Date of Award
Master of Science
O. G. Hall
C. S. Hobbs, H. J. Smith
The ruminant's diet consists mainly of roughages and forages. While there are a large number of grasses in the world, in any given area, only a relatively small number of them eu:e used. Investigators are constantly striving to increase the number of valuable forage species in their area by the introduction of new (to that region) species and/or the hybridization and improvement of old species.
Before a forage under investigation is recommended for an area it must undergo severe testing for a number of things. Besides general adaptability to soil and climatic conditions, the nutritive value of the forage should be thoroughly studied.
Utilization of the forage by the animals it is intended for, is of course, necessary for the final evaluation of a new or improved forage. However, animal feeding trials involve long periods of time, and are expensive. It is not possible to evaluate very many forages at a given time with this technique. Thus the ea^tificial rumen technique has been proposed as a technique to get preliminary information as to the possible value of forages for animals.
The major carbohydrate constituents of roughages are cellulose, hemicellulose and related compounds. Animals, so far as it is known, do not possess enzymes capable of breaking down these complex substances into simple compoTinds which can be absorbed. The degradation of complex carbohydrates is one aspect of the vital role performed by rumen bacteria in the digestion of forages. It is known that the extent to which rumen bacteria will break down cellulose and related compounds is dependent to a large degree upon the presence and availability of various nutrients needed by the bacteria. As the bacteria and the host animals may have different nutritive requirements, the "in vitro" results are not necessarily the same as from "in vivo" experiments. However, a number of experiments which will be discussed later have shown a close positive correlation between "in vivo" and "in vitro" forage digestion experiments.
Attention has been focused on the use of nitrogen fertilization to increase forage yields, and forage yields primarily have been the basis for the evaluation of nitrogen applications. It is well known that nitrogen fertilization up to certain levels will increase the yield of forage crops. However, very little is known about the effects of nitrogen fertilization of specific forages on microbial utilization of the forages and thus on the nutritional value of the forages to the animal.
The purpose of the experiments reported In this thesis was to compare rumen microbial utilization of three varieties of Bermuda grasses when fertilized with different levels of nitrogen and harvested at different stages of maturity. The percentage of the cellulose digested in the fdrages by rumen bacteria was used as the criterion of evaluation.
Mohammed, Atalla Said, "Effect of nitrogen fertilization and time of harvest on in vitro rumen microbial utilization on some Bermuda grasses. " Master's Thesis, University of Tennessee, 1962.