Cows that inherently move about in their environment with ease and comfort are what every breeder wants to have in their herd. They produce more milk, require less labor, are usually more reproductively sound and, ultimately, they make more profit in their lifetime. Lame cows are significant profit eaters and, as animal welfare becomes more and more important to our industry, lameness could become our Achilles Heel.
Genetics and Lameness
So what does genetics have to do with lameness? To date our phenotypic evaluations of feet and legs have yield heritabilities of 5% to 10%, so we have essentially said why bother breeding for improvement in mobility? Instead we choose to address it through feed and management and cull the problems from the herd. Well that approach is not resulting in a reduction in lameness. So let’s address the elephant in the room. Why are we not breeding for improved mobility in dairy cattle?
Other New End Result Indexes
In the past few months new outcome based indexes have been declared official and are now being used for fertility (Holstein USA’s Fertility Index), for immunity (CDN’s Mastitis Resistance Index) and for herds that depend on grazing ( CDCB’s Grazing Merit Dollars). As well, both TPI and NM$ had their formulas adjusted or expanded in December 2014. However the very important area of cow mobility does not even appear to be on the radar screen, when it comes to providing breeders with animal ratings for locomotion. Is mobility too big or too complex for our researchers, genetic evaluation experts, breeders and A.I. to tackle?
For seventy years we have had the Dairy Cow Scorecard which describes the ideal feet and legs and how they are to function. We also have very good type classification programs that analyse the form of feet and legs. But they do not capture data on how the feet and legs function. And yes it would take time and effort for classifiers to see all cows walk. But, if it was a requirement, would it not give the classifier the opportunity to more accurately assess this important area of a cow’s conformation? One significant factor that adds bias to the classification of feet and legs is that herds often have the hoof trimmer visit and trim all animals before the classifier visits. Can we expect that the heritability estimates for feet and leg traits will ever be above the current low values? Not likely.
Very few cows relative to the size of the recorded national herd get to dairy shows. Those that do get to shows seldom have major mobility problems and therefore judges infrequently make negative comments on a cow’s mobility. As well few elite gTPI, NM$, PTAT or gLPI dams, the mothers of the very top young bulls or heifers, are taken to shows, so show ring feet and leg evaluations are not a solution when it comes to improving animal mobility.
I have heard some people suggest that all heifers 6 to 15 months of age should be evaluated for their mobility. Perhaps that could be a more accurate assessment of how an animal naturally walks and it would replace the need to have every cow that is classified observed on the walk by the classifier. However that would require that the type classification program be expanded to include heifers. Who would benefit and who would pay for that expanded service?
Often veterinarians, feed advisors, consultants and herd managers evaluate a portion of a herd rating the cows for the locomotion from normal to severely lame. (http://www.zinpro.com/lameness/dairy/locomotion-scoring) However that information is usually for only a portion of the herd and is not linked to classifier evaluations for feet and legs.
Hoof trimmers could also analyse cows for mobility before they trim their feet but there again how would that information be captured and who would pay for it? Linking the results for a herd would also be a problem because only a portion of the herd is trimmed on any visit and what about the cows that are not trimmed?
What could a Mobility Index Look Like?
The Bullvine has not done an extensive study on what a mobility index might look like but from our experience as classifier, judges, researcher and breeders we offer the following suggested content and weightings:
Mobility Index = 50% (Walking Evaluation) + 20% (Rear Legs Rear View) + 15% (Feet and Pasterns) + 5% (Rear Legs Side View) + 5% (Thurls / Pins – location and width) + 5% (Chronic Conditions –i.e. crampiness)
Additional traits may also have an influence on mobility. However for brevity we have limited the traits included.
What Needs To Be Done?
Studying mobility is a big task. Likely requiring the evaluation of many many more animals than the current coordinated international multi research herd study underway. That study is for relating feed intake, production and genomic profiles to give animal ratings for feed efficiency. Also a lowly heritable but important trait. Both Holstein USA and Holstein Canada have conducted pilot studies on how to capture cow locomotion. But as yet they have not been able to find a way to expand the classification of feet and legs to include locomotion. However they should be congratulated for attempting to find solutions.
The truth is that this challenge is too large for any single organization to undertake and it is not limited to a single breed. At this point what is needed is a champion to bring all the stakeholders together to consider how to proceed. As has been the case for every other trait, determining genetic indexes requires phenotypic observations, genomic profiles, data analysis, extensive funding and likely new ways of evaluating body parts.
The Bullvine Bottom Line
Until breeders have a mobility index they will not be in an improved position to breed cows that move with ease and comfort in their environment. Limited mobility, limited production, limited reproduction, reduced profit, all contributing to the challenge of future industry viability and sustainability. It requires a collective stakeholder effort. The challenge is a big one but it is not impossible. Our industry needs to address the elephant in the room and not continue to remain silent on finding ways to improve cow mobility.