Genomic selection in dairy cattle simulated populations.

Genomic selection is arguably the most promising tool for improving genetic gain in domestic animals to emerge in the last few decades, but is an expensive process. The aim of this study was to evaluate the economic impact related to the implementation of genomic selection in a simulated dairy cattle population. The software QMSim was used to simulate genomic and phenotypic data. The simulated genome contained 30 chromosomes with 100 cm each, 1666 SNPs markers equally spread and 266 QTLs randomly designated for each chromosome. The numbers of markers and QTLs were designated according to information available from Animal QTL (http://www.animalgenome.org/QTLdb) and Bovine QTL (http://bovineqtl.tamu.edu/). The allelic frequency changes were assigned in a gamma distribution with alpha parameters equal to 0·4. Recurrent mutation rates of 1·0e-4 were assumed to apply to markers and QTLs. A historic population of 1000 individuals was generated and the total number of animals was reduced gradually along 850 generations until we obtained a number of 200 animals in the last generation, characterizing a bottleneck effect. Progenies were created along generations from random mating of the male and female gametes, assuming the same proportion of both genders. Than the population was extended for another 150 generations until we obtained 17 000 animals, with only 320 male individuals in the last generation. After this period a 25 year of selection was simulated taking into account a trait limited by sex with heritability of 0·30 (i.e. milk yield), one progeny/cow/year and variance equal to 1·0. Annually, 320 bulls were mated with 16 000 dams, assuming a replacement rate of 60 and 40% for males and females, respectively. Selection and discard criteria were based in four strategies to obtain the EBVs assuming as breeding objective to maximize milk yield. The progeny replaced the discarded animals creating an overlapping generation structure. The selection strategies were: RS is selection based on random values; PS is selection based on phenotypic values; Blup is selection based on EBVs estimated by BLUP; and GEBV is selection based on genomic estimated breeding values in one step, using high (GBlup) and low (GBlupi) density panels. Results indicated that the genetic evaluation using the aid of genomic information could provide better genetic gain rates in dairy cattle breeding programs as well as reduce the average inbreeding coefficient in the population. The economic viability indicators showed that only Blup and GBlup/GBlupi strategies, the ones that used milk control and genetic evaluation were economic viable, considering a discount rate of 6·32% per year.

Genetic parameter estimation for pre- and post-weaning traits in Brahman cattle in Brazil.

Beef cattle producers in Brazil use body weight traits as breeding program selection criteria due to their great economic importance. The objectives of this study were to evaluate different animal models, estimate genetic parameters, and define the most fitting model for Brahman cattle body weight standardized at 120 (BW120), 210 (BW210), 365 (BW365), 450 (BW450), and 550 (BW550) days of age. To estimate genetic parameters, single-, two-, and multi-trait analyses were performed using the animal model. The likelihood ratio test was verified between all models. For BW120 and BW210, additive direct genetic, maternal genetic, maternal permanent environment, and residual effects were considered, while for BW365 and BW450, additive direct genetic, maternal genetic, and residual effects were considered. Finally, for BW550, additive direct genetic and residual effects were considered. Estimates of direct heritability for BW120 were similar in all analyses; however, for the other traits, multi-trait analysis resulted in higher estimates. The maternal heritability and proportion of maternal permanent environmental variance to total variance were minimal in multi-trait analyses. Genetic, environmental, and phenotypic correlations were of high magnitude between all traits. Multi-trait analyses would aid in the parameter estimation for body weight at older ages because they are usually affected by a lower number of animals with phenotypic information due to culling and mortality.

Identifying the factors impacting on farmers' intention to adopt animal friendly practices.

Brazil, one of the leading countries in livestock production, has not yet developed legislation considering animal welfare issues and most of the actions to improve farm animal welfare (FAW) standards are developed by livestock industries and government focusing in meet the demands of exporting countries. Such actions resulted in FAW protocols and manuals for adoption of best management practices. In this context, farmers' decisions are of particular importance as they may comply with current FAW protocols or even decide to provide better FAW standards than required. A present example of farmers' decisions to provide better FAW standards than required by FAW protocols is in the adoption of environmental enrichment in pig farming. This practice is widely available to pig farmers, however, anecdotal evidence shows that the adoption rate is low. This study uses the theory of planned behavior (TPB) as a framework to identify the socio-psychological factors that influence pig farmers' intention to adopt environmental enrichment on their farms. The TPB hypothesizes that intention is determined by three psychological constructs: attitude, subjective norms, and perceived behavioral control. These three constructs are derived from behavioral, normative, and control beliefs, respectively. Self-identity was added as an additional construct to explain intention. A survey with 185 farmers was conducted. We used Partial-Least-Square Structural Equation Modeling (PLS-SEM) to identify the impact of attitude, subjective norms, perceived behavioral control, and self-identity on farmers' intention to adopt environmental enrichment on their farms. We used MIMIC models to identify the most important beliefs underlying farmers' intention to adopt environmental enrichment in their farms. Results show that the intention of farmers to adopt was mainly determined by their positive perceptions about their own capability to adopt environmental enrichment (perceived behavioral control), followed by their perceptions about the social pressure to adopt it (subjective norms), their positive evaluations of adoption (attitude), and self-identity. The most important behavioral beliefs were 'increase productivity', and 'decrease animals stress'. The most important normative beliefs were 'family', 'neighbor farmers', 'pig buyers', and 'experts'. The most important control belief was 'receive bonus when selling pigs'. These results revealed important implications to design public and private interventions aimed to stimulate the adoption of animal friendly practices.

