Produção e composição do leite, metabólitos sangüíneos e concentração hormonal de cabras lactantes da raça Toggenburg tratadas com somatotropina bovina recombinante

The objective of this trial was to study the effects of recombinant bovine somatotropin on milk yield and composition, blood metabolites and hormonal profile in lactating goats. Twenty-four Toggenburg goats were assigned to one of two treatments as follows: T1 (n=12) received injection of 250 mg of r-bST, every 14 days (four injections), and T2 (n=12) received injections of saline solution (control). No significant differences on milk yield and composition (fat, protein, and dry extract) were observed comparing r-bST-treated goats with non-treated animals. However, milk lactose content was higher (P<0.05) on goats that received r-bST (4.47 ± 0.2) than on those treated with saline solution (4.34 ± 0.2 %) while somatic cells count was lower on T1 (681.1 ± 689.9) than on T2 [(1,001.84 ± 610.9 (x103 cells/mL)]. Injection r-bST increased the concentration of non-esterified fatty acid compared to the saline-treated animals (309.67 ± 169.62 vs. 247.34 ± 126.38 mEq/L) but the opposite was observed for urea concentration (86.84 ± 33.81 vs. 121.16 ± 42.57 mg/dL). The r-bST treatment reduced the total cholesterol and HDL levels (82.46 ± 19.25 vs. 89.29 ± 23.66 and 155.95 ± 19.67 x 177.67 ± 32.79 mg/dL for T1 and T2, respectively) in lactating goats. Concentrations of albumin, glucose, total proteins, b-hidroxybutirate and thyroxin as well as body weight and body condition score all remained unchanged comparing both treatments. It can be concluded that r-bST increased milk lactose content, reduced somatic cells count, and changed the profile of blood metabolites of Toggenburg goats.