Genotype-environment interaction for milk production of Gyr cattle in Brazil and Colombia.

BACKGROUND: Genotype by environment interactions (G × E) can play an important role in cattle populations and should be included in breeding programs in order to select the best animals for different environments. OBJECTIVE: The aim of this study was to investigate the G × E for milk production of Gyr cattle in Brazil and Colombia by applying a reaction norm model used genomics information, and to identify genomic regions associated with milk production in the two countries. METHODS: The Brazilian and Colombian database included 464 animals (273 cows and 33 sires from Brazil and 158 cows from Colombia) and 27,505 SNPs. A two-trait animal model was used for milk yield adjusted to 305 days in Brazil and Colombia as a function of country of origin, which included genomic information obtained with a single-step genomic reaction norm model. The GIBBS3F90 and POSTGSf90 programs were used. RESULTS: The results obtained indicate G × E based on the reranking of bulls between Brazil and Colombia, demonstrating environmental differences between the two countries. The findings highlight the importance of considering the environment when choosing breeding animals in order to ensure the adequate performance of their progeny. Within this context, the reranking of bulls and the different SNPs associated with milk production in the two countries suggest that G × E is an important effect that should be included in the genetic evaluation of Dairy Gyr cattle in Brazil and Colombia. CONCLUSION: The Gyr breeding program can be optimized by choosing a selection environment that will allow maximum genetic progress in milk production in different environments within and between countries.

Analysis of the Pedigree and Ancestors of the Cutting Population of the Quarter Horse Breed.

The aim of this study was to evaluate the genetic diversity and to identify the most influential ancestors in the population of Brazilian Quarter Horses participating in cutting competitions. Data from 1,590 elite horses born between 1970 and 2015, which participated in cutting competitions between 1981 and 2018, were evaluated based on the pedigree file that contained 5,832 animals born since 1834. Evaluation of the quality of the pedigree data showed a mean number of known equivalent generations of 5.4 ± 1.5 and a mean generation interval of 11.7 ± 8.8 years. The inbreeding coefficient (1.98 ± 7.13%), relatedness coefficient (2.18 ± 0.01%), and individual increase in inbreeding (0.43 ± 0.01%) were low. The effective population size (Ne) was 136 animals. The probability of gene origin indicated effective numbers of founders, ancestors, and founder genomes of 255, 37, and 23 animals, respectively. The number of founders and ancestors was 1,852 and 899 animals, respectively, with 10, 50, and 100 ancestors explaining 39.2%, 67.9%, and 91.6%, respectively, of the genetic diversity of the population. The five most influential ancestors were Doc Bar, Peppy San Badger, Freckles Playboy, Poco Lena, and High Brow Cat, accumulating 30.7% of the marginal genetic contributions of the population. Few ancestors were responsible for the genetic diversity, resulting in the narrowing of the initial genetic base. Breeders depend on a small group of ancestors, which could be corrected by increasing the number of breeding animals and by directed mating using ancestors of different origins.

Estimation of (co)variance components for birth weight in Nellore cattle using alternative data editing criteria.

The aim of this study was to estimate the (co)variance components and breeding values for birthweight (BW) in Nellore cattle by considering or not identical weights that exhibit a high frequency within the contemporary group (CG). A total of 175,258 BW records of Nellore cattle born between 2002 and 2018 were used. The CG was formed by farm, year of birth, sex and feeding regime at birth. CGs with more than 16% of identical BW values were eliminated, generating a data file called BWd. Another file was created without removing these animals (BWt). A mixed linear model was used for statistical analysis, which included fixed and random effects. In both data files analysed, single-trait analysis was performed by Bayesian inference. The mean direct and maternal heritability for BW and the correlation between direct and maternal effects were 0.27, 0.07 and -0.07 for BWt, respectively, and 0.30, 0.093 and -0.07 for BWd. This method should affect the estimation of genetic merits of animals for BW, providing greater safety in the choice of sires.

Genome-wide identification of runs of homozygosity islands in the Gyr breed (Bos indicus).

Runs of homozygosity (ROH) are contiguous homozygous regions of the genome. These regions can be used to identify genes associated with traits of economic interest, as well as inbreeding levels. The aim of the present study was to analyse the length and distribution of ROH islands in Gyr cattle and to identify genes within these regions. A population of 173 animals selected for beef production and a population of 291 animals selected for dairy production were used. Differences in the number of short ROH (ROH1-2 Mb ) were observed between the two populations, while the number of long ROH (ROH>16 Mb ) was similar. ROH islands with the highest incidences (>0.50) overlapped in several segments of the genome in the two populations. The genes identified were associated with milk production, growth, reproduction, immune response and resistance traits. Our results contribute to the understanding of how selection can shape the distribution of ROH and ROH islands within the same breed when animals are selected for different purposes such as dairy or beef production.