7 research outputs found
Genotype ? hatch interactions as a source of bias in estimating genetic components of variance for eight-week weight in poultry
Produtividade acumulada como critério de seleção em fêmeas da raça nelore Accumulated productivity as selection criteria in nellore breed females
O presente trabalho teve por objetivo determinar os componentes de variância e estimar a herdabilidade da produtividade acumulada (PAC) de 15.070 fêmeas, criadas em diferentes rebanhos participantes do Programa de Melhoramento Genético da Raça Nelore. A PAC é um índice que considera a produção total de bezerros desmamados em kg, o tempo total de produção de bezerros e o início de parição. As análises estatísticas foram realizadas por meio do programa SAS (Statistical Analysis System) e os componentes de variância pelo método de máxima verossimilhança restrita utilizando o software MTDFREML. A média da PAC foi de 130kg de bezerros desmamados por vaca ao ano, e os efeitos do pai da vaca, rebanho e ano de nascimento da vaca foram significativos (P<0,0001) na variação dessa característica. O coeficiente de herdabilidade da PAC foi estimado em 0,15, indicando a existência de variabilidade genética suficiente para sua inclusão nos programas de melhoramento, o que resultaria na obtenção de fêmeas mais produtivas nos rebanhos.<br>This work had for objective to determine the variance components and to estimate the heritability of the accumulated productivity (ACP) of 15,070 females, reared in different participant herds of the Nellore Breeding Program. ACP is an index that considers the total production of calves weaned in kg, the total time of production of calves and the calving beginning. The statistical analyses were accomplished through the SAS program (Statistical Analysis System) and the variance components for the restricted maximum likelihood method using the software MTDFREML. The average of ACP was of 130kg of calves weaned by cow to the year, and the sire of cow effects, herd and year of the birth cow significatly (P<0.0001) affected in the variation of this characteristic. The coefficient of heritability of ACP was estimated in 0.15, indicating the existence of enough genetic variability for its inclusion in the improvement programs, what would result in the obtaining of more productive females in the herds
Direct and correlated responses to selection for post-weaning weight gain on ad libitum or restricted feeding in mice
Gene number estimation when multiplicative genetic effects are assumed — growth in flour beetles and mice
Efeito da seleção para peso pós-desmama sobre indicadores da eficiência produtiva de vacas da raça Nelore Effects of selection for post weaning weight on Nellore cow productivity efficiency indicators
O objetivo deste estudo foi avaliar indicadores da eficiência produtiva de vacas Nelore selecionadas para peso pós-desmama, enfocados nas relações peso bezerro e peso da vaca, nos rebanhos controle (NeC), não-selecionados para peso pós-desmama, seleção (NeS) e tradicional (NeT). As análises envolveram 3929 e 3906 pesos dos bezerros aos 120 (P120) e 210 (P210) dias de idade, respectivamente. Os pesos das vacas àquelas idades também foram considerados, obtendo-se 3824 (PV120) e 3777 (PV210) registros, respectivamente, para 120 e 210 dias. A análise incluiu 183, 375 e 554 vacas dos rebanhos NeC, NeS e NeT, respectivamente. Para as análises utilizou-se o procedimento GLM/SAS, em modelos que incluíram os efeitos fixos de rebanho, ano e mês de nascimento, sexo do bezerro, idade da vaca ao parto e as interações rebanho x ano de nascimento e ano x mês de nascimento. Todos os efeitos foram significativos. Os resultados mostraram respostas correlacionadas positivas na seleção para peso pós-desmama nos pesos dos bezerros e, em menor magnitude, no peso das vacas. As relações peso bezerro e peso da vaca apresentaram valores médios ajustados de 249,0±2,1; 253,7±1,6; e 255,8±1,2 g/kg para R120 e 362,9±2,8; 368,5±2,1; e 374,6±1,7 para NeC, NeS e NeT em R210, respectivamente, indicando que, nas duas idades, os rebanhos NeS e NeT produziram mais quilogramas de bezerro por quilogramas de vaca, quando comparados ao NeC.<br>The objective of this study was to evaluate the productivity efficiency indicators of cows selected for post-weaning weight, with emphasis in the calf-cow weight ratios, in a controlled herd (NeC), unselected for post-weaning weight, selection (NeS) and conventional (NeT). The analysis involved 3929 and 3906 calves weights at the 120 (P120) and 210 (P210) days of age, respectively. The cow weights at those ages were also considered, and the recorded numbers were 3824 (PV120) and 3777 (PV210), respectively, for 120 and 210 days. The analysis included 183, 375 and 554 cows from NeC, NeS and NeT, respectively. The SAS/GLM procedure was used in the data analyses. The model included the effects of herd, year and month of birth, and sex of calf, age of cow at calving, and the interactions herd x year, and year x month of birth. All effects were significant. The results showed a positive correlated response in the selection for post weaning on the calf weights and, low response, on cow weights. The calf weight/cow weight ratios showed average adjusted values of 249.0±2.1, 253.7±1.6 and 255.8±1.2 g/kg for R120, and 362.9±2.8, 368.5±2.1 and 374.6±1.7 g/kg for NeC, NeS and NeT at R210, respectively, and indicated that, at both ages, the NeS and NeT herds produced more kg of calf by kg of cow when compared to NeC
Relationships between quantitative and reproductive fitness traits in animals
The relationships between quantitative and reproductive fitness traits in animals are of general biological importance for the development of population genetic models and our understanding of evolution, and of great direct economical importance in the breeding of farm animals. Two well investigated quantitative traits—body weight (BW) and litter size (LS)—were chosen as the focus of our review. The genetic relationships between them are reviewed in fishes and several mammalian species. We have focused especially on mice where data are most abundant. In mice, many individual genes influencing these traits have been identified, and numerous quantitative trait loci (QTL) located. The extensive data on both unselected and selected mouse populations, with some characterized for more than 100 generations, allow a thorough investigation of the dynamics of this relationship during the process of selection. Although there is a substantial positive genetic correlation between both traits in unselected populations, caused mainly by the high correlation between BW and ovulation rate, that correlation apparently declines during selection and therefore does not restrict a relatively independent development of both traits. The importance of these findings for overall reproductive fitness and its change during selection is discussed