When selecting a sire for your cows there are many factors that can influence the appearance and performance of a bull so selecting “by eye” can be misleading. The only accurate way of assessing the genetic potential of an animal and what it can pass on to its youngstock is by using Estimated Breeding Values (EBVs).

EBVs are calculated using information from several sources –

• Measurements from the animal itself.
• Measurements from the animal’s herd mates.
• Measurements from the animal’s relatives and their herd mates.
• The degree to which one trait influences another – is known as correlation.
• The degree to which each trait is passed on to the next generation – is known as heritability.

EBVs are expressed relative to a common baseline which means comparisons can be made between bulls of the same breed but not of different breeds. This table shows the different EBVs for a Hereford bull and their accuracy compared with the breed average at the bottom. It is important to remember that because a calf has two parents, the values get halved so for example, if the cow’s birth weight EBV was 0kg and the sire’s was +1kg, the calf should end up as +0.5kg.

A few of the more common ones are listed below and what to look out for:

Example:
This bull is great if you want heavier calves all the way through from birth to finishing and for more fertile sons. However, due to the heavier birth weights you would be a lot more likely to have difficult calvings in both the cow and his daughters as well as a longer gestation period. If you’d like to discuss your herd’s genetics further or need more guidance on using EBVs please get in touch!