Perspective and Commentary: Chewing behavior of dairy cows: Practical perspectives on forage fiber and the management environment

Abstract

Our objective is to provide practical perspec- tives on how forage-fiber characteristics interact with feed- bunk management to affect the balance between eating time and ruminating and resting activity. We offer recom- mendations for forage and dietary particle size to imple- ment these concepts on farm. Peer-reviewed scientific literature, research abstracts, and some proceedings and popular press were used to support our perspectives on this topic. Peer-reviewed scientific literature, research abstracts, and some proceedings and popular press were used to support our perspectives on this topic. Chewing comprises eating and ruminating, which are complementary behaviors. Fiber plays a major role in stimulating chewing; source of fiber, dietary fiber content, degradability, fragility, and particle size influence its effect. The major role of forage particle size in many feeding situations is on eating rather than ruminating, since cows often chew feed to a relatively common particle size endpoint before swallowing, and the rumen is popu- lated with a particle distribution that is more uniform than the diet. The time spent eating should fall typically between 3 and 5 h/d and needs to be in balance with recumbent rumination. Cows that accomplish more rumi- nating in stalls and lying down consume more dry matter and produce milk with greater fat and protein content. Diets that allow the cow to meet her time budget require- ments contain >50% particles (as fed) on the 8-mm sieve of the Penn State Particle Separator and <5% on the 19- mm sieve to control sorting and eating time. The length of cut for forages should be adjusted based on maturity and fiber degradability, fragility or susceptibility to breakdown, and moisture content for crops such as corn silage. As for- ages become more mature, lower in degradability, and less fragile, they should be chopped shorter to ensure optimal eating and ruminating responses. Similarly, immature or more fragile forages should be chopped longer. We propose recommendations for theoretical length of cut and ration particle size distribution that incorporate these concepts.