Aspectos clínicos, comportamentais e metabólicos de vacas e novilhas submetidas ao uso de ocitocina exógena

Abstract

The use of oxytocin (OT) during milking crossbred cows, replacing the calf became common and many properties in the OT is used in virtually all cows "to facilitate milk letdown and increase production" without any criteria technician. Thus, it was evaluated in Experiment 1: behavior, production and metabolic indicators and stress in cows milked twice daily without the presence of the calf, in properties where OT is applied at the beginning and middle of milking all animals. We assessed eight cows in four treatments and eight replications. The treatments were established based on the form of application of the OT in the property (3 mL or 0.3 IU intravenously at the beginning and middle of each milking) and how to control the physiological solution (PS). The milk yield (L) and the residual milk were evaluated every three days. The animals were subjected to visual observation beginning and end of milking to evaluate performance. Blood samples were collected at the beginning and end of each treatment to determine the levels of cortisol, glucose, cholesterol, triglycerides, albumin and urea, and serum activity of AST. As the volume of milk collected using two doses of OT (beginning and middle of milking) was equivalent to OT at the middle of milking. The application of SF in the two periods resulted in lower volume of milk collected. It can be shown that milk production is influenced by exogenous OT with the possibility of addiction. The residual milk was lower in the treatment OT / OT with a significant difference (p ≤ 0.01) compared to SF / SF and OT / SF. Reactivity was observed in the treatment OT / OT and more frequent at the time of application of OT and / or SF, which suggests discomfort and stress associated with this process. Cortisol was elevated in all treatments and no significant difference (p ≥ 0.05), being higher in the treatment with OT / SF and OT / OT. In Experiment 2 we sought to assess weight gain, behavior through the levels of cortisol and metabolic indicators of 12 heifers (½ to ¾ Red Angus x Zebu) in two daily treatments: 20 IU / day, intramuscular (n = 6 ) dosage used for the residual milk, and 2 ml of 0.85% SF intramuscular. The weight gain was low in both groups with no significant difference with or without use of OT. Serum cortisol in both treatments and at all times has been high, however, there was a significant difference between groups at week 4 indicating the modulating effect of OT in the neuroendocrine response to stress Of the biochemical parameters in both experiments, aside from heifers treated with OT that where significant difference from week 3 compared with other levels of cholesterol, other parameters showed no significant difference between treatments. Further studies should be conducted to gain a better understanding of how the OT works on the metabolism of ruminants.