called ionophores. Ionophores were originally developed as coccidiostats for poultry, and prevent coccidiosis in cattle as well. Ionophores work by improving both feed efficiency and growth rate, and lower methane production as one result. These effectively work as growth promoters due to an increase in food and water uptake and increase the digestive effectiveness of the animal. Antibiotics are used in the cattle industry for therapeutic purposes in the clinical treatment of infections and prophylactically for disease prevention by controlling the growth of potentially harmful bacteria. Because of their effectiveness in the treatment and prevention of diseases, there is an increased efficiency of the farm. This results in reduced costs for cattle producers, and for consumers. Antibiotics are also present in antibacterial cleaning products, and in disinfection products used in farm and veterinary practices. A critical journalist has claimed that the lower population density in free-range animals need decreased antibiotics usage, and has conjectured that cattle would not get sick if they were not fed a corn-based diet. However, bovine respiratory disease, the most common reason for antibiotic therapy, has risk factors common in both forms of production (feedlot and pasture finished). Safety Due to concerns about antibiotics residues getting into the milk or meat of cattle, there are regulatory agencies and measures in place in order to ensure that foods produced do not contain antibiotics at a level which will cause harm to consumers in the United States and Canada. Growth stimulants The use of supplemental growth hormones is controversial. The benefits of using growth hormones includes improved feed efficiency, carcass quality and rate of muscle development. The cattle industry takes the position that the use of growth hormones allows plentiful meats to be sold for affordable prices. Using hormones in beef cattle costs $1.50 and adds between to the weight of a steer at slaughter, for a return of at least $25. Bovine somatotropin, or bovine growth hormone, is a naturally produced protein in cattle. Recombinant bovine somatotropin (rBST), or recombinant bovine growth hormone (rBGH), is growth hormone produced using microbes with modified (recombinant) DNA. The manufactured product Posilac, which was approved in the United States in 1993, was Monsanto's first genetically-modified venture in that country; however, its use has been controversial. As of 2002, testing could not yet distinguish between artificial hormones and those naturally produced by the animal itself, but as of 2011, it was remarked