The term, muscling, is often used to describe animals that are supposed to be better or worse producers of meat.  Better muscling can only mean three things:

1. A higher percentage of the carcass is muscle.  But this is simply determined by degree of maturity (weight in relation to mature weight) for continuously-grown animals.  See mature size.
2. A higher percentage of total muscle weight is in the higher priced cuts.
3. The muscle shape is shorter and bulgier.

Muscle distribution

Muscle weight distribution in small and large mature size Merino rams (from R. M. Butterfield. New Concepts of Sheep Growth, Epping, NSW Australia: Department of Vet Anatomy, University of Sidney, 1988)

Table 2.c.3  The percentage of total muscle weight in each "Standard Muscle Group" of mature large and small Merino Rams

Butterfield argues that the differences between the two groups would be even smaller when adjusted for differences in mature size.

Table 5.c.2. The percentage of total muscle weight of the "Standard Muscle Groups" of mature Merino and Dorset Horn rams

M. L. Thonney, St C. S. Taylor, J. I. Murray, and T. H. McClelland. Breed and sex differences in equally mature sheep and goats. 3. Muscle weight distributions. Anim. Prod. 45:277-290, 1987.

Dissection data are limited for sheep. Here are some examples from cattle taken from: R. T. Berg and R. M. Butterfield. New Concepts of Cattle Growth, New York:John Wiley & Sons, 1976. 240 pages.

Table 5.7 Distribution of muscle weight in breed groups of bulls, steers and heifers

Table 5.8 Lean meat in each cut as a percentage of total carcass lean in three beef 'breeds'

Key point:  There is little variation in distribution of muscle among breeds widely different in shape. Thus, although it may be possible to select for "better" muscle distribution, no one has done it yet in "normal" animals.

Key point 2:  Shorter and bulgier muscles may be more esthetically pleasing in lamb carcasses than longer and thinner muscles of the same weight.

Abnormal muscle distribution: