Characterising Forages for Ruminant Feeding

  • Dynes, R.A. (CSIRO Livestock Industries) ;
  • Henry, D.A. (CSIRO Livestock Industries) ;
  • Masters, D.G. (CSIRO Livestock Industries)
  • Published : 2003.01.01


Forages are the most important feed resource for ruminants worldwide, whether fed as pastures, forage crops or conserved hay, silage or haylage. There is large variability in the quality of forages so measurement and prediction of feeding value and nutritive value are essential for high levels of production. Within a commercial animal production system, methods of prediction must be inexpensive and rapid. At least 50% of the variation in feeding value of forages is due to variation in voluntary feed intake. Identification of the factors that constrain voluntary feed intake allows these differences to be managed and exploited in forage selection. Constraints to intake have been predicted using combinations of metabolic and physical factors within the animal while simple measurements such as the energy required to shear the plant material are related to constraints to intake with some plant material. Animals respond to both pre- and post-ingestive feedback signals from forages. Pre-ingestive signals may play a role in intake with signals including taste, odour and texture together with learned aversions to nutrients or toxins (post-ingestive feedback signals). The challenge to forage evaluation is identification of the factors which are most important contributors to these feedback signals. Empirical models incorporating chemical composition are also widely used. The models tend to be useful within the ranges of the datasets used in their development but none can claim to have universal application. Mechanistic models are becoming increasingly complex and sophisticated and incorporate both feed characteristics and use of biochemical pathways within the animal. Improvement in utilisation through the deliberate selection of pasture plants for high feeding value appears to have potential and has been poorly exploited. Use of Near Infrared Reflectance Spectroscopy is a simple method that offers significant potential for the preliminary screening of plants with genetic differences in feeding value. Near Infrared Reflectance Spectroscopy will only be as reliable as the calibration sets from which the equations are generated.


  1. AFRC. 1990. Nutritive requirements of ruminant animals: energy. Technical Committee on Responses to Nutrients. Report No 5. Nutr. Abstr. Rev. (Series B) 60:729-804.
  2. AFRC. 1991. Voluntary intake of cattle. Technical Committee on Responses to Nutrients, Report No 8. Nutr. Abstr. Rev. (Series B) 61:815-823.
  3. Agricultural Research Council. 1980. The Nutrient Requirements of Ruminant Livestock. CAB International. Wallingford, UK.
  4. Baker, S. K. and R. A. Dynes. 1999. Evaluation of the feeding value of pasture legumes. In: Genetic Resources of Mediterranean Pasture and Forage Legumes (Ed. S. J. Bennett and P. S. Cocks). Proceedings of an International Workshop on the Genetic Resources of Plant and Forage Legumes in Mediterranean Environments. Kluwer Academic Publishers. Netherlands. pp. 120-131.
  5. Baker, S. K., R. A. Dynes, D. A. Henry and D. B. Purser. 1998. Objective specification of the quality of hays and fodder. Rural Industries Research and Development Corporation Report. Canberra, Australia.
  6. Baldwin, R. L., J. France and M. Gill. 1987a. Metabolism of the lactating cow. I. Animal elements of a mechanistic model. J. Dairy Res. 54:77-105.
  7. Baldwin, R. L., J. H. M. Thornley and D. E. Beever. 1987b. Metabolism of the lactating cow. II. Digestive elements of a mechanistic model. J. Dairy Res. 54:107-131.
  8. Beever, D. E. and F. L. Mould. 2000. Forage evaluation for efficient ruminant livestock production. In: Forage Evaluation in Ruminant Nutrition (Ed D. J. Givens). CABI Publishing. Wallingford, UK. p 15-43.
  9. Beever, D. E., J. France and G. Alderman. 2000. Prediction of response to nutrients by ruminants through mathematical modelling and improved feed characterization. In: Feeding Systems and Feed Evaluation Models (Ed. M. K. Theodorou and J. France). CAB International Publishing. New York, Wallingford. pp. 275-297.
  10. Beever, D. E. 1993. Ruminant animal production from forages – present position and future opportunities. Proceedings of the XVII International Grassland Congress. Palmerston North, New Zealand. pp. 535-542.
