C. Parrott
Jun 1, 1992
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Journal
The Professional Animal Scientist
Abstract
Abstract Monensin sodium was approved in 1975 by the Food and Drug Administration (FDA) for use in feedyard cattle to improve feed efficiency. Early research studies both in vitro and in vivo demonstrated that monensin altered ruminal fermentation of cattle by reducing acetate and increasing propionate by the ruminal microflora. Later research indicated that monensin resulted in increased numbers of gram-negative bacteria and reduced grampositive bacteria within the rumen. The shift in bacteria is related to the cell wall structure of the organisms. Monensin continues to improve feed efficiency in high-energy rations, although research indicates that as energy levels are increased the percent improvement in feed efficiency is decreased. Controlled studies have demonstrated that monensin is effective in reducing metabolic disorders, lactic acidosis, and bloat, and is efficacious in controlling coccidiosis. Recent studies with individually fed cattle indicated that monensin reduced the variability of feed intake. Monensin has been cleared for combination usage with tylosin for the reduction of liver abscesses and with melengestrol acetate for the control of estrus and improved feedyard performance with heifers.