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 rum inant feedstuffs that are fibrous, low in nitrogen and of limited nutrition al value for other animal species. For the purposes of this paper we define rumen biotechnology as the application of knowledge of forestomach ferment ation and the use and management of both natural and recombinant rumen micr oorganism to improve the efficiency of ruminant production. Knowledge of ru men digestion that is relevant to modifying both the nutritive value of fee dstuffs and the rumen microbial ecosystem by biotechnology is reviewed. Exa mples of the use and potential of biotechnology to alter the amount and ava ilability of carbohydrate and protein in plants as well as the rate and ext ent of fermentation and metabolism of these nutrients in the rumen are disc ussed. The potential applications of biotechnology to rumen microorganisms are manifold and have been reviewed extensively whereas this paper concentr ates 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 candid ate enzymes; level of production, localisation and efficiency of secretion of the recombinant enzyme; stability of the introduced gene; fitness, survi val and functional contribution of introduced new strains. Ultimately, the success of rumen biotechnology will depend on the environmental and regulat ory concerns of the public being addressed. (C) 1999 Elsevier Science B.V. All rights reserved.