Fábio Luiz Buranelo Toral

Association of PIT1 genotypes with growth traits in Canchim cattle

O uso de marcadores geneticos pode favorecer a identificacao de animais geneticamente superiores em bovino de corte. O gene PIT1 codifica para o fator de transcricao Pit-1, critico para ativar a expressao dos genes da prolactina, hormonio de crescimento e PIT1. Esta pesquisa investiga o efeito do polimorfismo HinfI-PIT1 sobre caracteristicas de crescimento em 509 animais da raca Canchim, pertencentes a duas linhagens, GG1 e GG2. Os genotipos do gene PIT1 foram identificados pela tecnica PCR-RFLP. Os efeitos dos genotipos sobre valores fenotipicos para pesos ao nascimento (PN), pesos padronizados a desmama (P240) e ao ano (P365), ganhos medios diarios de peso do nascimento a desmama (GMND), e da desmama aos 12 meses de idade (GMD12) foram analisados pelo metodo dos quadrados minimos. Foram observados efeitos de interacao entre grupo genetico do animal e genotipo de PIT1 sobre P240, GMND e GMD12 (P < 0.05). Diferencas entre medias dos genotipos HinfI (-/-), HinfI (+/+) e HinfI (+/-) para P240 e GMND foram observadas em GG2 (P < 0,05), revelando superioridade do genotipo HinfI (-/-). As medias dos genotipos (+/+) e (+/-) para P240 e GMND, nao diferiram, sugerindo efeito de dominância do alelo HinfI (+). O alelo HinfI (-) mostrou-se favoravel sobre P240 e GMND em GG2, quando em homozigose. A diferenca de comportamento de PIT1 observada nos dois grupos geneticos pode sugerir a acao de loco de caracteristica quantitativa ligado ao gene PIT1, segregando apenas em GG2.

Use of nonlinear models for describing scrotal circumference growth in Guzerat bulls raised under grazing conditions

The objective was to use various nonlinear models to describe scrotal circumference (SC) growth in Guzerat bulls on three farms in the state of Minas Gerais, Brazil. The nonlinear models were: Brody, Logistic, Gompertz, Richards, Von Bertalanffy, and Tanaka, where parameter A is the estimated testis size at maturity, B is the integration constant, k is a maturating index and, for the Richards and Tanaka models, m determines the inflection point. In Tanaka, A is an indefinite size of the testis, and B and k adjust the shape and inclination of the curve. A total of 7410 SC records were obtained every 3 months from 1034 bulls with ages varying between 2 and 69 months (<240 days of age = 159; 241-365 days = 451; 366-550 days = 1443; 551-730 days = 1705; and >731 days = 3652 SC measurements). Goodness of fit was evaluated by coefficients of determination (R(2)), error sum of squares, average prediction error (APE), and mean absolute deviation. The Richards model did not reach the convergence criterion. The R(2) were similar for all models (0.68-0.69). The error sum of squares was lowest for the Tanaka model. All models fit the SC data poorly in the early and late periods. Logistic was the model which best estimated SC in the early phase (based on APE and mean absolute deviation). The Tanaka and Logistic models had the lowest APE between 300 and 1600 days of age. The Logistic model was chosen for analysis of the environmental influence on parameters A and k. Based on absolute growth rate, SC increased from 0.019 cm/d, peaking at 0.025 cm/d between 318 and 435 days of age. Farm, year, and season of birth significantly affected size of adult SC and SC growth rate. An increase in SC adult size (parameter A) was accompanied by decreased SC growth rate (parameter k). In conclusion, SC growth in Guzerat bulls was characterized by an accelerated growth phase, followed by decreased growth; this was best represented by the Logistic model. The inflection point occurred at approximately 376 days of age (mean SC of 17.9 cm). We inferred that early selection of testicular size might result in smaller testes at maturity.

Abordagens freqüentista e bayesiana para avaliação genética de bovinos da raça Canchim para características de crescimento

This study aimed to: a) to compare the covariance components obtained by Restricted Maximum Likelihood (REML) and by bayesian inference (BI); b) to run genetic evaluations for weights of Canchim cattle measured at weaning (W240) and at eighteen months of age (W550), adjusted or not to 240 and 550 days of age, respectively, using the mixed model methodology with covariance components obtained by REML or by BI; and c) to compare selection decisions from genetic evaluations using observed or adjusted weights and by REML or BI. Covariance components, heritabilities and genetic correlation for W240 and W550 were estimated and the predicted breeding values were used to select 10% and 50% of the best bulls and cows, respectively. The covariance components obtained by REML were smaller than the a posteriori means obtained by BI. Selected animals from both procedures were not the same, probably because the covariance components and genetic parameters were different. The inclusion of age of animal at weighing as a covariate in the statistical model fitted by BI did not change the selected bulls and cows.

