Effect of residual feed intake on fertility-related phenotypes in Nellore (Bos indicus) females

• Grant number: 22/08182-0
• Support Opportunities: Regular Research Grants
• Duration: April 01, 2023 - March 31, 2025
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Fabio Morato Monteiro
• Grantee: Fabio Morato Monteiro
• Host Institution: Instituto de Zootecnia. Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Nova Odessa , SP, Brazil
• Associated researchers: Maria Emilia Franco Oliveira ; Maria Eugênia Zerlotti Mercadante
• Associated scholarship(s): 24/08484-1 - Studies of reproduvtive measures in Nelore heifers, BP.TT; 23/11663-2 - Studies of reproduvtive measures in Nelore heifers, BP.TT

Abstract

The largest investments in beef cattle systems are associated with animal feed. Nutrition is of fundamental importance for the development of animals and has an important productive and economic role in the production animal breeding system. Thus, it is necessary to select animals that consume smaller amounts of food per kilogram of meat produced, and the selection of animals based on feed efficiency is a good alternative. A measure of food efficiency that has been used is the residual feed intake (RFI). However, studies indicate that females with low RFI (more efficient) have a lower amount of body fat when compared to females with high RFI (less efficient), resulting in a decrease in reproductive performance due to the decrease of some circulating hormones. Therefore, the objective of the present study will be to evaluate the reproductive performance of females classified for low and high RFI, in addition to evaluating the effect of selection for feed efficiency on the concentration of reproductive hormones. For this, 250 Nellore females (Bos indicus) with an average age of 14 months will be used, which will be allocated in two years of experiment. RFI of heifers will be estimated through the programs of the BLUPF90 family, based on the combination of genomic and phenotypic information from their ancestors and collaterals. Monthly ultrasound evaluations will be performed for information regarding the following phenotypes: antral follicle count (AFC), ovarian diameter, presence or absence of corpus luteum (CL), uterine pixel intensity and vulvar biometry. Blood collections will be performed by means of puncture of the coccygeal vein of the females contained in the management trunk, in all ultrasound evaluation routines. At the end of each year of the experiment, measurements of subcutaneous fat thickness will be carried out by carcass ultrasound. All low and high RFI females will undergo fixed-time artificial insemination (FTAI) to verify reproductive efficiency. Statistical analyzes will be performed using procedures from the Statistical Analysis System (SAS Inst., Inc., Cary, NC, US). (AU)