Butterfat

Although yet to have an impact on Australian milk prices, butter is the new superfood on global markets after about 50 years as the most vilified food in history. US dairymen are capitalising on butterfat component price which is now in excess of milk protein as protein price decreases. The net outcome is not higher milk price, but a shift in values.

As excited as we get on milk solid percentages, the real issue is kilograms of butterfat and milk protein. Traditional thinking is that as litres rise solids tests fall. Historically this does have some merit; certainly the reverse is normally true: as litres decline tests improve, however, the net result almost always is reduced kilograms of milk solids and reduced income per cow.

This does not negate our feverish pursuit of amino acid nutrition aimed at higher MP%’s and fertility, as amino acid optimisation is simply refined ration balancing for total animal performance/efficient feed conversion. However, butterfat production, and more particularly percentage, has tended to fall under the heading of cow health (rumen health) rather than an important income source. Further, high BF% is usually associated with a high fibre/low energy diet and low milk production.

Until recent years, we were not that concerned with butterfat production per se. However, the advent of depressed milk fat production as forage oil (fat) levels increased has become a significant issue when BF% falls to the extent of being a significant factor in milk price. All vegetable fats are unsaturated. The rumen saturates them by a process called biohydrogenation. If unsaturated fat intake exceeds the rumen’s capacity to saturate them, we see falling MP%’s. In worst case scenarios, BF% can crash to around 2.2% with significant impact on milk price, and worse, can take up to four months to restore normal percentages.

This situation is not entirely due to forage fat levels, although they have increased through breeding of higher energy forages, but biohydrogenation capacity of the rumen is highly related to rumen pH. An acidosis bout, or simply sub-optimal rumen pH (SARA), can inhibit the saturation of fat process and reduce BF%. Once Australian milk prices begin to reflect world butter pricing, this will become an important milk pricing issue. To feed a high fibre/low quality ration is not the answer as that will drop litres and impact per cow income even more. Like most things in life; this is a tension. A tension between high feed intakes of highly digestible rations, rate of passage (time feed is in the rumen) and fibre quality, and rumen pH.

Rumen pH: In our work on dietary fats in consultation with Professor Adam Lock (Michigan State University), and from his extensive research into milk fat depression, he advises, most commonly milk fat depression is a result of sub-optimal rumen pH.

Certainly adequate “effective fibre” is essential for good rumination/cud chewing and saliva production – our major rumen buffering agent, however, fibre can still be good quality in terms of digestibility and milk production, and yet be functional “effective fibre”. Under our ‘slug feeding system’ (grain particularly, but not discounting highly digestible pasture) as opposed to a TMR, the addition of buffering agents is essential (yeast, bi-carb etc). However, fibre is what I want to focus on here.

As we approach spring and forage harvesting, not only does this period have major impacts on profit as we grow something like 60% of our year’s pasture in six weeks of spring but how much we actually harvest between grazing and silage will not just determine our feed resources, but the cost of them. The lower the dry matter harvested through this period, the more expensive it becomes. Like cows’ fixed maintenance energy cost, diluted only by increased feed intake/milk production; our land also has fixed costs in ownership and facilities. The more we harvest from our land resource, the cheaper the feed becomes. Further, there is an odd correlation here: the higher the harvested dry matter the higher the quality, because to get high tonnages we must cut/graze frequently. Higher harvest frequency/increased digestibility/higher milk production.

Digestibility is the key in conserved forages. Digestibility will determine milk yield from both the perspective of nutrients delivered to the cow and hence milk production, but also the time that forage spends in the rumen. Long periods of forage in the rumen also reduces feed intake and milk again. Good quality silage can provide adequate effective fibre without reducing feed passage, especially in combination with quality pasture. We aim to have at least 2 or 3 kgs DM silage in a ration twelve months of the year. It will, as above, ensure adequate effective fibre/rumination/BF%, and help to keep the ration stable – no dramatic feed changes. In short, ‘right’ quality forage will provide both nutrient and physical form for rumen health/function.

Manure stands supreme as the ‘cow-side’ test. Structure first. Contents second (undigested fibre and grain). For the technically minded, take two differing manure samples and wash then in a sieve observing the residues. You don’t need starch analysis of manure to verify the visible contents in the sieve. You can actually hear good rumen function/health as manure hits the ground.

Finally; stress! Stress, particularly of human origin, will reduce butterfat production and a cascade of negative metabolic disorders resulting in both health and production issues. The rumen is the first site of dysfunction when cows are stressed.

John Lyne is a dairy production specialist with Dairytech Nutrition

www.dairytechnutrition.com.au