SEX AND YEAR EFFECTS ON CARCASS CHARACTERISTICS OF THREE-WAY CROSS BEEF CATTLE REARED AT TWO LOCATIONS

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Abstract
From 1973 to 1978, 3673 steers and heifers sired by Charolais (C), Simmental (S), Limousin (L) or Chianina (Chi) were born to first-cross dams under farm (Brandon, Man.) and range (Manyberries, Alta.) conditions. Dam crosses included the Hereford × Angus (HA) and crosses sired by C, S or L sires and out of H, A or Shorthorn (N) dams. All calves entered the feedlot at approximately 206 days of age. Brandon calves, fed at that location were brought to full feed (100% grain concentrate) by 220 days of age. Manyberries calves, fed at Lacombe, received a ration of cereal silage and grain concentrate with the silage component reducing from 70% to 30% over a period of 5 mo. The minimum slaughter age was 13.5 mo at both locations but age alone (13.5 and 15 mo) was the slaughter criterion at Brandon whereas Lacombe employed the dual criteria of liveweight and degree of finish. These location differences in feeding and slaughter criteria resulted in greater slaughter weights (278 vs. 265 kg), greater rib fat (1.61 and 1.09 cm) and a higher percentage of kidney fat (2.09 vs. 1.75%) for the Brandon animals. They were also reflected in the sex differences for age at slaughter (sexes equal at Brandon; heifers > steers at Lacombe) and degree of finish (sexes equal in rib fat at Lacombe; steers > heifers at Brandon). Heifers at Brandon had a larger percentage of hide (P < 0.0001) and lower dressing percentage (P < 0.0001) than steers. Percentage of head, front feet and hind feet were also less for heifers than steers at this location. Rib eye was greater for steers but heifers had greater rib eye area per unit weight (P < 0.0001) and a higher percentage of kidney fat (P < 0.0001). The sex ranking for percentage chuck, shank and flank was steers > heifers (P < 0.0001) and the reverse for percentages of rib, long loin and the combined cuts of rib, round and long loin (P < 0.0001). For percentages of lean in the long loin, rib and chuck the ranking was steers > heifers (P < 0.0001) with heifers > steers for percentage lean of round (P < 0.0001). Heifers relative to steers had significantly (P = 0.0001) lower percentages of bone in the round, rib and chuck and greater (P = 0.0001) lean to bone ratios for the combined trait of long loin and round. The sex differences observed at Lacombe for these traits were in good agreement with Brandon although sex by location interaction was not tested. Year differences were large but year-by-sex interactions were non-existent for virtually all carcass traits evaluated at both locations (P ≤ 0.05). Sire-by-sex and dam-by-sex interactions were also absent. Key words: Beef cattle, crossbreeding, carcass characteristics, year effects, sex effects