Estimating Direct and Maternal Effects on Residual Metabolizable Energy Intake in Holstein Calves

Two of the largest expenses in the dairy industry are the animals’ feed and the rearing of heifers. While in many countries feed efficiency in lactating cows has already been integrated into the genetic evaluation, studies in dairy calves are still scarce. Because maternal effects are known to influence important traits measured early in life, they may play an important role in dairy calf feed efficiency. The objective of this study was to estimate genetic parameters of feed efficiency in pre-weaned dairy calves and investigate the significance of maternal genetic effects on feed efficiency. Residual metabolizable energy intake (RMEI) of 471 Canadian Holstein calves in two time periods<br/>(RMEI1: first month of age; RMEI2: second month of age) was used as a measure for feed efficiency. Statistical analysis using animal models including maternal effects was performed with ASReml. Maternal effects significantly (p-value= 0.04) improved model fitting of RMEI1, with high negative genetic correlations between direct and maternal effects (-0.88±0.02). Without considering maternal effects, heritability estimates for RMEI1 and RMEI2 were 0.19±0.11 and 0.32±0.12, respectively. RMEI1 the direct heritability was 0.15±0.13, the maternal heritability was 0.27±0.12 and a total heritability of 0.02. The estimated genetic correlation between RMEI1 and RMEI2 (0.77±0.36) indicated that RMEI in the two periods may be considered separate traits. Further studies with more animals and herds, as well as an investigation on the potential relationships with other important traits should be carried out to understand whether and how RMEI could be incorporated in selection decisions. Despite the limited dataset used in this study, moderate heritability estimates indicate that selection for more feed efficient calves is possible.