Edson Vinícius Costa

Estimating additive and dominance variances for complex traits in pigs combining genomic and pedigree information.

Knowledge of dominance effects should improve ge-netic evaluations, provide the accurate selection of purebred animals, and enable better breeding strategies, including the exploitation of het-erosis in crossbreeds. In this study, we combined genomic and pedi-gree data to study the relative importance of additive and dominance genetic variation in growth and carcass traits in an F2 pig population. Two GBLUP models were used, a model without a polygenic effect (ADM) and a model with a polygenic effect (ADMP). Additive effects played a greater role in the control of growth and carcass traits than did dominance effects. However, dominance effects were important for all traits, particularly in backfat thickness. The narrow-sense and broad-sense heritability estimates for growth (0.06 to 0.42, and 0.10 to 0.51, respectively) and carcass traits (0.07 to 0.37, and 0.10 to 0.76, respec-tively) exhibited a wide variation. The inclusion of a polygenic effect in the ADMP model changed the broad-sense heritability estimates only for birth weight and weight at 21 days of age.

Using pedigree analysis to monitor the local Piau pig breed conservation program

portuguesA raca local brasileira Piau e um suino tipo banha a qual passou por um processo de selecao realizado pelo medico veterinario Antonio Teixeira Vianna em 1939, com o intuito de desenvolver um animal de dupla aptidao, em outras palavras que fosse adequado para a producao de carne e gordura. As principais caracteristicas da raca sao rusticidade, adaptabilidade e resistencia a doencas. O status de conservacao da raca e ameacado e em 1998 a Granja de Melhoramento de Suinos da Universidade Federal de Vicosa (UFV, Vicosa, MG, Brazil) iniciou uma criacao de suinos da raca Piau com o objetivo de conserva- la e utiliza-la em estudos geneticos. O objetivo do presente estudo e descrever o programa de conservacao da raca Piau da UFV e avaliar uma serie de parâmetros populacionais, a fim de gerar informacoes que possibilitem o monitoramento e a melhoria do programa. Para a analise da estrutura populacional foi utilizado arquivo de pedigree com 1349 individuos por meio do software ENDOG v. 4.8. O programa de conservacao da raca possui boa estrutura com registro de dados zootecnicos e pedigree desde a introducao dos primeiros animais na granja de melhoramento de suinos, juntamente com o controle de acasalamentos, o qual e baseado no acasalamento de animais com menor coancestralidade e na manutencao das familias fundadoras. A populacao de Piau avaliada possui numero efetivo de fundadores e ancestrais iguais a 9 e 8, respectivamente. O coeficiente de endogamia medio, coeficiente de relacao medio e tamanho efetivo da populacao sao 6,55 %, 19,74 % e 18,59, respectivamente. De acordo com os parâmetros avaliados e recomendado aumentar o tamanho efetivo da populacao, por meio da introducao de animais de outra populacao, uma vez que o pequeno numero de fundadores torna dificil o controle da endogamia. portuguesThe local Brazilian pig breed Piau is a lard-type pig that has undergone a breeding and selection process devised by the veterinarian Antonio Teixeira Vianna in 1939. The objective of the program was to develop a dual purpose animal, that is an animal suitable for the production of both fat and meat. The main characteristics of the Piau breed are rusticity, adaptability and high disease resistance. The conservation status of the breed is threatened, and in 1998, the Pig Breeding Farm at Universidade Federal de Vicosa (UFV, Vicosa, MG, Brazil) started a Piau herd for the purposes of conservation and use in genetic studies. The objectives of the present study were to describe the Piau genetic conservation program of the Universidade Federal de Vicosa (UFV) and to evaluate a range of population parameters to generate information for monitoring and improving the program. Population genetic structure analysis was performed using a pedigree file of 1349 animals and ENDOG v 4.8 software. The Piau conservation program has data and a collection of pedigree registers going back to the introduction of the first animals to the Pig Breeding Farm. The program used mating control, which is based on the mating of animals with the lowest pedigree- based relationships and on the maintenance of all the population’s founding families. The effective numbers of founders and ancestors in the studied Piau population are 9 and 8 animals, respectively. The average inbreeding coefficient (F), the avera- ge relatedness coefficient (AR) and the effective population size are 6.55 %, 19.74 % and 18.59, respectively. The findings support an increase in the effective population size of this population through the introduction of animals from other populations, as the small number of founders makes inbreeding control difficult.

Modelling lactation curves of dairy goats by fitting random regression models using Legendre polynomials or B-splines

Abstract: A total of 17 356 test-day milk yield (TDMY) records from 642 first lactations of Alpine goats were used to model variations in lactation curve using random regression models (RRM). Orthogonal Legendre polynomials and B-splines were evaluated to obtain adequate and parsimonious models for the estimation of genetic parameters. The analysis was performed using a single-trait RRM, including the additive genetic, permanent environmental, and residual effects. We estimated the mean trend of milk yield, and the additive genetic and permanent environmental covariance functions through random regression using different orders of orthogonal Legendre polynomial (three to six) and B-spline functions (linear, quadratic, and cubic, with three to six knots). This study further evaluated different number of classes of residual variances. The covariance components and the genetic parameters were estimated using the restricted maximum likelihood method. Heritability estimates presented similar trends for both functions. The RRM with a higher number of parameters better described the genetic variation of TDMY throughout the lactation. The most suitable RRM for genetic evaluation of TDMY of Alpine goats is a quadratic B-spline function with six knots, for the mean trend, curves of additive genetic and permanent environmental effects, and five classes of residual variance.

Meta-analysis of genetic-parameter estimates for reproduction, growth and carcass traits in Nellore cattle by using a random-effects model

Meta-analysis based on a random-effects model is used to summarise and overcome the variability between divergent parameter estimates. We proposed a meta-analysis of published heritability and genetic-correlation estimates for reproduction, growth and carcass traits in purebred Nellore cattle. In total, 197 heritability and 107 genetic-correlation estimates from 62 scientific publications were used here. Most of traits (gestation length; weights at birth, 120, 210, 365 and 550 days of age; mature weight and all carcass traits) presented direct heritability estimates ranging from 0.20 to 0.40. Age at first calving presented the lowest value among direct heritabilities (0.1498); whereas the higher values (>0.40) were found for scrotal circumference at different ages and for weight at 450 days of age. Low maternal heritability estimates (ranging from 0.06 to 0.11) were observed for all growth traits. With the exception of correlation estimates involving the age at first calving, all other correlations were positive. High correlations (>0.85) were found mainly for the same trait at different ages. The results reported here will give support to genetic evaluations when reliable estimates for different traits in purebred Nellore cattle are not available.