Effect of Forage Sterilization Method on Rate and Extent of Fiber Degradation by Ruminal Bacteria

Abstract

Sterilization of forage is necessary in order to examine the degradation of substrates by pure or defined mixed cultures. An initial study examined the loss of dry matter from alfalfa hay, orchardgrass hay, wheat straw and corn silage subjected to the following treatments: 1) soaking in water for 1 h, 2) boiling in water for 1 min, 3) autoclaving in water, 4) boiling then autoclaving and 5) autoclaving the dry substrate. For all substrates the least (P < .05) dry matter loss was with Treatment 5. A second study examined the effect of sterilization method, either autoclaving and dry substrate or treating with ethylene-oxide, on neutral detergent fiber content of orchardgrass hay. Neither sterilization method caused a significant change in neutral detergent fiber content compared with the unsterilized control. A third study examined the effect of forage sterilization method on in vitro fermentation of orchardgrass hay. Both the rate and extent of neutral detergent fiber degradation by mixed ruminal contents was greater (P < .01) for unsterilized and ethylene-oxide sterilized orchardgrass hay than for autoclaved hay. There was no difference in rate and extent of degradation between unsterilized and ethylene-oxide sterilized orchardgrass hay. Sterilization method may alter physico-chemical properties of forage; thus, the effect of forage sterilization method should be considered when using forage substrates to grow pure or defined bacterial cultures. Copyright © 1988. American Society of Animal Science . Copyright 1988 by American Society of Animal Science