Efeitos da restrição alimentar e administração de somatotropina recombinante bovina nos parâmetros plasmáticos de novilhas da raça Holandês durante o período pré-parto / Effect of Prepartum Feed Restriction and Bovine Recombinant Somatotropin Injection on Plasmatic Parameters of Prepartum Holstein Heifers
Fourty four heifers with BW = 477.2 ± 7.4 kg at the beginning were used. The experimental period ranged from 35 days prepartum to calving. These heifers were divided in four groups with 11 heifers each bST fed to allow 100% of the DMI plus rbST injections; RbST fed to allow 80% of the DMI plus rbST injections; CON fed to allow 100% of the DMI plus placebo injections and RES fed to allow 80% of the DMI plus placebo injections. The heifers receive three injections of rbST and placebo 14 days apart in the prepartum period. The diets of group bST and CON was according to 100% of requirements and DMI was calculates using the body weight, BCS, age, period of gestation and growth. The serumglucose, NEFA, calcium and phosphorus concentration were analyzed in blood samples through colorimetrymethod. Gamma glutamyltransferase and aspartate aminotransferase activity were measured by spectrophotometer. All statistical analyses were made using softweare SAS. Glucose, NEFA, urea, calcium, phosphorus and relashioship CP, GGT and AST were analyzed through MIXED procedure and the Tukey-Kramer test was applied for comparision means. For the BCS analyzis was applied Kruskal-Wallis test.The BST group had higher plasmatic concentrations of glucose than CON group (P = 0.0011). Similarly urea concentration was lower for BST group (P = 0.0099) during prepartum. The NEFA concentration was higher in REST than CON group (P = 0.0015). We did not find difference between groups for BCS, mineral profile and enzymatic profile.
Discussion:
The feed restriction increased NEFA concentration due to decreased DMI. On the BST group, we observed higher concentrations of glucose when compared with CON group, resembling to the results found by others. In accordance to our results previous studies, no difference concerning urea concentration in prepartum period in cows submitted to feed restriction or mineral profile for cows submitted to feed restriction and bST treatment was found. This strategy will also result in increased lipolysis, causes protein degradation stemmed from muscle tissue in an attempt to maintain the levels of glucose from gluconeogenesis from amino acids. Disagreeing the results described here, others observed higher BCS in cows submitted to ad libitum diet compared with feed restriction cows during prepartum. In this study feed restriction and bST on prepartum period can improve metabolic adaptation, but these two strategies do not act in synergy.