The application of rumen biotechnology to improve the nutritive value of fibrous feedstuffs: Pre- and post-ingestion

Rumen biotechnology has the potential to improve the nutritive value of ruminant feedstuffs that are fibrous, low in nitrogen and of limited nutritional value for other animal species. For the purposes of this paper we define rumen biotechnology as the application of knowledge of forestomach fermentation and the use and management of both natural and recombinant rumen microorganisms to improve the efficiency of ruminant production. Knowledge of rumen digestion that is relevant to modifying both the nutritive value of feedstuffs and the rumen microbial ecosystem by biotechnology is reviewed. Examples of the use and potential of biotechnology to alter the amount and availability of carbohydrate and protein in plants as well as the rate and extent of fermentation and metabolism of these nutrients in the rumen are discussed. The potential applications of biotechnology to rumen microorganisms are manifold and have been reviewed extensively whereas this paper concentrates on the technical difficulties that are limiting its progress. Current limitations include: isolation and taxonomic identification of strains for inoculation and DNA recombination; isolation and characterization of candidate enzymes; level of production, localisation and efficiency of secretion of the recombinant enzyme; stability of the introduced gene; fitness, survival and functional contribution of introduced new strains. Ultimately, the success of rumen biotechnology will depend on the environmental and regulatory concerns of the public being addressed.