EFFICIENCY OF FEED UTILIZATION BY THREE-BREED CROSS STEERS

Abstract

Feed efficiencies, defined as feed-to-gain or weight ratios, were computed on 1046 steers reared between 1973 and 1978 at the Brandon Research Station. The progeny were out of 10 specific F1 crosses of dams mated to Charolais (C), Simmental (S), Limousin (L), and Chianina (Chi) bulls with none of the F1 dams being backcrossed. Dam crosses included the Hereford × Angus (HA) and crosses sired by C, S, and L bulls out of Hereford (H), Angus (A), and Shorthorn (N) dams. Feed-to-gain ratios were calculated on a live animal postweaning basis (for both a 140-d test and total liveweight gain from on-test to slaughter) and a carcass basis (hot carcass weight and rough or untrimmed lean, fat, and bone weights of combined cuts). The combined cuts were the rib, long loin (comprising the short loin and the sirloin butt), and round. In the live animal traits, the progeny from the 10 F1 dam crosses did not differ, but on a carcass basis, the progeny from the "exotic" crosses had better feed-to-gain ratios than the HA cross. Differences among the progeny of the "exotic" crosses included: C crosses < L crosses, "exotic" × A and "exotic" × N < "exotic" × H for hot carcass weight; "exotic" × N < "exotic" × H for rough weight of the combined cuts; S crosses < L crosses and "exotic" × N < "exotic" × A for fat and bone weights of the combined cuts; and "exotic" × N < "exotic" × H for fat weight of the combined cuts. There were no significant breed of dam's sire (maternal grandsire) × breed of dam's dam (maternal grand-dam) effects. Differences in breed of dam's sire were C < S for 140-d test, C < L for total liveweight gain, and S < L for bone weight of the combined cuts. Breed of dam's dam differences were N < (A = H) for fat weight of the combined cuts. Breed of terminal sire effects revealed that the progeny from the S and C breeds were similar for all measures of feed efficiency and the L and C breeds were only similar for feed efficiencies expressed on a carcass basis. Progeny from the Chi breed were comparable to the progeny from the C breed but not to the progeny from the S and L breeds in these traits. Key words: Beef cattle, breed crosses, steers, feed efficiency