Genetic parameters and relationships of heifer pregnancy and age at first calving with weight gain, yearling and mature weight in Nelore cattle

Abstract

The objectives of the current study were to investigate the additive genetic associations between heifer pregnancy at 16 months of age (HP16) and age at first calving (AFC) with weight gain from birth to weaning (WG), yearling weight (YW) and mature weight (MW), in order to verify the possibility of using the traits measured directly in females as selection criteria for the genetic improvement of sexual precocity in Nelore cattle. (Co)variance components were estimated by Bayesian inference using a linear animal model for AFC, WG, YW and MW and a nonlinear (threshold) animal model for HP16. The posterior means of direct heritability estimates were: 0.45 ± 0.02; 0.10± 0.01; 0.23± 0.02; 0.36± 0.01 and 0.39± 0.04, for HP16, AFC, WG, YW and MW, respectively. Maternal heritability estimate for WG was 0.07 ± 0.01. Genetic correlations estimated between HP16 and WG, YW and MW were 0.19± 0.04; 0.25± 0.06 and 0.14± 0.05, respectively. The genetic correlations of AFC with WG, YW and MW were low to moderate and negative, with values of −0.18± 0.06; −0.22 ± 0.05 and −0.12± 0.05, respectively. The high heritability estimated for HP16 suggests that this trait seem to be a better selection criterion for females sexual precocity than AFC. Long-term selection for animals that are heavier at young ages tends to improve the heifers sexual precocity evaluated by HP16 or AFC. Predicted breeding values for HP16 can be used to select bulls and it can lead to an improvement in sexual precocity. The inclusion of HP16 in a selection index will result in small or no response for females mature weight.

Two-trait random regression model to estimate the genetic association of scrotal circumference with female reproductive performance in Nelore cattle

“…The estimates obtained here were similar to those reported in the literature for Zebu cattle raised in tropical environments. Boligon and Albuquerque [19] and Eler et al [20] estimated heritabilities of 0.10 and 0.18, respectively, for AFC1 in Nelore cattle. Pereira et al [7] and Panetto et al [21] reported estimates of 0.06 and 0.12 for FCI in Nelore and Guzerat cattle, respectively.…”

Age at first calving of Nellore cattle in the semi-arid region of northeastern Brazil using linear, threshold, censored and penalty models

“…One of the reproductive traits that is most easily obtained and routinely registered in most breeding females is age at first calving (AFC) (Malhado et al, 2010;Boligon, Albuquerque, 2011). Moreover, AFC could potentially be analyzed employing a threshold approach.…”

“…Moreover, AFC could potentially be analyzed employing a threshold approach. Usually the trait is analyzed by defining two categories, known as heifer pregnancy (Eler et al, 2004;Boligon, Albuquerque, 2011). However, a study with Nellore cattle argued that the use of polychotomous categories has a higher ability to detect genetic variation than the traditional binary approach (Marcondes et al, 2005).…”

Application of aggregate genotype in beef cattle breeding

“…The estimates from NBBA were compared with values from the literature and found to be consistent (Koots et al, 1994;Eriksson et al, 2003Eriksson et al, , 2004aPhocas & Laloë, 2004;Utrera, 2008). Missing genetic correlations for traits included in the TMI and H were provided from the literature (Koots et al, 1994;Bennett & Gregory, 2001;Boligon & Albuquerque, 2001;Eriksson et al, 2003;Crews et al, 2004;Eriksson et al, 2004aEriksson et al, , 2004bEl-Saied et al, 2006;Gutiérrez et al, 2007;Cervantes et al, 2010). When several estimates for a pair of traits were found in the literature, an average value was used.…”