Effects of feed supplementation on growth, blood parameters and reproductive performance in Sanga and Friesian-Sanga cows grazing natural pasture.

This study determined the effects of feed supplementation during the postpartum period on the weight gain, milk yield, blood profiles and reproductive performance of Sanga and Friesian-Sanga cows grazing on natural pasture. 20 Sanga and 20 Friesian-Sanga cows were randomly allocated either to serve as a control on grazing only or to be supplemented with 2.5 kg of concentrate a day for 10 weeks during the dry season. Each week, all cows were weighed and scored for body condition. Partial milk yield of cows was determined daily. Plasma concentrations of blood metabolites were assessed fortnightly from weeks 1 to 10 postpartum. Resumption of postpartum ovarian activity was determined by measuring progesterone concentration in the plasma from weeks 1 to 10. Supplemented cows had a better body condition score (6.2 versus 5.8; P < 0.05) and higher partial milk yield (1.94 versus 1.55 L/day; P < 0.01) than non-supplemented cows. Sanga cows had a better body condition score (6.2 versus 5.8; P < 0.05) but lower milk yield (1.58 versus 1.92 L/day; P < 0.01) than the Friesian-Sanga crossbreds. Total protein (P < 0.05) and albumin (P < 0.01) concentrations were higher in the supplemented than in the non-supplemented cows. Sanga cows recorded higher globulin (P < 0.05) and total cholesterol (P < 0.01) but lower albumin (P < 0.01) concentrations than Friesian-Sanga crossbred cows. Feed supplementation did not affect (P < 0.05) the interval from calving to resumption of ovarian activity, and the days to resumption of ovarian activity in the Sanga and Friesian-Sanga cows were also similar (P > 0.05). The results demonstrate the beneficial effects of feed supplementation in terms of improved body condition and metabolic status and increased milk yield.