Henrique Torres Ventura

A canonical correlation analysis of the association between carcass and ham traits in pigs used to produce dry-cured ham.

The association between carcass and ham traits in a pig population used to produce dry-cured ham was studied using canonical correlation analysis. The carcass traits examined were hot carcass weight (HCW), backfat thickness (BT) and loin depth (LD), and the ham traits studied were gross ham weight (GHW), trimmed ham weight (THW), ham inner layer fat thickness (HIFT), ham outer layer fat thickness (HOFT), pH (pH) and the Göfo value. Carcass and ham traits are not independent. The canonical correlations (r) between the carcass and ham traits at 130 kg were 0.77, 0.24 and 0.20 for the first, second and third canonical pair, respectively, and were all significant (p < 0.01) by the Wilks test. The corresponding canonical correlations between the three canonical variate pairs for the carcass and ham traits at 160 kg were 0.88, 0.42 and 0.14, respectively (p < 0.05 for all, except the third). The correlations between the traits and their canonical variate showed an association among HCW, GHW and THW, and between BT and HOFT. These results indicate that carcass traits should be used to cull pigs that are not suitable for dry-cured ham production.

Genetic evaluation of age at first calving for Guzerá beef cattle using linear, threshold, and survival Bayesian models

Age at first calving (AFC) is characterized as a censored trait due to missing values provided by recording mistakes and nonoccurrence or delay in calving communication. In this context, we aimed to compare several statistical methods for genetic evaluation of AFC in Guzerá beef cattle under a Bayesian approach. Seven different methods were used for this purpose. The traditional linear mixed model (LM), which considers only uncensored records; the LM with simulated records (SM), which is based on data augmentation framework; the penalty method, in which a constant of 21 d was added to censored records; the bivariate threshold-linear method considering (TLcens) or not (TLmiss) censored information; and the piecewise Weibull proportional hazards model considering (PWPHcens) or not (PWPH) censored records. Heritability estimates ranged from 0.19 (TLcens) to 0.28 (SM) in nonsurvival approaches; and 0.40 and 0.46 to PWPH and PWPHcens methods, respectively. In general, breeding values correlations between different methods and the percentage of selected bulls in common indicated reranking, with these correlation ranging from -0.28 (between SM and PWPH) to 0.99 (between TLmiss and LM). The traditional LM, which considers only uncensored records, should be preferred due to its robustness and simplicity. Based on cross-validation analyses, we conclude that the TLmiss could be also a suitable alternative for breeding value prediction, and censored methods did not improve the analysis.

Meta-analysis of genetic-parameter estimates for reproduction, growth and carcass traits in Nellore cattle by using a random-effects model

Meta-analysis based on a random-effects model is used to summarise and overcome the variability between divergent parameter estimates. We proposed a meta-analysis of published heritability and genetic-correlation estimates for reproduction, growth and carcass traits in purebred Nellore cattle. In total, 197 heritability and 107 genetic-correlation estimates from 62 scientific publications were used here. Most of traits (gestation length; weights at birth, 120, 210, 365 and 550 days of age; mature weight and all carcass traits) presented direct heritability estimates ranging from 0.20 to 0.40. Age at first calving presented the lowest value among direct heritabilities (0.1498); whereas the higher values (>0.40) were found for scrotal circumference at different ages and for weight at 450 days of age. Low maternal heritability estimates (ranging from 0.06 to 0.11) were observed for all growth traits. With the exception of correlation estimates involving the age at first calving, all other correlations were positive. High correlations (>0.85) were found mainly for the same trait at different ages. The results reported here will give support to genetic evaluations when reliable estimates for different traits in purebred Nellore cattle are not available.