Genetic Feed Efficiency Traits in Dairy Cattle: A Systematic Meta-Analysis

Efficient feed utilization is crucial for sustainable dairy cattle production. This systematic review and meta-analysis pooled heritability estimates for feed intake (FI), feed saved (FS), dry matter intake (DMI), feed conversion ratio (FCR), and residual feed intake (RFI) in dairy cattle and determined the genetic correla-tions between these traits and other production efficiency traits. Data from 68 studies published between 2000 and 2022 were analyzed using random effects meta-analysis and restricted maximum likelihood esti-mation. The pooled heritability estimates were as follows: 0.32 (95% CI: 0.29-0.36, I²=98%, P<0.0001) for DMI, 0.29 (95% CI: 0.10-0.46, I²=99%, P<0.0001) for FS, 0.17 (95% CI: 0.15-0.19, I²=89.3%, P<0.0001) for RFI, and 0.11 (95% CI: 0.08-0.13, I²=0%, P<0.0001) for FCR. Strong positive genetic correlations were observed between DMI and net energy of lactation intake (NELI) (0.90), RFI and average daily feed intake (ADFI) (0.80), and FCR and RFI (0.68). Conversely, negative genetic correlations were found between FCR and average feeding rate (AFR) (-0.38), FCR and average daily gain (ADG) (-0.34), FCR and longis-simus muscle area (LMA) (-0.28), and FCR and hip height (HIPHT) (-0.14). These findings suggest poten-tial indicators for selection indices and genetic improvement strategies, offering valuable insights for en-hancing breeding programs and optimizing feed utilization in dairy cattle. Ultimately, this contributes to more sustainable livestock production and improved food security.