In vitro fermentation of feed ingredients by fresh or frozen pig fecal inocula

In vitro techniques can offer a rapid, repeatable and cost-effective alternative to in vivo experiments. We investigated the gas production (GP) of nine different feeds commonly used in Italian and Maltese pig farms in order to assess the use of the Ankom system in this species and to compare the in vitro microbial activity fresh or frozen inocula derived from piglet feces. Proximate and polyphenolic analyses were determined for all substrates. Fermentation profiles were measured according to the cumulative GP technique. Analysis of GP values revealed significant differences in the fermentation patterns mainly due to substrate and inoculum effects. Fermentation parameters varied significantly according to the substrate ingredients. The frozen inoculum generally led to more total GP than for fresh, with the exception of hard wheat bran pellets (HWBP), pelleted pulp and mature carob. Conversely the fresh fecal inoculum had an earlier maximum time to reach maximum GP than the frozen, showing a higher maximum rate of GP in all substrates excepting for HWBP. A significant difference in frozen and fresh inocula was found for the complete formulation. Further studies are required to confirm the variation between fresh and frozen fecal inocula to a wider range of feed, including those that could have negative biological effects.