R. R. Aspilcueta-Borquis

Polymorphism in the A2M gene associated with high-quality milk in Murrah buffaloes (Bubalus bubalis)

The study of genes associated with host defense mechanisms, such as the A2M gene, plays a critical role in preventing diseases that reduce milk yield and its constituents. The aim of this study was to identify polymorphisms in the A2M gene in Murrah buffaloes (Bubalus bubalis), and investigate their associations with milk yield, fat and protein production, fat and protein percentages, and somatic cell count. Hair follicle samples of 136 animals were collected for DNA extraction, and polymorphisms were identified by polymerase chain reactions and sequencing. Statistical analyses were performed to ascertain the allelic and genotypic frequencies, the Hardy-Weinberg equilibrium, and association analysis was conducted between the polymorphisms and the traits studied. Comparative analysis between buffalo and bovine sequences revealed seven nucleotide substitutions. Alignments among the buffalo sequences identified three single nucleotide polymorphisms (SNPs), including one in exon 29, g.241A>G, which was used in subsequent statistical analyses. A Hardy-Weinberg test indicated that this SNP was in equilibrium in this population, and was significantly associated (P < 0.05) with fat production and fat and protein percentages. Therefore, this SNP can be used as a molecular marker for these traits.

Study of the effect of genotype–environment interaction on age at first calving and production traits in Nellore cattle using multi‐trait reaction norms and Bayesian inference

This study investigated the effects of genotype-environment interaction on yearling weight, age at first calving and post-weaning weight gain in Nellore cattle using multi-trait reaction norm models. The environmental gradient was defined as a function of the mean yearling weight of the contemporary groups. A first-order random regression sire model with four classes of residual variance was used in the analyses and Bayesian methods were applied to estimate the (co)variance components. The heritability estimates ranged from 0.284 to 0.547, 0.222 to 0.316 and 0.256 to 0.522 for yearling weight, age at first calving and post-weaning weight gain, respectively. The lowest genetic correlations between environment groups for each trait were 0.38, 0.02 and 0.04 for yearling weight, age at first calving and post-weaning weight gain, respectively. Differences in the correlation estimates were observed between traits in the same environments, with the magnitude of the estimates tending toward zero as the environment improved. The results highlight the importance of including genotype-environment interactions in genetic evaluation programs considering the differences observed between environmental groups not only in terms of heritability, but also of genetic correlations.