milk production was recorded individually on a daily basis and composition was analyzed each week. Coccigeal blood samples from each cow were obtained each week after the morning milking and analyzed for beta OH-butyrate, NEFA, urea and albumin. Milk production for the SP, PSC2, PSC3 and PSC4 treatments were 28.1; 30.8; 31.2 and 28.8 l/day, respectively (P > 0.05). The concentrations of protein or urea in milk were not affected by treatments. Grain supplementation decreased (0.57%) milk fat concentrations (P < 0.05), but the level of grain feeding had no effect among treatments (P > 0.05). Plasma beta OH-butyrate decreased (P < 0.05) with concentrate supplementation; meanwhile plasma NEFA and urea were not affected by concentrate supplementation or by increasing the level of grain feeding, averaging 0.31 mmol/l and 32.0 g/l, respectively (P > 0.05). It can be concluded that under these experimental conditions increasing the level of concentrate supplementation did not modify milk production or composition, the live weight or the body condition on dairy cows on spring pasture receiving a high daily herbage allowance.