Genetic parameters of age at first calving, weight gain, and visual scores in Nelore heifers

Abstract

This study aimed at estimating the heritability of age at first calving and of performance traits included in the selection index and the genetic correlations between age at first calving and these performance traits. Data were extracted from the Conexão Delta G database and only data from herds in which heifers were bred younger than 24 months of age were used, resulting in a file with 331,310 evaluated animals. The following traits were included in the analyses: age at first calving, birth to weaning gain, post-weaning weight gain, visual scores of conformation, precocity, and muscling evaluated at weaning and in yearling heifers. Covariance components were obtained by bi-character analyses between traits. An alternative age at first calving was also taken into account, in which all heifers were used, including those that were mated and did not calve. Covariance components and estimates of the effects included in the model were obtained using the software program DMU. Heritability estimates were 0.11 and 0.13 for age at first calving and alternative age at first calving, 0.38 for birth to weaning gain, and 0.13 for post-weaning weight gain. Visual score estimates ranged between 0.16 and 0.18 at weaning and 0.19 and 0.29 in yearlings. Genetic correlation estimates of the traits were low, but in the desirable direction. Selection for birth to weaning gain and visual scores does not have a negative effect on age at first calving or alternative age at first calving.

Genetic Parameters for Age at First Calving and First Calving Interval of Beef Cattle

“…The authors confirmed the high statistical significance and proportion of explained variability by this effect. AFC expression also strongly depends on the breeding season when the heifer was born and mated [ 14 ]. In contrast, a low proportion of explained variability was published by Szábo et al [ 15 ].…”

“…Before conception, heifers must be sexually mature with regular heats and reach optimal body conformation, condition, and weight [ 24 ]. However, the higher nutritional requirement (due to selection on carcass traits and larger-sized animals) can negatively affect the reproductive performance of females kept on pasture [ 14 ].…”

Genetic study of quantitative traits supports the use of Guzerá as dual-purpose cattle

“…In Brazilian beef cattle, the most commonly used trait as an indicator of fertility and sexual precocity is the scrotal perimeter (SP), which is easy to measure and exhibits a positive genetic correlation with testicular biometry traits (e.g., length, width, and testicular volume), sperm motility and mass activity and a negative genetic correlation with major and total sperm defects [7]. Additionally, age at first calving (AFC) is highly correlated with fertility and reproductive efficiency in both beef and dairy cattle, thus affecting heifer precocity [8,9]. The AFC exhibits heritability of moderate magnitude, approximately 0.20, and favorable (i.e., negative) genetic correlation with milk yield and growth traits in Guzerá cattle [10].…”

Effect of age at first conception as selection criteria on growth and carcass traits in Nellore cattle

“…Therefore, determining the heritability estimates of BW might boost economic productivity by improving growth traits and limiting the associated birth weight problems (Hohnholz et The moderate values for AFCo and AFCa heritabilities indicated that these traits would respond to the selection. Thus, due to the economic importance of sexual precocity-indicator traits for the beef production system and the genetic differences between individuals, the selection can be an effective tool to obtain genetic changes in the herd, thus reducing AFCo and AFCa (Claus et al 2017).…”