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.

Physiological responses and animal behavior in Bonsmara-Hereford crosses vs. Hereford purebred on environment stress

Adaptative traits (rectal temperature-RT, respiratory rate-RR) and grazing behavior (Grazing, Ruminating and Rest time, and Sun or Shade time) of Bonsmara-Hereford crossbred-BH, n = 15, and purebred Hereford-HH, n = 18, yearling heifers, in a grazing system of Uruguay. Environment characterization was made using THIadjusted by radiation and wind speed (no, mild, and severe heat weaves), and the comprehensive climatic index-CCI (no, middle, moderate and severe stress). Adaptative traits were measured twice a day, weekly, in two consecutive days in summer and winter at 08h00 and 16h00. Grazing behavior was observed from 07h00 to 21h00 each 600 s twice in summer. The records were analyzed using a mixed model. Significant effect of genotype was observed in mild heat waves for RR and RT in the afternoon (BH lower than HH). For CCI in a.m., the RR was lower than HH in BH in severe stress, while in p.m., the RR was lower in all of CCI levels. RT in p.m. in moderate and severe was lower in BH than in HH. In winter, no differences were found. In grazing behavior, HH rests longer than BH doe; also, HH spends more time in the shade (34 %) than BH does (22 %). BH genotype showed better thermoregulation and grazing behavior at higher temperatures compared to HH.(AU)

Fatores genéticos e ambientais sobre a probabilidade de prenhez precoce em bovinos Caracu / Genetic and environment factors on probability of early pregnancy of Caracu cattle

Em bovinos, critérios de seleção, associados à precocidade sexual, vêm sendo atualmente pesquisados para a sua inclusão em programas de seleção, visando à diminuição da idade de entrada dos animais em reprodução, com conseqüências positivas sobre a receita do rebanho. O objetivo deste trabalho foi estimar a herdabilidade da probabilidade de prenhez precoce (PPP) de fêmeas Caracu, característica associada à puberdade e que pode ser considerada como indicadora do início da atividade reprodutiva, usando para isso, um arquivo com 5.273 observações. A significância dos efeitos da produção de leite da mãe na primeira lactação, da idade da mãe ao parto e da idade à desmama das novilhas sobre a PPP, foi analisada por meio do procedimento logístico de regressão. Empregou-se a análise Bayesiana para a estimação de herdabilidade da PPP mediante um modelo de touro, onde foram incluídos os efeitos de grupo de contemporâneos, produção de leite na primeira lactação, touro e resíduo. A média a posteriori da herdabilidade da PPP foi de 0,13, que, embora baixa, evidenciou a presença de ação gênica aditiva na determinação desta característica, o que possibilitaria a obtenção de progresso genético na mesma.

Selection criteria associated to sexual precocity have increased their importance and in order to reduce the age at first calving they have been including in selection programs with positive consequences to the profit of the herds. The present study estimated the heritability for probability of early pregnancy (PPP), a trait associated with puberty, that could be considered as indicative of the beginning of the reproductive activity in females, using records on 5273 females. In order to verify the significance of the effects of milk yield in first lactation, age at calving of the dam and weaning age of the heifer on PPP logistic regression was applied. Heritability for PPP was estimated by Bayesian method, using a sire model. This model included the effects of contemporary group, milk yield in first lactation (in classes), sire and residual. The "posteriori" mean of heritability was 0.13. This value, although not high, showed the presence of genetic additive action on the determination of this trait.

Genetic and environment factors on probability of early pregnancy of Caracu cattle / Fatores genéticos e ambientais sobre a probabilidade de prenhez precoce em bovinos Caracu

Selection criteria associated to sexual precocity have increased their importance and in order to reduce the age at first calving they have been including in selection programs with positive consequences to the profit of the herds. The present study estimated the heritability for probability of early pregnancy (PPP), a trait associated with puberty, that could be considered as indicative of the beginning of the reproductive activity in females, using records on 5273 females. In order to verify the significance of the effects of milk yield in first lactation, age at calving of the dam and weaning age of the heifer on PPP logistic regression was applied. Heritability for PPP was estimated by Bayesian method, using a sire model. This model included the effects of contemporary group, milk yield in first lactation (in classes), sire and residual. The "posteriori" mean of heritability was 0.13. This value, although not high, showed the presence of genetic additive action on the determination of this trait.(AU)

Em bovinos, critérios de seleção, associados à precocidade sexual, vêm sendo atualmente pesquisados para a sua inclusão em programas de seleção, visando à diminuição da idade de entrada dos animais em reprodução, com conseqüências positivas sobre a receita do rebanho. O objetivo deste trabalho foi estimar a herdabilidade da probabilidade de prenhez precoce (PPP) de fêmeas Caracu, característica associada à puberdade e que pode ser considerada como indicadora do início da atividade reprodutiva, usando para isso, um arquivo com 5.273 observações. A significância dos efeitos da produção de leite da mãe na primeira lactação, da idade da mãe ao parto e da idade à desmama das novilhas sobre a PPP, foi analisada por meio do procedimento logístico de regressão. Empregou-se a análise Bayesiana para a estimação de herdabilidade da PPP mediante um modelo de touro, onde foram incluídos os efeitos de grupo de contemporâneos, produção de leite na primeira lactação, touro e resíduo. A média a posteriori da herdabilidade da PPP foi de 0,13, que, embora baixa, evidenciou a presença de ação gênica aditiva na determinação desta característica, o que possibilitaria a obtenção de progresso genético na mesma.(AU)