Reproductive efficiency of F1 and reciprocal backcross beef cows under contrasting environments

Abstract

A population of 860 F1 and reciprocal backcross females representing Hereford (H), Angus (A), Shorthorn (N), Charolais (C) and Simmental (S) breeding were evaluated for reproductive efficiency under two contrasting environments (Brandon, Manitoba and Manyberries, Alberta). The F1 included the HA, CN and SN and the reciprocal back-crosses were HCH, CCH, ACA, CCA, HSH, SSH, ASA, SSA, NSN, SSN, NCN and CCN. All females were bred to Limousin bulls. The data collected from 1980 to 1986 comprised 3108 mating opportunities and 2523 pregnancies. For dam crosses common to both locations (HA, SN and specific dam crosses involving S) differences in performance criteria occurred with females at Manyberries recording greater cow losses, higher conception and weaning rates, and more weight of calf weaned than at Brandon. Combining these performance elements gave the females at Manyberries an advantage for weight of calf weaned per mating opportunity (162 ± 3.2 vs. 152 ± 3.0 kg). Barren culls comprised the largest proportion of cow losses at both locations with HA and NSN greatest and ASA lowest at Brandon, and SSH greatest and SN lowest at Manyberries, all significant at P ≤ 0.05. None of the differences for C cross females was significant (P > 0.05). Weaning rates per mating opportunity for dam crosses common to both locations indicated the ASA highest and the SSH lowest at both locations, the difference being 22.9% at Brandon and 13.2% at Manyberries. For the HA, CN and C backcross comparisons, the highest weaning rate per mating opportunity was recorded for the HA (73.3%) and the lowest for the CCA dam cross (62.4%). At both locations, the SN dams produced the most weight of calf weaned per mating opportunity with the lowest values recorded by the HA and NSN dam cross at Brandon and the HSH dam cross at Manyberries with the CN dam cross recording the highest values and the CCA and ACA the lowest. For all performance criteria calves out of F1 dams had an advantage over calves from backcross dams. Key words: Beef cattle, cow productivity, crossbreeding