R.A. Torres

Estudo da curva de crescimento de ovinos Santa Ines

Records of 7,271 weights of 952 lambs measured from birth up to 196 days of age between 1983 and 2000, available from the Agricultural Research Corporation of Paraiba database, were used to model the average growth curve of Santa Ines sheep. The influence of environmental effects on the estimated parameters of the Brody, Von Bertalanffy, Logistic, Gompertz and Richards functions was evaluated using the NLIN procedure of SAS. The growth curve was well fitted by all models but larger residual variation was obtained by the Brody and Logistic models. According to the absolute average residual error, the Gompertz model showed a better fit than the models Von Bertalanffy and Richards. Growth curves differed for males and females, born from single and twin lambing. Contemporary group, type of birth and sex significantly affected the estimation of parameters A and K. The correlation between parameters A and K was negative. Improvements in feeding management and forage storage may decrease the indirect effects of climate and contribute to reduce variation in the growth curves.

Estimação de parâmetros genéticos para características de crescimento de ovinos Santa Inês utilizando modelos uni e multicaracterísticas

Records of birth weights at 196 days of age of 927 lamb progenies of 45 sires and 323 dams of Santa Ines sheep, controlled from 1983 to 2000, were used with purpose of evaluating three models that considered or no the maternal genetic effect and covariance between direct and maternal genetic effects, to estimate variance components and genetic parameters by single and two-trait analyses. The (co)variance components and genetic direct and maternal parameters were estimated by restricted maximum likelihood methods, under animal model. The model that included additive direct and maternal effects showed higher value for log likelihood for all the studied traits. Model without maternal effect overestimated the variances and heritability for direct genetic effect (0.56 to 0.23). The importance of maternal effect decreased with growth, as the age of the lambs increased. The variances and heritability estimates in two-trait models for genetic direct genetic effect were higher than those obtained by single-trait models. The genetic correlations between the traits were high and positive. The maternal effect was important for all the studied traits. The two-trait models allowed better estimate of the direct additive variance, causing higher heritability value.

Exigência de proteína bruta e energia metabolizável para codornas de corte EV1

The crude protein and metabolizable energy requirement for weight gain, body weight, feed consumption, and feed consumption : weight gain ratio during three periods (7- 21; 21-42 and 7-42days of age) of the growing phase of meat type quail (EV1) were estimated in a completely randomized design, with eight treatments and six replicates of 12 quails per experimental unit. The treatments consisted in a factorial combination 4 x 2 (22, 24, 26 e 28% PB x 2900 e 3100kcal de EM/kg). Body weight and weight gain from 7 to 21 days of age were quadratic affected by protein level of diets. Feed consumption linearly decreased with the increasing of diet energetic level. Feed: weight gain ratio increased linearly with crude protein level and decreased with metabolizable energy level of diets. Body weight at 42 days of age was not affected by metabolizable energy and crude protein levels of the diets. From 7 to 42 days of age the protein and metabolizable energy of diets did not affect quail body weight and feed: weight gain ratio. Quails fed on 2900kcal of EM/kg of diet showed higher feed consumption in comparison to quails fed on 3100kcal of EM/kg diets. Maximum performance of EV1 quails are reached in diets with 27% of crude protein (CP) and 2900kcal of ME/kg of diet in the initial period (7-21 days of age) and 22% of CP and 2900kcal of ME/kg of diet in the whole period (7-42 days of age).

Exigências em proteína bruta para codornas de corte EV1 em crescimento

Crude protein requirements for EV1 meat type quails were estimated using 288 quails of both sexes in a completely randomized experimental design with six crude protein levels (23, 25, 27, 29, 31 and 32%) and four replicates of 12 quails per experimental unit. The following traits were recorded in each experimental period (from hatch to 21 days and from hatch to 42 days of age): body weight (g), weight gain (g), feed intake (g), and feed:weight gain ratio. From hatch to 21 days of age quadratic effects of crude protein levels on live body weight, weight gain and feed intake were observed and maximum performances were estimated for quails fed 30.2; 30.1; and 30.8% crude protein diets, respectively. Quadratic effect of protein level on body weight at 42 days of age was significant and quails fed 30.2% crude protein diets showed maximum performance. Quails fed 29.5 and 32.6% crude protein diets from hatch to 42 days showed maximum weight gain and feed intake while feed:weight gain ratio was negative and linearly related to crude protein level of diet. Crude protein requirement for weight gain (male and female), from hatch to 21 days of age is estimated in 30.1% and from hatch to 42 days of age in 29.5%.

Exigências de proteína bruta e energia metabolizável em codornas de corte durante a fase de crescimento

Crude protein (CP) and metabolizable energy (ME) levels during five experimental periods of seven days each of the growing phase for European quail were determined. A total of 384 quails of both sexes were used in a completely randomized design in a 2×4 (energy and crude protein) factorial treatment with six replications of eight quails each. The metabolizable energy levels were 2900 and 3000kcal of ME/kg of diet and the crude protein levels were 22, 24, 26 and 28%. The analyzed variables were weight gain (g), accumulated weight (g), feed consumption (g), feed:gain ratio (g/g). Performance responses were evaluated by linear and quadratic regression of the traits on crude protein levels. Higher weight gains from the following protein and metabolizable energy levels combinations: 28.0% PB and 2900 kcal EM/kg (first period); 25.7% CP and 3100kcal ME/kg (second period); 27.9% and 2900kcal ME/kg (third period); 24.8% PB and 3100kcal/kg (fourth period) and 23.1% CP and 2900kcal/kg (fifth period).

