12 January 1996

State of milk best cow health check?

By Jessica Buss

MILK analysis may be a more useful indicator of cow health and nutrition than metabolic blood profiles.

This was the message of Swedens Dr Bo Pearson speaking last week at the University of Nottingham Feed Manufacturers Conference.

The disadvantages of blood profiles are their high cost and that some of the contents are unstable and alter during transport to the lab, he said.

"But milk is ideal for measuring parameters suitable for evaluating health and production efficiency of dairy cattle because samples are sent routinely for testing."

In addition to the tests for cell counts, fat and protein, he claimed that a measurement of ketones would determine plasma glucose concentration.

Low levels would signal an energy deficiency associated with ketosis (see p35). "Continuously low plasma glucose levels result in a much lower pregnancy rate to first inseminations and an increased risk of cystic ovaries," he said. "Clinical or subclinical ketosis can reduce milk yield by 3-4kg a day."

Milk urea levels reflect protein in relation to energy status in the cow diet, he claimed. When a balanced diet is fed the milk urea concentration is between 0.02-0.03%. At lower concentrations protein is being underfed in relation to energy.

When the level is above 0.03%, the diet is too high in protein or energy deficient.

"Days to pregnancy increase when milk ureas are too low and too high," he said.