Estratégias nutracêuticas no período de transição em bovinos leiteiros e seus efeitos sobre parâmetros metabólicos e fertilidade

Abstract

The negative energy balance (NEB) is associated with changes in the fertility of dairy cows, therefore different nutritional and pharmacological strategies are being used to minimize the negative effects of the NEB in order to increase fertility. Pre-partum recombinant bovine somatotropin (rbST) administration can lead to a reduction in serum non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA) in the postpartum period, in addition to improving postpartum ovarian follicular development. Similarly nutritional strategies during the pre and postpartum period have a positive impact on health, productivity and fertility of dairy cows. Recent studies show that the use of amino acids in the diet during the transition period may have beneficial effects in metabolism. Faced with this problem, this thesis presents three papers whosethe objectives were: 1) Determine the effect of pre-partum administration of somatotropin in dairy heifers on the markers of NEB, resumption of ovarian activity and milk production. 2) Determine the effect of methionine, choline supplementation isolated and in combination on esteroidogenic potential of the fist postpartum dominant follicle. 3) Determine the effect of methionine, choline supplementation isolated and in combination on embryo development and global DNA methylation. Pre-partum somatotropin treatment in dairy heifers increased intrafollicular IGF-I and mRNA expression of LH receptor and steroidogenic acute regulatory protein in follicular cells of the first postpartum dominant follicle. These changes were associated to increased intrafollicular and serum estradiol concentration, which can potentially increase the chance of ovulation of the first postpartum follicular wave. Despite that, somatotropin did not affect other metabolic and productive parameters in the early postpartum period. Supplementing methionine, choline or both during the transition period seemed to have no effect on postpartum follicular development of the first postpartum wave in Holstein cows. However, supplementing methionine, during the transition period increased follicular cells 3β-HSD expression, methionine and choline supplementation also induced a down regulation of pro-inflammatory genes, indicating a lower inflammatory processes in follicular cells. Regarding to embryo development, supplementation of methionine, only during the transition period reduce global DNA methylation, moreover, supplemented methionine increase lipid accumulation in preimplantation embryos. The use of nutraceutical strategies during the transition period increased the steroidogenic potential of the first postpartum dominant follicle and increase the expression of genes related steroidogenesis also a down regulation of proinflammatory genes indicating beneficial effects on fertility in dairy cattle. Moreover, the methionine supplementation seems to impact the preimplantation embryo in a way that enhances its capacity for survival since there is strong evidence that endogenous lipid reserves serve as an energy substrate.