Use of recombinant bovine somatotropin (rbST) in dairy buffaloes I: production and physicochemical composition of milk

ABSTRACT This study aimed to evaluate the effect of recombinant bovine somatotropin (rbST) on milk yield and the proportion of buffalo milk components during lactation. Twenty-two buffaloes randomly distributed in two experimental groups were used: Group rbST - application of 500mg rbST every 14 days, between 63 and 154 days in milk (DIM); Control Group - without treatment. Weekly, the milk yield of buffaloes was measured and a sample was collected for physicochemical analysis. The response variables were evaluated as repeated measures, using the Repeated procedure through the GLM procedure of SAS. Means of each variable after rbST and Control were: Milk yield - 6,54 vs. 6,68 kg; Fat - 6,31 vs. 6,34%; Protein - 3,86 vs. 3,81%; Lactose - 4,96 vs. 5,02%; Milk solids - 16,05 vs. 16,03%; Defatted dry matter - 9,75 vs. 9,74%; Somatic Cells Count - 329,90 vs. 171,68 (x 1000/mL); and electrical conductivity- 2,87 vs. 2,81mS/cm. The use of 500mg of rbST administered every two weeks, between 63 and 154 DIM did not affect milk yield, proportion of milk constituents and SCC of dairy buffaloes.