Aldrin Vieira Pires

Curvas de crescimento para codornas de corte

Objetivou-se com este trabalho comparar modelos nao lineares para descrever o crescimento de codornas de corte machos e femeas do nascimento ao 42° dia de idade. Foram utilizados 24.679 registros de peso corporal de codornas de corte da linha femea LF1, pertencente ao Programa de Melhoramento de Codornas da UFVJM, em Diamantina, MG. As codornas de tres geracoes sucessivas foram pesadas a cada sete dias (nascimento, 7, 14, 21, 35 e 42 dias de idade). Os modelos de Brody, von Bertalanffy, Richards, Logistico e Gompertz foram ajustados ao conjunto de dados observados. Os parâmetros dos modelos foram estimados, para machos e femeas separadamente, pelo algoritmo de Gauss Newton, utilizando-se o procedimento NLIN do SAS. Os criterios utilizados para escolha do modelo de melhor ajuste da curva de crescimento foram o coeficiente de determinacao (R2), o desvio padrao assintotico (DPA), o desvio medio absoluto dos residuos (DMA) e o indice assintotico (IA). Dos cinco modelos utilizados, apenas o modelo de Richards nao apresentou convergencia, tanto para machos como para femeas. O menor valor para o indice assintotico (IA) foi observado para o modelo de Gompertz em machos (26,57) e o Logistico para femeas (25,02), indicando serem estes os modelos que mais se ajustaram aos dados.

Avaliação genética para peso corporal em um rebanho Nelore

The heritabilities for direct and maternal genetic effects and genetic correlations between these effects were estimated for weight at 205 (P205), 365 (P365), and 550 days (P550) in a Nelore herd in northern Minas Gerais. The statistical model included direct and maternal additive effects, in addition to the fixed effects of contemporary group (farm, gender, diet, season - dry and water -, and year of birth) and the covariate age of cow at calving (linear and quadratic effects). The variance components and genetic values were estimated by REML method. The genetic trend was obtained using the regression of the annual mean genetic value in relation to the year birth. The heritability estimates for the direct additive effect () for P205, P365, and P550 were equal to 0.60, 0.69, and 0.75, respectively. These coefficients showed high magnitude, indicating that the herd in question presents a great additive genetic variability and therefore it is expected a great progress using genetic selection. By the analysis of genetic trend, it was verified a development in animals genetic values over the years studied.

Desempenho de codornas de corte submetidas a diferentes níveis de proteína bruta e energia metabolizável

Objetivou-se avaliar o desempenho de codornas de corte, submetidas a diferentes niveis de proteina bruta (PB) e energia metabolizavel (EM). Avaliaram-se 720 codornas distribuidas em delineamento em blocos ao acaso, em esquema fatorial (5x3), com cinco niveis de PB (18, 20, 22, 24 e 26%) e tres niveis de EM (2700, 2900 e 3100kcal kg-1). As analises foram realizadas utilizando-se o programa SAEG (2007). No periodo inicial, houve efeito quadratico da PB e EM sobre o consumo de racao (CR), efeito quadratico da PB e linear da EM sobre o peso corporal (PC), efeito linear da interacao EM e PB sobre o ganho de peso (GP) e conversao alimentar (CA). No crescimento, efeito quadratico da EM e PB sobre o CR, efeito linear da EM e PB sobre o PC e CA, efeito quadratico da PB e linear da EM sobre o GP. Na terminacao, efeito linear da EM e PB sobre o CR, PC e CA, efeito linear e quadratico da EM e PB sobre GP. Na fase inicial, recomenda-se 26% de PB e 3100kcal EM kg-1. Para a fase de crescimento, sugere-se 3100kcal EM kg-1 e 23% de PB, ja, para a fase de terminacao, recomenda-se 26% de PB e 3100kcal EM kg-1.

Genetic evaluation of European quails by random regression models

The objective of this study was to compare different random regression models, defined from different classes of heterogeneity of variance combined with different Legendre polynomial orders for the estimate of (co)variance of quails. The data came from 28,076 observations of 4,507 female meat quails of the LF1 lineage. Quail body weights were determined at birth and 1, 14, 21, 28, 35 and 42 days of age. Six different classes of residual variance were fitted to Legendre polynomial functions (orders ranging from 2 to 6) to determine which model had the best fit to describe the (co)variance structures as a function of time. According to the evaluated criteria (AIC, BIC and LRT), the model with six classes of residual variances and of sixth-order Legendre polynomial was the best fit. The estimated additive genetic variance increased from birth to 28 days of age, and dropped slightly from 35 to 42 days. The heritability estimates decreased along the growth curve and changed from 0.51 (1 day) to 0.16 (42 days). Animal genetic and permanent environmental correlation estimates between weights and age classes were always high and positive, except for birth weight. The sixth order Legendre polynomial, along with the residual variance divided into six classes was the best fit for the growth rate curve of meat quails; therefore, they should be considered for breeding evaluation processes by random regression models.

