Milk Production and Energy Indicators in Semi-housed Dairy Cows Treated With Low Doses of Recombinant Bovine Somatotropin During Transition Period

The aim of this study was to determine the effect of low doses of recombinant bovine somatotropin (rbST) on energy balance parameters and milk production in transition dairy cows on a semi-housed system. Seventy two Holstein-Frisian cows were used and allotted in: treatment group (rbST, n=36), treated from 3d prepartum to 6th pospartum week with 250 mg/14 days (d) of bST and control group (C, n=36), not treated. Blood samples were obtained during rbST treatment from both groups to determine non esterified fatty acids (NEFA), -hydroxybutyrate (HBA), cholesterol, urea and albumin concentrations and aspartate amino transferase (AST), glutamate deshidrogenase (GD) y gamma glutamil transferase (GGT) enzyme activities; body condition and live weight as well. Milk production was registered since partum to 7th postpartum week. Energy balance parameters were similar between groups (P>0.05) and milk production was higher in rbST than C (36.3 vs. 34.3 L/cow/d, P 0.05), except for metritis being higher in control group (22.2 vs 5.4%; P<0.05). Results obtained allow to infer that the treatment of grazing dairy cows with low doses of rbST in transition period increases milk production without a detrimental effect on energy balance.