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Objective: The aim of this study was to identify suitable polynomial regression for modeling the average growth trajectory and to estimate the relative development of the rib eye area, scrotal circumference, and morphometric measurements of Guzerat young bulls. Methods: A total of 45 recently weaned males, aged 325.8±28.0 days and weighing 219.9±38.05 kg, were evaluated. The animals were kept on Brachiaria brizantha pastures, received multiple supplementations, and were managed under uniform conditions for 294 days, with evaluations conducted every 56 days. The average growth trajectory was adjusted using ordinary polynomials, Legendre polynomials, and quadratic B-splines. The coefficient of determination, mean absolute deviation, mean square error, the value of the restricted likelihood function, Akaike information criteria, and consistent Akaike information criteria were applied to assess the quality of the fits. For the study of allometric growth, the power model was applied. Results: Ordinary polynomial and Legendre polynomial models of the fifth order provided the best fits. B-splines yielded the best fits in comparing models with the same number of parameters. Based on the restricted likelihood function, Akaike's information criterion, and consistent Akaike's information criterion, the B-splines model with six intervals described the growth trajectory of evaluated animals more smoothly and consistently. In the study of allometric growth, the evaluated traits exhibited negative heterogeneity (b<1) relative to the animals' weight (p<0.01), indicating the precocity of Guzerat cattle for weight gain on pasture. Conclusion: Complementary studies of growth trajectory and allometry can help identify when an animal's weight changes and thus assist in decision-making regarding management practices, nutritional requirements, and genetic selection strategies to optimize growth and animal performance. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the genetic divergence between lineages of quail and their crosses to the performance characteristics through multivariate analysis. Four lines of quails were used in a complete diallel system, provided training to 16 groups of progenies, four parental pure: L1, L2, L3 and L4; six genetic groups crossbred F1: G12, G13, G14, G23, G24 and G34; and six reciprocal F1 crossbred genetic groups. The variables were evaluated: mean body weight at birth, at 28, at 35 and 42 days of age; the average consumption of diet from birth to 35 and 42 days of age; feed conversion birth at 35 and 42 days of age; and the weight gain from birth to 35 and 42 days of age. The performance of genetic groups was assessed by multivariate analysis of variance and the first canonical variable, using the tests of the largest eigenvalue of Roy and Roy union-intersection for multiple comparisons. The study of genetic diversity was done by canonical variate analysis and by the optimization method of Tocher. The first three canonical variables explained 88.82% of the genetic variation between groups. The genetic divergence between the analyzed genetic groups allowed the formation of four groups: 1-L1, G12, G23, G21 and G41; 2-G13 and G31; 3-L4 and G43; 4-G32; 5-G14 and G24; 6-G42 and 7-L2, L3, identifing L4 G34 as the lineage that most influenced the formation of new groups. [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate genetic parameters and phenotypic parameters of egg production curve, using the segmented polynomial model( " xp " - the peak age of the birds in attitude, "P" - at peak production level, "s" - rate of decline in weekly egg production after peak, and "t" - time between the onset of lay and peak egg production). We used data from the weekly egg production from 25 to 64 weeks of age from 2,398 arrays of a lineage of broilers chickens. Estimation of covariance components, lieritability and correlations for these parameters curve posture were obtained by restricted maximum likelihood. Genetic trends were estimated with the average breeding values the of parameters of the curve as a function of birth year of the arrays. The mean heritabilities were low to medium magnitude, 0.25 (xp), 0.18 (P), 0.17 (s) e 0.10 (t). Genetic correlations among the parameter "t" and the other parameters of the curve were positive ranging from 0.21 to 1.00, being lower between "t" and "s", and higher between the parameters xp and t. Between the parameters xp and P the correlation was also positive, of an average magnitude (0.39). Correlations were negative between parameters "s" and "xp", and "s" and "P", presenting itself lower between "s" and "xp" (-0.17) and higher between "s" and "P" (-0.91). The genetic trends found for the parameters of the model indicated a reduction in time between the production's onset and peak, and age at production's peak. The level of production showed a decline in breeding value over the period evaluated. It can be observed a potential genetic gain for the egg's production parameters' curve; however, it must be paid special attention to the positive genetic correlations between the parameter xp and P. What can lead to an increase in the level of production and may lead to an increase in age at peak production. The same applies to the parameters xp indicating that birds with earlier peaks may present lower persistence. [ABSTRACT FROM AUTHOR]