Editor’s note: The following information was provided by Rock River Laboratory, Inc. in Watertown, Wis.

At Rock River Laboratory Inc., our recent focus has centered on feed carbohydrates.

Carbs are nothing new or novel; however, finding what percentage of fiber or starch is available for gain or milk production is a constantly evolving challenge.

Cattle digest fiber and starch during the day in a curved fashion, meaning digestion will eventually plateau. The shape of the fiber or starch digestion curve is unique to each feedstuff and is directly related to how much energy is in that feedstuff. Nutrition professors from Cornell, Miner, and others have advanced ruminant-ration models using dynamic digestion measures (called digestion rates or Kd’s) meant to capture the shape of digestion curves.

Rock River Laboratory has developed a new calculation titled Dynamic Kd, which incorporates true Lag 24, 30, and 48h NDFDs. This approach is significantly related to TTNDFD, developed by Dave Combs from the University of Wisconsin. Using all three time points and letting the data draw the digestion curve creates a more precise measure for nutritionists to use to improve dairy and feedlot rations. The three time points also better predict feed conversion efficiency. 

The Dynamic Kd means agree with CNCPS v6.1 base library values and can be used in most ration-balancing software packages that accept Kd rates. Guidelines were developed using over two years of raw data are available through Rock River Laboratory.