  11. Blaxter, K. L. 1962. The Energy Metabolism of Ruminants. Hutchinson, London.
  12. Blaxter, K. L., F. W. Wainman and J. L. Davidson. 1966. The voluntary feed intake of food by sheep and cattle in relation to their energy requirements for maintenance. Anim. Prod. 8:75-83.
  13. Crampton, E. W. 1957. Interrelations between digestible nutrient and energy content, voluntary dry matter intake and the overall feeding value of forages. J. Anim. Sci. 16:546-552.
  14. Dewhurst, R. J. and A. J. F. Webster, 1989. Development of a practical deterministic model for the prediction of true metabolizable energy in forages and compound feeds. In: Energy Metabolism of Farm Animals. European Association of Animal Production Publication No. 43. (Ed. Y. Van der Honing and W.H. Close) Pudoc, Wageningen, The Netherlands, pp. 223-230.
  15. Dijkstra, J., H. D. St. C., Neal, D. E. Beever and J. France. 1992. Simulation of nutrient digestion, absorption and outflow in the rumen: model description. J. Nutr. 122:2239-2256.
  16. Dynes, R. A. 1996. The animal; options for managing intake. Aust. J. Agric. Res. 47:277-87.
  17. Dynes, R. A. and D. A. Henry. 2002. Biomechanical properties of plant species in annual pastures grazed to different levels of feed on offer. Anim. Prod. Aust. (in press).
  18. Forage and Grazing Terminology Committee. 1991. Terminology for Grazing Lands and Grazing Animals. Pocahontas Press. Blacksburg, Virginia.
  19. Forbes, J. M. and F. D. Provenza. 2000. Integration of learning and metabolic signals into a theory of dietary choice and food intake. In: Ruminant Physiology Digestion, Metabolism, Growth and Reproduction. (Ed P. B. Cronje). CABI Publishing. Wallingford, UK. pp. 3-19.
  20. Freer, M., A. D. Moore and J. R. Donnelly. 1997. Grazplan: Decision support system for Australian grazing enterprises-2. The animal biology model for feed intake, production and reproduction and the GrazFeed DSS. Agric. Syst. 54:77-126.
  21. Gerrits, W. J. J., J. Dijkstra and J. France. 1997a. Description of a model integrating protein and energy metabolism in preruminant calves. J. Nutr. 127:1229-1242.
  22. Gerrits, W. J. J., J. France, J. Dijkstra, M. W. Bosh, G. H. Tolman and S. Tamminga. 1997b. Evaluation of a model integrating protein and energy metabolism in pre-ruminant calves. J. Nutr. 127:1243-1252.
  23. Goering, H. K. and P. J. Van Soest. 1970. Forage fiber analysis (apparatus, reagents, procedures, and some applications). Agric. Handbook No 379, US Department of Agriculture, Agricultural Research Service.
  24. Henry, D. A., G. Moore and R. A. Dynes. 2002. Variability in nutritive value allows better selection of perennial pasture legumes. Anim. Prod. Aust. (in press).
  25. Masters, D. G., H. C. Norman and R. A. Dynes. 2001. Opportunities and limitations for animal production from saline land. Asian-Aust. J. Anim. Sci. 14, Special Issue, 199-211.
  26. Minson, D. J. 1990. Forage in Ruminant Nutrition. Academic Press. London, UK.
  27. Minson, D. J., C. E. Harris, W. F. Raymond and R. J. Milford. 1964. The digestibility and voluntary feed intake of S22 and H.I. ryegrass, S170 tall fescue, S48 timothy, S215 meadow fescue and Germinal cocksfoot. J. Br. Grassl. Soc. 19:298-305.
  28. Moore, J. E., J. C. Burns and D. S. Fisher. 1996. Multiple regression equations for predicting relative feed value of grass hays. Proc. American Forage and Grassland Council, June 13-15, Vancouver, BC AFGC, Georgetown TX.
  29. Moore, J. E. and W. E. Kunkle. 1999. Evaluation of equations for estimating voluntary intake of forages and forage-based diets. J. Anim. Sci. Suppl. 77:204.
