Arm & Hammer Animal Nutrition

When Did Lower Milk Fat Production Become "Normal"?

The decrease in milk fat production on a 1,500-cow New York dairy occurred a little at a time. Point-by-point, fat production quietly slipped away—not setting off any alarms or concerns, but eroding nonetheless. The lowered production simply seemed “normal.” The slide was so insidious and happened so slowly, the dairy owner and his management team didn’t notice it until the herd’s milk fat test hit 3.2%. And stayed there. 

Just a few years earlier, the herd’s milk fat production held steady around 3.7% or a little higher. But that was then. Now the herd faces a low milk component scenario that is all too common. 

Everybody notices big dips in performance. But slowly sinking milk fat production gradually becomes accepted since the losses are not as instantly dramatic—and dairies may struggle with strategies to overcome reductions. For farms that are paid on components, slipping milk fat production can become a significant lost income opportunity. 

But you do not have to accept suppressed milkfat levels as normal in your herd. Instead, search for ways to optimize milk fat production.

Search for Solutions
Part of the challenge is that there are many influencers on milk fat production including rumen buffering, ration fat source, excessive ration sorting, forage-to-concentrate ratio, stage of production, diseases like mastitis, parity, seasonality, genetics and more.

Far and away, reduced rumen pH due to highly fermentable diets is the biggest contributor to lower milk fat production. That’s because today’s diets include more fermentable carbohydrates and along with minimized fiber (physically effective NDF) levels. In short, rations rely more on microbial protein and fermentation than in the past. 

Variable feed ingredient quality also plays a role in ration performance, and can lead to rumen upsets due to fluctuating pH levels.

“The optimal rumen pH should be between 6.0 and 6.2, but there is daily fluctuation below this level even in healthy cows” explains Gabriella Varga, Animal Science professor at Penn State University. The length of time pH is low and the number of bouts below 5.5 are what impact clinical and subclinical cases of rumen acidosis, as well as impact milk fat production. 

In addition, feeding high grain, low roughage rations encourage milk production but depresses milk fat percentages, especially when roughage is restricted to 30% or less of the dry matter fed. 1 

Generally speaking, when rations include ground, rolled, heated, steam-flaked or pelletized grain it increases starch digestibility and propionic acid production in the rumen. Furthermore, the variable amounts of fatty acids from feeds like DDGS, gluten and hominy, cottonseed and other oilseeds, combined with increasing dietary starch and other fermentable feeds can contribute to lower milk fat production, too.


Also keep in mind that there’s a difference between milk fat depression and low milk fat production.2


Nutritional strategies that follow the same set of principles are key to solving both challenges.

Optimize Milk Fat Production


Take the following steps to overcome low milk fat production and boost herd productivity:

1. Increase inclusion rate of rumen buffers. 
The recommended inclusion rate for sodium bicarbonate is 0.75% to 1.0% of TMR dry matter.3 When fed at that rate, a cow eating 60 pounds of dry matter per day should receive at least 0.5 pounds of buffer per day—not the 0.25 pounds too many cows currently receive. 

Rumen buffers help stabilize rumen acids, increasing feed intake while reducing off-feed bouts and improving rumen performance for enhanced productivity. Rumen upsets from inadequately buffering is a leading cause of acidosis—which is a top contributor to lower milk fat production.

2. Better manage DCAD levels for high production and fresh cow diets. A plethora of data indicate that dairies should take advantage of increased DCAD levels. A 2014 University of Maryland meta-analysis4 showed a linear response (P < 0.001) to increasing DCAD levels for a number of important production parameters. For each 10-point increase in DCAD [(sodium + potassium) - (chloride + sulfur)] increased:
• Milk fat percentage by 0.10%
• Milk fat grams per day by 0.35
• Rumen pH by 0.033 units
• Neutral detergent fiber (NDF) digestibility by 1.5%
• Fat-corrected milk/DMI by 0.013

In addition, multiple trials5 from Clemson University have shown a positive influence on rumen biohydrogenation when a stabilized potassium carbonate source was evaluated. 

Research confirms potassium can help reduce the incidence and severity of lower milk fat production by allowing for more of the desirable rumen biohydrogenation pathway to occur.

3. Use wet chemistry analysis to obtain accurate ration nutrient levels. Don’t rely on book values. The nutrient values—like protein, fiber and starch levels—of various feedstuffs are not consistent from load to load. 

For instance, data presented at the 2013 American Dairy Science Annual Meeting showed significant differences in rumen dry matter digestibility, protein bypass, and substantial variation within feeds for soybean meal, canola meal, corn distillers grain, corn gluten, soy hulls and expeller meal.6


Also consider alleviating overcrowding when possible to prevent cows from slug feeding, include milk fat traits in breeding decisions, reduce mastitis incidence and step-up feeding mixing and delivery management. 

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