Digital dermatitis genetic index for dairy cows
This genetic index can help you breed cows who are less susceptible to Digital Dermatitis and reduce the likelihood of going lame.
How to use the Digital dermatitis PTAs
The Digital Dermatitis Index is published on a scale from -2 to +2 and expressed as a percentage.
Similar to Lameness Advantage, positive values are favourable in the Digital Dermatitis Index. This means that for every per cent increase in an animal's index, there will be a corresponding one per cent decrease in their daughter's digital dermatitis cases.
This translates into, on average, four fewer cows with digital dermatitis per year in a herd of 100 cows if a +2 digital dermatitis bull is used instead of a -2 digital dermatitis bull.
Why is the index published as a standalone index?
The Digital Dermatitis Index is published as a stand-alone index alongside the Lameness Advantage Index. This is because digital dermatitis makes up part of the Lameness Advantage Index so is already included in the £PLI, £SCI and £ACI figures.
The process of bull selection will, therefore, not change; the £PLI, £SCI or £ACI should be used as an initial screening tool, then traits of interest to your herd should be considered to progress your herd genetically.
These specific traits will vary between herds depending upon system, management and breeding goals but health traits, now including the Digital Dermatitis Index, should be taken into consideration when selecting bulls. Health traits may have a low heritability but including them in your breeding decisions will have a cumulative positive effect on your herd.