PSI-3 Heritability Estimates and Correlations Between Dry Matter Intake and Stayability

Abstract The objective of this study was to determine heritability and genetic correlation estimates between dry matter intake (DMI) and Stayability in Angus cattle originating from the John E. Rouse Beef Improvement Center. From the years 2015–2021, 640 steers were fed in confinement using a GrowSafe System® to measure individual DMI. The duration of feeding varied each year; however, mean test length was 49 ± 0.31 days with a 21-day warm-up period to allow for acclimation to the environment and ration. A bivariate animal model was used. Stayability was evaluated using a binary, probit threshold model while DMI was evaluated as a continuous trait. In addition to the 640 steers with intake, a total of 1,673 pedigree-related cows possessed a Stayability observation. Cows were awarded a ‘1’ if they maintained functionality within the herd for six years. Those not achieving the six-year threshold were given a ‘0’. Mean DMI calculated for the steers was 10.11 ± 0.12 kg/day while the mean for stayability was 0.59 ± .15 (59% of females in this study remained in the herd for at least six years). Fixed effects in the model included contemporary group and age. Contemporary groups were defined as year, pen and test duration for DMI. Contemporary groups for Stayability were solely the year of birth for a given cohort. Individual animal was included as a random effect for both Stayability and DMI to account for the direct genetic effects for both traits. A 3-generation pedigree file containing 3,421 angus influenced animals with 785 unique sires and 2,425 unique dams was used to link the steers to the cows in this study. Residual covariance between DMI and Stayability in this study was fixed at 0. The heritability estimate for DMI was 0.26 ± 0.12 making it moderately heritable with a phenotypic variance of 9.29 kg2 ± 0.55. The heritability estimate for Stayability was quite low 0.02 ± 0.39. The genetic correlation between DMI and Stayability determined by this model was 0.8211 ± 1.2. Though the heritability is low for Stayability, these results suggested that Angus cows that exhibit higher feed intake tend to have more longevity within the herd.