Recorded as part of the Real Science Lecture Series, this webinar features Dr. Rick Grant, President Emeritus of the William H. Miner Agricultural Research Institute. He discusses a practical, data-driven approach to Precision Chewing Management. Moreover, he explains the critical role of forage particle size in supporting dairy cow health, rumen function, feed intake, and milk production.
Drawing on decades of research in dairy nutrition, forage management, and cow behavior, Dr. Grant explains how nutritionists can design feeding programs that optimize the relationship between eating behavior, rumination, and resting time. This approach aims to improve cow welfare and productive performance. He opens the presentation by introducing Precision Chewing Management. In addition, he highlights the importance of the “Big Three” dairy cow behaviors: eating, resting, and ruminating. Furthermore, he explains why efficient eating and ample recumbent rumination drive both cow welfare and farm profitability. (00:00 – 05:15)
From there, Dr. Grant then examines how the physical environment and diet interact to influence cow behavior. While stall design, stocking density, and heat stress affect behavior, forage quality and particle size remain powerful nutritional tools. These tools directly influence chewing activity and rumen function. (03:26 – 06:20)
Building on that foundation, he explores the relationship between undigestible NDF (uNDF240) and forage particle size. Dr. Grant introduces the concept of physically effective uNDF240 (PEuNDF240). He explains how combining indigestible fiber measurements with particle size helps producers predict intake, rumination behavior, and milk production responses. (06:21 – 13:46)
Next, Dr. Grant presents research showing how physically effective fiber influences dry matter intake. He identifies what he describes as the “sweet spot” for optimizing chewing behavior. Also, he demonstrates how producers can dynamically adjust forage particle size according to forage maturity, weather conditions, and fiber digestibility characteristics. Therefore, feeding programs can adapt to changing conditions throughout the year. (08:09 – 13:46)
After establishing the importance of physically effective fiber, the presentation shifts to the biological significance of recumbent rumination. Dr. Grant reviews evidence showing that cows that spend more time ruminating while lying down typically maintain better rumen pH. They also consume more feed and produce greater amounts of milk fat and protein than cows that spend more time ruminating while standing. (13:47 – 23:52)
In addition, Dr. Grant explores the mechanics of eating behavior and how chewing transforms forage before it ever reaches the rumen. He reviews research showing that cows significantly reduce forage particle size during eating. As a result, he argues that forage processing should closely mimic the particle size distribution cows naturally create through chewing. This will help producers better align feed preparation with cow biology. (21:46 – 27:38)
To further support this concept, Dr. Grant reviews studies comparing sieve fractions using the Penn State Particle Separator. He demonstrates why particles retained on the 8 mm screen appear especially important for promoting efficient chewing activity and supporting rumen function. Moreover, these particles help maximize milk production. (24:31 – 27:38)
With these findings in mind, Dr. Grant transitions into practical forage-processing recommendations. He explains how producers can adjust theoretical length of cut (TLC) based on forage maturity, moisture content, and crop type. Moreover, he highlights how modern forage systems can benefit from a more dynamic approach to chop-length management. Instead of relying on fixed targets, producers should adjust to current conditions. (30:15 – 37:01)
The discussion continues with practical benchmarks for Penn State Particle Separator distributions in lactating, fresh, and dry cow diets. Dr. Grant explains how excessive long particles encourage sorting behavior and reduce feeding efficiency. On the other hand, overly fine particles can impair rumen function and digestion. (30:15 – 37:01)
Looking ahead, Dr. Grant outlines several promising research opportunities involving non-forage fiber sources, forage fragility, particle-size automation technologies, and precision monitoring systems. These systems measure eating and rumination behavior in real time. Together, these innovations may help producers refine Precision Chewing Management even further in the future. (37:02 – 43:36)
Finally, he concludes with an extensive Q&A session covering practical implementation challenges, byproduct feeding, fresh cow hdiets, dry cow recommendations, forage moisture management, meal behavior, and particle-size strategies for different production systems. (44:40 – End)
