In recent years, the most revolutionary increases in beef cattle weights and feeding efficiencies have resulted from the development and use of growth stimulants, feed additives, and antibiotics. These nonnutritive products not only improve the rate and efficiency of gain but prevent certain diseases as well. Their use has significantly improved beef cattle production efficiency and provided a greater return per dollar invested than any other factor in the livestock industry. Growth stimulants deposit increased protein in the animal without changing protein or energy intake. They are designed to provide a constant slow release of active ingredients into the animal's bloodstream. In animals implanted with growth stimulants, the blood levels of hormone will fluctuate according to physiological factors associated with digestion and absorption of nutrients in the feed. The nutritional state of the animal and the quality and quantity of feed consumed will also determine the effectiveness of the growth stimulants.
Stenquist, Norris J., "Growth Stimulants and Feed Additives" (1990). All Archived Publications. Paper 206.