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The objective was to identify the best multi-breed model for the genetic evaluation of test-day milk yield (TDMY) in a Girolando population. The observations were measured from 2000 to 2014, totaling 122,507 observations of 13,544 first-lactation cows and a complete kinship matrix of 66,384 animals. Four different methodologies were evaluated: homoscedastic or heteroscedastic multi-breed model with Gaussian destruction (MAM-G-Ho or MAM-G-He) and homoscedastic or heteroscedastic multi-breed model with Student's t-distribution (MAM-T-Ho or MAM-T-He). The criteria for choosing the best model were the deviance information criterion (DIC), deviance based on the Conditional Predictive Ordinate (DCPO), and deviance based on the Bayes factors (DBF). According to the selection criteria, the MAM-T-He presented the lowest values of DIC, DCPO, and DBF, indicating a better quality of fit for the population in question. Heritability estimates were of medium magnitude for TDMY, varying from 0.27±0.02 to 0.39±0.03 in the different models. Spearman's correlations based on estimated breeding values used to compare the ranking of animals between Student's t and Gaussian models were low (0.63 to 0.72) when considering all sires or when considering 10, 20, or 30% of the best sires. These results support the implementation of robust models that account for sources of heteroscedasticity to increase the accuracy of genetic evaluations in the multi-breed population of the Girolando breed.

We evaluate genotype × environment (G × E) interactions for age at first calving (AFC) and calving interval (CI) of Nellore cattle in northeastern Brazil using four hierarchical reaction norm models (HRNMs). The best-fit model for the traits was the one step heteroscedastic hierarchical reaction norm model. Heritability was close to zero in the worst environments and increased as the environments improved (from 0.06 to 0.12 for AFC and from 0.01 to 0.03 for CI). The correlations between the intercept and the slope of the reaction norms for CI and AFC were from medium to high magnitude (0.75 ± 0.10 and 0.90 ± 0.04, respectively), indicating that animals with higher average breeding values had the greatest responses to the improvement of environmental conditions. The variation in heritability indicates different response to selection according to the environment in which the animals of the population are evaluated. The G × E was evident in bulls with more female offspring. In conclusion, our data demonstrate that selection for AFC in medium- and high-level environments leads to higher genetic gains.

Made available in DSpace on 2018-11-12T17:25:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-07-01. Added 1 bitstream(s) on 2021-07-14T17:50:15Z : No. of bitstreams: 1 S0100-204X2015000700615.pdf: 529779 bytes, checksum: 681efc3c925914a355208611f6e530cf (MD5) Resumo: O objetivo deste trabalho foi verificar a presença da interação genótipos x ambientes (GxA) para peso aos 365 dias de idade, em bubalinos da raça Mediterrâneo, com o uso de modelos de normas de reação via regressão aleatória. O modelo animal padrão e os modelos de normas de reação foram testados, tendo-se avaliado o modelo hierárquico norma de reação (MNR) com um e com dois passos. O modelo hierárquico homocedástico de norma de reação com um passo (MHNRHO1P) apresentou o melhor ajuste, com base em três critérios de comparação. As estimativas de herdabilidade direta para esse modelo variaram de 0,19 a 0,78, conforme a melhoria do ambiente. Além disso, houve mudança dos valores genéticos diretos (efeito escala) de alguns reprodutores, o que indica a existência de interação GxA. As correlações de Spearman foram altas, tanto na comparação do modelo animal padrão com os MNR, como na comparação entre os níveis de baixa, média e alta qualidade no MHNRHO1p. Portanto, embora haja interação GxA, a classificação dos reprodutores não é significativamente afetada pelos modelos. A maioria dos bubalinos é formada por animais de genótipo robusto, que são menos sensíveis a mudanças ambientais. Abstract: The objective of this work was to verify the presence of the genotypes x environments interaction (GxE) for weight at 365 days of age in the Mediterranean breed of buffaloes, using models of reaction norms through random regression. The standard animal model and the models of reaction norms were tested, and the hierarchical model reaction norm (MRN) was evaluated with one and two steps. The homoscedastic hierarchical model of reaction norms with one-step (HMRNHO1s) had the best fit, based on three criteria for comparison. The direct heritability estimates for this model ranged from 0.19 to 0.78, with environment improvement. Besides, direct breeding values (scale effect) changed for some breeders, which indicates the existence of GxE interaction. The Spearman correlations were high, both in the comparison between the standard animal model and MRN, as in the comparison between low, medium, and high management levels in HMRNHO1s. Therefore, although there is GxE interaction, the ranking of breeding animals is not significantly affected by the models. The majority of buffaloes is formed by animals with robust genotypes, which are less sensitive to environmental changes. Instituto Federal do Norte de Minas Gerais Universidade Estadual Sudoeste da Bahia Departamento de Ciências Biológicas Universidade Estadual Paulista Departamento de Produção Animal Universidade Estadual Paulista Departamento de Produção Animal