Genetic parameters, genetic trends, and principal component analysis for productive and reproductive traits of Guzera beef cattle

The objectives of this study were to estimate genetic parameters and genetic trends and perform principal component analysis for the following traits: body weight adjusted at 210 days of age (W210), one year (W365), and yearling or 450 days of age (W450); weight gain from birth to weaning or 210 days of age (WGBW), from weaning to 365 days of age (WGW365), and from one year to yearling (WGY); and scrotal circumference adjusted at 365 (SC365) and 450 (SC450) days of age of Guzera beef cattle. Variance components were estimated under a two-trait animal model using the restricted maximum likelihood method. The fixed effects included in the model were birth season, contemporary group, and covariable age of dam at calving as linear and quadratic effects. Heritability estimates ranged from 0.10 (WGY) to 0.41 (W450 and SC450). The studied traits could be used as selection criteria because of their sufficient additive genetic variability to respond to the selection process. However, lower selection efficiency is expected for WGBW and WGY. Genetic trends studied were significant for all traits, except WGY. The W365 and W450 traits belonged to the "Genetic Merit Total" index and responded to selection with favorable genetic gain per year. The traits that were not included in the selection index showed favorable positive genetic correlations attributed to the indirect selection processes. The principal component analysis identified two groups of traits. The first group related to body weight and weight gain and the second related to the scrotal circumference, indicating that selection could be applied to one group of traits within each observed group. The genetic gains were attributed in the same direction for the other traits belonging to the groups. Thus, we recommend selecting animals for W365 based on first group, and SC365 based on second.(AU)

Estrutura populacional e parâmetros genéticos de uma população de bovinos Guzerá

O monitoramento dos resultados de um programa de seleção de bovinos de corte serve para avaliar o progresso genético alcançado e para que os resultados obtidos sirvam de elementos orientadores de ações futuras. Neste trabalho, os objetivos foram estimar parâmetros genéticos e tendências genéticas para características de importância econômica em bovinos da raça Guzerá, estimar parâmetros populacionais e os coeficientes de endogamia e relaciona-los com valores genéticos e com o índice de seleção recomendado para a raça (MGT). Para isto, dados de 18.491 animais, oriundos de 43 fazendas foram cedidos pelo Programa de Avaliação Genética da Raça Guzerá (PAGRG). As características estudadas foram área de olho de lombo (AOL), espessura de gordura entre a 12ª e a 13ª costela (EG), espessura de gordura na garupa (EGP8), idade ao primeiro parto (IPP), perímetro escrotal aos 365 (PE365) e 450 (PE450) dias de idade, período de gestação (PG), peso adulto da vaca (PAV), peso corporal ao nascimento (PN), aos 120 (P120), aos 210 (P210), aos 365 (P365), aos 450 (P450) dias de idade e produtividade acumulada em fêmeas (PAC). Os parâmetros populacionais estimados foram taxa de endogamia por geração, tamanho efetivo da população, intervalo de gerações e o número efetivo de fundadores e de ancestrais. Os parâmetros genéticos e valores genéticos foram estimados pelo método da máxima verossimilhança restrita, em análises uni e bi-características. Tendências genéticas foram obtidas por regressão linear das médias dos valores genéticos anuais, em função do ano de nascimento. A estatística t foi usada e a hipótese nula considerava o coeficiente da regressão como sendo zero. As características apresentaram suficiente variação genética aditiva, sendo passíveis de seleção e estas se mostraram favoravelmente correlacionadas geneticamente, exceto...

