As we move fully into spring, it is time to have our butterfat-risk tool kit out and ready for deployment. It is remarkable the gains in butterfat levels that have been widely reported. It does seem that we are in a new place. As the discussion continues about the exact cause of this incredible reality, we can’t forget that no matter what the magic is, milkfat synthesis does get impacted seasonally.

In some geographies, the low-fat risk may be in the spring flush when cows are really cranking out milk. This is most likely a simple dilution with both protein and fat percentages being lower in larger volumes of fluid. In other geographies, all seems good until real heat stress sets in and low-fat test issues become problematic. In any case, the cows seem to have a good grasp on the calendar, and milkfat synthesis trends are predictable. Yes, we may be starting from a higher base than ever in history, but the risk of lower levels will still be there.

Given this situation, I thought I would review a few of the tools that have seemed to have the most impact in my personal experience. I am sure there are ration and additive/technology strategies that I have not personally used, but I will stick to things that have been meaningful in my experience feeding cows.

We should start with the basics

To build a significant part of milkfat, the cows need fiber. The acetic acid used to create the fat molecule comes from fiber fermentation in the rumen. This important nutrient needs to be comprised both of fiber with digestibility potential as well as fiber in the form of roughage to keep the rumen in good health.

As well, when you look at the nonfiber components of the typical dairy ration, namely simple carbohydrates like starch and sugar, a ration deficient in fiber/roughage will likely be too high in starch/sugar. In summary, we need enough fiber that has roughage value to keep the cow’s rumen healthy, and we need enough of this fiber to be digestible to be converted to acetic acid. Along with a hundred other details, we need this fiber/roughage component to comprise enough of the diet that starch is kept at a safe and moderate level.

It is helpful to remember that the rumen microbes that convert digestible fiber into the building blocks for butterfat are a largely different population than the species that ferment the starch in corn. The rumen of a feedlot steer is significantly different from the rumen of a grazing brood cow.

The high-producing dairy cow is somewhere in the middle. We need to consider both fiber-digesting microbes as well as starch digesters to make milk and keep a dairy cow healthy.

Mind these principles

So, the first few techniques of supporting good spring/summer fat test levels are to consider these principles. Be sure you have enough physical roughage in the diet to keep the cows chewing their cud. Every time the cow rechews and swallows the same feed, buffers are produced in the saliva. Dietary measures to describe this ration technique would include physically effective neutral detergent fiber (peNDF) and undigested neutral detergent fiber after 10 days (uNDF240). Adding Penn State Particle Separator measurements to these nutrients will be the best and next step.

Next, be sure that forage digestibility is adequate to create the building blocks for milkfat by watching nutrients like neutral detergent fiber digested by 30 hours (NDFd30) in forage test results. The majority of this digestible fiber will come from forage. However, ingredients like soybean hulls will add to the creation of building blocks for milkfat. As we watch these levels of fiber, keep a safe maximum on starch and sugar to help the population of fiber-digesting microbes remain at adequate levels.

Corn and other sources of rapidly fermentable carbohydrates tend to drop the pH in the rumen, and this is problematic to the fiber-digesting bugs. The normal rumination and rechewing of roughage particles help with this as every bolus swallowed carries with it buffers to support rumen pH. We also can add buffers to the ration. This is perhaps the oldest dietary strategy to support milkfat. The science is good, and this technique should be employed. Basal levels of bicarb or other buffers should be in place all year with expected increases in feed rate during the spring and into summer heat stress.

The primary ration nutrient to help describe the buffering capacity of a ration is the dietary cation-anion difference (DCAD). Most dairy producers are more familiar with a negative DCAD as a descriptor of close-up or prefresh diets in a technique to manage milk fever risk. This same math can describe the rumen buffering ability from a positive DCAD. We are most interested in the amount of sodium and potassium in the rumen. Both of these minerals can be easily added to diets to help keep rumen pH in a safe zone for the fiber-digesting rumen microbes.

The next very important point in managing milkfat risk is detailing the type of fat in the diet. To avoid a journal article-style rabbit hole, we will just say that fat coming from grain sources including corn, distillers grain, brewers grain, and so forth is problematic to milkfat synthesis.

The details are complicated, but the cows know the drill. If you feed, for example, too many distillers, you will hurt butterfat. A recent meta-analysis of peer-reviewed journal articles showed a linear reduction in milkfat with each increase in unsaturated fat added to the diet. It is real. There is no need to relitigate this on your dairy.

These bad fats can be described in various ways, and I think this adds to the confusion by the dairy producer. Terms ranging from vegetable oils, unsaturated fats, and linoleic acid to 18:2 fatty acids all mean pretty much the same thing, and if you feed too much — it is a problem.

What can we do?

So, if some fats are bad, and we can’t simply keep adding starch to meet the energy needs of a heat-stressed dairy cow, what is one to do? The good fats are unfortunately more expensive. Various commercial products are available and can literally add to milkfat (16:0 fatty acids/palm fat) or help support the overall energy needs of the cow to maintain body condition and help the animal be ready for rebreeding. In other words, some commercial fats help support butterfat and others support body condition. Both are important and various combinations can be included in dairy diets to meet specific needs.

There are a few other feeding strategies that can help support milkfat in a more nuanced way. Among these are various direct-fed microbials, enzymes, yeast-based additives, and rumen-available methionine. These can all help.

We also need to not forget that management techniques like reducing overcrowding, raising the number of meals per day, and enhancing cow-cooling efforts will all pay dividends in setting up cows for success in maintaining butterfat. This summer may be the time to start utilizing milk fatty acid analysis by strings or pens to see more details on how your cows are making butterfat.

Almost all of these strategies will increase feed costs unless you take the “more forage” approach and let the cows potentially reduce total milk production. At times, that might be the right thing to do. In every case, however, thinking about supporting good milkfat production will also be a plus for overall cow health. Keeping cows healthy is always the right thing to do.

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(c) Hoard's Dairyman Intel 2023
May 18, 2023

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