Ham weight loss and its dynamics in pigs from sires diverging in estimated breeding value for infrared-predicted ham weight loss

Cumulative ham weight loss predicted through visible-near-infrared (VIS-NIR) spectroscopy (CWLp) is considered an indicator trait for indirect selection aimed at reducing actual ham weight loss. However, its effectiveness needs to be validated in practice. This study aimed to evaluate the effects of two groups of sires, diverging in the estimated breeding value (EBV) for CWLp, on the actual cumulative weight loss (CWL) and its dynamics observed during dry-curing in their progeny. The ultimate goal was to validate the use of CWLp as an indicator trait in selective breeding to enhance dry-cured ham production. The study focused on sires from the Goland C21 purebred line, where the breeding objectives include traits related to green ham quality. Since 2010, acquiring VIS-NIR spectra from individual ham subcutaneous fat 24 h after slaughter has been standard practice in the sib-testing programme. These data enabled the prediction of green ham fat quality traits and, since 2021, the computation of CWLp. Starting from a batch of 70 commercial AI C21 boars, two groups of sires were established: one group (bottom sires) consisting of the 15 boars with the highest EBV for CWLp, and another group (top sires) including the 15 boars with the lowest EBV. These two groups were randomly mated with a total of 180 crossbred sows. From the resulting progeny, a random sample of 341 individuals was selected for the study and raised as heavy pigs. After slaughter, the left ham from each pig was weighed ten times during the dry-curing process. Seven non-linear models (Cumulative Weibull, Chapman-Richards, Negative Exponential, U-Richards, U-Gompertz, U-von Bertalanffy and U-Logistic) were compared to describe the individual CWL dynamics. Cumulative Weibull and Chapman-Richards models showed the best fitting (R² = 0.996, RMSE < 0.86%), and the Chapman-Richards function was used to estimate individual curves for CWL. Progeny of top sires exhibited a significantly different CWL kinetics, with a decreased rate of CWL compared to the progeny of bottom sires. They also exhibited lower CWL after 12 and 18 months of dry-curing (-2.4 and -2.6%, respectively, P-value < 0.05) and improved green ham quality traits such as subcutaneous fat depth (+4.4%, P-value < 0.05), and marbling and fat depth scores (P-value < 0.001). These findings indicate that selecting breeding candidates for CWLp has the potential to enhance dry-cured ham production.