Made available in DSpace on 2020-12-10T17:02:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The research aim was to evaluate the genotype-environment interactions (GxE) through a study of the reaction norms of Nellore cattle raised in the North and Northeast regions of Brazil at the age at first calving (AFC), with scrotal circumference at 365 and 450 days of age (SC365 and SC450), gestation length (GL) and accumulated productivity (ACP). Bayes hierarchical models with defined parameters at structured levels or stages were used. The Markov chain Monte Carlo method was used to obtain genetic parameter estimates. The environmental gradient of each trait was defined using a 99% credibility interval of the contemporary group's solutions. The animal model showed a better fit for AFC data, and the two-step reaction norms model was the best for the other characteristics. Heritabilities were 0.21 +/- 0.01 for AFC; and ranged from 0.27 +/- 0.04 to 0.58 +/- 0.02, 0.26 +/- 0.05 to 0.57 +/- 0.02, 81 +/- 0.03 to 0.03 +/- 0.02, 0.05 +/- 0.02 to 0.86 +/- 0.03 along the environmental gradient for SC365, SC450, GL and ACP, respectively. Correlations between intercept and slope of the reaction norms allied with reaction norms graphic plots of the ten sires with the greatest number of calves suggest the presence of GxE complex for SC365 and SC450, and thcE scale effect for GL and ACP. However, high correlations between the environments indicate that the GxE for SC450 and ACP is of a low magnitude and its inclusion in genetic evaluations would not influence the population selection. State Univ Southwest Bahia, Itapetinga, BA, Brazil State Univ Southwest Bahia, Dept Biol Sci, Jequie, BA, Brazil Fed Inst Amapa, Porto Grande, Amapa, Brazil Natl Assoc Breeders & Researchers, Ribeirao Preto, SP, Brazil Univ Fed Ceara, Juazeiro Do Norte, Ceara, Brazil Sao Paulo State Univ Unesp, Sch Agr & Vet Sci, Jaboticabal, SP, Brazil Sao Paulo State Univ Unesp, Sch Agr & Vet Sci, Jaboticabal, SP, Brazil CAPES: 001

Resumo: O objetivo deste trabalho foi avaliar a sensibilidade ao ambiente em bovinos da raça Nelore por meio de diferentes modelos de normas de reação e estimar o progresso genético no gradiente ambiental. Determinaram-se os parâmetros ganho de peso da desmama ao sobreano (GP345) e o peso ajustado aos 205 dias de idade (P205). Um modelo animal padrão (MA), dois modelos hierárquicos de normas de reação com homocedasticidade de variância residual e dois com heterogeneidade foram utilizados. O modelo hierárquico de normas de reação homocedástico com um passo apresentou o melhor ajuste. Os coeficientes de herdabilidade diretos do ambiente baixo para o ambiente alto, no gradiente ambiental, foram de 0,03 a 0,63 e de 0,13 a 0,62, respectivamente, para GP345 e P205. As correlações entre o intercepto e a inclinação da norma de reação foram de: 0,93, para GP345 (direto); 0,95, para GP345 (materno); 0,92, para P205 (direto); e 0,82, para P205 (materno). As correlações indicam que animais com alto valor genético tendem a responder positivamente aos melhores ambientes. As tendências genéticas mostraram ganhos para os efeitos diretos, principalmente nos melhores ambientes. Há variação genética quanto à sensibilidade dos animais, nos diferentes ambientes, fato que permite a seleção de animais com genótipos mais adequados para a produção em determinado ambiente. Abstract: The objective of this work was to evaluate the sensitivity of Nelore cattle to the environment by different models of reaction norms and to estimate the genetic progress in environmental gradient. The parameters weight gain from weaning to yearling (WG345) and adjusted weight at 205 days of age (W205) were determined. A standard animal model (AM), two reaction norm hierarchical models with residual variance homoscedasticity, and two with heterogeneity were used. The homoscedastic reaction norm hierarchical model with one step showed the best fit. The direct heritability coefficients from the low environment to the high one, in environmental gradient, were 0.03 to 0.63 and 0.13 to 0.62, respectively, for WG345 and W205. The correlations between the intercept and the slope of the reaction norm were: 0.93, for WG345 (direct); 0.95, for WG345 (maternal); 0.92, for W205 (direct); and 0.82, for W205 (maternal). The correlations indicate that animals with high genetic value tend to positively respond to better environments. The genetic trends showed gains for the direct effects, mainly in the best environments. There is genetic variation for sensitivity of animals, in different environments, a fact that allows of the selection of animals of more appropriate genotypes for the production in a particular environment.

