This study aimed to estimate the genetic parameters of stayability (STAY) at different calvings using a single-step genomic best linear unbiased prediction (ssGBLUP) approach, comparing Gaussian-linear and threshold models in Italian Charolais and Limousine beef cattle. It also examined the genetic relationship between STAY and other traits to identify potential indicators of longevity and assessed the impact of STAY selection on economically important traits. STAY, a key trait for farm profitability, is defined as the probability of a cow surviving and remaining productive in the herd until a determined age. We evaluated STAY from the second to third calving and subsequent intervals (e.g., STAY23, STAY78), along with two fertility traits and several conformation traits. Data included 47,362 Limousine cows and 9,174 Charolais cows from 2,471 to 1,774 herds, respectively, born between 1977 and 2023. Analyses were performed fitting univariate threshold and Gaussian-linear animal models to estimate genetic parameters for STAY traits (STAY2 to STAY8) using ssGBLUP. Also, bivariate models were used to estimate genetic correlations between STAY and fertility and conformation traits. Heritabilities for STAY ranged from 0.13 to 0.11 and from 0.21 to 0.14 for Limousine, and from 0.14 to 0.11 and from 0.21 to 0.19 for Charolais, using Gaussian-linear and threshold models, respectively. Significant re-ranking of genotyped sires based on STAY traits was observed, particularly for more distant calvings (STAY8) compared to earlier ones (STAY3), indicating that STAY traits are genetically distinct. Genetic correlations were positive between STAY and conformation traits for Limousine. In Charolais, many traits were uncorrelated, but some conformation traits showed positive correlations, except for rump convexity, which had negative correlations with STAY. In conclusion, the heritability estimates of STAY suggests that genetic improvement for longevity in Limousine and Charolais herds is feasible. Selecting sires with consistently high genomic breeding values for STAY across early and late calvings highlights the importance of long-term longevity. Genetic correlations indicate that selection based on conformation traits could enhance herd survival by improving cow resilience for the Limousine. Instead for the Charolais some conformation traits showed positive correlations with STAY, while rump convexity had negative association, potentially affecting longevity.
Keywords: beef cattle; conformation traits; functional longevity; genetic association; single step.
Maximizing the longevity of cows is a crucial economic factor in cattle farms. A significant cost for farmers is maintaining heifers as replacements for older cows. Stayability (STAY) is a trait that measures the likelihood of a cow remaining productive in the herd until a certain age. This trait reduces replacement costs and improves herd efficiency, increasing farm profitability. This study focuses on the genetic factors influencing longevity in Italian Charolais and Limousine beef cattle. We estimate the genetic components of STAY at different calvings using genomic information and explore its relationship with body conformation and fertility. This study investigates the longevity of Limousine and Charolais cattle to understand genetic and environmental factors affecting survival across calvings. By incorporating STAY into genetic evaluations, it is possible to develop more effective breeding strategies based on longer-lasting and more productive herds. We also examine intra-herd heritability, herd effects, and genetic correlations with fertility and conformation traits. Our results highlight breed-specific differences, suggesting the need for tailored breeding strategies to enhance cattle longevity.
© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.