Economic-impact variability among F1 Nellore–Angus herd sires reared together and used in multiple-sire mating groups

This study investigated variation of calf number and resulting economic impacts of F1 crossbred sires that were reared together as calves and used in multi- sire, natural-service breeding groups. Birth (n = 540) and weaning (n = 533) calf records were evaluated retrospectively in a crossbred research herd. Sires per annual breeding group varied from 6 to 9; females exposed per bull ranged from 12.5 to 19.5 across years. Bulls born in the same year were reared together, and all bulls were pastured together when not in breeding groups. Calf performance and economic value were determined annually per sire. Mixed model analyses were conducted that included fixed categorical effects of calf birth year, F1 sire type (Angus-sired vs. Nellore-sired), sire nested within type, calf sex, and the interaction of F1 sire type with calf sex. Large differences were observed in calf numbers and performance. Weaned calves produced annually per sire ranged from 0 to 48, when average expectations were 10.5 to 15.2. Average annual calf performance per sire ranged from 29.7 to 49.4 kg for birth weight and 197.4 to 241.4 kg for weaning weight. Annual economic contribution per sire ranged from $0 to $29,582 when considering half of calf value as being attributed to the sire. Commercial cow- calf producers should consider potential sire variability for calf numbers and birth date in combination with traditional calf performance for improved economic assessments in their herds.