Β-glucans and MOS, essential oil, and probiotics in diets of broilers challenged with Eimeria spp. and Clostridium perfringens.

The aim of this study was to evaluate the effectiveness of ß-glucans and MOS, essential oil (mixture of carvacrol and thymol), and the probiotic based on Saccharomyces boulardi, as an alternative to anticoccidial agents. In this experiment, six hundred seventy-two 1-day-old male broiler chicks were housed in batteries for 28 d. The experimental design of 4 randomized blocks with 24 cages each, and 7 birds per cage, consisted of an initial phase from 1 to 14 d of age, and a growth phase, from 15 to 28 d of age. The rations were formulated based on corn and soybean meal as energy and protein ingredients, respectively. All birds were inoculated with Eimeria spp and C. Perfringes at 14 d of age, and with C. Perfringes only at 21 d of age. The results showed the best weight gain in the initial phase when the anticoccidial agent was applied, whereas the use of additives in growth and entire experimental phases showed superior results in all treatments for this parameter. The birds that did not receive additives in the rations had the worst feed conversion in both phases and along raising. The results showed no significant differences between the treatments for the scores of lesions in the digestive tract and counts in the cecum, however, the red lesions increased numerically in the duodenum and jejunum of birds fed diets without the inclusion of additives. The use of additives indicated effectiveness for the parameters of performance in broilers challenged with C. Perfringes and Eimeria spp. at 14 d of age, and with C. Perfringes at 21 d of age.

Genetic parameters for growth characteristics of free-range chickens under univariate random regression models.

Repeated measures from the same individual have been analyzed by using repeatability and finite dimension models under univariate or multivariate analyses. However, in the last decade, the use of random regression models for genetic studies with longitudinal data have become more common. Thus, the aim of this research was to estimate genetic parameters for body weight of four experimental chicken lines by using univariate random regression models. Body weight data from hatching to 84 days of age (n = 34,730) from four experimental free-range chicken lines (7P, Caipirão da ESALQ, Caipirinha da ESALQ and Carijó Barbado) were used. The analysis model included the fixed effects of contemporary group (gender and rearing system), fixed regression coefficients for age at measurement, and random regression coefficients for permanent environmental effects and additive genetic effects. Heterogeneous variances for residual effects were considered, and one residual variance was assigned for each of six subclasses of age at measurement. Random regression curves were modeled by using Legendre polynomials of the second and third orders, with the best model chosen based on the Akaike Information Criterion, Bayesian Information Criterion, and restricted maximum likelihood. Multivariate analyses under the same animal mixed model were also performed for the validation of the random regression models. The Legendre polynomials of second order were better for describing the growth curves of the lines studied. Moderate to high heritabilities (h(2) = 0.15 to 0.98) were estimated for body weight between one and 84 days of age, suggesting that selection for body weight at all ages can be used as a selection criteria. Genetic correlations among body weight records obtained through multivariate analyses ranged from 0.18 to 0.96, 0.12 to 0.89, 0.06 to 0.96, and 0.28 to 0.96 in 7P, Caipirão da ESALQ, Caipirinha da ESALQ, and Carijó Barbado chicken lines, respectively. Results indicate that genetic gain for body weight can be achieved by selection. Also, selection for body weight at 42 days of age can be maintained as a selection criterion.