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Producing well is faring well, isn’t it?
By I. Anna S. Olsson (April 2011)
Most animal welfare scientists would say that production is an unreliable measure of welfare. Many farmers and animal scientists on the other hand would say that an animal that produces well is an animal that is faring well. It’s generally true that an animal that is downright diseased is probably not one which produces well, but other than that the relationship is far from straightforward. This is clearly illustrated in an interesting and important study of dairy cow foot health and production published in Animal Welfare 4/20101.
A team of scientists from Universidad Austral de Chile and Warwick University in UK trained Chilean herdsmen to use a standard system to detect lameness and to recognize the specific foot health problem behind the detected lameness. When a lame cow was found, she was treated for the specific hoof problem detected. Seven farms and 1635 cows were included in the study. Foot health data was then correlated with data on milk production for the specific cows.
For all causes of lameness, milk yield increased in the month after treatment. For lameness due to some of the causes, there was also a significant reduction in production over several months before treatment, as the diagram illustrates.
But for one of the foot problems, double sole, those cows that were diagnosed with the problem had higher milk yield before they became lame than cows that were not lame at all. And for another, digital dermatitis, lame cows produced more milk even when suffering from the untreated condition than those that were not lame at all.
What does this tell us? First – and this is probably the most important finding in the study – which it pays off for farmers to be on the lookout for lame cows and to treat them. For the individual cow, in general production goes down when she’s lame and returns up after treatment. Second, that it would be good for both farmers and cows if problems were detected earlier. The cows were treated as soon as their problem was found, but as the figure shows, production had been decreasing for several months prior to that, suggesting that they had probably had foot health problems long before these were detected. Third, that the relation between production and health/welfare is complex. On the level of the individual cow, production does indeed seem to reflect health: as a cow was developing hoof problems her milk production was going down. But on the group level, this relation is not clear. For one thing, apparently those cows that are high-yielding seem to be at more risk of developing hoof problems (as had already been determined in other studies2). And cows with digital dermatitis in fact remained more productive than non-lame cows also when they were suffering from the untreated foot disorder.
Thus, when the farmer observes that a single cow unexpectedly produces less than she did the month before, he has every reason to suspect her health and welfare is affected. But the fact that a single cow produces more than the average can’t be used as evidence that she is healthy and faring well.