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Growth Patterns of Bovine Muscle, Fat and Bone¹

University of Alberta, Edmonton, Canada and University of Sydney, Sydney, Australia

Abstract

The major tissues of the bovine carcass—muscle, fat and bone—show differential growth during development. Bone growth, previously described as early developing, is better described as having low growth impetus. Muscle tissue shows intermediate growth impetus and fat tissue shows high impetus, particularly after the fattening phase begins. Differential growth of tissues influences carcass composition and, thus, carcass merit; therefore, factors influencing differential tissue growth should be understood in order that carcass composition might be controlled within acceptable limits.

Weight at slaughter has an important influence on carcass composition. In normal slaughter ranges, as weight increases muscle percentage decreases, fat percentage increases and bone percentage decreases.

A high plane of nutrition increases the percentage of fat. Its influence on muscle-bone ratios relative to total muscle plus bone, is not clear.

A low plane of nutrition retards fat and muscle development. The effect on bone is not clear from experiments conducted to date. Semistarvation depletes fat and muscles with some depletion of bone. Realimentation leads to compensation whereby muscle and bone relationships are restored and fat tissue proportion increases in relation to the plane of nutrition and the length of the compensation period.

Breed or genetic differences in relative tissue growth are found in weight at the onset of the fattening phase and in muscle-bone ratios. Sexes differ in weight at the onset of the fattening phase. Bulls show delayed fattening, compared to steers and reach higher muscle-bone ratios in their carcasses.

Relative tissue growth also affects conformation, i.e. the proportions in various cuts. Fattening leads to an increase in proportions of those cuts which include major fat depots, particularly ventral parts of the carcass.

Differential growth also occurs within the musculature but this is mostly restricted to the early postnatal period. Plane of nutrition and perhaps other treatments can affect muscle weight distribution in the early postnatal period but would be expected to have little effect in later stages of growth. Evidence is accumulating that differences in conformation are not caused by differences in muscle-weight distribution.

Experiments designed to include an assessment of carcass composition and conformation (as denned above) should include serial slaughter of animals in order that tissue growth patterns within and among groups can be accurately documented.

¹ Invitational paper presented at the Meats Session, 59th Annual Meeting of the American Society of Animal Science, University, of Nevada, Reno.

² Professor of Animal Genetics, University of Alberta.

³ Professor and Head, Department of Veterinary Anatomy, University of Sydney.

This article has been cited by other articles:

				K. W. Bruns, R. H. Pritchard, and D. L. Boggs The relationships among body weight, body composition, and intramuscular fat content in steers J Anim Sci, May 1, 2004; 82(5): 1315 - 1322. [Abstract] [Full Text] [PDF]