A previous post on this site (here) described research demonstrating that pregnant heifers that had multiple digital dermatitis (DD) lesions:
- were 55% as likely to conceive at first service and remained open for an average of 25 extra days;
- produced 334 kg less 305-day milk in first lactation;
- had 5.16 times greater risk of having DD in first lactation.
The authors of that research recommended that a DD control program should be a priority for pregnant heifers.
But before a control program can be implemented, a reliable method of detecting DD in these animals is required. Since their hooves are seldom seen by a hoof trimmer and are typically obscured by bedding, what are the alternatives?
At the 2016 Western Canadian Dairy Seminar, University of Calgary graduate student Casey Jacobs described how she used ‘pen walks’ to detect DD in pre-calf heifers. The hind feet of 3,026 group-housed animals on 28 Alberta dairy farms were inspected either while they moved freely in their pens or while they were restrained in headlocks. For 292 heifers on 5 farms, the presence or absence of DD lesions detected in this way was compared with hoof inspection in a trim chute (the ‘gold standard’).
Pen walk detection correctly classified 74% of the heifers that had a DD lesion and 97% of those that did not. Expressed in another way, 85% of the heifers identified in a pen walk as having DD actually had DD lesions when inspected in a trim chute. Conversely, 94% of the heifers diagnosed DD-free had no DD lesions in the trim chute. Fourteen of the 28 farms had no detectable DD in their pre-calf heifers. After adjusting for misdiagnosis, the true prevalence of DD lesions among pre-calf heifers in the other 14 farms ranged from 1% to 17%.
The bottom line: pen walks are reliable enough to be used for the diagnosis of DD in pre-calf heifers, providing a means to initiate DD control in these animals.