Rumination is an innate behavioral need of dairy cattle and they exhibit stereotypies (or repetitive behaviors) when it is inhibited. Rumination facilitates digestion, particle size reduction, and subsequent passage from the rumen to promote dry matter intake. Rumination also increases saliva secretion and improves rumen function by buffering.

When ruminating, whether lying or standing, cows are quiet and relaxed with heads down and eyelids lowered. Cows prefer to ruminate while lying down with rumination occurring in about 80% of resting bouts. Consequently, poor management that impairs lying time may also reduce rumination. Total sleep time in cattle is short, and rumination provides the physiological rest and rejuvenation provided by sleep. Rumination is positively related to feeding time and feed intake: following periods of high feed intake, cows spend more time ruminating, usually after about a 4-hour lag. Restricting intake reduces rumination: a 2.2 pound decrease in dry matter intake is associated with a 44 minute per day reduction in rumination according to early Dutch research.

Cows voluntarily control rumination and stop chewing when disturbed. Under acute and chronic stress environments, rumination may be depressed. The figure summarizes several key components of the management environment that will reduce the cow’s expected rumination response to dietary fiber amount, fiber digestibility and fragility, and particle size. Although research needs to be conducted, if rumination is chronically depressed by 10 to 20 percent due to a poor management environment, then we can logically predict compromised rumen function and greater risk for associated problems such as sub-acute acidosis and poor digestive efficiency, lameness, and lower milk component output.

Cows ruminate for approximately 450-550 minutes per day and a decrease in rumination time is often a good signal that something is negatively affecting rumen function and cow well-being. Rumination is highly sensitive to cow well-being. Rumination often responds to a stressor 12 to 24 hours sooner than traditionally observed measures such as elevated temperature or other clinical signs, depressed feed intake, or reduced milk yield. Recently, on-farm systems have become available to monitor rumination as well as other behaviors such as overall activity (for estrus detection). Consequently, monitoring rumination to enhance the comfort and well-being of dairy cattle is likely to become increasingly important. Monitoring and acting on rumination data should help dairy farmers:

• Find and breed cows in estrus.
• Detect health problems earlier such as metabolic disorders, mastitis, and lameness.
• Identify nutritional and management issues before they become problems.
• Modify traditional fresh-cow checks with less disturbance of cows and time in headlocks, less labor, more focus on high-risk cows.
• Change treatment and culling decisions: cow can be monitored after treatment to decide whether it is working.

Rumination economics: this behavior is highly sensitive to changes in dietary physically effective NDF and fiber digestibility, cow health and well-being. Its use as a routine on-farm monitoring tool is expected to grow since it will allow earlier identification of problems and more timely intervention.