Investigation of Reciprocal Cross Effects in F2 Nellore–Angus Calves

Abstract

The objectives of this study were to analyze calf performance traits and sex ratio frequencies in reciprocal Bos indicus–Bos taurus F2 Nellore–Angus calves (n = 539). The F2 calves were produced using reciprocal Angus-sired (AN) and Nellore-sired (NA) F1 sires and F1 dams, resulting in four F2 cross types. Calf weight traits were analyzed using mixed models. Deviations from 50% calf sex ratios were tested against expected binomial thresholds. Dam type influenced Julian birth date (p < 0.05) with calves from AN cows born 5 to 6 days earlier than calves from NA cows. Sire type and dam type affected birth weight (p < 0.05) with calves from NA parents approximately 2.5 kg heavier than those from AN parents; weaning weight did not differ for parent F1 type. However, an interaction between sire and dam types affected weaning weight (p = 0.038) where AN x AN calves were 5 to 8 kg lighter than other crosses. Sire type influenced calf sex distribution at birth (p = 0.036) and at weaning (p = 0.026) with NA sires producing over 66% male calves. These results suggest birth weight reciprocal differences due to parental line of descent typically observed among F1 Bos indicus–Bos taurus crosses can persist in subsequent generations.