Masters Theses

Date of Award

8-1964

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

O.G. Hall

Committee Members

C.S. Hobbs, R.S. Temple

Abstract

Agriculture in Tennessee has been undergoing a tremendous change during the last decade, with an increasing conversion from a cash and row crop system to a grassland system of farming. The ultimate goal of grassland farming is to get more milk, meat, wool, and other products per acre at less cash cost than under the conventional method of farming. Because of the climatic conditions and topography of the land, Tennessee is very adaptable to this system of farming. Grassland farming is very important to the beef producer, because this system of farming will allow for the production of high-quality feeds as forages; thus, it has a di minishing effect on the narrow margin of profit in the beef cattle enterprise. The preservation of quality in forages used for the wintering of cattle is very important to the success of a grassland system of farming. and the most economical method of insuring the keeping quality of forages in East Tennessee is to produce high-quality silages, The quality of a silage is dependent upon many factors, namely: variety of the forage, stage of maturity, moisture content at ensiling time, ensiling techniques, and preservative used on those forages of low sugar content. The preservative used to insure desirable fermentation is very important in legume silage making, and many different types of preserva-tives have been used successfully. Antibiotics are known to control natural fermentation. Therefore, it has been postulated that forage quality might be improved by the addition of an antibiotic which would beneficially alter fermentation. Quality in forages is very important because it effects animal performance, and for years researchers and others have used such de-scriptive terms as low, medium, and high quality for indicating the suitability of forages to provide feed nutrients for animal production. The most common and oldest method used by man for the evaluation of a particular feed has been feedlot performance. Because of the expense and facilities involved in conducting feedlot studies, the development of a short-term laboratory method for the assessment of the nutritive value of forages has long been a goal of animal nutritionists. Various workers have attempted to circumvent the more laborious methods of evaluation by proposing the use of regression equations for predicting the value of a forage from its chemical composition. These methods have not been entirely satisfactory, because the equations are based on single feed constituents and do not account for all the modifying effects encountered when dealing with animal investigations. For a realistic approach to the nutritive evaluation of a forage, the stated level and stage of animal production should be known. A forage may be evaluated as adequate when it is supplied in the correct quantity, pos-sesses palatibility, and its per-unit concentration of usable nutrients is high enough to permit the animal to meet its nutritional requirements. A study which would measure feedlot performance, digestion coefficients, and microbial activity would be very useful for evaluating a forage on this basis. The major objective of this research problem was to compare and evaluate corn and alfalfa silages preserved with zinc bacitracin, as determined by the three methods of investigation mentioned above. The specific objectives of this investigation were as follows. 1. To determine the feeding value of control and antibiotic-treated corn and alfalfa silages when fed to steer calves ad libitum with a low level of protein supplement. 2. To determine the feeding value of control and antibiotic-treated corn and alfalfa silage when fed to heifer calves ad libitum with a medium level of concentrates. 3. To determine the digestibility of control and antibiotic-treated corn and alfalfa silages when fed with cottonseed meal or a concentrate mixture. 4. To determine the amount of microbial activity supported by the control and antibiotic-treated corn and alfalfa silages by measuring cellulose digestion in vitro. 5. To study the relationship that exists between feedlot performance, digestion coefficients, and in vitro cellulose digestion.

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