Phenotype (P) = Genotype (G) + Environment (E)

The way an animal looks and performs (phenotype) is influenced by:

  • It’s genetics (genotype)
    • Half of an animal’s genetics comes from the sire and the other half comes from the dam.
    • The animal’s genetics are determined at conception.
    • Only the animal’s genes are passed on to the next generation.
  • The environment in which it is run
    • Factors such as age (of animal and its dam), birth type (e.g. singles or twins) health, nutrition, climate and the management conditions an animal is exposed to will all influence how the animal performs. You may hear these referred to as fixed effects.

At both single and multi-vendor sales the following environmental factors being managed differently can influence the animal’s phenotype:

  • feeding regimes in the lead up to sale. For example, one vendor may have had bulls on high-quality feed for 6 months prior to the sale, and another have had bulls on a lower-quality feed for only 3 months prior. A single vendor may have had bulls running in different paddocks.
  • Bulls are likely to range in age. Older bulls may be physically heavier as they have had more time to grow compared to their younger counterparts.
  • health history. For example, some animals may have previously suffered from injury or illness, which has impacted on their growth to date.
  • dam age e.g., some animals may be out of first-calf heifers. First-calf heifers typically have lighter calves than mature cows.

While environmental factors influence how an animal appears on sale day, they don’t change its underlying genetics. Genetic evaluations separate the genetic component of an animal’s phenotype from the environmental component.

Key messages

How a bull physically presents on sale day is not necessarily a reflection on his genetic potential.

Genetic evaluations account for the environmental factors (fixed effects) to give the best estimate of an animal’s genetic merit.