Abstract

PALACIOS-ESPINOSA, Alejandro; VERDE, Omar; AVILA-SERRANO, Narciso-Ysac  and  MENENDEZ-BUXADERA, Alberto. Genetic analysis of live weight and pregnancy rate at first calving in Brahman cattle from Venezuela. Rev. mex. de cienc. pecuarias [online]. 2020, vol.11, n.2, pp.576-589.  Epub Oct 23, 2020. ISSN 2448-6698.  https://doi.org/10.22319/rmcp.v11i2.4813.

The live weight (LW) of 2,777 animals (1,377 females and 1,400 males with 53,258 individual data between 30 and 600 days of age), born between February 2000 and June 2011, was analyzed using a random regression (RR) model to estimate the genetic components of (co)variance throughout the age-sex scale. The pregnancy rate (PR) and the LW adjusted to 548 days of age (WA548) were studied using a multitrait (MT) model, an increase in the heritability (h2) estimates for PR compared to the classical univariate model (0.08 ± 0.03 vs. 0.11 ± 0.02) was observed, increasing the accuracy of the genetic value (GV) for PR in 15.7 %. The genetic correlation (rg) between the PR and the WA548 was 0.31 ± 0.11. The RR showed that, through time, the LW could not be considered as an expression of the same trait in both sexes, as the rg were less than 0.60. The principal component analysis showed that there are important changes in the animal growth on the age scale represented in these data. A prominent dimorphism of genetic origin manifested, estimated as the difference between the male and female GVs in LW, which shows a positive relationship with the GVs of PR.

Keywords : Heritability; Genetic correlations; Multitrait model; Random regression model; Sexual dimorphism.