Influence of individual animal characteristics on beef cattle performance while grazing northern temperate rangeland

• Cow weight gain on pasture varied widely with age. • Cow and calf gain was lower during fall for dams with higher RFI. • Cows that gained more weight had smaller calves at weaning (cows > 9 yr age). • Calves grew faster in fall when their crossbred dams had higher genomic heterozygosity. This study evaluated the effects of age, genomic retained heterozygosity (gRHET), and residual feed intake corrected for back-fat thickness (RFI fat ) on weight gain in heifers, cows, and calves grazing native pasture over three years (2021–2023), during summer and fall in a northern temperate region. Three groups were studied: A) annual cohorts of 1-year-old heifers and 3-year-old Kinsella Composite (KC) crossbred cows (n = 182); B) a multi-aged purebred Angus cow herd (3–11 years; n = 133) monitored for one year; and C) a multi-aged KC crossbred cow herd (3–9 years; n = 132) tracked for one year. Average daily gain (ADG) was generally higher in summer than fall, except in 2023 within the multi-aged cattle when increased fall precipitation influenced ADG in crossbred cows. Pre-weaning calves gained more weight in summer ( P <0.001). Among crossbred cows, age and RFI fat were key predictors of ADG, with older cows (>9 years) consistently gaining less weight (3yr old = 0.49±0.073; 9yr old = 0.22±0.15; P <0.05). RFI fat measured as heifers was negatively associated with their ADG (β = -0.0937; P = 0.02) in multi-aged cattle, particularly during fall, suggesting moderate life-stage consistency. In purebred Angus cows, fall ADG also declined with age, and cow and calf performance were linked: higher cow ADG often correlated with lower calf weaning weights, especially in older cows (>10-yr old), indicating a trade-off in energy allocation. Additionally, higher maternal gRHET in crossbreds was associated with increased calf ADG in fall (β = 0.63; P = 0.022), supporting the value of retained heterozygosity in grazing-based production systems. These results highlight the importance of intrinsic traits, age, genomic diversity, and early-life feed efficiency, in optimizing productivity in pasture-based beef systems.