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Dairy   Puzzling results from a study on lameness and milk production A California study suggests that cows with lesions on their feet produce less milk, but research conducted by a Teviotdale vet and milk farmer seems to belie that by DON STONEMAN Has lameness surpassed mastitis as the dairy industry’s most costly disease? Veterinarian and dairy farmer Gerard Cramer suspects that this is the case, but his research now seems to be posing more questions than it answers. Cramer is pursuing a doctorate in veterinary medicine and expects to finish his thesis on the incidence of lameness in Ontario dairy cattle in the New Year. He milks cows on the family farm near Teviotdale in Wellington. Cramer estimates that 28 per cent of cows in the freestall barns studied were lame, as were 13 per cent of cows tied in their stalls. Lameness was measured using a couple of visual measurement scores -- locomotion scoring in freestall barns and leg scoring in traditional tiestall buildings. Both scores are relatively new tools used by dairy scientists to determine the extent and severity of lameness by observing individual animals in a herd. With locomotion scoring systems, the observer monitors gait and back posture of individual animals in freestall barns and assigns a score ranging from one to five. A score of one means that an animal is not lame at all, while a score of five indicates that it is hobbling on three legs. In tiestall barns, lameness is scored by observing how cows stand. The “rotation” of the front claws or toes on the feet is measured from an observation position directly behind the cow. Cramer uses “leg scoring,” a system developed in Holland. In a 2003 study, Kathy Zurbrigg, a health surveillance specialist with the Ontario agriculture ministry, used a slightly different system called a “claw score.” With that system, the observer, a Dairy Farmers of Ontario inspector, either scores a cow’s toes as normal or rotated outwards. In Cramer’s leg scoring system, cows claws were “normal,” “mildly rotated,” or “severely rotated.” Cramer is trying to find a correlation between leg scores and the lesions that hoof trimmers find when they work with cows. Five hoof trimmers volunteered to record when they found lesions on every cow they worked with over 15 months -- about 14,000 cows, Cramer says. The prevalence of 11 different types of lesions was measured. In turn, Cramer and a research student scored 1,000 cows for visual signs of lameness. The analysis still isn’t completed, but his early results are puzzling. Different lesions were found in freestall and tiestall barns. Over the long term, there seemed to be no production differences between cows with signs of lameness and those without. In fact, a preliminary examination of the data seemed to indicate that cows with lesions on their feet were “making more milk” than cows without abscesses and other lesions. After hoof trimming, the cows with lesions tend to lose that advantage in milk production. Furthermore, they don’t seem to gain it back, according to dairy herd improvement records, Cramer says. A study in California found that cows produced about 4.2 pounds (1.85 litres) of milk per day less for each increase of one locomotion score unit. But Cramer questions the veracity of the California study because it wasn’t published in a peer-reviewed scientific publication. Last fall, the Canadian Veterinary Journal published a 2003 study by Kathy Zurbrigg and Neil Anderson, who is also with the Ontario agriculture ministry, on cow comfort in 371 Ontario dairy herds, using observations of cows with an arched back as a measure of the incidence of lameness. (The study noted that 80 per cent of lactating dairy cows in Ontario are housed in tiestall barns.) More than half of the herds observed had at least one cow with an arched back and the prevalence of an arched back ranged up to as many as 21 per cent of a herd. An arched back while a cow is standing is a sign of a more acute stage of lameness. In a lesser stage of lameness, the arched back is observed when cows are walking, but not necessarily when standing. Cramer hopes that his work on lameness will build on that study. Whether it is of economic importance or not, Cramer says lameness doesn’t look good to consumers of milk. They can tell a lame cow when they see one, he says, but they don’t know when a cow has mastitis. BF