"Meat quality" is a broad term which has recently become associated with current debates surrounding the discovery of horse and pig meat in Tesco 'beef' burgers. Meat quality in the context of ultrasound, however, refers to the measurement of fat and muscle depth on the live animal (intramuscular fat and muscle size/area are also sometimes measured), often with an ultimate goal of genetic improvement of the herd or flock. This involves selecting those animals capable of producing offspring with the best results to breed from, whilst carefully taking other important factors into account - birthing ease, milk production, growth rate and so on - which may or may not be correlated in some way with the measurements obtained via ultrasound.

There are, of course, no pre-defined optimal values or "right answer" for fat or muscle depth in either a sheep or a cow generally or even within specific breeds. Measurements are instead interpreted in the context of each other, and in more sophisticated systems, combined with other data to come up with a final value or score.

Signet Breeding Services, for example, calculate EBVs (Estimated Breeding Values) for each animal in their system which relies heavily upon ultrasound measurements (click here to learn about the system that they use) but also taking other factors into account.

This is becase genetic improvement of a flock or herd, either for aesthetic reasons or for carcase quality (or preferably a combination of both, as is the case with Miserden Texels) must always be accomplished without losing sight of the fundamentals of the animal, the most obvious yet frequently neglected one being the ability of the animal to reproduce itself.

Frequently in the history of livestock breeding (and indeed in the canine world) animals have been so heavily selected for one or two characteristics to the neglect of factors such as birthing ease or mothering ability, that we are left with an animal completely incapable of independent reproduction. For this reason, Signet Breeding Services builds calving ease for cows and mothering ability for ewes into its EBVs.

Other factors involved in any discussion of meat quality include tenderness. This trait is over 60% heritable, but is also influenced by the age of the animal (muscle bundle size increases with age up to four years, increasing coarseness of the meat; collagen and elastin content also increase with age and work),  aging process of the carcass, as well as various methods employed to influence tenderness such as by restricting feed for a period in order to stimulate a compensatory growth response.

Summary

Ultrasound has become an invaluable tool for grading carcass quality and for scanning live animals for genetic improvement programmes. Regardless of the exact method employed, however, any attempt to grade an animal based on ultrasound data alone will be incomplete. Individuals or organisations looking to introduce meat grading must integrate it as part of a complete system which takes other important factors - such as mothering ability and growth rates - into account.