Evaluation of reciprocal differences in Bos indicus × Bos taurus backcross calves produced through embryo transfer: II. Postweaning, carcass, and meat traits1

Abstract

Angus (A) x Bos indicus (B; Brahman or Nellore) reciprocal backcross, embryo transfer calves belonging to 28 full-sib families were evaluated for differences in feedyard initial BW, feedyard final BW, carcass weight, LM area, adjusted fat thickness, intramuscular fat, and Warner-Bratzler shear force. Two methods of analysis were investigated; method I made no distinction between how the F(1) parents were produced, whereas method II distinguished the 2 types of F(1) parents (AB vs. BA, corresponding to A x B vs. B x A, respectively). No significant reciprocal differences for these weight and carcass traits were detected under method I analyses, although the same trend existed for subsequent BW rankings as for birth weight and weaning weight. For each weight phase, the cross that involved a larger proportion of B in the sire in relation to the amount in the dam (F(1) x A and B x F(1)) ranked heavier than the respective reciprocal cross (A x F(1) and F(1) x B). As a whole, A backcross calves had larger (P < 0.001) LM area, more (P < 0.001) marbling, and lower (P < 0.001) Warner-Bratzler shear force than B back-cross calves, but no consistent trends were detected between reciprocal crosses for any of these traits, in contrast with the trends observed for the weight traits. Furthermore, males were heavier than females entering (P < 0.001) and leaving (P < 0.001) the feedyard, produced a heavier carcass (P < 0.001), and had larger LM area (P < 0.05) with less adjusted fat (P < 0.001). No difference existed between the sexes for Warner-Bratzler shear force or marbling. No interactions involving sex, sire type, and dam type were observed for any of these traits. The results were similar under methods I and II analyses, with the exception that a significant sire type x dam type interaction was observed for initial feedyard BW. Results from this study suggest that for weight-related traits, both the breed constitution of the embryo transfer calf and the cross that produces the calf play an important role in its ultimate performance for B crossbred calves. For body composition and meat-related traits, it appears that the breed makeup of the embryo transfer calf itself is more important to animal performance than the specific cross used to produce the calf.