Monensin, Protein Supplementation and Tylosin for Feedlot Cattle

Scientific research has made substantial contributions to the efficiency of American agriculture. Livestock producers in particular have benefited from the extensive study of animal nutrition. Nutrient requirements of animals and the nutrient composition of feeds are essential to efficient and economical feeding of farm animals. Research over many years has provided considerable information on animal requirements and feed composition. While there are still many gaps of knowledge in those areas, available information allows wise choice in selecting feedstuffs and using them in various combinations to meet animal requirements for various productive purposes. Feed costs represent the single largest expenditure in a livestock feeding enterprise. Extensive research has therefore been devoted to investigation of method to improve the efficiency with which animals utilize feed. Awareness of food shortages in developing nations has placed additional importance on techniques which improve the feed efficiency of domestic livestock. Cattle feeders have benefited from the availability of growth stimulants and antibiotics which can improve growth rate and feed efficiency. Honensin is a feed additive which was made available to cattle feeders in 1975. While its action is distinct from antibiotics, the product has been shown to improve the efficiency of energy conversion in growing and finishing cattle. The effects of monensin on protein utilization are not well established. A primary objective of the feeding experiments reported was to determine the influence of monensin on the dietary protein needs of cattle fed corn silage growing rations and high-concentrate finishing rations. Of additional interest was the response to difference sources of supplemental protein, either soybean meal or urea, when fed with monensin in a growing ration. Another objective was to determine the usefulness of feeding an antibiotic, tylosin, in combination with monensin in a high-corn grain finishing ration