4.1.2.1 Large and small mature breeds
Meat & Livestock Australia March 5, 2021
Animals from different breeds are usually:
compared at the same weight
compared at the same age
compared at the same stage of maturity
Comparison at the same live weight
In the example in Figure 4.5 a) when cattle were killed at 300 kg the large mature size breed would be 60% mature, whilst the small mature size breed would be 75% mature. When these stages of maturity were superimposed on the body composition graph in Figure 4.5 b) it can be seen that the large mature size carcases would be less mature and therefore would be expected to have less fat, a slightly greater proportion of muscle and a greater proportion of bone than the small mature size breed.
Comparison at the same age
In the example in Figure 4.6 a) when cattle were killed at 100 weeks the large mature size breed would be 80.9% mature, whilst the small mature size breed would be 83.3% mature. When these stages of maturity were superimposed on the body composition graph in Figure 4.6 b) it can be seen that the large and small mature size breeds still ranked the same as for the previous comparison, but the magnitude of the differences were substantially less. Therefore at the same age the large mature size carcases would be expected to have slightly less fat, a similar increase in the percentage of muscle and a slightly greater proportion of bone than the small mature size breed.
Comparison at the same stage of maturity
In the example in Figure 4.7 a) cattle were killed at 80% of their mature size. When this was superimposed on the body composition graph in Figure 4.7 b) it can be seen that large and small mature size breeds have the same body composition.
All three comparisons are valid examples of what happens commercially. From the butchers perspective the comparison at the same weight is relevant, whilst if the producer is constrained by a rapid cessation to the season, comparison at the same age is relevant. If the feed supply is not constrained by season then producers tend to turn animals off at the same stage of maturity (i.e. the same composition).
Figure 4.8 demonstrates the above effects using data from the Meat and Livestock Commission and USDA experiments. The results show that comparisons between breeds at the same weight resulted the largest breed differences, whilst the effects were smaller when made at the same age and virtually eliminated when comparisons were made at the same fatness (or stage of maturity).