In a cow’s perfect world, over 80% of rumination should occur when the cow is lying down. The technical terms would be sternal recumbency and recumbent rumination. Resting with the sternum, or breastbone, on the ground and a slight left-side preference is the cow’s optimal resting and ruminating posture. This posture is thought to allow correct positioning of the rumen within the body for the most effective rumination.
Benefits of recumbent rumination include more saliva production and physiological rejuvenation. Sleep is fairly limited in cattle, and rumination provides some of the physiological benefits of sleep. In a competitive freestall environment, ruminating in a stall may also provide protection from pen mates. Management that reduces lying time often reduces rumination.
Rumination is sensitive to well-being, and management factors such as overstocking, empty feedbunks, and heat stress reduce rumination by 10% to 20% or more. When freestalls and feedbunks are overcrowded, we have observed higher rumen pH for cows that accomplish more rumination while in a stall. Overcrowding stalls does not always affect daily rumination time, but it does depress the percentage of rumination occurring in a stall.
There is a positive relationship between rumen pH, de novo fatty acids (made from scratch in the mammary gland), and milkfat yield. Cows that ruminate within a freestall should have better rumen pH for fiber fermentation and the potential for more milk components. In fact, recent work at the University of Guelph by Trevor DeVries’s group found that cows with longer time spent ruminating while lying down ate more feed and produced milk with higher fat and protein content than cows who ruminated more while standing up.
Cows that can easily access feed 24 hours a day, seven days a week . . . and have the freedom to ruminate in a stall . . . tend to have higher rumen pH. Avoiding low rumen pH boosts fiber fermentation, microbial growth, and milk components. Posture seems just as important as time for rumination. If you consider the stall to be your cow’s office, then encourage her to lie down on the job!