B.D. Valente

Efeito de diferentes níveis de proteína e energia sobre o rendimento de carcaça de codornas européias

The effect of protein and energy levels on 42nd day carcass yield of European quails (Coturnix coturnix coturnix) was evaluated. A completely randomized design with five replicates and eight quails per experimental unit was used. The treatment consist on diets with two energy metabolic levels (2900 and 3100kcal EM/kg) and four protein levels (22, 24, 26 and 28% of crude protein). The traits analyzed were body weight and weight and yield of carcass, tight, breast, fat and edible viscera. No significant effects of crude protein and metabolic energy levels on carcass traits were found.

Interação genótipo × ambiente e estimativas de parâmetros genéticos de características ponderais de bovinos Tabapuã

Dados de pesos aos 205 (P205) e 365 (P365) dias de idade, de 28.946 animais Tabapua, provenientes de 152 fazendas dos diversos estados brasileiros, nascidos no periodo de 1976 a 1995, foram utilizados nesta analise. Foram avaliadas as interacoes genotipo-ambiente, bem como estimadas herdabilidades direta e materna pelo metodo de maxima verossimilhanca restrita em modelo estatistico, que incluiu efeitos fixos de grupo contemporâneo, idade da vaca ao parto (covariavel) e efeitos aleatorios geneticos direto e materno. As estimativas de herdabilidade direta e materna para P205 nas regioes Sul (R1), Sudeste (R2), Centro-Oeste (R3) e Nordeste (R4) foram: 0,02 e 0,31 (R1), 0,17 e 0,19 (R2), 0,20 e 0,09 (R3) e 0,06 e 0,16 (R4). Para P365, foram 0,05 e 0,03 (R1), 0,20 e 0,03 (R2), 0,51 e 0,62 (R3) e 0,15 e 0,05 (R4). As correlacoes geneticas encontradas para as caracteristicas P205 e P365, ambas consideradas caracteristicas distintas nas regioes R1, R2, R3 e R4, foram: 1,00 e 0,99, 0,84 e 0,99, -0,86 e -0,73, 0,98 e 0,93, 0,51 e 0,45, 1,00 e 0,12 para R1/R2, R1/R3, R1/R4, R2/R3, R2/R4 e R3/R4, respectivamente. Esses resultados indicam que, na desmama (P205), o efeito da interacao genotipo x ambiente foi observado somente nas combinacoes que envolveram a regiao Nordeste (R4) e as regioes Sul (R1) e Sudeste (R2). Para pesos pos-desmama (P365), o efeito dessa interacao foi evidenciado em todas as combinacoes que incluiram a regiao Nordeste.

Estruturas de covariância de peso em função da idade de animais Nelore das regiões Sudeste e Centro-Oeste do Brasil

Body weight records from 90 to 450 days of age of Nellore animals from the Southeast and Center West of Brazil were used do estimate covariance structures of age dependent random effects for each region using random regression models. Covariance components of the regression coefficients were estimated by EMREML using the software REML90. The fixed effects of contemporary groups and additive genetic, additive maternal and permanent environment random effects were modeled by quadratic Legendre polynomials. The comparisons included structures of covariance and correlation of random effects, direct and maternal heritabitability and the ratio between genetic variances from different regions. The heritability, covariance and correlation structures showed similar patterns for both regions. Residual variance and permanent environment variances were smaller for Center West region as well as the maternal genetic additive from 150 to 400 days of age. Fixed effect trajectories in function of age of different contemporary groups showed different patterns, suggesting the necessity of specific set of regression coefficient estimates for each contemporary group. The maternal additive genetic variance showed higher heterogeneity between regions than the direct additive genetic variance.

