Milk BHB Heritability Estimates and Genetic Correlations with Production Traits in Grazing Dairies in Chile

This study aimed to estimate the heritability of β-hydroxybutyrate (BHB) in milk and evaluate its genetic correlations with other traits in grazing dairy herds from southern Chile. The analysis was based on a comprehensive data set provided by a Dairy Herd Improvement Association (DHIA) cooperative (Cooprinsem, Osorno, Chile). The data set included records from 617 grazing farms and 712,629 lactations spanning from 2019 to 2024. The final data set included 254,979 lactations from 50,794 cows. Milk BHB concentrations were higher in early lactation and remained relatively low and stable thereafter. Heritability estimates for BHB followed a parabolic trend, with the lowest values observed during early and late lactation, and a pronounced peak of approximately 0.20 occurring in Month 7. Genetic correlations between BHB and other traits were notably stronger than their phenotypic counterparts, suggesting robust underlying genetic relationships. In particular, the genetic correlation between BHB and milk yield shifted markedly over time, starting at approximately 0.35 ± 0.02 in Month 1 and declining to around −0.30 ± 0.03 by Month 10, whereas the phenotypic correlation remained weakly negative throughout the lactation period.

© 2026, The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association

© 2026, The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association