2 February 1996

HIGHER PROTEIN, LOWER FAT MILK FROM STARCH

STARCH-BASED rations fed to dairy cows improved milk protein content and reduced fat when compared with fibrous diets at the Lelystad research centre.

Researcher Ronald Zom said: "Cows produced milk with 4.34% fat and 3.41% protein when fed a fibrous ration. But similar feed intakes of a starch-based ration with comparable energy levels, resulted in milk with 4.26% fat and 3.66% protein.

"The important difference between grass and maize silage is the starch percentage of the dry matter. Grass energy is derived from cell walls while maize energy is derived from slowly degradable starch," said Dr Zom.

Starch digestion produces propionic acid and glucose, precursors of glycogen which acts as a readily available energy store in muscle and the liver.

"It might be that less amino acids will be derived from glycogen for glucose synthesis freeing more amino acids to form milk protein," said Dr Zom.

Reductions in milk fat percentages were also achieved in a zero grazing trial which replaced beet pulp with maize husk cob silage. Grass fed ad lib and 6.0kg DM of beet pulp a day was replaced with 4.8kg DM a day of corn cob mix plus 1.2kg a day of extracted soya- bean meal. Fat levels were similar between 994g and 948g a day for both diets. But daily yields averaged 23.5kg in maize-fed cows compared with 22.5kg on beet based diets. Protein was also higher when fed maize at 832g a day compared with 794g a day for cows fed beet pulp. &#42

Lelystad research stations robotic milker.

Cows fed starch based rations at Lelystad research station produced lower fat and higher protein milk than those fed fibrous rations.