Nicotinic Acid and Dilution Rate Effects on In Vitro Fermentation Efficiency

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Abstract
A six-unit, continuous flow in vitro fermentation system was used to investigate the effects on fermentation efficiency of three levels of nicotinic acid at dilution rates of 4.8 and 9.5%·hr−1. Twenty-five grams of corn:hay:urea (79:20:1) substrate was added to each 1-liter fermenter daily in four trials. Each trial consisted of a 5-day fermenter stabilization and a 9-day collection. For the first two trials, inoculum was obtained from an animal not adapted to nicotinic acid, while for the second two trials, inoculum was obtained from an adapted animal. Fermenter gas production volumes were measured and then analyzed for CH4 and CO2. Liquid effluent was analyzed for total and individual volatile fatty acids, total and TCA precipitable N and pH. Feed substrate and feed residue after fermentation were analyzed for dry matter, total N and gross energy. Total N and energy recoveries were calculated. Direct nicotinic acid supplementation into the fermenters failed to change (P>.05) any of the measured characteristics, although CO2 production increased by 5%/100 ppm. However, ferementations that were started with inoculum from an adapted animal resulted in greater precipitable N and VFA production (P<-01) than did those started with inoculum from a nonadapted donor. The faster, 9.5%·hr−1 flow rate fermenters produced more VFA and propionic acid and less CO2 and CH4, but substrate digestibility was decreased by 3%. Additionally, 8% more of the total substrate energy was recovered in fermentation products at the faster flow rate than at the slower flow rate. Nicotinic acid is unlikely to effect fermentation efficiency directly, but could have indirect effects through changes in rate of ingesta passage and concomitant effects thereof. Copyright © 1981. American Society of Animal Science . Copyright 1981 by American Society of Animal Science

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