The Journal of Nutrition Vol. 127 No. 5 May 1997, pp. 809S-809S
Copyright ©1997 by the American Society for Nutritional Sciences

Introduction¹

George C. Fahey Jr.

Department of Animal Sciences, University of Illinois, Urbana, IL 61801

FOOTNOTES

LITERATURE CITED

Ruminants that make a contribution to the food supply of humans number nearly two billion. Domestic ruminants provide 70% of the total animal protein eaten, 80% of the milk consumed and 10% of the natural fiber used by humans. Many scientists believe that there is a need to double ruminant animal protein production in the next 25 y to improve the protein intake status of the world's rapidly growing human population.

Forages play a pivotal role in ruminant animal nutrition. But as a source of nutrients, forage has the most variable composition of any feedstuff, being affected by a whole host of factors. Efficient use of forage by ruminants can be achieved only by a clear understanding of these factors and the manner in which they can be manipulated.

Enhancing utilization of forage fiber by ruminants offers a tremendous research challenge. As the research base expands, questions become more complex and techniques required to address these questions become more elaborate. Analysis of the chemical constituents of plant cell walls and the structural characterization of these components are important in efforts to improve forage fiber utilization. Therefore, it is necessary to develop and use appropriate analytical methods. Jung (1997) summarizes the latest information on analytical methodologies used to quantify forage fiber and relates this to important chemical characteristics of the plant cell wall. The newer, more sophisticated methods of analysis will be used only if they are capable of more accurately predicting animal performance responses.

Significant improvements can be made in digestibility of most forage species by using conventional plant breeding methods. Successful use of these methods requires that plant traits be measured rapidly and at minimal expense and that they are highly correlated with animal performance. Several traits are now used, but the most common one is in vitro digestibility. Buxton and Redfearn (1997) summarize the literature on plant-associated factors that affect forage utilization by ruminants. Major topics covered by these authors include the effects on digestibility of the amount of fiber in plants, sources of and reasons for cell wall indigestibility, and improvements in forage quality achieved through plant breeding technology.

Degradation of plant cell wall material by gastrointestinal tract microorganisms and their enzymes is the key event in ruminant-based agricultural systems. Perhaps the most important aspects of forage cell wall digestion from the microbiological perspective include microbial adhesion to fiber, the interactions among different microbial species, and the enzymology of the digestion process. From the animal perspective, factors such as particle size reduction in the rumen, kinetics of cell wall digestion and passage, and feeding management effects on fiber digestibility are important if we are to optimize the use of forages in ruminant diets. In their contribution to this conference, Varga and Kolver (1997) describe the opportunities, both microbial- and animal-related, that exist relative to the enhancement of fiber digestion by ruminants.

FOOTNOTES

LITERATURE CITED

• Buxton D. R., Redfearn D. D. Plant limitations to fiber digestion and utilization. J. Nutr. 1997; 127:814S-818S [Medline][Medline]
• Jung H. G. Analysis of forage fiber and cell walls in ruminant nutrition. J. Nutr. 1997; 127:810S-813S
• Varga G. A., Kolver E. S. Microbial and animal limitations to fiber digestion and utilization. J. Nutr. 1997; 127:819S-823S [Medline]

0022-3166/97 $3.00 ©1997 American Society for Nutritional Sciences