Date of Award
Master of Science
O.G. Hall, L.L. Christian, C.C. Chamberlain
Beef cattle production in the southern United States and especially in Tennessee has increased at a phenomenal rate during the past decade. This increase in cattle numbers has resulted in a greater demand for forage crop production. No other area of this country has enjoyed a more favorable opportunity for intensive grassland beef production. Greater demands for winter feeds have been accompanied by an increase in forage production. Many areas of Tennessee and especially the eastern portion, which is less favorable for hay production, have met this increased demand for cheap forages with silages. Because of the high energy content and palatability of the com silage, it has been of increasing importance for beef cattle. More emphasis has been placed on intensive forage production in this area as the available labor supply has been decreasing along with a narrowing margin in farm operations. Therefore, the total pounds of digestible nutrients produced by a forage crop has received more at-tention. The cost of silage operations accompanied by the increased labor costs per unit and decreased margin in cattle operations has necessitated the cattle farmer to make optimum use of his available land, labor, feeds, and cattle. As in row crop production of all kinds, silage production has been directed toward highest possible yields per acre. This increase in yield has been due primarily to the introduction of more productive varieties, better management in silage production, and the extensive use of more fertilizers per acre. Increased plant population per acre and the use of more productive varieties have created a greater demand for available plant food. Since the prices of fertilizer have remained relatively stable, the cattle farmer has been able to increase silage yields more economically with fertilizer than through any other means. Nitrogen has been the element most commonly increased in use for silage production. Some people have postulated that this increase in nitrogen application in silage production may result in a detrimental build-up of nitrates and nitrites in the silage. The first report in recent years of a vitamin A deficiency in beef cattle being fed on a conventional ration has led investigators to examine several possible causative agents. Some workers have postulated that the nitrate accumu-lation in plants causes an interference in carotene conversion to vitamin A. Inadequate data have been reported to substantiate this theory. One of the purposes of this research was to determine the effect of high levels of nitrogen fertilization on the nitrate build-up in corn silage. Another objective of this work was to determine the effects of this build-up, if indeed it did occur, on subsequent performance of beef cattle fed these silages with and without vitamin A supplementation as the major component of the wintering ration in addition to determining any carry-over effect during the finishing period. Realizing that the high level of nitrogen (300 pounds per acre) is not recommended nor economical, it was the objective of this study to allow for possible detrimental levels of nitrate to accumulate. The low level of nitrogen (100 pounds per acre) is the level generally recommended. However, with increasing plant population per acre and more productive varieties the recommended economical level of nitrogen application may increase in the future. Therefore, these data may answer some questions as to the effect of these higher levels of nitrogen application on cattle performance. A comparison of some other techniques for forage evaluation was made. Another objective was to determine the digestibility of these silages with cattle and sheep. An in vitro technique was employed to measure possible differences in the silages that might be reflected in rumen microbial activity. Cellulose breakdown was used as a measure of microbial activity in these studies. An objective evaluation was made of these silages as determined by cattle performance, digestibility, and cellulose digestion by rumen microbes. Further, the various techniques were evaluated as measures of forage nutritive value.
Wilson, Garlin Ray, "Effect of nitrogen fertilization on the nutritional value of corn silage as determined by feedlot performance of beef heifers, digestion trials, and in vitro studies. " Master's Thesis, University of Tennessee, 1964.