The relationship between the weight of a tissue in a single joint and the total weight of the tissue in a side of beef

Extract

1. Using the data from the dissection of 24 sides of beef from Hereford, Dairy Shorthorn and Friesian steers on four levels of nutrition a critical study has been made of the relation of the weight of tissue in an anatomical joint to the total weight of the same tissue in the whole side.

2. There was a significant eifect of breed and level of nutrition in the case of bone. The heaviest breed (Friesians) had a bigger proportion of bone in those bones which support the animal (i.e. the radius-ulna, humerus, femur and tibia-fibula) than had the lighter breeds (Herefords and Shorthorns). The effect of level of nutrition was not the same for all the bones and was difficult to interpret. There was little or no significant effect of breed or level of nutrition on the distribution of muscular or fatty tissue among the joints.

3. The relation of the weight (in kg.) of a tissue (x) in a joint to that in the whole side (y) was expressed by groups of equations of the form, y = a+bx, there being a separate group for bone, muscular tissue, subcutaneous fatty tissue, intermuscular fatty tissue and total fatty tissue. Tables are provided giving the values for the constants ‘a’ and ‘b’ and standard errors of prediction joint by joint for each tissue.

4. No general significance could be attached to the values for the constant ‘a’ but for each tissue there was a correlation between the value for ‘b’ and the inverse of the average weight of tissue in the corresponding joint. For each tissue there were one or two joints which were significantly aberrant. Aberrance is associated either with exceptionally high or with exceptionally low levels of errors of prediction.

5. The high order of magnitude for the standard errors of prediction for estimating muscular tissue (± 12·2 1b. or more) and for estimating total fatty tissue (± 12·7 1b. for the loin), led to exploring the following rule of thumb method.

6. The weight of muscular tissue in a carcass is approximately one-third of the live-weight of the animal, the weight of bone, tendon etc. is onequarter of the weight of muscular tissue and the remainder of the weight of a carcass is the weight of fatty tissue.

7. Using the weights of the animals on the farm, the weight of the sides after hanging in the slaughter house overnight, and the weights of the tissue after dissection it was shown that the above method of estimation gave values for muscular tissue within ± 10·1 1b., for fatty tissue ± 11·8 1b. and for bone etc. ± 3·1. These values compare favourably with those calculated from the weight of muscular tissue in a joint (±12·2 1b. for the foreshin), and fatty tissue (neglecting thorax ±7·0 1b. and 13th rib ±9·8 1b.) ± 12·7 1b. for the loin. The estimate of bone etc. from the weight of radiusulna (± 1·7 1b.) was somewhat better.

8. The general conclusion is that in studies of meat quality, and of the effect of breed and plane of nutrition on meat quality (including carcass conformation) it will be necessary to dissect the whole side or carcass joint by joint, tissue by tissue and muscle by muscle. There are no adequate short cuts.