Exigência de proteína bruta para codornas européias no período de crescimento

A completely randomized design with five treatments and six replicates of 15 quails per experimental unity was used to estimate crude protein requirements for European quails (Coturnix coturnix coturnix) during the periods 18-28, 28-42 and 42-56 days of age. The experimental diets were formulated with 18, 20, 22, 24, and 26% of crude protein and 2900kcal/kg EM/kg. The protein requirements during 18-28 days of age were respectively 25.7; 25.2 and 25.5% for weight gain, weight gain/feed intake ratio and for body weight. During the 28-42 period the crude protein requirement for body weight was 24.6%, but there was no effect of crude protein level on weight gain and weight gain/feed intake ratio. The effect of crude protein level on weight gain, weight gain/feed intake ratio and body weight during 42-56 period was not significant. The European quails Coturnix coturnix coturnix have lower protein level requirement for body weight during 28-42 days of age in comparison to 18-28 period. No reliable estimates of crude protein requirements were obtained for body weight, weight gain and weight gain/feed intake ratio after 28 days of age.

Uso de redes neurais artificais na predição de valores genéticos para peso aos 205 dias em bovinos da raça Tabapuã

Data from 19,240 Tabapua animals from 152 farms located in different states of Brazil, born from 1976 to 1995, were used to predict the genetic value of body weight at 205 days of age (BV_P205) of Tabapua beef cattle using Artificial Neural Networks (ANN) and LM algorithm - Levenberg Marquardt training for data entry. Due to the use of networks with supervised learning, the predicted breeding values for P205 from BLUP were used as desired output. The breeding values for P205 obtained from RNA and those predicted by BLUP were highly correlated. The ranked breeding values for body weight at 205 days through RNA and those predicted by BLUP (VG_P205_RNA) showed a variation in the classification of animals indicating risks in the use of ANNs procedure for genetic evaluation of this trait. Insertions of new animals require new training data always dependent on BLUP.

Critérios de seleção para características de crescimento em bovinos da raça Nelore

Data records of 28,050 animals from Nellore breed were used to compare selection criteria for beef cattle based on weight gain from birth to weaning (GBW), number of days to gain 160kg during the pre-weaning period (D160), daily weight gain from weaning to 18 months (GW18) and number of days to gain 240kg during the pos-weaning period (D240). Direct heritability estimates of GBW (.20) and D160 (.19) were similar while the direct heritability estimate of GW18 (.07) was larger than D240 (.03). Maternal heritability estimate of D160 (.16) was larger than maternal heritability of GBW (.06). High and negative correlation (-.95) was observed between GBW and D160. The association between maternal effect of GBW and direct effect of GW18 was positive (.33) while null correlation estimate betweeen D160 and D240 was observed for direct genetic effect. According to the estimated genetic parameters growth rate can be changed by both selection criteria (BBW and D160), during the pre-weaning period, although both selection criteria would not select the same animals, mainly if the selection criteria were based on maternal genetic effect during pre-weaning period and the direct genetic effect during the pos-weaning period. Maternal effect was not an important selection criterion for the studied traits. The low estimated correlations between pairs of traits for the pre and pos-weaning periods, also suggest that the selection criterion for each period, based on the studied traits, can be chosen independently.

Interação genótipo x ambiente e estimativas de parâmetros genéticos dos pesos aos 205 e 365 dias de idade de bovinos Nelore

Body weight records at 205 (205BW) and 365 (365BW) days of age of 46,408 Nelore animals, born from 1976 to 2000 period in 530 Nelore herds of several states of Brazil, were used to evaluate genotype by environment interactions and to estimate genetic and maternal heritability by restricted maximum likelihood methodology. The statistical model included the fixed effects of contemporary group and age of cow (covariate), and the random direct and maternal additive genetic effects. The genetic correlation for 205BW and 365BW, each one considered as different traits in each of the South (S), Southeast (SE), Central west (CO), North (N) and Northeast (NE) regions were 0.86 and 0.84, 0.64 and 0.35, 0.75 and 0.42, 0.79 and 0.86, 0.92 and 0.81, 0.95 and 0.83, 0.83 and 1.00, 0.88 and 0.81, 0.33 and 0.85, 0.63 and 0.99 for S/SE, S/CO, S/N, S/NE, SE/CO, SE/N, SE/NE, CO/N, CO/NE and N/NE, respectively. There is a significant genotype by environment interaction for 205BW in the combination involving the S/CO, S/N, S/NE, CO/NE, and N/NE regions. There are significant genotype by environment interaction effects in the combination involving the S/CO and S/N regions for 365BW. Based on genetic x environment interaction results, regional genetic evaluation is recommend for the very distinct regions.

