Fats in feed useful, but balance is tricky business

3 May 2002




Fats in feed useful, but balance is tricky business

FEEDING fats to enhance milk composition can be tricky, as feeding either the wrong fat supplement or too much can lead to the opposite effect than anticipated, says one nutritionist.

Jonathan Blake told producers at the KT meeting that fats were useful for enhancing milk composition.

"As a rule of thumb, the amount of fat in dairy rations should be the same as the amount produced in milk."

But grass silage was a major source of fat. It typically contains about 3.5% fat, equal to an intake of about 0.5kg a day, assuming a silage intake of 11kg.

Including rumen-protected fats in the ration could increase milk fat %. But feeding about 400g a day of liquid unsaturated fats and oils would have the opposite effect, reducing milk fat by about 0.5%. Dr Blake believed that was due to fats disrupting rumen function and reducing feed intake.

"Whole oilseeds offer a safer alternative than liquid fats. Feeding 1.25kg oilseed rape or 2.5kg a day of whole soyabeans to supply 400g a day of oil has no effect on milk fat %. But exceeding these levels will again reduce fat % and feed intake."

To lower milk fat % for quota purposes, fish oil is a useful tool. It lowers milk fat % without reducing feed intake. "But do not overdo it, milk fat can fall as low as 2%," he warned.

Dr Blake also said feeding fats usually depressed milk protein % regardless of fat type. &#42

Buffer feeding cows with maize or grass silage will prevent low milk fat with spring grazing, says Jonathan Blake.

Increasing milk fat %

&#8226 Promote forage intake

&#8226 Feed dry cows extra energy.

&#8226 Use maize instead of cereals.

&#8226 Include protected fat supplements

Increasing milk protein %

&#8226 Avoid over fat cows at calving.

&#8226 Feed more bypass protein.

&#8226 Offer more concentrates.

&#8226 Mixed forage diets.

PRACTICAL OPTIONS


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