Comportamento ingestivo de bovinos leiteiros alimentados com farelo de crambe

O objetivo deste trabalho foi estudar os efeitos da utilizacao de farelo de crambe em substituicao ao farelo de soja sobre o comportamento ingestivo de bovinos leiteiros. Foram utilizados quatro machos castrados Holandes x Zebu, fistulados no rumen, com peso vivo medio de 664kg, distribuidos em delineamento quadrado latino 4 x 4. Os tratamentos consistiram em quatro dietas isoproteicas e isoenergeticas, formuladas com relacao volumoso:concentrado 60:40 com base na materia seca (MS). O volumoso foi composto de silagem de milho (51% MS) e feno de Tifton (49% MS), e o concentrado formulado com niveis crescentes de substituicao do farelo de soja pelo farelo de crambe em 0%, 2,8%, 6,4% e 11,0% na MS da dieta. O comportamento ingestivo foi avaliado por meio do metodo direto de avaliacao visual, em intervalos de 10 minutos, durante periodos de 24 horas. Registraram-se a frequencia de alimentacao, a ruminacao e o ocio, bem como a posicao do animal (em pe ou em decubito). As variaveis em pe e em decubito nao diferiram entre os tratamentos, assim como os tempos gastos em alimentacao, ruminacao e ocio. O consumo de materia seca e de FDN expressos em g/dia e gFDN/dia, respectivamente, a eficiencia de ruminacao expressa em gMS/min, a eficiencia de ruminacao expressa em gFDN/dia e o tempo de mastigacao total nao diferiram significativamente. No entanto, a eficiencia de alimentacao (gMS/min) variou de forma linear decrescente com a inclusao do farelo de crambe. Os periodos do dia influenciaram todas as atividades. O maior tempo de alimentacao foi observado nos periodos apos o fornecimento da dieta, e a maior atividade de ruminacao foi verificada no periodo noturno. A substituicao de farelo de soja por farelo de crambe nao afetou o comportamento ingestivo, exceto para o parâmetro eficiencia de alimentacao. Nesse sentido, considerando o comportamento ingestivo, recomenda-se a substituicao do farelo de soja por farelo de crambe para alimentacao de bovinos leiteiros.

Características de desempenho e de carcaça em diferentes genótipos de codornas de corte

This study was carried out to compare and relate the performance and carcass traits of different quail genotypes from hatch to 35 days of age. A total of 1176 one-day-old quails of both sexes were allotted in a completely randomized experimental design, in a 7x2 factorial scheme (genotypes x sexes), in seven replicates with 12 quails per experimental unit. Quails of each genotype were weighed weekly from hatch to 35 days of age. At 35 days of age two males and two females of each genotype and replicate were sampled and slaughtered to evaluate carcass weight and main cut yield. Statistical analyses were performed by GLM and CORR procedure from the Statistical Analysis System (SAS, 2000, version 9.0), with the MANOVA option of the SAS device to assess the differences between the genotypes and the correlation between variables. There was no interaction (P≥0.05) between genotype and sex with the performance characteristics of weight and weight gain. However, there was a significant effect of genotype x sex (P<0.05) for the characteristics carcass,breast, thigh and drumstick weights. In general, quails of genetic groups UFV1, UFV2 and UFV3 were heavier from 7 to 35 days of age. We observed that for the correlation the tendency is that quail that showed higher body weight and weight gain will have greater housing and main cuts weight.

Seleção de características morfofuncionais de cavalos da raça Mangalarga Marchador por meio da análise de componentes principais

Records from 14,288 animals of the Mangalarga Marchador breed, born from 1990 to 2005, were used to discard morphofunctional traits in a principal component analysis. The following traits were used: height at withers, height at croup, lengths of head, neck, back, croup, hip length and body, widths of head, hip width, thorax perimeter, cannon bone circumference and gait score. For the traits considered it was observed that 7 principal components showed variation lower than 0.7; suggesting that seven variables could be discarded. The reason is that when variable are highly correlated with the principal components of smaller variance, their variation is practically insignificant. Based on those results the recommendation is to maintain the following traits for future research with this database: gait score, height at croup, length of back, length of croup, width of head and cannon bone circumference.

Generalized linear mixed models for the genetic evaluation of binary reproductive traits: a simulation study

The objective of this study was to evaluate the use of probit and logit link functions for the genetic evaluation of early pregnancy using simulated data. The following simulation/analysis structures were constructed: logit/logit, logit/probit, probit/logit, and probit/probit. The percentages of precocious females were 5, 10, 15, 20, 25 and 30% and were adjusted based on a change in the mean of the latent variable. The parametric heritability (h2) was 0.40. Simulation and genetic evaluation were implemented in the R software. Heritability estimates (ĥ2) were compared with h2 using the mean squared error. Pearson correlations between predicted and true breeding values and the percentage of coincidence between true and predicted ranking, considering the 10% of bulls with the highest breeding values (TOP10) were calculated. The mean ĥ2 values were under- and overestimated for all percentages of precocious females when logit/probit and probit/logit models used. In addition, the mean squared errors of these models were high when compared with those obtained with the probit/probit and logit/logit models. Considering ĥ2, probit/probit and logit/logit were also superior to logit/probit and probit/logit, providing values close to the parametric heritability. Logit/probit and probit/logit presented low Pearson correlations, whereas the correlations obtained with probit/probit and logit/logit ranged from moderate to high. With respect to the TOP10 bulls, logit/probit and probit/logit presented much lower percentages than probit/probit and logit/logit. The genetic parameter estimates and predictions of breeding values of the animals obtained with the logit/logit and probit/probit models were similar. In contrast, the results obtained with probit/logit and logit/probit were not satisfactory. There is need to compare the estimation and prediction ability of logit and probit link functions.