Butterfat yield not percent should be target when cows are on spring grass

UFAC- UK National Sales Manager Mike Chown advises caution before following processor pressure to increase butterfat percent. While some processors are pushing farmers to increase milk quality at grazing, he says producers must ensure it is cost effective and should not over- estimate the potential responses claimed by some ingredient suppliers.

Numerous factors work against producing high butterfat percent at grazing. Butterfat requires the production of acetate in the rumen to supply lipogenic energy. At grass, where effective fibre levels are low the rumen tends towards a glucogenic fermentation which will drive milk yield rather than butterfat.

Furthermore modern Holstein cows are genetically geared to produce around 3.6% fat.

So producing higher fat percent at grass will be a challenge and in many cases the price paid per additional percent might be insufficient to cover additional costs. Most contracts have a price per percent paid up to a base level. Butterfat increases above this attract a lower pence per percent rate which declines as butterfat increases.

In one example contract, butterfat content up to the base level of 3.5% is paid at 3.75p/%. From 3.5-4.0% the rate is 1.75p/% while above 4.0% fat the payment is cut again to 0.75p/%. So the starting point before taking any action to increase butterfat must be to understand what you are going to be paid.

One strategy which can be more profitable is to work with the cows and optimise what grass can deliver by looking to maintain or improve milk yield to increase total weight of solids, which is, after all what you are effectively paid for.

For most herds, the most efficient way to influence milk quality in order to maximise the milk contract is to focus on fat yield produced (kg fat/ day) rather than butterfat percent.

Butterfat yield not percent should be target when cows are on spring grass Mike Chown To do this requires a minimum 65% of the rumen VFA’s produced to be acetate and 17% butyrate. Dietary factors affecting acetate and butyrate are effective structural fibre in the diet, VFA’s from conserved forages, the forage to concentrate ratio, the type of concentrates fed and rumen pH. For an efficient rumen and increased milk volume we also require a minimum level of 15% propionate in the total rumen VFA’s. Propionate is required as it is the precursor for glucose which is the major energy source for the cow and milk lactose production, so driving milk yield. Factors affecting propionate production are starch, sugar and non-fibre carbohydrates in the ration. High levels of propionate will give good yields with lower milk fat – and this is what grazing delivers. A careful balancing of the total ration to achieve optimum milk yield and butterfat is critical.

What about feeding more dietary fat?

There has been a lot of talk in the press about feeding higher levels of dietary C16:0 fat to boost butterfat percentage, but the numbers don’t stack up. At current prices this is unlikely to leave room for an increase in margins.

Currently C16:0 fat is costing around £1150/tonne on farm, or £1.15 per kilo. At a typical feed rate of 300g, you are looking at a 34p increase in feed costs. Despite talk of an increase of 0.4% butterfat, a more realistic expectation would be an increase of no more than 0.3% extra fat.

Using the contract example from earlier on, and assuming a farm is above the base level of 3.5% fat but below 4.0%, the potential costs and returns are shown in the table.

It is often argued that C16:0 fat will increase milk yield too and at 39MJ/ kg you are certainly feeding enough for an extra two litres on paper. However, this energy is not directly available to the cow and does not contribute to the VFA’s and other energy sources the cow needs. It mainly influences milk fat content and contributes to excess body weight loss.

More milk can increase fat production cost-effectively

Grazed grass will drive milk yields and provided the rumen function is optimal it will be possible to avoid any butterfat depression. This will actually produce more kilos of butterfat than chasing butterfat percent.

Taking our example 30 litre cow, at 3.7% fat, the cow would produce 1110g of fat per day. At 4.0% fat, the typical increase from feeding C16:0, this will increase to 1200g.

If by maximising the rumen function yield is increased to 32 litres at 3.8% fat, she will produce 1216g of fat with lower feed costs, meaning the milk will generate more margin.

The key will be to promote efficient use of grass to support higher yields is maintaining rumen health by providing effective structural fibre to complement grazing. In addition it is important to ensure the diet contains the correct balance of energy and protein. As grazed spring grass is high in rumen degradable protein, purchased feeds need to supply DUP and Promega is an ideal feed in this situation. The correct protein sources will help support milk yield and protein production.

When selecting a fat supplement, UFAC has developed a more cost effective product to optimise yield of solids. Omega Cream is a rumen inert high C16:0 product with a unique combination of fatty acids including omega 3’s, plus Glycerine to maximise feed conversion efficiency, herd health and fertility.