Desempenho e morfometria da mucosa de duodeno de frangos de corte alimentados com farelo de canola, durante o período inicial

A trial was carried to verify the effect of increasing levels (0, 10, 20, 30 and 40%) of canola meal in diets of broiler chickens, on performance and mucous morphology, during the starting period (1 - 21 days). 1,000 male chicks one-day-old were used, distributed in a randomized experimental assay, with five treatments, four replicates and 50 birds per experimental unit. At the 1 st , 21 st and 41 st days, the birds and the rations were weighed and at the 21 st day two birds of each experimental unit were sacrificed for collection of a duodenum segment for evaluation of intestinal morphometry. The results demonstrated that increasing levels of canola meal induced to a linear reduction in weight gain, weight and feed intake and worst feed conversion. During the growing period (21 to 41 days), in which all of the birds received similar diet, a decrease was observed in the weight and weight gain, with the increase of the levels of canola meal, while parameters feed conversion and feed intake were similar. Data regarding mucous morphology, submitted to the regression analysis, demonstrated that there was increase in crypt depth in accordance of increasing levels of canola meal. It is possible to include up to 20% of canola meal without damages on broiler performance and in the digestive tract.

Genotype × environment interaction in individual performance and progeny tests in beef cattle

The study reported here evaluated genotype × environment interaction in individual performance and progeny tests in beef cattle. Genetic parameters for final weight (FW), ADG, and scrotal circumference (SC) of 33,013 Nellore young bulls tested on pasture or in feedlots were analyzed. The posterior means (and highest posterior density interval with 90% of samples [HPD90]) of heritability for traits measured on pasture-raised and feedlot-raised animals were 0.44 (HPD90 = 0.40 to 0.48) and 0.50 (HPD90 = 0.43 to 0.56) for FW, 0.26 (HPD90 = 0.23 to 0.29) and 0.26 (HPD90 = 0.20 to 0.32) for ADG, and 0.53 (HPD90 = 0.48 to 0.59) and 0.65 (HPD90 = 0.55 to 0.74) for SC, respectively. The posterior means (and HPD90) of genetic correlations for FW, ADG, and SC on pasture and in feedlots were 0.75 (HPD90 = 0.66 to 0.87), 0.49 (HPD90 = 0.31 to 0.66), and 0.89 (HPD90 = 0.83 to 0.97), respectively. When the selection intensity was kept the same for both the environments, the greatest direct responses for FW and ADG were exhibited by the animals reared and selected in feedlots. The correlated responses relative to production on pasture and based on selection in feedlots were similar to the direct responses, whereas the correlated responses for production in feedlots and based on selection on pasture were lower than the direct responses. When the selection intensity on pasture was higher than the selection intensity in feedlots, the responses to direct selection were similar for both the environments and correlated responses obtained in feedlots by selection on pasture were similar to the direct responses in feedlots. Analyses of few or poor indicators of genotype × environment interaction result in incorrect interpretations of its existence and implications. The present work demonstrated that traits with lower heritability are more susceptible to genotype × environment interaction and that selection intensity plays an important role in the study of genotype × environment interaction in beef cattle.

Residual variance structures to estimate covariance functions for weight of Canchim beef cattle.

This study was carried out to evaluate the use of different residual variance structures to estimate covariance functions for weight of Canchim beef cattle. The covariance functions were estimated by the Restricted Maximum Likelihood method, in an animal model with fixed effect of contemporary group (year and month of birth and sex), age of dam at calving as covariable (linear and quadratic effects) and mean growth trajectory while the random effects considered were the direct additive genetic and maternal effects, permanent individual environment and maternal and residual effects. Different structures were used for residual variance: ordinary polynomials of different orders (linear to fifth) and step functions with 1, 5, 10, 15 and 20 classes. Homogeneous residual variance was not adequate. The four-ordered variance function and the step function with 20 classes presented the best fit and the class division was more efficient than residual functions. The estimated heritabilities were between 0.16 and 0.25, and the greatest ones were obtained close to 360 days and at the end of the study period. The estimated heritabilities were similar for models with homogeneous residual variance, four-ordered residual function and step model with 20 classes of heterogeneous variances. The best description of residual variance, for weights at different ages of Canchim beef cattle, was by step function with 20 classes of heterogeneous variances. However, as existing classes with the same variances, they can be grouped to reduce the number of parameters to be estimated.

