Body Temperature and Reproductive Performance of Beef Heifers Supplemented With Rumen-Protected Methionine

José Henrique Dominguez,Eduardo Schmitt,Cássio Cassal Brauner,Marcio Nunes Corrêa,Francisco Augusto Burkert Del Pino,Ederson Dos Santos,Fernanda Lopes,Fabrício Amadori Machado,Josiane De Oliveira Feijó,Viviane Rohrig Rabassa,Matheus Gomes Lopes

doi:10.5296/jas.v8i3.16793

Abstract

This study aimed to assess the reproductive performance and body temperature of beef heifers supplemented with rumen-protected methionine (RPM) in an extensive grazing system and mated during the summer. One hundred 5/8 Angus 3/8 Brahman heifers were homogeneously divided into the control group (n=48, CG) supplemented with mineral salt ad libitum and methionine group (n=52, MG) who received the same supplementation plus 4 g of methionine per 100 g of mineral salt. The groups were fixed-time artificial inseminated (FTAI) 45 days after starting the supplementation. On day 0 of the FTAI protocol, ten animals per group received data-logger thermometers attached in progesterone implants recording the body temperature of the animals every 30 minutes. Pregnancy diagnosis was performed on days 30 and 60 after the artificial insemination to determine the rates of conception, pregnancy, and pregnancy loss. At the beginning of the supplementation, both groups had similar weights (MG was 304.6 kg and CG 304.4 kg), while on days 0 and 30 about the FTAI protocol, the MG was higher weight (365.9 vs. 346.7 and 384.8 vs. 371.5 Kg). During the FTAI protocol, the MG had lower body temperatures (38.77 vs. 38.99 °C) and a tendency to have larger dominant follicles than the CG (11.76 mm x 10.8 mm). Although it did not impact reproductive performance, the observed higher weight, dominant follicle sizes, and lower body temperatures during FTAI protocols show the potential benefits of methionine supplementation in beef heifers mated during the summer.

Highlights

The major meat and milk producing regions of the world are found in tropical and subtropical climates characterized by large thermal amplitudes, which is a constant challenge for the thermoregulation of the animals to increase productivity
The results are presented as means ±standard error of the mean. The animals of both treatments had been daily mineral supplement intake corresponding to 100 g/animal/day of the mixture, which correspond that the Methionine Group (MG) had a consumption of 4g of methionine/day, and it is the only difference in the mineral supplementation
Forage availability for the MG and Control Group (CG) pickets was 710, 780, and 695; and 916, 832, and 780 kg dry matter (DM)/ha, respectively, for samples collected on D-45, day 0 (D0) and D60 of the experiment

Summary

Introduction

The major meat and milk producing regions of the world are found in tropical and subtropical climates characterized by large thermal amplitudes, which is a constant challenge for the thermoregulation of the animals to increase productivity. Heat stress can have direct effects on tissues, and can indirectly cause systemic alterations due to a reduced feed intake, which affects several metabolic processes that lead to decreases in production and performance (Baumgard et al, 2014). The circulating concentrations of non-esterified fatty acids (NEFA) are lower during heat stress, even with high levels of stress hormones, such as epinephrine, glucagon, and cortisol, which are potent lipolytic agents (Zhao et al, 2018). Pathways such as proteolysis are prioritized for energy production, an observation that continues to generate discussions on the mechanisms controlling nutrient partitioning during stress (Rhoads et al, 2009; Baumgard et al, 2013)

Objectives

Methods

Results

Conclusion