Thoughts on fiber utilization in swine.

There is continued incentive for the development of alternative feed resources for use in swine production. The availability of distillery by-products may be expected to increase as the use of corn and cereal grains for ethanol production expands. The acceptability of distillery by-products, milling by-products, forages and other fibrous feeds as energy sources for swine depends on such factors as cell wall content of the plant, degree of microbial fermentation in the large intestine, and extent of absorption and utilization of the volatile fatty acids produced. Physiological effects of dietary fiber, including effects on gastric emptying, rate of transit of digesta, gut motility, digestive secretions, and absorption and utilization of breakdown products need quantification. Limited evidence suggests that there are genetic differences in the response of pigs to dietary fiber and in their ability to utilize it as an energy source. Recombinant DNA technology offers the possibility of cloning cellulase genes from microorganisms for application in swine feeding programs. The extent to which biotechnology will be applied in swine feeding will depend ultimately on the economic incentive for developmental effort and on unknown biological limitations of the pig and its gastrointestinal microbial ecosystem.