Características estruturais e agronômicas da Brachiaria brizantha cv. Xaraés submetida a doses de nitrogênio

The objective of this experiment was to evaluate the structural characteristics and agronomic traits of Brachiaria brizantha cv. Xaraes under different nitrogen levels (0, 125, 250, 375 and 500 kg.ha-1 of N) grown in Campus Rondonopolis, Mato Grosso, in the period 10/12/2006 to 08/23/2007. The treatments were arranged in a randomized design with four repetitions. The results were submitted to statistical analysis by grouping the data into two periods: rain and throughout the year. The N influenced the number of leaves appeared at the time rainy, and the number of green leaves. The number of leaves was influenced by N rates during the rain and throughout the year. There was an increase of 27% in the average length of the leaf blade to the dose of 343.9 kg ha-1 N for the rainy season. The density of tillers was influenced by N rates for both evaluation periods. Since the height of the plants was influenced by N rates for the two seasons evaluated. The increased availability of dry per hectare was 87.5% for the highest N in the water (333.3 kg ha-1 N) compared with the control treatment. Nitrogen fertilization positively influences all characteristics related to growth and production mass, especially during the rainy season, when the fertilization must be divided into four or five doses, with no need for fertilization in the dry season.

Genetic analysis of resistance to ticks, gastrointestinal nematodes and Eimeria spp. in Nellore cattle

The aim of the present study was to obtain genetic parameters for resistance to ticks, gastrointestinal nematodes (worms) and Eimeria spp. in Nellore cattle, analyze the inclusion of resistance traits in Nellore breeding programs and evaluate genetic selection as a complementary tool in parasite control programs. Counting of ticks, gastrointestinal nematode eggs and Eimeria spp. oocysts per gram of feces totaling 4270; 3872 and 3872 records from 1188; 1142 and 1142 animals, respectively, aged 146 to 597 days were used. The animals were classified as resistant (counts equal to zero) or susceptible (counts above zero) to each parasite. The statistical models included systematics effects of contemporary groups and the mean trajectory. The random effects included additive genetic effects, direct permanent environmental effects and residual. The mean trajectory and random effects were modeled with linear Legendre polynomials for all traits except for the mean trajectory of resistance to Eimeria spp., which employed the cubic polynomial. Heritability estimates were of low to moderate magnitude and ranged from 0.06 to 0.30, 0.06 to 0.33 and 0.04 to 0.33 for resistance to ticks, gastrointestinal nematodes and Eimeria spp., respectively. The posterior mean of genetic and environmental correlations for the same trait at different ages (205, 365, 450 and 550 days) were favorable at adjacent ages and unfavorable at distant ages. In general, the posterior mean of the genetic and environmental correlations between traits of resistance were low and high-density intervals were large and included zero in many cases. The heritability estimates support the inclusion of resistance to ticks, gastrointestinal nematodes and Eimeria spp. in Nellore breeding programs. Genetic selection can increase the frequency of resistant animals and be used as a complementary tool in parasite control programs.

Genetic parameters and alternatives for evaluation and ranking of Nellore young bulls in pasture performance tests

The objective of this study was to estimate (co)variance components for weight at 550 days, average daily gain and an index with both traits, and to compare alternatives for evaluation and ranking of Nellore young bulls in pasture performance tests. The heritability estimates were 0.73, 0.31 and 0.44 for weight at 550 days, average daily gain and index, respectively. Animals were ranked according to their predicted breeding values or the phenotypic deviations in relation to the mean of the test. Although the correlations between breeding values and phenotypic deviations were high, there were differences in the number of animals selected in common when the selection criteria were the predicted breeding values or the phenotypic deviations. Mixed models are more appropriate than the least squares method and should be utilized in the evaluation of young bulls in performance tests.

Seleção e classificação multivariada de modelos de crescimento não lineares para bovinos Nelore

This study aimed to evaluate cluster analysis in classifying and selecting non linear models to describe Nelore beef cattle growth based on different goodness of fit criteria tests. A total of 12 non linear models were evaluated based on the following criteria: the determination coefficient (R2), error mean square (QME), Akaike information criterion (AIC), Bayesian information criterion (BIC), mean quadratic error of prediction (MEP) and predicted determination coefficient (R2p). The Brody model showed the best adjustment for the data set.