GROWTH AND MATERNAL PERFORMANCE OF TWO-YEAR-OLD F1 AND RECIPROCAL BACKCROSS HEIFERS IN TWO ENVIRONMENTS

Abstract

Growth patterns and calf performance of 2-yr-old F1 and reciprocal backcross females were compared in two contrasting environments, semi-intensive management (Brandon, Man.) and extensive range management (Manyberries, Alta.). At Brandon, 621 heifers of Hereford × Angus (HA), Simmental × Shorthorn (SN), Charolais × Shorthorn (CN) 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 Manyberries, 271 heifers of HA, SN, CN and reciprocals of SH, SA and SN were evaluated. They were bred to Limousin bulls. The HA heifers were the lightest at 14, 18, 24, 26 and 30 mo of age at both locations. Location differences for dam crosses in common ranged from 5% at 14 mo to 19% for 30 mo weight (Brandon > Manyberries). At all ages, the 3/4 C 1/4 N and the 3/4 S 1/4 N dam crosses were the heaviest at Brandon and Manyberries, respectively. Differences in weights at all ages between the CN and their reciprocal backcrosses were not significant at Brandon. The SN dams exceeded their reciprocal backcrosses in weight at all ages at Brandon (P < 0.01) but none of the differences were significant at Manyberries. Very few of the differences recorded for gestation length and birth weight at either location were significant. Progeny from HA dams were the lightest at birth and when significant differences existed for gestation length the longest were associated with the 3/4 "exotics." At both locations, progeny from HA dams were lightest and the progeny from the 3/4 "exotics" the heaviest at weaning. Females at Manyberries produced calves that were 3.3% heavier at weaning than those at Brandon. The highest weaning weight ratios were recorded for the 3/4 S 1/4 A, 3/4 S 1/4 N and SN dam crosses at both locations and these dam crosses were intermediate in weight at 30 mo. Total overall conception for breed crosses common to both locations for breeding at 14 and 26 mo was 77.0% vs. 75.8% and 82.1% vs. 79.5% for Brandon and Manyberries, respectively. Few differences were observed between dam crosses for conception rate. At Brandon, CX females required significantly more services per conception at 14 mo of age than SX females which reflected itself in lower conception rates. Compared with the SX females, the CX females had 11.8% lower conception to 1st service and 4% lower total conception. Calves born at Manyberries experienced greater calving difficulty but this was not reflected in higher calf mortality rates. Key words: Beef cattle, growth, preweaning traits, crossbreeding