Lameness is a huge - if not the single biggest - animal-welfare challenge facing the dairy industry. “Lameness is a really big issue,” says Temple Grandin, well-known Colorado State University animal scientist and animal behavior consultant.
Most experts agree the incidence of lameness in the dairy industry lies between 25 and 30 percent, which is unacceptably high. It also is largely underestimated on farm.
“If you ask someone, ‘What percentage of your cows do you think are lame?’ two studies have shown that they underestimate it by about half,” Grandin said during a recent lameness webinar hosted by Dairy Herd Management.
Lameness also is one of the most costly diseases to the dairy industry, affecting fertility, cow survival and milk production.
Now there also is evidence linking body condition score and lameness. In fact, it suggests poor body condition is a cause, not a consequence, of lameness. Here’s why body condition is an important risk factor for lameness that demands your attention.
An overlooked cause
Lameness is often the result of poor facility design, cow comfort and management. Poor body condition, on the other hand, has long been thought of as an unfortunate outcome of lameness, not part of the cause. Evidence contradicting this perception was first published by Cornell University researchers in the July 2009 issue of the Journal of Dairy Science.
The study found an association between overall body condition and the thickness of the fatty tissue in the digital cushion of the hoof.
“So the better condition (cows) are in, the more digital cushion they will have,” explains Rodrigo Bicalho, veterinary researcher at Cornell University.
Conversely, cows with low body condition have thinner digital cushions, which sets them up for lameness problems.
“If you look at your hand, the cushion in the palm of your hand is equivalent to the cushion that cows have in their foot inside the claw,” Bicalho says. “We also have it on the bottom of our feet.”
Where lameness starts
In the cow, the digital cushion lies between a bone in the claw called the third phalanx and the corium tissue beneath it. (Please see “Where lameness starts” figure to the right.)
“The function of the digital cushion is to dampen the compression that is exerted (on the corium) by the body, by the bones in the legs,” Bicalho says. “It’s part of (her) suspension system. It’s the same thing we have in cars… to help absorb impact.”
Less digital cushion translates into increased trauma to the corium, which can result in sole ulcers and white line disease, the telltale hoof lesions associated with lameness.
“Sole ulcers are a disruption or interruption of horn production by the corium,” Bicalho explains. “Then you also have the abscesses, most commonly white line disease, which is also a consequence of trauma to the corium tissue.”
Early lactation: a critical time period
Vigilance during early lactation is especially important for heading off lameness associated with poor body condition.
“As cows go through body condition loss in early lactation, the actual fat pad (digital cushion) decreases in thickness, too,” says Gerard Cramer, consulting veterinarian with Cramer Mobile Bovine Veterinary Services in Stratford, Ontario, Canada. “There’s a relationship between the thickness of that fat pad and the incidence of ulcers and white line disease.”
The Cornell study found that thinning of the digital cushion was most prominent during the 120-day window after calving. This is when body fat reserves are summoned by the cow to make milk.
Loss in thickness of the digital cushion seemed to bottom out around 120 days in milk, Bicalho says, “and after that it starts to recover.”
However, the damage has already been done to the sensitive tissues in the hoof that are at risk for injury.