28 March 1997

MP feeding system is wide of mark for high yielding cows

The British Society of Animal Science held its annual meeting at Scarborough, Yorks, this week. FWs livestock team reports

THE metabolisable protein (MP) feeding system used for UK dairy cow rationing is inefficient when used for high yielders.

Thats according to a recent study at ADAS Bridgets, Martyr Worthy, Hants, which shows that the MP system over-predicts milk protein output of cows yielding over 25kg a day.

The information from this study and work at the Scottish Agricultural College still in progress should soon allow the MP system to be improved by redefining the MP equation used, claimed John Metcalf of ADAS Bridgets. It would then be possible to adapt the system for use with higher yielding cows, he told the BSAS conference.

"Lower output cows averaging up to 25kg a day fitted the MP system quite well. But at higher yields it appears that we are underestimating protein," he said.

This is because the MP system predicts that a cows protein requirements increase in direct proportion to the milk protein output at the energy level fed. This assumes that once the protein requirement for maintenance is met, the need for protein increases on a straight line basis. So for each unit of protein output, the amount of protein needed in the ration increases in equal proportions.

However, because the system was developed using lower yielding cows the range of protein shown to be sufficient may be outside the range needed by higher yielders. The feed protein needed for each unit of protein output may be higher than was predicted when the MP system was developed, he explained.

The inadequacies of the MP equation could also be caused by underestimating the cows maintenance requirement or because MP could not be measured accurately in the feeds used, so the accuracy of the diet formulations was poor.

&#8226 This project was funded by the MDC and BOCM Pauls.

The MP system underestimates the protein requirements of high yielders, says ADAS Bridgets John Metcalf.