Administração da somatotropina bovina sintética (rbST) sobre a produção e composição do leite, perfil metabólico e hemograma de vacas leiteiras em período de transição

Abstract

Somatotropin (ST) or growth hormone (GH) is a protein hormone produced and secreted by the anterior pituitary, located in the upper brains of the animals, provides significant increases in milk production, increased productive efficiency of dairy cows and consequently greater economic returns, without adverse effects on animal and human health. Transition period corresponds to the first three weeks before birth and three weeks postpartum. The objective of this study was to evaluate the administration of somatotropin (rbST) on milk composition, blood count and metabolic profile of dairy cows in the transition period. A total of 24 Girolando cows with different ages, body scores and average weight of 490 kg were used. The animals were randomly allocated as they reached -21 days relative to delivery to +28 days postpartum. Females were separated into two groups: Control Group: (without application of somatotropin); Test Group: half-dose of rBST (equivalent to 250 mg of recombinant bovine somatotropin), 12 animals per treatment and control was done weekly. The rbST was applied subcutaneously in the right ischioretal fossa at a dose of 250mg (Boostin®, Coopers do Brasil). The experimental period was 90 days. Diets were formulated according to the NRC 2001 software for pre and postpartum. Milk samples were collected on the first and second milking of the day during the controls. Milk quality assessments included protein, fat and lactose analyzes that were performed electronically by infrared absorption on Benthy 2000® equipment. The blood was collected weekly, a coccygeal vein or jugular vein in empty tubes of 5 mL containing EDTA, for the complete blood and biochemical processing (glucose, urea, total cholesterol, HDL cholesterol, LDL, VLDL, triglycerides, total protein, albumin, calcium, betahydroxybutyrate and non esterified fatty acid). For analysis of blood metabolites, 10mL samples were collected from the coccygeal vein or jugular vein in evacuated tubes, always before feeding in the morning. The results were analyzed according to a completely randomized design, with two treatments and twelve replicates. The results were submitted to covariance analysis whose main treatment was the application of somatotropin. Statistical analyzes were analyzed using a SAS computational package. Animals treated with somatotropin presented an increasing linear trend (P <0.05) for milk production (24.90 vs. 22.52 kg day1) and fat content (3.78 vs. 3.41%) compared to group control. The effect of time was observed (P <0.05) for milk production (kg / day), protein and lactose (kg / day) and fat content (%). No effects of rbST on prepartum were observed for the concentration of metabolites. Cows receiving rbST did not present higher concentrations of glucose and total cholesterol at calving. Somatotropin (rbST) decreased total calcium and ionic calcium concentrations at calving. Cows receiving rbST treatment showed higher postnatal glucose concentration. Time effect was observed for the total protein concentration and an interaction effect of rbST was obtained by time for ionic calcium concentration. Cows that received somatotropin in prepartum had lower neutrophils compared to the control group. Time effect was observed for leukocytes (μL), neutrophils (μL and%), lymphocytes (%) and neutrophils / lymphocytes ratio in prepartum. The effect of the interaction was not observed for the prepartum blood count parameters. The effect of time was observed postpartum only for the leukocyte (μL). There was no postpartum interaction effect for neutrophils (μL and%) and lymphocytes (μL and%). The use of rBST for dairy cows in the transitional period increased milk production. The rBST positively influenced the blood metabolites and had no effect on the blood count.