Efeito da suplementação de Cobre e Zinco de alta biodisponibilidade sobre novilhas nelore precoce e de seus respectivos embriões em receptoras nas condições amazônicas

Abstract

The present thesis aimed to evaluate the effects of copper (Cu) and zinc (Zn) supplementation in the form of hydroxy trace minerals on the mineral status and reproductive performance of donor heifers and recipient cows. Chapter I presents a literature review addressing reproductive efficiency and sexual precocity in Nellore heifers, as well as trace mineral supplementation and its effects on reproduction. In Chapter II, the effects of Cu and Zn supplementation, in the form of hydroxy trace minerals, were evaluated on oocyte and embryo production, mineral status, and reproductive performance of donor heifers and embryo recipient females. In addition, the influence of sexual precocity and physiological variables on pregnancy probability was investigated. Supplementation with hydroxy trace minerals did not affect pregnancy rate or early and late embryonic losses in either donors or recipients. However, donor precocity significantly influenced fertility outcomes: embryos derived from late-maturing heifers showed higher pregnancy rates (44%) than those from early-maturing heifers (23%) (P = 0.01). Serum copper concentrations decreased throughout the breeding season across all treatments (P < 0.0001). A positive association was observed between serum zinc concentration and body condition score in recipient females (P = 0.04). These findings suggest that the benefits of hydroxy trace mineral supplementation may be more evident under conditions of mineral deficiency or greater nutritional challenge. In Chapter III, the effects of Cu and Zn supplementation, in the form of hydroxy trace minerals, were evaluated on productive performance, mineral status, reproductive characteristics, and pregnancy rate of bovine females. Additionally, the relationships among these variables were investigated using multivariate analyses and logistic regression models. Hydroxy trace mineral supplementation increased serum Zn concentration (P = 0.0183) and reduced plasma Cu concentration (P = 0.0132), indicating changes in mineral metabolism. However, no improvements were observed in body weight, body condition score, average daily gain, or reproductive variables (P > 0.05). Logistic regression and principal component analyses confirmed the absence of associations between mineral concentrations, productive parameters, and pregnancy probability. Under adequate management and nutritional conditions, hydroxy trace minerals did not improve reproductive efficiency.