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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #105668
Title: CHALLENGES IN THE NUTRITION OF HIGH-PRODUCING RUMINANTS

Author
item Satter, Larry
item Jung, Hans Joachim
item VAN VUUREN, A - LELYSTAD THE NETHERLANDS
item ENGELS, F - WAGENINGEN NETHERLANDS

Submitted to: Proceedings of International Symposium on the Nutrition of Herbivores
Publication Type: Review Article
Publication Acceptance Date: 4/17/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The cell wall, or fiber fraction, of forages is generally assumed to limit performance of ruminants under intensive production systems. Several factors influence extent of cell wall digestion. Both rate of digestion and the fraction of cell wall that is potentially digestible determines in vivo digestibility, but the latter is more important. Lignin presents a physical lbarrier to digestion, but through cross-linking with cell wall polysaccharide can also limit chemical access of hydrolyzing enzymes to the carbohydrate structure. Rumen microbes can attack cell wall carbohydrates only from the lumen side of cell walls because of the lignified primary cell wall. Only 15-30% of the dietary N that we feed to ruminants ends up in body tissue or in milk. It will be difficult to improve this by more than a few percentage points. Feeding protein sources that are more resistant to degradation in the rumen, strategic supplementation of amino acids, and stimulation of microbial growth in the rumen are approaches to improving efficiency of protein utilization by ruminants. Modern agriculture, including ruminant production systems, are heavily dependant upon fossil fuels for feed production. An amount of fossil fuel energy equaling nearly six times the energy contained in the food is necessary to get an average English meal to the table. Ruminants can utilize feeds and crop residues that cannot be used directly by people, and therefore, do not necessarily compete directly with humans for calories. The energy cost of producing these feedstuffs should not all be charged against ruminants. The challenge will be to find ways of producing and utilizing plant biomass for livestock feed with less dependence upon fossil fuel.