Effect of Cu and Zn supplementation with high bioavailability on the reproductive performance of precocious Nellore heifers and their respective embryos in F1 heifers (Nellore x Angus) in Amazonian conditions

Abstract

This project aims to strengthen research ties between the States of Amazonas and São Paulo in the beef cattle production. Thus, the objectives of this project are: 1) To assess whether yearling Nellore heifers that were induced to puberty by hormonal protocol have the same reproductive performance compared to heifers that reached puberty spontaneously. 2) Assess whether trace minerals (Cu, Zn and Mn) supplementation with high bioavailability can increase the reproductive performance of yearling Nellore heifers and F1 (Nelore x Angus) embryo recipients. For this, 2 experiments will be carried out, Exp. I will be carried out in the State of São Paulo (ESALQ / USP) and Exp. II in the State of Amazonas (ICSEZ / UFAM). In Exp. I, 220 Nellore heifers with 8 months of age will be allocated in 4 treatments arranged in a 2 x 2 factorial scheme, in which the nutritional factor consists of the use of Cu, Zn and Mn of high bioavailability (hydroximinerals) or conventional mineralization (sulfates) in the diet of prepubertal heifers. The reproductive factor consists of heifers induced to puberty via hormonal protocol or heifers that reach puberty spontaneously. At 15 months of age, heifers will be separated into pubertal and non-pubertal heifers. Heifers with a corpus luteum (CL) on 2 ultrasound (US) with 7 days apart will be considered spontaneously pubertal. Heifers without CL at 15 months of age will be submitted to a hormonal protocol for ovulation induction, and will be considered as heifers induced to puberty. After this stage, all heifers will be inseminated using the standard IATF protocol. After AI, the pregnancy rate will be evaluated at 20, 30 and 60 days after AI, to estimate embryonic losses and the final pregnancy rate. In Exp. II, twenty-eight heifers from Exp. I, 7 from each treatment, will accessed to Ovum pick up (OPU) on the day of removal of P4 in the TAI protocol of Exp. I for the production of 300 embryos in vitro. Two hundred F1 heifers (Angus x Nellore) with about 300 kg of body weight will be used as embryo recipients at 15 months of age. The recipients will be maintained in 8 paddocks (4 for each treatment) with native grass from the low Amazon lowland regions, with half of the recipients being supplemented with hydroximinerals and the other half will receive only conventional mineralization (sulfates). The recipients will receive the embryos by TETF, and the pregnancy rate will be determined at 20, 30 and 60 days of pregnancy, in the same way as in Exp. I. Exp. II, aims to answer a scientific question, but with great practical and economic impact: heifers and / or embryos of heifers said to be precocious (induced by hormonal protocol at puberty) have good pregnancy results. And, the supplementation of high bioavailability micro minerals can increase the pregnancy rate of heifers and / or embryo recipients. These responses have great appeal in livestock in both States, as well as nationally. These projects can help to develop livestock in the State of Amazonas, which is still very low-tech and of low productivity. The intensification of the beef cattle production chain leads to economic development and better quality of life in the countryside, in addition to generating employment and income, keeping the man in the countryside. (AU)