Modeling growth curves in Thoroughbred foals raised on pasture in Argentina

Thoroughbred breeding holds significant economic importance on a global scale and Argentina is a prominent participant in this industry. Suboptimal growth of Thoroughbred foals below their genetic potential could have consequences on their athletic ability. But, unlike some livestock, maximal growth in horses is not advantageous, as it can lead to skeletal problems. Therefore, the meticulous monitoring of foal growth is indispensable for effective horse breeding. This longitudinal study examined 18,639 weight records obtained from 2631 foals (0–19 months old) across an 11-year period. The objective of this study was to identify the most suitable models for fitting growth curves of pasture-raised Thoroughbred foals. Seven model was separately fitted to the records using SAS's NLIN procedures. The goodness of fit of the models was based on Akaike's Information Criterion, Mean Square Error and Root Mean Square Error statistics. The study concluded that the Polynomial G3 model best describes the growth patterns of Thoroughbred foals in Pampas region, providing the final equation for predicting the average population weight of these foals based on their age in months: Body weight = 58.8 + 41.65 t − 1.82 t²+ 0.041 t³ (where t is age in months). This model's accuracy was consistent across sex, eliminating the need for separate models based on sex. This equation allows us to estimate the foals' body weight as a function of their age, providing a valuable tool for monitoring their growth and development. These insights have the potential to enhance breeding practices and optimize management strategies within horse production systems in a region renowned for its pasture-based management approach.