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University of Wisconsin, Madison 53706
Abstract
The objective of this study was to measure the influence of live and carcass shape on composition. Twenty-four steers and 16 gilts were selected to represent two species and to equally represent two distinct shapes (muscular and non-muscular). An attempt was made to visually standardize live weight, degree of fatness and chronological age at the time of live selection and because of certain errors in subjective appraisal, it was necessary that the influence of these variables be held constant by statistical procedures. The bovine pelvic limbs and the entire porcine carcasses were dissected into bone, skin, fat and muscle. All individual muscles and muscle groups were analyzed for ether-extractable lipids.
The results provided the following conclusions:
Non-muscular animals were considerably fatter than anticipated when evaluated subjectively and muscular ones were slightly thinner than anticipated.
Even though ingesta and fatness were not standardized, muscular animals appeared to yield proportionately heavier carcasses, i.e., have higher dressing percentages.
Muscular animals contained approximately 2% more fat-free muscle and this was due primarily to a one unit higher muscle-bone ratio. This indicates that the relationship of muscle and bone is not necessarily constant for meat animals.
Regardless of the tendency for a few muscles to be proportionately larger, in most instances the majority of muscles and bones represented a constant proportion of the total muscle and skeleton mass respectively for the pelvic limbs and carcasses studied.
After the effects of weight and fatness were held constant, the yield of various anatomical parts of the carcass were similar for both shape groups. Therefore, such measures as percent ham and loin are a direct reflection of fatness and are not affected by degree of muscularity.
Animal or carcass shape is a significant factor in determining composition but its role is minor when compared to fatness. The importance of muscularity may be overlooked when carcass composition is determined by such techniques as specific gravity or proportion of trimmed wholesale or retail cuts in which bone is not removed and thus permitted to influence the net result.
1 Departments of Meat and Animal Science and Dairy Science, University of Wisconsin, Madison. Muscle Biology Laboratory Manuscript No. 30.
2 Present address: U.S. Army, Petersburg, Virginia 23803.
3 Ankony Angus Corporation, Grand Junction, Colorado 81501.
4 The authors greatly appreciate the financial support of the Ankony Angus Corporation of Grand Junction, Colorado, and the cooperation of Dubuque Packing Company, Dubuque, Iowa; Oscar Mayer & Company, Inc., Madison, Wisconsin and Wilson-Sinclair Company, Inc., Cedar Rapids, Iowa, for making it possible to complete this study.
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