Monitoring the results of a breeding program for beef cattle is used to evaluate the genetic progress achieved and the results serve as guiding elements for future actions. In this work, the objectives were to estimate genetic parameters and genetic trends for traits of economic importance in Guzerat beef cattle, estimate population parameters and coefficients of inbreeding and its relationship with breeding values and the selection index recommended for the breed (MGT).For this, data from 18,491 animals from 43 farms were granted by the Programa de Avaliação Genética da Raça Guzerá (PAGRG). The traits studied were rib eye area (REA), fat thickness between the 12th and 13th rib (FT), rump fat thickness (RF), age at first calving (AFC), scrotal circumference at 365 (SC365) and 450 (SC450) days of age, gestation length (GL), mature weight of the cow (MWC), body weight at birth (BWB), 120 (BW120), 210 (BW210), 365 (BW365) and 450 days of age (BW450) and cumulative productivity in females (AP). The population parameters estimated were rate of inbreeding per generation, effective population size, generation interval and the effective number of founders and ancestors. The genetic parameters, breeding values were estimated by restricted maximum likelihood, by one and two-trait analysis. Genetic trends were calculated from a linear regression of mean predicted breeding values (PBV) based on birth year. At-statistic was used to test the hypothesis that the regression coefficient for each equation is equal to zero. The traits showed sufficient additive genetic variation, being capable to respond to selection and proved to be genetically correlated among them, except AP, FT and RF, which showed low genetic correlations with other traits. The genetic trend indicated that the animal?s mean breeding value has changed over time for the traits studied...

Interação genótipo-ambiente em características de crescimento de bovinos da raça Nelore

A identificação de interação genótipo-ambiente em bovinos de corte pode auxiliar o processo de seleção, aumentando a eficiência da avaliação genética de reprodutores submetidos à ambientes distintos. Características medidas pós-desmame estão mais sujeitas aos efeitos da interação genótipoambiente do que na fase pré-desmame. Assim, o objetivo deste trabalho foi verificar a existência do efeito da interação genótipo-ambiente sobre os pesos corporais aos 365 (P365), 450 (P450) e aos 550 (P550) dias de idade de bovinos Nelore criados nos estados de Goiás, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Pará e São Paulo. Os componentes de (co)variância, parâmetros genéticos e os valores genéticos preditos foram estimados para cada característica, por estado e para o conjunto total de dados, pelo método da máxima verossimilhança restrita. Correlações de Spearman entre as classificações dos touros por estado quanto ao valor genético para cada característica ou considerando cada estado individualmente e em conjunto (todos os estados), assim como a correlação genética entre observações da mesma característica, medida em dois estados distintos foram utilizadas para avaliar o efeito da interação genótipo-ambiente sobre as características estudadas. Correlações de Spearman não significativas indicaram mudança de posição na classificação de touros e conseqüente existência de interação genótipo-ambiente. A ocorrência desta interação também foi constatada em algumas ocasiões por estimativas de correlação genética entre observações da mesma característica em estados diferentes, para P365 foi observada indícios de interação entre SP e GO (0,71), SP e MT (0,68) e também entre SP e PA (-0,11), para P450, MT e MG (-0,28), GO e PA (0,62) e SP e PA (0,66), para a característica P550, MT e MG (-0,38), MG e PA (0,73), MG e SP (-0,34) e para...

The properly identification of genotype-environment interaction in beef cattle herds can help the selection process and improve genetic evaluation of sires submitted in different environments. Post weaning traits may be more influenced by the genotype-environment interactions than others. So, this paper objective was verify genotype-environment interaction in, beef cattle, body weight at 365 (P365), 450 (P450) and 550 (P550) days of age in herds distributed in six Brazilian states, Goiás (GO), Mato Grosso (MT), Mato Grosso do Sul (MS), Minas Gerais (MG), Pará (PA) and São Paulo (SP). Genetic parameters, (co)variance components and genetic values were estimated for each trait, each state and for all states together, using maximum restricted likelihood method. Spearman correlations among sire?s classifications due to its genetic value, for each trait, by state individually or in group (using data from all states), genetic correlation between the same trait measured in two different states were used to evaluate genetic-environment interaction over the traits studied. Non significant Spearman?s correlation indicated position changes at sires classification and consequently genotype-environment interaction. This interaction occurrence was also observed between genetic correlations of the same trait measured in two different states. Genetic correlation for P365, between SP and GO states were (0, 71), SP and MT (0, 68) and also between SP and PA (-0, 11). For P450, MT and MG (-0, 28), GO and PA (0, 62) and SP and PA (0, 66). P550, MT and MG (-0, 38), MG and PA (0, 73), MG and SP (-0, 34) and SP and PA (-0, 86). There so, selection conduced considering data obtained in one state could be different than one based in others. Beef cattle summary organized by state would be indicated if this one would be economically viable