Genetic residual feed intake and its genetic association to other breeding goal traits

Abstract

Selecting for improved feed efficiency in dairy cows is relevant for optimising the utilization of local feed resources, improving sustainability, while reducing the climate footprint from dairy production. The current study analyses feed efficiency based on real data on feed intake and methane in Norwegian Red cows (NR). The goal is to include feed efficiency in the current NR breeding program. Genetic residual feed intake (gRFI) is a measure of the difference between actual an expected feed intake. It has been proposed as a promising feed efficiency trait as it is genetically uncorrelated with the energy driving processes such as milk production and body weight of the cow. Therefore, the objective of this study was to calculate gRFI, predict breeding values (EBVs) and estimate genetic associations between gRFI and other traits.

Daily feed intake, body weight, milk yield, and methane emissions from 2,412 NR cows, with on average 433 repeated records, from 14 herds were measured between 2019 and 2024. Two multivariate linear animal repeatability models in DMU were used for estimation of (co)variance components between all traits. Genetic (co)variances for daily traits such as feed intake measured as daily dry matter intake (dDMI) or daily energy intake (dEI), milk yield or energy-corrected yield (ECM), and bodyweight were further used to obtain regression coefficients of the energy sinks (milk and bodyweight on feed intake) and compute gRFI. Heritability of gRFI was low, 0.07. The EBVs for gRFI showed variation and there were differences between animals, with BLUP breeding values ranging from -10.9 to 12.5 for dEI (daily energy-intake from both roughage and concentrate). The correlation between EBVs of gRFI and EBVs of daily body weight and milk yield were close to 0, as expected. The EBVs for gRFI was not standardized, low gRFI was therefore desirable. The correlation of gRFI EBVs to indexes from Geno’s routine genetic evaluation ranged from -0.1 to 0.19 and were in general low. The strongest unfavourable correlations were found between gRFI and 305-days milk production traits and exterior. Somatic cell count, calving ease, calf size, silent heat, and number of inseminations had favourable correlations with gRFI (-0.10 to -0.06). These results indicate that improving feed efficiency defined as gRFI in the Norwegian Red population are possible, but before implementing gRFI as a novel trait in the breeding program the genetic correlations must be established and the definition should be improved in order for gRFI to be uncorrelated with current production traits in the TMI.