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U. S. Department of Agriculture and University of Nebraska, Lincoln
Abstract
The Hereford, Angus and Shorthorn breeds and all reciprocal crosses among them were included in an experiment designed to evaluate heterosis effects in crosses among these breeds. Data were collected on four crops of steers (1960, 1961, 1962 and 1963). The last three crops were individually self-fed from weaning to slaughter, and detailed carcass cut-out data were obtained on them. Carcass grade and carcass measurement data were collected in a commercial beef cooler for the 4 years. In addition, carcass cut-out data on boneless, closely trimmed cuts (retail product), fat trim and bone from one side of each carcass were collected the last 3 years. The individual wholesale cuts that comprise retail product were analyzed, and the results for the separate cuts were similar to those for retail product for the entire carcass. Carcass data were obtained on 374 steers for the 4 years and on 286 for the last 3 years.
There were significant (P<.01) heterosis effects for carcass weight and net merit (452 days). The heterosis effect on net merit is of appreciable economic significance. Net merit was computed as the value of the boneless, closely trimmed cuts (retail product) minus feed costs from weaning to slaughter. Differences in carcass grade were considered in computing net merit. Differences in survival to slaughter were not considered in computing net merit.
Interactions of years with breed of sire and breed of dam were relatively unimportant. Heterosis effects attributable to sires within a breed were not generally important. Thus, the heterosis observed was a characteristic of breeds rather than of specific sires within breeds.
Heterosis effects were greater in the Hereford-Angus and Hereford-Shorthorn crosses than in the Angus-Shorthorn cross. Thus, the Hereford breed contributed more than either the Angus or Shorthorn breed to the average heterosis effects.
Generally, there were significant (P<.01) heterosis effects on age-adjusted traits associated with carcass composition. The crossbreds were fatter. However, when these traits were adjusted for weight the heterosis effects on composition were negligible. Thus, the heterosis effects on carcass composition were through heterosis effects on weight at a constant age.
Breed effects existed for many of the traits studied. While breed differences in carcass weight at 452 days were small, differences in carcass composition and feed efficiency resulted in rather large breed differences in net merit. Herefords ranked highest in net merit, the Shorthorns were lowest and the Angus were intermediate. Carcasses from Herefords graded approximately one-third grade lower, reflecting their lower level of marbling.
1 Department of Animal Science. Published with the approval of the Director as Paper No. 1765, Journal Series, Nebraska Agricultural Experiment Station. Contribution from North Central Regional Project NC-1, Improvement of Beef Cattle through Breeding Methods.
2 Beef Cattle Research Branch, Animal Husbandry Research Division, A.R.S., U.S.D.A., Lincoln, Nebraska.
3 Beef Cattle Research Branch, Animal Husbandry Research Division, A.R.S., U.S.D.A., Crawford, Nebraska.
4 Acknowledgment is made to George A. Hormel & Co., Fremont, Nebraska, especially to Roger A. Orr for cooperation received in obtaining carcass data.
5 Acknowledgment is made to Burdette Breidenstein, Department of Animal Science, University of Illinois, for cooperation in providing the carcass cut-out data.
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