Genetic associations between feed intake and conformation traits in two populations

To use conformation traits as predictors of feed intake, it is necessary to obtain accurate estimates of genetic correlations between feed intake and conformation traits, however those correlations can vary across countries. The objective was to estimate genetic correlations between two feed intake traits (dry matter intake (DMI) and residual feed intake (RFI)), and conformation traits within United States (US) and the Netherlands (NL). Records were available on feed intake from 83 nutritional experiments conducted in NL (n=1665, 1991-2011) and US (n=1920, 2007-2013), and on conformation records from those cows plus their relatives (NL=37,241 and US=28,809). The model included fixed effect corrections for location × experiment × ration, age of cow at calving, location × year × season, and days in milk for feed intake traits, and for herd × classification-date, age of cow and lactation stage at classification for conformation. The included random effects were the additive genetic effect and residual. Heritability estimates for DMI were 0.32 in NL and 0.29 in US, whereas heritability estimates for RFI were 0.25 in NL and 0.22 in US. Heritability estimates for conformation traits varied between 0.25 and 0.60 in NL, and between 0.17 and 0.40 in US. The highest estimated genetic correlation was between DMI and chest width (CW) in both countries (NL=0.45 and US=0.61), followed by stature (ST; NL=0.33 and US=0.57),body depth (BD; NL=0.26 and US=0.49) and body condition score (BCS; NL=0.24 and US=0.46). Genetic correlation estimates between feed intake traits and conformation traits were slightly higher in US than in NL, but the trend was similar in both countries. Conformation traits (i.e. ST, CW and BD) showed potential to be used as predictors of DMI.