Alfredo Ribeiro de Freitas

Curvas de crescimento na produção animal

The properties of seven nonlinear models were discussed concerning its applications in the fitting of growth curves in animal production. The models used: Brody, Richards, Von Bertalanffy and two alternatives of Gompertz and Logistic models, were fitted by Gauss Newton method to weight-age data from eight animal species: freshwater prawn Macrobrachium rosenbergi, pepper frog, rabbit, poultry, sheep, goat, swine and cattle. Considering results of the fitted models such as convergence or not, coefficient of determination and biological interpretation of parameters, it was concluded that: a) the Logisticmethod y = A/(1 + e-kt)m estimated body weight in all species, while the Von Bertalanffy model was not adequate only for freshwater prawn Macrobrachium rosenbergi; b) both Gompertz models were adequate for freshwater prawn Macrobrachium rosenbergi, pepper frog, poultry, swine and cattle; c) for each specie, at least two nonlinear of the seven models showed adequate to estimate the body weight of the animal species studied, because the coefficients of determination were above 92.0%.

Adubação nitrogenada em capim-coastcross: efeitos na extração de nutrientes e recuperação aparente do nitrogênio

Foi conduzido experimento em Latossolo Vermelho Distrofico tipico, em Sao Carlos, SP, para avaliar o efeito de doses e fontes de nitrogenio (N), no teor, extracao dos nutrientes e na recuperacao do N aplicado em capim-coastcross (Cynodon dactylon cv. Coastcross). Foram aplicadas sobre a superficie do solo cinco doses de N (0, 25, 50, 100 e 200 kg ha-1corte-1), na forma de ureia ou de nitrato de amonio, em cinco periodos consecutivos, durante a estacao chuvosa. Foram determinados os teores e calculada a extracao de nutrientes e a recuperacao do N. Houve aumento na extracao dos nutrientes com o aumento da producao de forragem, com elevados valores principalmente para N e K. Para altas producoes de forragem (tratamento 500 kg ha-1 ano-1de N) e para as duas fontes de nitrogenio as extracoes dos macronutrientes foram maiores para K e N, seguidas de Ca, S, P e Mg e dos micronutrientes Fe, Mn, Zn e Cu. A recuperacao media de N da ureia foi de 68% do N obtido do nitrato de amonio, que variou, em media, de 68 a 75%.

Evidências de interação genótipo x ambiente sobre características de crescimento em bovinos de corte

The objective of this study was to evaluate the genotype x environment interaction for body weight at weaning (WW) and 12 months of age (W12), average daily gain from weaning to 12 months of age (ADG), and performance based on a principal components index (PC) involving these three traits, in a Canchim (5/8 Charolais + 3/8 Zebu) herd. The environment was the season (semester) of birth, and two methods were used to evaluate the genotype x environment interaction: Method 1 - genetic parameters estimated by the derivative free maximum likelihood method (REML), using two-trait analyses (the same trait in the two seasons), and a model that included the effects of year and month of birth, sex and age of cow as a covariate (linear and quadratic effects), and the random effect of animal; and Method 2 - same methodology as Method 1, but with two statistical models, with or without the uncorrelated random effect of sire - season of birth, testing the difference between the two models using the likelyhood ratio test. By Method 1, the genetic correlations for the same trait in the two environments (seasons) were equal to 0.87, 0.97, 0.91 and 0.88 for WW, W12, ADG and PC, respectively. The heritability estimates were very similar for both environments, for all traits studied. By Method 2, the sire-season of birth effect was significant for all traits studied. These results show evidence of genotype x season of birth interaction for the traits studied, suggesting that, in this herd, genetic evaluation and selection should take this interaction into account.

Herdabilidades e correlações genéticas de características de machos e fêmeas, em um rebanho bovino da raça Canchim

The objective of this study was to estimate the heritabilities and the genetic correlations of body weight (BW12) and scrotal circumference (SC12) of males at twelve months of age and culling age (DH, days in herd) of females, and number (NW10) and kilograms (KW10) of weaned calves produced by females up to ten years of age, in a Canchim (5/8 Charolais + 3/8 Zebu) beef cattle herd. Data were composed of 1370, 826, 826, 2726 and 1051 observations of DH, NW10, KW10, BW12 and SC12, respectively. The variance and covariance components were obtained by the bayesian method, with a statistical model that included, besides the additive direct and residual random effects, the fixed effects of year of birth for all traits, month of birth for BW12 and SC12, and the covariate age for SC12. The heritability estimates, obtained by the one-trait analyses, were equal to 0.38, 0.52, 0.24, 0.33 and 0.34 for BW12, SC12, DH, NW10 and KW10, respectively, indicating that all traits have enough genetic variability to show response to selection. The genetic correlations of DH (0.33 and 0.33, respectively), NW10 (0.38 and 0.30, respectively) and KW10 (0.61 and 0.41, respectively) with BW12 and SC12, obtained by the two-trait analyses, suggest that selection for increased body weight and scrotal circumference of the males at twelve months of age will not result in decreased days in herd for the females, and decreased number and kilograms of weaned calves produced by the females up to ten years of age.

