23 August 1996

Right recipe is vital to give milk protein boost…

By Jessica Buss

THE key to increasing milk protein lies in supplying more of the right mixture of specific essential amino acids that are limiting milk protein synthesis.

But supply more of just one limiting amino acid, and another becomes limiting if the cow still has the potential to produce more milk protein, explains Chris Reynolds of the University of Reading. The cow has an upper limit for milk protein synthesis. This depends on her milk yield and other factors such as hormonal signals.

Protein synthesis

"To achieve a cows genetic potential for milk protein synthesis and supply other body requirements we must provide a diet that creates a mixture of proteins in the small intestine.

When digested this must provide all the amino acids required for milk synthesis," says Dr Reynolds. So far research at CEDAR, University of Reading has supplied amino acids in the right mixture directly into the blood and this has increased milk protein content most dramatically. Increasing the supply of the required amino acids through feeding is, however, more difficult.

Its important the correct mixture of essential amino acids is supplied. In some studies supplying non-essential amino acids alone has had a negative effect on milk protein.

"One aim of the CEDAR work is to help develop a computer animal model of amino acid digestion and metabolism in the cow and how the response varies in different diets," he says. Eventually this animal model would predict farm responses to amino acid supply.All we can currently do through cow nutrition is ensure a good supply of quality protein sources, says Dr Reynolds. First balance the protein and carbohydrate supply to the rumen to produce high quality microbial protein. Then supply some rumen undegradable protein sources such as fish meal.

Some production studies have shown that methionine and lysine are often the most limiting amino acids, especially in maize based-diets.

High quality forage can boost milk protein content. But the real key lies in supplying the right cocktail of essential amino acids.