Effect of bunk management on feeding behavior, ruminal acidosis and performance of feedlot cattle: A review

†Alpharma Inc., Fort Lee, NJ 07024

ABSTRACT Nutritionists and feedlot managers commonly attribute metabolic digestive disturbances such as subclinical acidosis to large daily shifts in feeding behavior and erratic feed intake by cattle. This perception is based on the fact that following a period of feed deprivation, free choice access to a high-concentrate diet can result in acidosis. Whether daily variability in voluntary intake of a high-grain diet by full-fed cattle compromises health or alters maintenance of ruminal pH at levels high enough for optimal ruminal function (i.e., pH <5.8) is less clear. Periodic abundance of available starch allows amylolytic bacteria (e.g., Ruminobacter amylophilus, Streptococcus bovis, Lactobacillus spp.) to proliferate and produce excessive quantities of fermentation acids. Presumably heightened volatile fatty acid production stimulates satiety receptors in cattle, which in turn results in the commonly observed “off-feed” or low intake syndrome. Despite this well-accepted relationship, comparatively few studies have actually demonstrated that voluntary variability in ad libitum feed intake impairs growth performance of cattle. Ruminal pH profiles differ substantially among cattle, even among those fed identical diets in equal amounts at the same time. It seems, therefore that factors other than meal size, and feeding regimen determine an animal's susceptibility to subclinical acidosis and ultimately influence growth performance. Feedlot management practices developed to regulate feeding behavior, and decrease variations in feed intake by penned cattle include programmed feeding, multiple feed deliveries per day, and consistent timing of feed delivery. However, the efficacy of these practices in reducing animal-to-animal variability is assessed largely on the basis of intake per pen, with little or no appreciation for the variation in feed intake among individuals. Further characterization of this variability in feeding behaviors among penmates could provide the foundation for further refinement of present feeding practices.

Implications

The majority of pen-fed cattle can and do tolerate fluctuations in feed delivery and consumption. Recent data have shown marked individual variability in feed intake, feeding behavior, and ruminal pH profiles. The role of management in subclinical acidosis may remain unclear if pen average data continue to be the evaluation benchmark. It is imperative to monitor individual animal feeding behavior (using technology such as radio frequency) so that the variables related to metabolic disorders can be identified. A growing body of data demonstrates that feedlot cattle on finishing diets can readily adapt (physiologically and behaviorally), such that day-to-day intake variability does not negatively affect performance; however, cattle may be less able to adapt to changes during the transition period. Future studies should include evaluations of intake variation and the incidence of subclinical acidosis during the transition period when instability in ruminal microflora and pH are highest.

Key Words: Acidosis, Cattle, Feed Intake, Feeding Behavior, Management

© 2003, by the American Society of Animal Science. All rights reserved.

J. Anim. Sci. 2003. 81(E. Suppl. 2):E149-E158