The objective of this study was to use pedigree analysis to evaluate the population structure and genetic variability in the Murrah dairy breed of water buffalo (Bubalus bubalis) in Brazil. Pedigree analysis was performed on 5,061 animals born between 1972 and 2002. The effective number of founders (fe) was 60, representing 6.32 % of the potential number of founders. The effective number of ancestors (fa) was 36 and the genetic contribution of the 17 most influent ancestors explained 50 % of the genetic variability in the population. The ratio fe/fa (effective number of founders/effective number of ancestors), which expresses the effect of population bottlenecks, was 1.66. Completeness level for the whole pedigree was 76.8, 49.2, 27.7, and 12.8 % for, respectively, the first, second, third, and fourth known parental generations. The average inbreeding values for the whole analyzed pedigree and for inbreed animals were, respectively, 1.28 and 7.64 %. The average relatedness coefficient between individuals of the population was estimated to be 2.05 %-the highest individual coefficient was 10.31 %. The actual inbreeding and average relatedness coefficient are probably higher than estimated due to low levels of pedigree completeness. Moreover, the inbreeding coefficient increased with the addition of each generation to the pedigree, indicating that incomplete pedigrees tend to underestimate the level of inbreeding. Introduction of new sires with the lowest possible average relatedness coefficient and the use of appropriate mating strategies are recommended to keep inbreeding at acceptable levels and increase the genetic variability in this economically important species, which has relatively low numbers compared to other commercial cattle breeds. The inclusion of additional parameters, such as effective number of founders, effective number of ancestors, and fe/fa ratio, provides better resolution as compared to the inclusion of inbreeding coefficient and may help breeders and farmers adopt better precautionary measures against inbreeding depression and other deleterious genetic effects.

Objetivou-se estimar parâmetros e avaliar a tendência fenotípica e genética de pesos ajustados para 205 (P205); 365 (P365) e 550 (P550) dias de idade, em bovinos da variedade Nelore Mocho, nascidos a partir de 1980, pertencentes a rebanhos localizados na região Nordeste do Brasil. Foram utilizados registros genealógicos de 45.785 animais nascidos entre 1960 e 2009. Os parâmetros e os valores genéticos foram estimados com o método de máxima verossimilhança restrita livre de derivadas (REML) sob o modelo animal, usando aplicativo computacional MTDFREML. A tendência fenotípica e genética das características de crescimento foram estimadas pela regressão do valor genético sobre o ano de nascimento do animal. O coeficiente de herdabilidade direta dos pesos ajustados nas três idades foram 0,19 ± 0,02 (P205); 0,24 ± 0,03 (P365) e 0,18 ± 0,03 (P550), indicando que há potencial de ganhos pela seleção nesses pesos. A herdabilidade materna do P205 foi igual a 0,12 ± 0,02. A tendência genética direta foi igual a 0,016; 0,043 e 0,041kg/ano, para P205, P365 e P550, respectivamente, enquanto a fenotípica foi 1,34; 2,10 e 2,84kg/ano para essas características na mesma sequência, mostrando assim o quanto os ganhos fenotípicos foram superiores aos genotípicos, possivelmente favorecidos por melhorias no manejo dos rebanhos. O monitoramento dos parâmetros e das tendências fenotípica e genética do desenvolvimento ponderal na variedade Nelore Mocho do Nordeste, se apresenta como procedimento importante para nortear a definição de estratégias de manejo com potencial para aumentar os ganhos genéticos de forma consistente. This study aimed to estimate parameters and evaluate the phenotypic and genetic trend adjusted weights at 205, 365 and 550 days of age in Nellore cattle variety Polled born from 1980 belonging to herds located in Northeastern Brazil. Genealogical records of 45,785 animals born between 1960 and 2009 were used. The parameters and breeding values were estimated by restricted maximum likelihood derivative free (REML) under the animal model using computational application MTDFREML. Phenotypic and genetic trends of growth traits were estimated by linear regression of breeding value on year of birth of the animal. The direct heritability coefficient of adjusted weights at the three ages were 0.19 ± 0.02 (P205), 0.24 ± 0.03 (P365) and 0.18 ± 0.03 (P550), indicating that there is potential for gains for selecting these weights. Maternal heritability of P205 was equal to 0.12 ± 0.02. The direct genetic trend was equal to 0.016, 0.043 and 0.041kg / year to P205, P365 and P550, respectively, while the phenotype was 1.34, 2.10 and 2.84kg / year for these characteristics in the same sequence, thus showing how the phenotypic gains were higher than genotypic, possibly favored by better management of the herds. The monitoring of parameters and phenotypic and genetic trends of growth development in Nellore variety Polled in the Northeast, is presented as an important procedure to guide the development of management strategies with the potential to increase genetic gains consistently.

