macrolide antibiotics, liver abscesses, feedlot cattle


Liver abscesses are a cause of concern for many feedlots across the country as they lead to a decrease in feedlot performance of finishing cattle as well as a decrease in the final carcass value. Loss in carcass value is due to not only the abscessed liver being condemned, but also due to trim loss associated with the condemned liver. The macrolide drug tylosin phosphate is the drug of choice for metaphylactic treatment of liver abscesses in feedlot cattle. The Food and Drug Administration approved the drug for over-the-counter use, however, from January 2017 all medically important (used in human health) antibiotics that are to be fed in production animal diets will require a veterinary feed directive. The objective of the veterinary feed directive program is to decrease the use of medically important antibiotics in animal production. These veterinary feed directives are similar to a prescription and will encourage the use of the drug in accordance to FDA-guidelines associated with that drug. Macrolide antibiotics are considered medically important and will need a veterinary feed directive. Therefore, it is imperative to look at different methods to control liver abscesses in feedlot cattle. Various studies have noted that macrolide antibiotics (such as tylosin phosphate) are effective against pathogens for moderate to prolonged periods after initial use. The purpose of this study was to determine whether feeding tylosin phosphate periodically throughout the finishing period will have a comparable effect on decreasing liver abscesses as when we would feed tylosin phosphate continuously through the finishing period.


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