Data from a divergent experiment for birthweight (BrW) environmental variability were used to estimate genetic parameters for BrW trait and its environmental variability by fitting both homoscedastic (HO) and heteroscedastic (HE) models. A total of 5 475 records of BrW from animals born from inbred dams, and 7 140 pedigree records were used. The heritability of BrW using the model HO was 0.27, with the litter effect much more important, 0.43. The model HE provided a genetic correlation between the trait and its environmental variability that was very high and negative, -0.97, and a high value for the additive genetic variance for environmental variability, suggesting an artefact in the model. The residual skewness was found to be essentially null. A model considering the genetic correlation null was also fitted, and used to obtain the breeding values for the selection process. Moreover, the trait was considered as maternal resulting in similar estimates under the model HO, but more reasonable for the genetic correlation between the trait and its environmental variability of 0.48 with a value of 0.25 for the additive genetic variance regarding environmental variability under the model HE. This led to the conclusion that environmental variability of BrW in mice must be selected via dams. Estimated parameters in a reduced dataset without inbred animals did not substantially change this conclusion.

The alpaca is the most important fiber producer of the South American camelid species, and is an important source of income for the Andean communities. Nowadays, fiber diameter is considered the main selection objective in alpaca populations throughout the world. However, fiber diameter increases with the age of the animals, and it would be preferable to select those animals that maintain a thin fiber throughout their life span. The goal of this study was to describe the genetic relationship between fiber diameter at weaning age (6 mo) and the evolution of fiber diameter along the life span. The analysis of the evolution of fiber diameter was studied as a useful model for canalization and as a longitudinal trait by hierarchical Bayesian analysis. The results suggested that substantial genetic variation exists for fiber diameter and also for the variability and linear growth of the fiber diameter. Thus, a genetic selection program is plausible to modify the evolution of fiber diameter with time, together with a favorable correlated decrease in fiber diameter.

A total of 15,645 records of birth weight (BrW), weaning weight (WW) and average daily gain (ADG) from 6055 cows belonging to 2121 different dam lines were analyzed to quantify the contribution of cytoplasmic line (l) effects to phenotypic variance of preweaning growth traits in a sample of Asturiana de los Valles beef cattle breed. Only dam lines with 2 or more cows having performance records in the database were used. Bayesian estimates were obtained fitting eight different univariate and multivariate models defined depending on the inclusion or not of the permanent maternal environment (c) and the l effects. Univariate models that included both the c and the l effects had the best fit with data (assessed by computing the logarithm of the conditional predictive ordinate; logCPO) for BrW and ADG while for WW this was the case for the model that only included the c effect. For multivariate models, the best fit with data was obtained for the model that only included the c effect (logCPO = − 245,899) while the second "better" model was that which only include the l effect value (logCPO = − 241,108). In general, whatever the estimation model used, estimates of heritability for the direct (h 2 ) and maternal (m 2 ) genetic effects and the genetic correlation between them (r am ) obtained in the current study for BrW were slightly higher (r am more negative) than the most recent estimates reported in the breed. However, this is not true for WW and ADG when multivariate estimation models include the l effect. In these cases, estimates of h 2 and m 2 for WW and ADG tend to be lower and r am less negative than those previously estimated. In conclusion, the cytoplasmic line may have a marginal effect on growth performance in beef cattle but not sufficient in magnitude to justify including the l effect in models in beef improvement schemes.