Phenotypic and genetic parameters for repeated measures of Longissimus muscle area and subcutaneous fat thickness in Nelore cattle

• Grant number: 11/09152-2
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: June 01, 2011
• End date: November 30, 2011
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Genetics and Improvement of Domestic Animals
• Principal Investigator: Joslaine Noely dos Santos Goncalves Cyrillo
• Grantee: Joslaine Noely dos Santos Goncalves Cyrillo
• Host Institution: Instituto de Zootecnia. Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Nova Odessa , SP, Brazil

Abstract

Real-time ultrasound is currently used for the collection of in vivo data of traits that are important for carcass evaluation in beef cattle. The objective of this study was to estimate heritability and repeatability coefficients for ultrasound-measured carcass traits in Nelore cattle. The following traits were measured by ultrasound in male and female animals ranging in age from 10 to 26 months: Longissimus muscle area (LMA), backfat thickness (BF), and rump fat thickness (RF). The variance components were estimated by single-trait analysis using the derivative-free restricted maximum likelihood method under an animal model. The complete data file contained 3,077 records of 1,172 animals born between 2003 and 2008. Two analyses were performed using a repeatability model: a) all records of LMA, BF and RF of animals aged 10 to 26 months, and b) considering two distinct periods (11 to 17 and 18 to 24 months of age). The heritability estimates ranged from 0.35 to 0.65 for LMA, from 0.20 to 0.39 for BF, and from 0.22 to 0.43 for RF, demonstrating that direct selection for these traits will result in genetic gain. The repeatability estimates were moderate, ranging from 0.42 to 0.73. The highest repeatability estimates were obtained for LMA in both the first (0.70) and second (0.73) analysis. The repeatability estimates suggest that ultrasound measures are precise, but higher precision is obtained for LMA when compared to the measures of subcutaneous fat thickness. The latter should be obtained during periods of greater feed availability to increase their precision. (AU)