Reciprocal cross differences in Brahman-Hereford F2 cows: reproductive and maternal traits

Data from 75 F2 Brahman-Hereford cows of four specific breed combinations, F2 HB (produced by F1 HB sires x F1 HB dams, where ??????HB?????? refers to cattle sired by Hereford bulls and out of Brahman cows), F2 BH (produced by F1 BH sires x F1 BH dams), HB x BH and BH x HB, were evaluated for maternal performance at the Texas A&M Research Center near McGregor. Differences between breed combinations were analyzed for calf crop born (CCB), calf crop weaned (CCW), calf survival (CS), birth weight (BW), weaning weight (WW), and cow weight at palpation (PW). The adjusted means for F2 HB, F2 BH, HB x BH, and BH x HB were 0.84 ???? 0.06, 0.57 ???? 0.07, 0.82 ???? 0.06, and 0.62 ???? 0.08, respectively, for CCW. F2 HB cows had a 0.27 ???? 0.09 higher percent calf crop weaned than F2 BH cows (P < 0.01) and a 0.22 ???? 0.11 higher percent calf crop weaned than BH x HB cows (P < 0.05). HB x BH cows had a 0.25 ???? 0.08 higher percent calf crop weaned than F2 BH (P < 0.01) and a 0.20 ???? 0.10 higher percent calf crop weaned than BH x HB cows (P < 0.05). As 6-year-olds, the adjusted means for cow weight at palpation for F2 HB, F2 BH, HB x BH, and BH x HB cows were 523.65 ???? 20.49 kg, 602.61 ???? 23.63 kg, 492.84 ???? 16.98 kg, and 515.93 ???? 22.96 kg, respectively. Averaged across all ages, HB x BH cows weighed 56.59 ???? 15.29 kg less than F2 BH cows (P < 0.001) and 41.11 ???? 18.92 kg less than BH x HB cows (P < 0.05). Also, F2 HB cows weighed 40.45 ???? 17.68 kg less than F2 BH cows (P < 0.05). In this herd, HB-sired cows had higher reproductive efficiency than BH-sired cows. Also, HB-sired cows tended to be lighter than BH-sired cows. Although these differences existed, exact causes could not be determined primarily due to confounding between the birth year of the cow and the sire breed of the cow.