Depressed About Butterfat?

Posted by rebecca on Jun 13, 2013, 4:49 PM

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Grass - know your enemy! Are your butterfats dropping? More reports are coming through about this annual problem. What can be done?

Well, first we need to look at what is causing it. Milk fat is relatively easily and quickly manipulated, which is both good and bad.

Grass is a great source of long-chain polyunsaturaed fats that are great for improving embryo survival. However, they also undergo some changes in the rumen (biohydrogenation) resulting in intermediary fats that can rapidly depress fat production in the udder. This is bad enough yet add in sub acute acidosis and it fats wil fall further.

Grazing is known to be a risk for acidosis, with many studies showing that rumen pH can drop just as easily as on a high starch winter ration.

Through in a lack of effective fibre and the picture is complete. Fibre is converted in the rumen to acetate, which is converted to butterfat. A lack of fibre helps reduce the rumen pH, making the sub-acute acidosis more likely.

Don't forget! Calving pattern will have an influence, with seasonal calving herds having more cows at the top of the yield curve, so milk fats will be naturally lower.

So, what can be done? Buffer feeding with long fibre can help (offering some in the collecting yard in feeders) as well as choosing feeds that have a good supply of fibre in them (high NDF diets). Lower sugar levels will help. Yeasts, such as Yea-Sacc, can help stabilise rumen pH but take 2-4 weeks to become effective.

The addition of the C16 fats (such as ButaCup) can be an effective tool, provided at least 250-300g per day is fed. The cost and practicality make this a less favourable option.

In summary, grazing nearly always causes a depression in butterfat. Careful forage management and correct choice of concentrates, such as the Massey FiMLAC Q-HS or SuperLac ranges, will help offset some of the natural effects grazing will bring.

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