Source: Dairy Research Blog
Canada will have its first genetic and genomic evaluations for Digital Dermatitis (DD) in December 2017, which is the first step towards the direct genetic improvement of hoof health in Canadian Holsteins. This success story has resulted from various research initiatives since 2009, culminating to a national project funded under the Dairy Research Cluster 2 (led by University of Guelph) and then the development of genomic evaluations for Digital Dermatitis in Holsteins.
Collection of Data from Canadian Farms
One of the most important hoof lesions recorded is digital dermatitis, which has an incidence rate of 18% among cows presented to the hoof trimmers and a heritability of 8%. CDN therefore developed a genetic and genomic evaluation system specifically aimed at improving resistance to digital dermatitis in Holsteins. The first evaluation from Digital Dermatitis (DD) was officially published in December 2017 based on 300,000 records collected on 125,000 cows in 1,200 herds by 70 hoof trimmers.
Producers interested in this new trait for herd management and genetic improvement should encourage their hoof trimmer to contribute data to the national data collection system and work with their representative from CanWest DHI or Valacta to have their herd data flow through to CDN.
CDN introduced a new state-of-the-art methodology to calculate the genetic evaluation for each animal, which is automatically a genomic evaluation for genotyped animals. For sires to receive an official progeny proof for Digital Dermatitis, they must have hoof trimmer data reported for daughters in at least five different herds and a minimum Reliability of 70% after including any genomic information available. Given the volume of data currently available, over 2,500 Holstein sires surpass these requirements. This means that roughly two-thirds of the Top LPI proven sires will initially have an official progeny proof for Digital Dermatitis. On the other hand, every genotyped sire, both progeny proven or not, will receive a genomic evaluation for this trait and the Reliability for most genomic young bulls in A.I. will exceed 60%. Average Reliability values are higher for progeny proven sires, surpassing 80% for those with an official LPI in Canada and averaging 67% for those with a MACE LPI in Canada. All females will also receive an evaluation for Digital Dermatitis and Reliability levels will generally surpass 60% for genotyped heifers and cows.
As for all functional traits, the average DD proof for sires is set to 100. Sires with a higher Relative Breeding Value (RBV) are expected to have a higher proportion of healthy daughters. On average, sires with a rating of 100 are expected to have 82% of their daughters without any case of digital dermatitis and this percentage increases by 1% for every one point increase in RBV for Digital Dermatitis. With a heritability of 8%, these evaluations provide an opportunity for sire selection to reduce the incidence of digital dermatitis in your herd in conjunction with good herd management practices associated with improved hoof health.
For more information visit the Canadian Dairy Network’s website at: www.cdn.ca.