Growth patterns of first-cross and reciprocal backcross beef cows in two environments

Abstract

Growth patterns of first-cross (F1) and reciprocal backcross cows, 3–5 yr old, were evaluated under two contrasting environments: extensive range conditions at Manyberries, Alberta, and semi-intensive management at Brandon, Manitoba. Cows resulting from crossing Hereford (H) × Angus (A), Simmental (S) × Shorthorn (N), Charolais (C) × Shorthorn and reciprocal backcrosses from Charolais × Hereford (CH), Charolais × Angus (CA), Charolais × Shorthorn (CN), Simmental × Hereford (SH), Simmental × Angus (SA), and Simmental × Shorthorn (SN) were evaluated at Brandon. At Manyberries, HA, SN and reciprocal backcrosses of SH, SA and SN were evaluated. All cows were bred to Limousin (L) bulls. Cow weights and backfat estimates were recorded at breeding, calving and weaning. The HA cows were the lightest group for all weigh periods at both locations. At all weigh periods, the SSN (3/4 S 1/4 N) dam crosses at Manyberries and the CCN (3/4 C 1/4 N) and CCH (3/4 C 1/4 H) at Brandon were the heaviest. At Brandon, females gained weight during gestation and usually lost weight during summer nursing. Cows at Manyberries usually gained weight during nursing, with significant gestation weight loss. Nursing status of the cow had a significant effect on weight change, with barren status providing an opportunity for large compensatory gains. The CN dams were significantly heavier at all weigh periods than their 1/4 C back-crosses. At Brandon, the SN dam cross weights exceeded those of their reciprocal backcrosses at breeding, calving and weaning and at calving for the 1/4 S dams. At Manyberries, SN weights exceeded those of the 3/4 S crosses at weaning. Over the duration of study, average backfat estimates for cows at Brandon exceeded those at Manyberries (10.8 and 8.6 mm, respectively). Specific dam crosses performed differently at the two locations, and commercial cattlemen need to closely evaluate the F1 and backcross comparisons to determine the optimal level of performance under their particular management and environmental conditions. Key words: Beef cattle, growth, nursing status, crossbreeding, environment