Beef cattle

Genetic correlations between the probability of calving by 30 months of age and the traits evaluated by the Embrapa Geneplus Program

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Abstract

One of the purposes of a breeding program is to provide breeders with genetic evaluations for traits that are demanded by the producers themselves, helping them to achieve their selection objectives. In this context, the inclusion of the probability of calving by 30 months of age (PC30) trait was proposed for the Nellore breed, considering that, in Brazilian beef cattle production, Nellore cattle are the predominant breed and the average age at first calving is approximately 40 months. The objective was to estimate the genetic correlations between PC30 and the traits evaluated by the Embrapa Geneplus Program. PC30 was calculated for all females with a valid record of weaning weight: females that calved by 30 months of age were assigned as two, while those that did not calve by that age were assigned as one, totaling 24,622 records from over one million animals in the pedigree. The other traits evaluated were: birth weight (BW), weight at 120 days (W120), weaning weight (WW), yearling weight (YW), slaughter conformation at yearling (SCY), ribeye area (REA), backfat thickness (BFT), scrotal circumference (SC), age at first calving (AFC), and stayability (STAY). Variance components were estimated through two-trait analyses using a linear animal model, including fixed effects of contemporary group and covariates, as well as the random effects of the animal's additive genetic effect and, for maternal traits (BW, W120, W240), a maternal genetic and permanent maternal environment effect. The heritability estimate for PC30 was 0.06 ± 0.01. The genetic correlations for PC30 and the direct effect of most of the traits were low or close to zero, particularly for growth traits such as BW (-0.09 ± 0.07), W120 (0.04 ± 0.08), WW (0.04 ± 0.08), and YW (0.04 ± 0.06), indicating null or little genetic association between growth and reproductive precocity. The genetic correlation between PC30 and the maternal effect of BW, W120, and WW was -0.21± 0.08, -0.16 ± 0.07, and -0.20 ± 0.07, respectively. Similarly, low correlations were found with REA (0.06 + 0.08), BFT (0.30 ± 0.10), and SCY (0.27 ± 0.08), suggesting that selection for earlier calving would not have a major impact on carcass traits (REA, BFT, and SCY). In contrast, a high and favorable correlation was observed between PC30 and AFC (-0.95 ± 0.05), as expected. A moderate and favorable correlation was also found with STAY (0.47 ± 0.09), suggesting that females that calve earlier tend to remain productive for a longer period in the herd. Overall, PC30 is a promising indicator of reproductive efficiency, showing independence from growth and carcass traits but a strong and favorable correlation with AFC, which has a heritability estimate of 0.03 ± 0.01. This suggests that PC30 could replace or complement AFC.

Keywords: 2026

How to Cite:

Carvalho Filho, I., Katsuragi, R., Menezes, G. & Toral, F., (2026) “Genetic correlations between the probability of calving by 30 months of age and the traits evaluated by the Embrapa Geneplus Program”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2283884. doi: https://doi.org/10.31274/wcgalp.23532

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