Last week I heard of the sales representative for an anonymous feed company arguing their cake was definitely very positive for butterfat for the technical reason that it was called ‘Cream flow’! I will therefore be naming my next child ‘Usain Bolt’ in order to guarantee a sprinter in the family.

It is the time of year when butterfats are under more pressure irrespective of management system and diet. This is a seasonal cycle in production seen everywhere, and we assume driven by metabolic changes with daylength/temperature (if anyone knows the answer to this please shout).

Within this seasonal variation there are very particular diet drivers of butterfat production. They are;

• Unsaturated fat – too much of the wrong type of fats produces rumen metabolites which depress milk butterfat production, potentially very considerably. Unsaturated fats are often described as oils due to their liquid nature. They are found in significant levels in some concentrate feeds, but usually the largest source of variation in oils in the diet is in forages. Forages can be high or low, both grass crops and maize silages, and a change in forage can have a big effect on butterfat. There is essentially an absolute amount of oil before problems occur, but this amount can be modified in certain ways discussed below.
• It is the fermentation of fibre which produces the precursors of butterfats. Think about this and we realise that in order to improve butterfat fibres that we feed need to be fermentable. Feeding really indigestible fibre as is sometimes advised is unlikely to be much help unless rumen pH is low due to a lack of physical fibre. There is very much the law of diminishing return with structural fibre in diets – if there is enough fibre in there then adding more coarse forage fibre is unlikely to help, except for lowering yields and so removing the yield dilution effect on butterfat to the detriment of income!
• Low Rumen pH conditions lowers the threshold for oils to cause butterfat depression. The three aspects of the rumen pH are fast fermenting carbohydrate (starch and sugar) lowering pH, fibre causing rumination to raise pH, and consistent cow management to allow smooth feed intake. When one of these is unbalanced then pH will drop. Tackling this involves looking at the starch sources and the speed of their fermentation in the rumen – a change in starch sources may be needed as some digest much quicker than others (even before they would cause low pH lots of fast starch will lean to lower butterfat and may need addressing in a butterfat issue). It is also making sure of the correct quantity and nature of the fibre. Lastly cow management at this time of year when everyone is so busy is easy to overlook. Precise and consistent feeding and milking has a much bigger impact on rumen pH than we give it credit for.
• Yeasts and moulds have a proven negative impact on butterfat. This is not an uncommon factor on farm – coming towards the end of crimp pit or cereal store with considerable spoilage? How about silage pits in the warmer weather? No point going to considerable expense elsewhere if this is part of the issue.