Forage Matters: Keep the Cow Herd Rumen Healthy During Winter Drylot

By James Rogers

Over the holiday season, humans may experience stomach churning caused by a change in diet to rich holiday food. Stomach churning is not enjoyable for humans to experience and calls for a bottle of antacid. Stomach churning is a good thing, however, for cows. A cow’s stomach churning indicates a healthy rumen system, which is the movement of the rumen and reticulum to mix all the ingested food with rumen fluid and microbes. Additional indicators of a healthy rumen are a balance of fiber- and starch-digesting bacteria and a neutral pH. 

Cow herds across the Northern Plains spend the grazing season out on a pasture and range consuming forages with rumen fiber-digesting microbes. Once the grazing season is over, many cow herds spend the winter months in a drylot. Moving from pasture and range to a drylot is a major diet change and, if done incorrectly, can damage the rumen in a way that a bottle of antacids can’t fix.

A management goal for the cow herd during the drylot period should be to maintain a healthy rumen environment. Once grass returns in the spring and the cow herd is returned to grazing, the rumen is churning and a re-adjustment period back to grazing is not required. 

This diet shift can mean changing from forages containing 80% moisture to dry hay with 15% moisture. Depending on the nutrient content of the hay, a supplement may compensate for any nutrient deficiencies. There is no way of knowing forage nutrient content without forage testing. This means that the cow herd must adjust to the type of forage being consumed and the supplement type, grain (which has high starch content) or co-product (which has high digestible fiber content).

Moving from a high forage to a high concentrate (starch) diet can cause rapid changes in the rumen environment. If a change in diet occurs too quickly, the rumen walls can get damaged. This causes a decrease in rumen pH, a shift in the type of rumen bacteria and a decrease in stomach churning, which can lead to bloat, acidosis or founder. This can happen when a starch supplement is fed beyond 0.5% of body weight daily. This effect can be avoided if a cow is fed highly digestible fiber such as in soybean hulls, corn gluten feed or dried distillers grain.

Another management strategy to control drops in rumen pH is to ensure adequate fiber in the diet. Fiber stimulates cud chewing and saliva production, which buffers a drop in rumen pH. Fiber that supports rumen health is related to particle size and is referred to as “effective fiber” or scratch factor. Many producers will grind or chop hay that has low nutrient content and blend it with a supplement that is fed together as a mixed ration. Effective fiber is reduced, however, if the hay is ground too finely. To maintain effective fiber, a half-inch chop is recommended.

A huge part of maintaining a healthy cow herd is maintaining a healthy rumen. Cows are stressed when their diet is changed. Once the cow herd has transitioned to a drylot, maintain a steady, consistent dry matter feed intake. Ensure there is adequate fiber in the diet to stimulate rumen-churning and cud-chewing and always have ample water supplies available.