Don’t Settle for Milk Fat Depression
There are times when you may wonder why the milk fat of your herd has dropped. Milk fat depression is a condition that affects dairy cows globally. The cause can be well known like heat stress or more subtle. Because of its multi-faceted nature, milk fat depression can be difficult to address, making it a frustrating situation for dairy farmers and nutritionists alike, particularly when milk fat prices are high and you know milk fat loss is cash lost. Fortunately, there are options to improve milk fat production and get those herds back on track.
Influences on milk fat
Milk fat depression is when a cow quickly loses up to 50 percent of milk fat yield without losing overall milk yield or other components. The factors impacting milk fat percentages or yield include nutritional and non-nutritional and can be short- or long-term. Milk fat depression factors related to nutrition can include the amount of fiber in the ration, the types of feed ingredients, whether ionophores are used or not, and the overall feeding strategy. In milk fat depression caused by nutritional factors, the lowest point of milk fat production typically occurs 7 to 18 days later1.
Genetics, animal breed, seasonality, and the physiological state of the animal also contribute to milk fat production. Most cases of milk fat depression caused by non-nutritional factors show a decrease in fat within 10 hours of onset, with the point of lowest milk fat three or four days later.
Milk fat depression may go unnoticed since milk yields and other components remain strong. Understanding what causes milk fat depression can ultimately help reduce the risk of it. Due to the variety of possible causes, farmers and nutritionists don’t have many options in their control but they can look to the nutritional factors in play.
Dairy herds fed rations lower in neutral detergent fiber (NDF) or high in plant oils, including oilseeds, are more likely to see instances of milk fat depression due to the rumen environment. The rumen environment results in an increase in the altered biohydrogenation pathway, which is a different fatty acid profile versus the normal biohydrogenation pathway. The increase of trans-10, cis-12 conjugated linoleic acid means a decrease in milk fat production because the amount of preformed fatty acids from the rumen decreases.
Other risk factors for milk fat depression include lack of rumen modifiers, slug feeding2 and grazing on pasture in the early spring and summer when pastures are in their early growth stages.
What is biohydrogenation?
Where feed and cows are concerned, we must look to the rumen. An efficient and optimized rumen achieves biohydrogenation—which is how the rumen helps create fully saturated fatty acids that are taken up by the udder to produce milk fat. The rumen has two approaches to forming fully saturated fatty acids, both of which require linoleic acid. In the rumen, linoleic acid is converted to stearic acid through both approaches. However, each approach is physiologically different for the cow. One approach results in increased levels of fatty acid intermediates that are considered to be potent inhibitors of milk fat synthesis, causing milk fat depression2. The other approach maintains ruminal biohydrogenation and microbial environment, which results in higher levels of milk fat production.
Figure 1. By maintaining the normal state of ruminal biohydrogenation through the cis-9, trans-11 C18:2 fatty acid, a cow’s butterfat production will remain at a higher level compared to the trans-10, cis-12 C18:2 fatty acid pathway.
Reducing the risk of milk fat depression
One way to help minimize milk fat depression is to adjust the ration so it has fewer plant oils. You can also work with your nutritionist to maintain an effective amount of fiber in the ration.
There’s another option for dairy producers: intelligent nutrition. University trials show that adding methionine source MHA® Feed Additive (which provides 2-hydroxy-4-(methylthio) butanoate, or HMTBa as its Ca salt) to dairy rations can maximize milk fat as a percentage and total milk fat yield3,4. The research found that cows fed MHA® Feed Additive can better achieve ruminal biohydrogenation4, while also stabilizing the diversity and types of microbiota in the rumen, even when they’re eating a ration that should cause milk fat depression5.
Figure 2. HMTBa helps maintain the normal state of ruminal biohydrogenation, allowing the maximum amount of output of stearic acid. Stearic acid is taken up by the mammary gland for milk fat production.
With milk fat price high, now is the time for milk producers and nutritionists to look at their ration and find ways to optimize nutrition to reduce the risk of milk fat depression in their herd.
Contact your local NOVUS dairy expert for more information on MHA® Feed Additive and practical management tips that support your financial goals.
References
- Harvatine KJ, Boisclair YR, Bauman DE. Recent advances in the regulation of milk fat synthesis. animal. 2009;3(1):40-54.
- Bauman, DE, and Griinari, JM. 2001. Regulation and nutritional manipulation of milk fat: low-fat milk syndrome. Livestock Production Science. 70:15-29.
- Baldin, M, Zanton, G, and Harvatine, KJ. 2018. Effect of 2-hydroxy4-(methylthio) butanoate (HMTBa) on risk of biohydrogenation induced milk fat depression. J. Dairy Sci. 101:376–385.
- Baldin, M, Tucker, HA., and Harvatine, KJ. 2019. Milk fat response and milk fat and urine biomarkers of microbial nitrogen flow during supplementation with 2-hydroxy-4-(methylthio) butanoate. J. Dairy Sci. 102:6157–6166.
- Pitta, DW, Indugu, N, Vecchiarelli, B, Hennessy, M, Baldin, M, and Harvatine, KJ. 2020. Effect of 2-hydroxy-4-(methylthio) butanoate (HMTBa) supplementation on rumen bacterial populations in dairy cows when exposed to diets with risk for milk fat depression. J. Dairy Sci. 103:2718–2730.
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