The objective of this study was to evaluate the population genetic structure of Nellore cattle in northeastern Brazil. Pedigree information was collected from 175,231 animals born from 1967 to 2007. Probability of gene origin, inbreeding, average relatedness coefficient (AR), completeness pedigree, effective population size and generation interval were calculated. Generation interval was high due to the long period of time animals were used as reproducers. The bottleneck effect was evidenced as a result of intensive use of limited breeders over the last years. Low values were observed ​​in the effective number of founder animals (434) and ancestors (427) comparing with the number on the base (175,231) and reference populations (130,038). Generally, the variability explained by the founders and ancestors is considered low. The average coefficient of inbreeding (0.11%) and AR (0.14%) estimated for this population is considered low and can be partly explained by the increased population effective number in recent periods; however, it may be underestimated by shallow pedigree.

O objetivo deste trabalho foi avaliar a interação genótipo × ambiente (IGA) quanto ao peso ajustado aos 365 dias de idade, em bovinos da raça Nelore Mocha do Nordeste do Brasil, por meio de modelos de norma de reação, via regressão aleatória com abordagem bayesiana. Os modelos analisados incluíram o efeito fixo de idade da vaca (linear e quadrático) e os efeitos aleatórios genético aditivo e de grupo de contemporâneos. O modelo de norma de reação com variância residual homogênea e um passo (MHNRHO1P) proporcionou melhor ajuste aos dados do que os modelos com variância residual heterogênea e o modelo animal padrão (MA). As estimativas de variância genética (64,41±13,24 kg² a 842,31±58,29 kg²) e herdabilidade (0,11±0,01 a 0,63±0,02) aumentaram com a melhoria do gradiente ambiental. As correlações de Spearman variaram de 0,69 a 0,99, entre as classificações dos reprodutores com maiores valores genéticos nos MA e MHNRHO1P, nos diferentes ambientes, o que indica alteração na classificação, especialmente dos valores genéticos obtidos pelo MA nos ambientes superiores. A identificação desse nível de IGA torna necessárias as avaliações específicas dos indivíduos e rebanhos para os ambientes de baixo, médio e alto nível de produção. The objective of this work was to evaluate the genotype × environment interaction (GEI), for the adjusted weight at 365 days of age, in Polled Nellore cattle from Northeastern Brazil, by using reaction norm models through random regression in a Bayesian approach. The analyzed models included the fixed effect of cow's age (linear and quadratic), and the genetic additive and contemporary group random effects. The one-step reaction norm models with homogeneous residual variance (RNHM1sHm) yielded better data adjustments than the models with heterogeneous residual variance, and the standard animal model (AM). The estimates of genetic variance (64.41±13.24 kg² to 842.31±58.29 kg²) and heritability (0.11±0.01 to 0.63±0.02) increased as the environmental gradient improved. Spearman correlation values ranged from 0.69 to 0.99, among the classification of breeders with the highest breeding genetic values in AM and RNHM1sHm, in distinct environments, indicating changes in classification, particularly in the genetic values obtained by AM in high-quality environments. The identification of such degree of GEI requires that specific evaluation of individuals and herds are performed for environments of low, medium and high production.