Avaliação da persistência na lactação da raça Guzerá, utilizando modelos de regressão aleatória

The heritability and the genetic and permanent environment correlations were estimated among six different measures of persistency in the lactation of Guzerat cow, using the Random Regression Model. A total of 8,403 records from 1,034 first lactation cows were evaluated. The Random Regression Model was calculated by the logarithmic function of Ali and Schaeffer and Legendre polynomials to get coefficients for fixed, additive genetic and permanent environment effects. Ali and Schaeffer was the function that better fit to the data, but it had convergence problems. The results showed that persistence is a trait with moderate heritability, and low correlation with genetic value for 305-d milk production which allows to select animals in order to alter the format of the curve of production without affecting the total productivity. The measure of persistence that calculates the difference of milk production between the medium and initial phases was highly correlated with 305-d milk production.

Sensibilidade de valores genéticos de codornas de corte em crescimento às modificações de níveis de proteína das dietas

Um total de 5240 informacoes de peso de progenies provenientes de 200 reprodutores e 400 reprodutrizes, alimentadas com dietas com niveis de proteina bruta que variaram de 24 a 30%, e nivel de 2900kcal de energia metabolizavel, foi utilizado para avaliar a sensibilidade de valores geneticos de duas linhagens de codornas de corte, EV1 e EV2, em relacao as mudancas de niveis proteicos das dietas, utilizando-se modelos de regressao aleatoria. As codornas com maior valor genetico aditivo para peso no ambiente medio (nivel proteico igual a zero em uma escala de -1 a 1) respondem de maneira positiva ao aumento do nivel proteico da dieta, sendo mais importante para a linhagem EV2 e de pouca expressao para a linhagem EV1, no 21o dia de idade. No 42o dia de idade, codornas da linhagem EV1 apresentam aumento de dispersao dos valores geneticos com o aumento dos niveis proteicos da dieta, indicando heterogeneidade de sensibilidades dos valores geneticos aditivos a mudanca ambiente, ou a existencia de interacao genotipo x ambiente. Codornas EV2 apresentaram aumento de dispersao dos valores geneticos em funcao do nivel proteico em ambas as idades. A interacao genotipo x nivel proteico interfere em menores idades na expressao fenotipica da linhagem EV2. As herdabilidades estimadas apresentaram alta variacao e maior magnitude para maiores niveis de proteina bruta na dieta, indicando maior resposta a selecao para niveis mais elevados de proteina da dieta, a excecao da linhagem EV1, no 21o dia de idade. Avaliacoes geneticas realizadas para codornas alimentadas com dietas contendo determinado nivel proteico nao permitiriam a predicao de valores geneticos validos para outros niveis proteicos das dietas, a excecao da linhagem EV1, no 21o dia de idade.

Utilização de modelos de norma de reação com variância residual heterogênea para estudo de valores genéticos de peso de codornas de corte em função de níveis de proteína bruta na dieta

The sensitivity of genetic values for body weight of meat type quails predicted at 21 and 35 days of age under diets with different crude protein levels was evaluated. Data from subjects belonging to two strains (EV1 and EV2) were used to fit a random regression model under heterogeneity of residual variance assumption. The random regression coefficients for intercept (bo) and slope (b1) were positively correlated in all analyses results, but the correlation was higher in the EV2 data analyses for both ages. Results indicated that additive genetic variance and heritability change as a function of the environment gradient for both genetic strains and ages. The reaction norms for EV1 strain suggest there is genotype by environment interaction (G x E) for both ages as there were remarkable changes in the ranking of body weight breeding values for different crude protein levels. Furthermore, changes in the magnitude of the genetic effects dispersion as a function of protein level of diet indicates there is G x E in EV1 and EV2 strains. Therefore, the prediction of breeding values for body weight of quails under a specific level of crude protein in the diet does not hold for different environments regarding the level of this nutrient.