Icing milk fever

by Amina Ali

ome private practitioners have found that supplementing cows with phosphorus appears to help them recover from "milk fever" -- a condition principally caused by a low calcium level, resulting in initial excitation and then weakness after calving.

Now, University of Guelph population medicine professors Wayne Martin and Ken Leslie are co-ordinating a field study to determine if phosphorus supplements can help the estimated 15 per cent of cows that don't respond to the usual calcium treatments for milk fever.

"The non-response rate is just too high, from both an animal-welfare and economic-loss point of view," says Martin.

Cows' calcium levels often fall after calving, as calcium in the blood is diverted to the udder. Calcium and phosphorus are tied together in metabolism, so supplementing with phosphorus may boost recovery from the low calcium conditions of milk fever.

As part of the study, the Ontario Association of Bovine Practitioners will be blood sampling up to 1,500 cows this summer. The 15 per cent of these cows that don't respond to the typical calcium treatment will then be randomly given either a phosphorus supplement or a placebo. Neither the veterinarians nor the farmers will know which cows are being given the phosphorus treatment.

All these precautions will make it easier for Martin and Leslie to see if there's a conclusive difference in recovery rates between those cows given phosphorus and those that are not. By taking blood samples at each stage, the researchers can test cows' calcium and phosphorus levels and study their metabolism, including liver function, more closely. By examining the cows' metabolic profiles, the researchers hope to get a handle on predicting which cows will recover from milk fever.

Martin and Leslie say the study has significant applicability because it's being done on farms. And if it's shown that phosphorus supplements work well, then they may bemay then be better able to predict which cows are more prone to the disease. If the treatment works, it begs for more detailed physiological studies to help understand why. In either case, the study will help farmers and vets prevent and treat the disease. It's hoped this will be a big step in the ongoing struggle to prevent death and improve cow health.

"It's a timely trial," says Martin. "Veterinarians need to know whether they should be using phosphorus and what positive and negative effects it has."

The Ontario Association of Bovine Practitioners is funding the trial. The phosphorus supplements are being supplied by Pfizer.