March 22, 2016 10:32 AM
The author is the director of nutrition research and innovation with Rock River Lab Inc, and adjunct assistant professor, University of Wisconsin-Madison’s Dairy Science Department.

Adequately processed kernels separated from the stover and leaves using the float test.

The title might fool you into thinking we’re discussing NFL stats, but the focus is actually a topic with more potential impact to dairy and beef cattle performance: kernel processing score (KPS).

In 2005, Dave Mertens of the USDA Dairy Forage Research Center and his former graduate student, Gonzalo Ferreira, developed the KPS approach to estimate how well corn grain was processed within corn silage. The two USDA researchers compared this newly developed ranking (KPS) against rumen digestion, finding a positive relationship. The measure has since grown in popularity and is held as a gold standard to evaluate silage chopper performance.

KPS, sometimes referred to as corn silage processing score (CSPS), evaluates kernel breakage by drying the silage, shaking the dried silage across several sieves, and then determining the starch content that passes through a 4.75 mm screen. More simply put, this process determines the percent of grain from the sample that is roughly the size (width) of a 0.22 caliber bullet or smaller.

Historically, we perceive that if the kernel seed coat was cracked or damaged, our processing was adequate. Due to shrinking margins and increasing demand to gain every pound of performance per pound of TMR (total mixed ration), coupled with a much better understanding of starch breakdown thanks to research and farm experience, the aim of corn silage processing has greatly intensified.

Hitting the KPS goal

Particle size, measured as KPS, helps to better define a new benchmark. KPS is critical because the surface area of exposed starch in grain is directly related to energy available for milk or gain. Beef steer or dairy cow digesting bacteria and enzymes break down accessible starch into energy. This energy’s relation to performance is outlined with Mertens’ defined goals:

• KPS more than 70 percent — Goal

• KPS 50 to 70 percent — Adequate

• KPS less than 50 percent — Poor

Corn silage with KPS at 70 percent or greater will nearly always outperform similar silage with KPS less than 50 percent, with greater gains and milk production in the higher score. As mentioned previously, our industry has embraced KPS and worked to improve year over year. In the figure, we can visualize how the KPS ranking has improved from 2013 to 2015. The number of optimal versus adequate or low silages has increased. Yet, even in 2015, roughly one-half of all silages did not meet the 70 percent KPS goal. There is clearly opportunity and margin to be captured within this realm.

There is also continuing research in this area, with leading researchers such as Randy Shaver at the University of Wisconsin, evaluating how KPS may change during harvest and ensiling or be related to better animal performance measures. As we continue to learn more, new information continues to show that greater kernel breakage results in improved animal performance and profitability.

Harvest time evaluation

Nutrition consultants and their dairymen should consider closely evaluating kernel breakage and making adjustments as harvest takes place. Each year, corn grain hardness is vastly different thanks to the growing season. Score monitoring during harvest can be completed using the following two simple approaches:

1. On-farm float test: This is a surrogate for laboratory KPS. It is quick and simple, but is not quantitative.

a. Collect two to three representative handfuls of fresh chopped whole-plant corn into a calf pail or 5-gallon bucket, half full with water.

b. The leaves and stover will float on the top of the water and the grain will sink. You can skim the water surface with your hand to remove fiber and then use a kitchen strainer to separate and view the grain.

i. Focusing on the grain processing, you want to view adequate to complete kernel destruction, as depicted in the photo.

c. Enlist the pack tractor operator, bagger, or person tending to the silo to check kernel processing quality via the float test to start and finish each harvest day.

2. Laboratory analysis: Aim for 60 percent KPS or better at harvest. While this test is slower and more costly, it is quantitative for better benchmarking and more specific results.

a. Send a representative whole-plant chopped corn sample to your laboratory. Opt to check KPS daily through harvest and make adjustments accordingly.

Work with your harvest and consulting team to check your score both at the harvest event and when feeding out. Set a benchmark for your farm and harvest team. Do you know how your silage scored? Make plans to improve each year with better performance and profitability in mind.

This article appeared in the February 2016 issue of Hay & Forage Grower on page 24 and 25.

Not a subscriber? Click to get the print magazine.