Sale catalogues and supplementary sheets may include raw performance data about the animals available for purchase. This usually includes the most recent recordings of liveweight, ultrasound scan measurements (e.g. eye muscle area, rib fat depth, rump fat depth and intramuscular fat) and scrotal circumference.
While these provide a snapshot of the animal at the time of sale (e.g. consideration of the animal’s actual size, feed requirements and muscularity profile), raw data should not be used as an indication of an animal’s genetic merit (i.e. what it will pass on to its progeny).
This is because, as we learnt in Module 1 – Concepts of animal breeding and genetics, performance (phenotype) is a result of both the animal’s genetics (genotype) and environmental factors that it has been exposed to over its lifetime. When comparing the differences in raw performance between bulls, you cannot accurately assess whether these differences are due to genetics, environment (including differences in nutrition, management, age, age of dam and whether the animal was raised as a single or twin) or a combination.