Avaliação genética de características de crescimento de ovinos Santa Inês utilizando modelos de regressão aleatória

Records on weights from birth to 196 days of age of 927 lambs of Santa Ines hairless sheep, from 1983 to 2000, were used to estimate genetic parameters and to predict breeding values by random regression models and to compare these estimates with those obtained by two-traits model. The random regression models were fitted by quadratic and cubic orthogonal Legendre polynomials. The heritability estimates of direct effect increased from birth to 196 days of age. The heritabilities for the maternal effect increased from birth to 56 days, and decreased after that age. The heritabilities for direct effect obtained by two-trait and random regression analyses showed opposite tendency. While the estimates obtained by two-trait analyses decreased from birth to 196 days of age, those obtained by random regression models increased. The heritabilities for maternal effect, obtained by both models, showed the same behavior, however with different magnitude. The Spearman correlation between estimated breeding values by both models was low. The heritability and genetic correlations estimated by random regression model were more consistent than those estimated by two-trait model.

Comparação de modelos de regressão aleatória para estimação de parâmetros genéticos em caprinos leiteiros

Random regression and Legendre polynomial (LP) of different orders were used for modeling the genetic, permanent environmental and residual variances of test day milk yield in dairy goats. The models included the fixed effects of contemporary group, age of dam at kidding as a covariate and the fixed regression of LP for the average lactation curve and the additive genetic, permanent environmental and residual as random effects. According to the values of the logarithm of the likelihood function, AIC and BIC using higher orders of LP (fifth order for the genetic effect and seventh order for the permanent environmental effect) improved the fitting of the models. The model with four classes of residual variances provided the best fit. The eigenvalues of the (co)variances matrix among the regression coefficients suggested the possibility of reducing the dimension of the models. The estimates of genetic variances and genetic and permanent environmental correlations for test day milk yields obtained from polynomials of higher orders are not biologically expected. The LP of fifth order for the addictive genetic and seventh order for the permanent environmental effects was the best fitted model. However, a LP of fourth order for the addictive genetic and of sixth order for the permanent environmental effects may be considered as a more parsimonious model for the estimation of variances of test day milk yield in dairy goats, by random regression.

Simulação de dados para avaliação genética de rebanhos de gado de corte

Utilizou-se o programa GENESYS para simular rebanhos de gado de corte selecionados, durante cinco geracoes, por meio da selecao individual ou selecao com base no melhor preditor linear nao-viesado (BLUP). Foram comparados os valores fenotipicos medios e a endogamia media, resultantes da aplicacao desses metodos. A caracteristica quantitativa simulada foi o ganho de peso diario, com fenotipo medio inicial de 1kg e herdabilidade de 0,35. Os valores da razao sexual nas populacoes de selecao foram de 1:50 e 1:25 (macho: femeas), correspondendo aos tamanhos efetivos da populacao de 23,53 e 57,69 animais, respectivamente. Os ganhos geneticos individuais foram maiores para a selecao baseada no BLUP, atribuidos a sua mais alta acuracia na predicao dos valores geneticos. Considerando-se cada metodo de selecao, nao houve diferencas significativas entre os dois tamanhos efetivos quanto aos valores fenotipicos medios por geracao. A endogamia media aumentou em ambos os metodos de selecao e tamanhos efetivos. Maior aumento e oscilacao nos valores ocorreram para a selecao baseada no BLUP no menor tamanho. Embora a selecao tenha sido realizada por pequeno numero de geracoes, os resultados permitiam discriminar as combinacoes que proporcionaram maior incremento de endogamia.

Seleção de variáveis de desempenho de suínos por meio da análise de componentes principais

Dados de 435 animais de uma populacao F2 de suinos foram utilizados para avaliar a possibilidade de reducao da dimensao do espaco multivariado, por meio da tecnica de componentes principais. Foram avaliadas as seguintes caracteristicas de desempenho: tamanho da leitegada ao nascer (TLN), tamanho da leitegada a desmama (TLD), numero de tetos (NT), pesos ao nascer (PN), aos 21 (P21), aos 42 (P42), aos 63 (P63) e aos 77 (P77) dias de idade e ganho medio de peso diario (GPD), consumo de racao (CR) e conversao alimentar (CA) dos 77 aos 105 dias de idade. Seis componentes principais, obtidos a partir da matriz de correlacao, apresentaram variância inferior a 0,7 (autovalores inferiores a 0,7), o que sugere seis variaveis para descarte, por apresentarem maiores coeficientes, em valor absoluto, a partir do ultimo componente principal. As variaveis descartadas apresentaram correlacao linear simples significativa com as demais. Em razao do grande numero de variaveis redundantes, 54,5% delas podem ser eliminadas, sendo recomendada a avaliacao de apenas TLN, NT, P77, CR e CA, sem que haja perda consideravel da informacao.

Ratios between variability components of simulated quantitative traits with genetic effects of dominance and overdominance

Ratios were assessed between variability components of quantitative traits simulated from the genome incorporating non-additive genetic effects in random mating populations and short-term phenotypic selection. A trait of low (h2 = 0.10) heritability and another of high (h2 = 0.60) heritability were studied, both influenced by 600 bi-allelic loci. Five gene action models were simulated, of which four included complete and positive dominance for 25, 50, 75 and 100% of the loci (D25, D50, D75 and D100, respectively); and one model included positive overdominance for 50% of the loci. Every model included additive effects of the alleles for 100% of the loci. The main quantified ratios were d2 (dominance variance/phenotypic variance) and d2a (dominance variance/additive variance). For both traits, d2 and d2a increased according to the increase in the variance of dominance with the growing inclusion of loci with dominance deviation and under overdominance. For the same model, both ratios, especially d2, are greater under high heritability, that indicates that the dominance effects explain the greater part of the total variability of this trait under selection.