26 January 1996

Diet change can be simple way to lift milk quality

By John Burns

and Jessica Buss

MANIPULATING fat and protein to meet milk buyer requirements may be as simple as changing one or two key ingredients in the diet.

This is evident from a three- year, EU-funded study on milk quality at ADAS Bridgets Research Centre, Hants.

"We are becoming more able to devise diets that work within two to three weeks to change milk composition to match the market requirements," says ADAS Bridgets director, Bridget Drew. "Fat and protein can be shifted almost independently or together as required."

Supplying more starch as either ground or caustic-treated wheat was found to increase milk protein to 3.5% without a corresponding increase in fat %. Milk proteins of 3.6% were also achieved by diet manipulation without lifting fat by increasing both rumen by-pass starch, such as maize meal, and by-pass protein, such as SoyPass, in the diet. Their ration comprised 9.2kg grass silage, 2kg brewers grains, 3kg wheat, 2.4kg maize meal, 0.7kg molasses, 0.5kg SoyPass, 0.9kg soya bean meal, 0.2kg fishmeal, vitamins and minerals.

Dr Drew claims other studies show that feeding a balanced diet including 7.4kg DM of naked oats helped cut fat to 3.2%. "It is possible to make enormous differences in fat %, ranging from 3.2 to 4.6%, without shifting protein, and major changes in fatty acids also occurred," she says.

Milk high in unsaturated fatty acids and low in saturated fatty acids is produced by feeding 2-3kg DM of either naked oats, whole soya beans or processed rape cake. The resulting milk may be less likely to cause heart disease and will make butter that spreads straight from the fridge.

But Dr Drew warns producers supplying the liquid market against aiming for low protein milk. Low proteins often reflect poor feeding, which may reduce cow fertility. &#42

&#8226 Meet minimum legal fat (3.5%) and protein required for liquid milk market.

&#8226 Produce for market paying on constituents, with high payments for protein.

&#8226 Aim for specific fat to protein ratio,or high casein milk for cheesemaking.

Dr Bridget Drew… Designing diets to change milk composition.