Heritability Estimates of Age at First Calving and Correlation Analysis in Angus Cows Bred in Hungary

This study aimed to examine the age at first calving (AFC) in Hungarian Angus herds. This study was conducted on the basis of data from 2955 registered cows, classified into five groups (based on different Angus types), and 200 breeding bulls, which were the sires of the cows. The data were made available by the Hungarian Hereford, Angus, and Galloway Breeders' Association. The variance and covariance components, heritability, breeding value (BV), and genetic trends of AFC between 1998 and 2021 were evaluated. A general linear model (univariate analysis of variance) was used to examine the various effects, while best linear unbiased prediction was used to estimate the population genetic parameters and BV, and linear regression analysis was used for the trend analysis. The average AFC obtained was 28.1 ± 0.1 months (SD = 5.3 months), showing a relatively large variance (CV = 18.9%). The environmental factors that influenced the development of the phenotype were the cow's birth season (28.99%, p < 0.01), cow's birth year (28.7%, p < 0.01), the cow's sire (18.32%, p < 0.01), and the herd (11.77, p < 0.05). The cow's color variant (8.10%, p > 0.05) was not significant and did not influence the AFC in this study. The direct heritability of AFC (h² = 0.51 ± 0.06) was higher than data in the literature (0.38 ± 0.05); however, the maternal heritability was low (h²_m = 0.00 ± 0.03). The correlation between direct and maternal genetic effects was zero (r_dm = -0.97 ± 1.00). The phenotypic trend of AFC increased by +0.03 months per year, which was not statistically significant. The genetic trend calculation showed no significant changes. Based on the h² and BV results, it seems that selecting a suitable sire can effectively reduce the AFC of daughters. Since AFC is also an important trait in economic terms, it would be appropriate to include AFC BV in the bull catalog.