Monensin and Lasalocid Effects on Fermentation in Vitro

Abstract
A six-unit continuous flow fermentor was used to determine effects of the ionophores, monensin and lasalocid, on efficiency of fermentation of high grain and roughage substrates. In each trial, the substrate was supplemented with 33 or 44 ppm monensin and 32.5, 65 or 130 ppm lasalocid and compared with a control fermentation. Fermentations of diets with and without ionophores were compared for total and individual VFA production, total and precipitable protein produced, ammonia, pH, methane produced, substrate disappearance and total energy and N balance. Ionophore additions depressed methane production (P<.001), from 4.1 to 2.7 kcal/day in the high grain fermentations and from 3.0 to 2.2 kcal/ day in the roughage fermentations. Individual VFA production patterns were generally shifted without affecting total VFA production, although in some specific fermentations production was depressed. Butyric acid production was usually decreased by either ionophore, while propionic acid was generally increased in high grain but not roughage substrate. Lasalocid, but not monensin, depressed isovaleric acid production. Energy digestibility remained largely unchanged by ionophore addition (averaged 3% lower). The amount of substrate N digested and the resulting amounts of total effluent N showed marked depressions as a result of ionophore supplementation. This could account for the 29 and 48% (P<.001) depression in ammonia production observed for the two substrates. Total bacterial growth in these fermentors, however, as indicated by tungstic acid precipitable N content of the effluents, was not inhibited by either lasalocid or monensin. The general effects of lasalocid on fermentation in vitro appeared to be quantatively similar to those of monensin, although larger quantities of lasalocid appeared to be required for equal biological effects. The expected in vivo effects of these ionophores are to shift VFA fermentation patterns, depress methane and alter the site of dietary protein digestion. Copyright © 1982. American Society of Animal Science . Copyright 1982 by American Society of Animal Science

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