Cattle reference growth curves based on centile estimation: a GAMLSS approach

Abstract

In this paper we provide an alternative to create reference growth curves for female Hereford cattle breed based on the generalized additive models for location, scale and shape (GAMLSS) framework. The proposed methodology avoids some known problems present in the quantile regression, such as crossing quantiles and unsuitability in extreme centiles. Since GAMLSS are semi-parametric regression-type models, any statistical distribution can be considered to explain the behaviour of a given response variable (e.g., body weight) and we are able to model any and all of the parameters of the response variable distribution, it can easily deal with highly complex growth curves (e.g., presenting multiple cycles), heteroskedasticity and skewed data issues, commonly present in this field. We apply the abovementioned methodology, showing that the animal age directly affects median, variability and skewness characteristics of its growth curve. Finally, this approach may be applied in any other animal or plant growth, and it can be used as a powerful decision-making tool by producers.