Roughage use in finishing cattle diets

By Warren Rusche, South Dakota State University Extension

Key points

Roughage serves as a functional ingredient in finishing cattle diets, with key roles in supporting rumen health.

Conventional wisdom assumes that roughage inclusions should be no greater than necessary for rumen health (less than 10% of diet dry matter) to maximize feed efficiency.

Greater inclusions of roughage may reduce risk of digestive upset and simplify management with minimal efficiency losses.

Role of roughage in feedlot diets

Roughage plays a critical role in digestion and metabolism of dietary nutrients. One key function is the promotion of rumination and regurgitation, which results in greater saliva production and increased ability to buffer acid in the rumen. In addition, longer particles of roughage serve to support rumen wall health and to regulate feed intake.

For these reasons, a minimum amount of roughage is considered critically important in high-starch finishing cattle diets to reduce risk of digestive upsets and optimize net energy intake by cattle. According to the most-recent survey data, the most common roughage inclusion in North America for finishing cattle diets is between 8-10% of diet dry matter.

Nutritionists typically limit roughage inclusion in finishing diets because those ingredients are less digestible (and thus lower in energy) compared to grain and biofuels co-products. Increasing the amount of roughage reduces net energy concentration of the diet, and consequently reduces predicted daily gain. Roughage also costs more per unit of energy compared to concentrates in most cases, so it is no surprise that roughage inclusion is limited to the minimum necessary for rumen health.

Building a case for greater roughage inclusion

However, a one-size-fits-all recommendation often misses opportunities to improve results. Feeding a slightly reduced energy density diet by including more roughage may not be as detrimental to cattle performance as often believed. In some instances, increasing the amount of roughage inclusion increases net profit.

Reduced risk of digestive upset and improved gut health are the likely drivers behind these responses. Lower roughage diets should improve gains and feed efficiency, at least in theory. However, to capture that potential performance, every aspect of feeding management must be nearly ideal. Any deviations in mixing procedures, amount of feed offered, or timing of feed delivery or intake increases the likelihood of off-feed events.

Unfortunately, circumstances are rarely perfect in production systems. Equipment failure and workload conflicts may interfere with management plans. Weather events, such as blizzard conditions in the winter or heat waves in the summer, disrupt feeding behavior and increase the odds of erratic feed intake.

In those circumstances, feeding a few extra percentage points of roughage may reduce risk. In SDSU research trials evaluating silage inclusion in finishing cattle diets, doubling the amount of corn silage fed was less detrimental to output than expected. We think that one reason for that response is maintaining consistency in feed intake, especially as cattle near the end of the feeding period.

Increased roughage reduces risk caused by feed intake disturbances, whether caused by weather or delivery disruptions. For instance, winter snowstorms often cause delays in getting cattle fed. In addition, cattle alter feeding patterns during weather events, such as blizzards or heat waves. If cattle must wait for feed, a typical response would be for them to consume their diet aggressively, opening the door for digestive upsets. Feeding less starch (by increasing fiber from roughage) reduces that risk.

Cattle feeders who raise their own feed are in a great position to use roughage sources produced on-farm to their advantage. Marketing feeds, such as silage or crop residue, through cattle can increase net farm income. Increasing silage inclusion in SDSU studies resulted in greater beef production per acre of cropland compared to lower roughage diets.

Choosing a production plan that does not target maximum performance may seem contradictory to commonly accepted practice. However, building in a safety measure in the form of added roughage might improve efficiency when measured across an entire system.