Methodology Research for Range Forage Evaluation

Range livestock nutrition involves the nutritional evaluation of a heterogenous plant cover which is modified continually by plant growth patterns and widely diverse environmental conditions. Plant analyses, animal growth and tissue composition indicates that energy, protein, phosphorus and vitamin A are the nutrients most apt to be deficient in the diet of grazing range livestock, although other deficienices, toxicities and metabolic malfunctions occur on a less extensive basis. Techniques have been developed utilizing esophageal and ruminal fistulated animals as biological sampling agents. Although further refinements are indicated, these techniques represent the best methods for obtaining an unbiased sample of ingested forage. The preparation of a fistula sample for subsequent analyses is most critical because the apparent composition, especially the carbohydrate fraction, changes during subsequent drying. The use of indicators to measure the digestibility and fecal excretion and, consequently, feed intake of grazing animals presents unique problems under range conditions because of animal management, environmental conditions and plant species. Although not completely solved, these problems do not seem to be insurmountable at this time. Selective grazing as measured by differences in botanical and chemical composition of the ingested forage compared to forage available is most pronounced.