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

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Abstract

This study evaluated the effects of age, genomic retained heterozygosity (gRHET), and residual feed intake corrected for back-fat thickness (RFIfat) 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 RFIfat were key predictors of ADG, with older cows (>9 years) consistently gaining less weight (3 yr old = 0.49 ± 0.073; 9 yr old = 0.22 ± 0.15; P < 0.05). RFIfat 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.