  30. Norman, H. C., D. G. Masters, R. A. Dynes, D. A. Henry and M. J. Lloyd. 2002. Liveweight change and wool growth in young sheep grazing a mixed saltbush and balansa clover pasture. Anim. Prod. Aust. (in press).
  31. National Research Council. 1984. Nutrient Requirements of Beef Cattle 6th Edition. National Academy of Sciences. Washington, DC.
  32. National Research Council. 1987. Predicting Feed Intake of Food-Producing Animals. National Academy of Sciences. Washington, DC.
  33. Poppi, D. P. 1996. Predictions of food intake in ruminants from analyses of food composition. Aust. J. Agric. Res. 47:489-504.
  34. Poppi, D. P., M. Gill and J. France. 1994. Integration of theories of intake regulation in growing ruminants. J. Theor. Biol. 167:129-45.
  35. Provenza, F. D. and J. A. Pfister. 1991. Influence of plant toxins on food ingestion by herbivores. In: Recent Advances on the Nutrition of Herbivores (Ed. Y. W. Ho, H. K. Wong, N. Abdullah and Z. A. Tajuddin). Malays. Soc. Anim. Prod. Kuala Lumpur. pp. 199-206.
  36. Reid, R. L. 1994. Milestones in forage research (1969-1994). In: Forage Quality, Evaluation and Utilization (Ed. G. C. Fahey Jr). Based on the National Conference on Forage Quality, Evaluation and Utilization. University of Nebraska, Lincoln. 13-15 April 1994. pp. 1-58.
  37. RIRDC. 2000. Fodder Industry Atlas. Rural Industry Development and Investment Corporation. Canberra, Australia.
  38. Rohweder, D. A., R. F. Barnes and N. Jorgensen. 1978. Proposed hay grading standards based on laboratory analyses for evaluating quality. J. Anim. Sci. 47:747-759.
  39. Standing Committee on Agriculture (SCA). 1990. Ruminants, Feeding Standards for Australian Livestock. CSIRO Publications, Australia.
  40. Taylor, G. B., R. C. Rossiter, L. Klein and W. J. Collins. 1989. The intake and digestibility of dry mature subterranean clovers. Proc. XVI International Grasslands Congress. Nice, France. pp. 809-810.
  41. Tilley, J. M. A. and R. A. Terry. 1963. A two-stage technique for in vitro digestion of forage crops. J. Br. Grassl. Soc. 18:104-111.
  42. Ulyatt, M. J. 1973. The feeding value of herbage. In: Chemistry and Biochemistry of Herbage (Ed. G. W. Butler and R. W. Bailey). Academic Press. London, UK. pp. 131-178.
  43. Van Soest, P. J. and R. H. Wine. 1967. Use of detergents in the analysis of fibrous feeds. IV. Determination of plant cell wall constituents. J. Assoc. Offic. Anal. Chem. 50:50-55.
  44. Weston, R. H. 1982. Animal factors affecting voluntary feed intake. In: Nutritional Limits to Animal Production from Pasture (Ed. J. B. Hacker). Commonwealth Agricultural Bureaux. Slough. pp. 183-198.
  45. Weston, R. H. 1985. The regulation of feed intake in herbage-fed ruminants. Proc. Nutr. Soc. Aust. 10:55-62.
  46. Weston, R. H. 1996. Some aspects of constraint to forage consumption by ruminants. Aust. J. Agric. Res. 47:175-198.
  47. Weston, R. H. and P. J. Davis. 1991. The significance of four forage characters are constraints to voluntary feed intake. Proc. of the III International Symposium on the Nutrition of Herbivores. Selangor Darul Ehsan, Malaysia. p. 31.
  48. Wilson, J. R. and P. M. Kennedy. 1996. Plant and animal constraints to voluntary feed intake associated with fibre characteristics and particle breakdown and passage in ruminants. Aust. J. Agric. Res. 47:199-226.
  49. Wilkins, R. J. 2000. Forages and their role in animal systems. Forage Evaluation in Ruminant Nutrition. (Ed. D. I. Givens, E. Owen, R. F. E. Axford and H. M. Omed). CAB Publishing. Wallingford, UK. pp. 1-14.