The effect of first-lactation calving season, milk production, and morphology on the survival of Simmental cows
Giovanni Buonaiuto, Giulio Visentin, Angela Costa, Giovanni Niero, L. Degano, Damiano Cavallini, Ludovica Maria Eugenia Mammi, Alberto Palmonari, Andrea Formigoni, N. López‐Villalobos
Abstract
Longevity in dairy and dual-purpose cattle is a complex trait which depends on many individual and managerial factors. The purpose of the present study was to investigate the survival (SURV) rate of Italian Simmental dual-purpose cows across different parities. Data of this study referred to 2 173 primiparous cows under official milk recording that calved between 2002 and 2020. Only cows linearly classified for type traits, including muscularity (MU) and body condition score (BCS) were kept. Survival analysis was carried out, through the Cox regression model, for different pairwise combinations of classes of milk productivity and MU, BCS, and first-calving season. Herd-year of first calving was also considered in the model. SURV (0 = culled; 1 = survived) at each lactation up to the 6th were the dependent variables, so that, for example, SURV2 equal to 1 was attributed to cows that survived first lactation and entered the second. Survival rates were 98, 71, 63, 56, and 53% for 2nd, 3rd, 4th, 5th, and 6th lactation, respectively. However, it is important to consider that in this study all first-calving cows culled before the linear evaluation - carried out between mid and late lactation in this breed - were not accounted for. Results revealed that SURV2 was not dependent on milk yield, while in subsequent parities low-producing cows were characterized by higher SURV rates compared to high-producing ones. Additionally, cows starting the lactation in autumn survived less (47.38%) than those starting in spring (53.49%). This suggests that facing the late gestation phase in summer could increase the culling risk. The present study indicates that the SURV rate in Italian Simmental cows is influenced by various factors in addition to milk productivity. Overall, this finding can be of particular interest for various dual-purpose breed, as cows’ body conformation and muscle development are highly important aspects for farmers undertaking culling decisions.