
Higher milk component yield directly impacts profitability for dairy producers. And it offers an important measurement of cow health and nutrition.
With today’s high feed prices, many producers are looking to boost forage inclusion to help reduce ration cost. However, if not done correctly, the lower-cost ration can come at the expense of milk component yield.
Maintaining strong milk component production can be accomplished while you evaluate different feedstuffs. This strategy requires keeping a close eye on neutral detergent fiber (NDF) levels in the ration.

In general, NDF measures the relatively slower digesting portion of all the feedstuffs. Most forages with a high NDF have a filling effect, which can limit feed intake. As you know, increasing production of milk solids can only occur by encouraging feed intake.
It is important to fully understand the fiber components of the ration to ensure balance and productivity. Evaluate these five measurements when it comes to fiber:
- aNDF, previously reported in lab analyses as NDF, which describes the total fiber content of the feedstuff.
- NDF digestibility over a period of time (NDFd), which is typically measured and reported through 30 hours, but can be measured at 24 or 48 hours.
- Ballast or “fill” of NDF, called undigestible NDF or uNDF240, which is the undigestible residue after 240 hours (10 days!) fermentation.
- The potentially digestible NDF or pd-NDF content, is the difference between aNDF and uNDF240 on a dry matter basis (aNDF – uNDF240).
- Rate of aNDF digestibility (kdNDF).
Taken together, these data points explain how digestible the forages are on the farm, how quickly the digestion takes place and what the limitations to digestion might be. Weather events don’t always allow you to harvest forages at the optimal time, which compromises NDF digestibility.1,2
Tweaking NDF
More and more producers are turning to yeast probiotic feed additives to improve the NDF digestibility of pd-NDF within the ration.
1 Ward RT. Opportunities and limitations in the use of NDF fiber digestibility values. Cumberland Valley Analytical Services, Inc. Penn State University Dairy Cattle Nutrition Workshop. Nov. 9-10, 2005. Grantville, Pa.
2 Allen M. Forage fiber digestibility in relation to dairy cow performance. Proceedings of the Intermountain Nutrition Conference. 2006.
3 Guedes CM. Effect of S. cerevisiae yeast on ruminal fermentation and fiber degradation of maize silage in cows. Animal Feed Science and Technology. 2008(145):27-40.
4 Oba M and Allen MS. Evaluation of the Importance of the Digestibility of Neutral Detergent Fiber from Forage: Effects on Dry Matter Intake and Milk Yield of Dairy Cows. J. Dairy Sci. 1999; 82:589–596.
6 Levucell SC Milk and Component Yield Improvement Excel Worksheet. LCNAE036. Revised April 27, 2020.
7 United States Department of Agriculture. Announcement of Class and Component Prices. May 2021. Accessed June 25, 2021. Available at: https://www.ams.usda.gov/mnreports/dymclassprices.pdf.