Efeito de fontes e doses de nitrogênio na produção e qualidade da forragem de capim-coastcross

Forage production and quality of coastcross grown on a dark red latosol (Hapludox) were evaluated in 1998-1999 and 1999-2000, from November to April, in Sao Carlos, Sao Paulo state, Brazil, under a tropical altitude climate. The experimental design was a randomized block design, in a split-plot arrangement, with four replications. In the main plots were allocated ten treatments, organized in a 2 ´ 5-factorial scheme (two nitrogen sources: urea and ammonium nitrate, and five N levels: 0, 25, 50, 100, and 200 kg N/ha/cutting, in five consecutive cuttings - repeated measures). Data were analyzed by MIXED procedure of SAS, using a repeated measure model. Nitrogen fertilization increased DM yield, CP concentration, in vitro DM digestibility, and nitrate concentration, and reduced DM and NDF concentrations in the forage. In the first year, N doses associated with 80% of the maximum forage yield were 88 and 78 kg/ha, corresponding to average dry matter yields of 2,769 and 3,202 kg N/ha/cutting, respectively, for urea and ammonium nitrate. In the second year, N doses which produced 80% of the maximum forage yield were 91and 116 kg/ha, respectively, for urea and ammonium nitrate, corresponding to average DM yields of 2,312 and 3,073 kg ha/cutting, respectively.

Parâmetros genéticos para características de tamanho e condição corporal, eficiência reprodutiva e longevidade em fêmeas da raça Canchim

The objectives of this study were to estimate heritability for culling age (TPR), ages at first (IDPP), at second (IDSP) and at third calving (IDTP) and genetic correlations of these traits with adjusted and unadjusted weights for condition score, body size indexes and condition score at first mating, at first calving and at mature age. Variance and covariance components were estimated by REML using univariate and bivariate models including the fixed effect of contemporary group and additive direct genetic and residual as random effects. Heritability estimates obtained from univariate analyses were 0.10 ± 0.05 (IDPP), 0.08 ± 0.05 (IDSP), 0.14 ± 0.06 (IDTP) and 0.06 ± 0.00 (TPR) and indicate low response to selection on these traits. Genetic correlation estimates suggest that selection for increasing mature weight will reduce culling age but for heavier weight at first mating, at first calving and at maturity will not significantly change ages at first, at second and at third calving. Selection on body size indexes and on cow weights adjusted for condition score may result in similar correlated responses for reproductive traits and longevity which would be higher than those from selection on unadjusted cow weights.

Estudo da interação genótipo × ambiente sobre características de crescimento de bovinos de corte utilizando-se inferência bayesiana

The objective of this study was to evaluate the genotype × environment interaction for weaning and yearling weights, daily weight gain from weaning to 12 months of age and the growth performance in Canchim (5/8 Charolais + 3/8 Zebu) beef cattle estimated by a principal components analysis including those three traits. The environment was defined by season of birth (first and second semesters of the year). Genetic parameters were estimated by bayesian method with the Gibbs sampler using bivariate analyses (considering the trait in each of the two seasons as a different one) and models that included the fixed effects of year and month of birth, sex and age of cow (linear and quadratic) and the random effects of animal and residual. The results suggested that genetic evaluation and selection in Canchim beef cattle for the traits studied should consider the genotype and season of birth interaction.

Relação da Circunferência Escrotal e Parâmetros da Qualidade do Sêmen em Touros da Raça Nelore, PO

In 960 Nellore purebred bulls, of 11.4 to 135 months of age, belonging to farms located in the Sao Paulo, Goias and Para states, was studied the possible association among the size of the scrotal circumference (CE) and sperm quality parameters, progressive motility (MOT) and sperm pathologies: the major (DEFMAI), minor (DEFMIN) and total (DEFTOT) defects. The bulls were divided by age in groups: minor than 18, from 18 to 24, from 24 to 30, from 30 to 36 and major than 36 months of age. This study was accomplished with the purpose of obtaining sizes of CE that may indicate the functional status of the testicles through the quality of the semen that can be used to predict the reproductive potential of the animals destined to the selection of bulls. Of the correlation of CE with MOT, by age group, resulted an association (R = 0,60; P<0.0001) of these parameters in the bulls up to 18 months of age, which CE above 26 cm indicated semen of high MOT (60 to 80%). The correlation between CE and sperm pathologies was very low and negatives. It was concluded that in the young bulls the size of CE indicates the quality of the semen, therefore it can be used as a criteria for the selection of animals of high reproductive potential.

Estimativas de ganho genético por diferentes critérios de seleção em genótipos de alfafa

Este estudo foi desenvolvido objetivando comparar diferentes criterios de selecao, indicar o metodo de selecao que propicia maiores estimativas de ganho genetico e identificar genotipos superiores de alfafa quanto a caracteristicas produtivas, morfologicas e bromatologicas. Foram avaliadas a producao de materia seca, altura de planta, tolerância a doencas, aceitacao fenotipica pelos animais, proteina bruta, digestibilidade in vitro da materia seca, fibra em detergente neutro e relacao caule/folha de 92 acessos provenientes do INTA-Argentina, tendo como testemunha o Crioula. Os Indices de Mulamba & Mock, distância do genotipo ao ideotipo e Elston foram os mais adequados a esse tipo de estudo. Os genotipos Sequel, CUF 101, Siriver 2, Florida 77, Diamond, Sequel 2, LE N 2, Medina, Kern, Rio Grande, DK 166, DK 181, Perla SP INTA, WL 516, Rocio, LE Semit 711 e LE N 3 foram os indicados a selecao pelos maiores indices de Mulamba e Mock, distância do genotipo ao ideotipo e indice de Elston.

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.