Genomic Evaluation for Digital Dermatitis in Canada

By Steve Mason on

A previous post described a Canadian research project aimed at linking hoof lesion data collected by trimmers with the Hoof Supervisor® system into the national Dairy Herd Improvement (DHI) database for use in genetic selection. More recently, Francesca Malchiodi with the Canadian Dairy Network presented a project update at the ICAR 2018 Conference held in Auckland, New Zealand. The video of her presentation is here.

Earlier research had demonstrated that, although heritabilities for hoof lesion traits are low, ranging from 1% to 7%, there is enough variability between bulls to select them for enhanced resistance to hoof lesions. For example, the figure below compares sire Relative Breeding Values (RBV) for digital dermatitis (DD) to the percentage of DD-free daughters for a number of current sires. When ranked in this way, less than 7% of the daughters of the top 10% of sires had DD while 24% of the daughters of the bottom 10% of sires had DD.

A genome-wide association study has also been performed for DD and sole ulcers. Results indicate the presence of certain genes that have significant effects on these hoof lesions, which is promising for selection of increased resistance.

Recent Developments

The data collection and exchange project has four major objectives including:

  1. Standardization of hoof lesion data collected by hoof trimmers across Canada
  2. Development of a data flow process from hoof trimmers to Canadian DHI and onto the Canadian Dairy Network (CDN, the national dairy genetics organization)
  3. Development of a DHI management report for dairy producers
  4. Development of genetic and genomic evaluations for hoof health

Objectives one and two are completed, while three and four remain in progress.

Standardization of hoof health data has been achieved by collecting data from hoof trimmers equipped with Hoof Supervisor® software.

An interface between Canadian DHI and the Hoof Supervisor® system has been developed, which allows trimmers to download some DHI information (cow identification, days in milk, dates of calving, breeding and pregnancy, etc.) directly into Hoof Supervisor® prior to a herd visit. This enables herd and animal identification data to be attached to the Hoof Supervisor® records. Following herd visits, trimmers routinely transfer Hoof Supervisor® data (lesions, severity, actions) back to Canadian DHI, which then sends the data to CDN. There are presently 28 hoof trimmers contributing data in this manner and another group of 8 to 10 trimmers are expected to start shortly.

The current focus of the project is the development of a new DHI herd management report for hoof health which will allow herds to benchmark themselves against other herds provincially and nationally for major economic hoof lesions.

Next Steps

The next major part of the project involves the development of a genomic evaluation system for hoof health. This system may use methodology called “single-step”, whereby genotyped cows from herds with hoof health data serve as the reference population as opposed to progeny proven sires. Canadian hoof trimmers and Canadian DHI have been essential to successful data collection so far. Nevertheless, more hoof trimmer participation is needed in order to sustain evaluations for hoof health beyond the project. The goal is to have routine hoof health records from 10-20% of cows in herds across Canada. With this quantity of data, selection for hoof health will be possible well into the future.

source: Lynsay Beavers and Brian Van Doormaal, Canadian Dairy Network

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