There has been a developing controversy surrounding the use of antibiotics as growth promoters for food animals. These drugs are used at low doses in animal feeds and are considered to improve the quality of the product, with a lower percentage of fat antibiotic resistance review article pdf a higher protein content in the meat. Other benefits of the use of antibiotic growth-promoters include control of zoonotic pathogens such as Salmonella, Campylobacter, Escherichia coli and enterococci.
The term “antibiotic growth promoter” is used to describe any medicine that destroys or inhibits bacteria and is administered at a low, subtherapeutic dose. The use of antibiotics for growth promotion has arisen with the intensification of livestock farming. Infectious agents reduce the yield of farmed food animals and, to control these, the administration of sub-therapeutic antibiotics and antimicrobial agents has been shown to be effective. Although the mechanism underpinning their action is unclear, it is believed that the antibiotics suppress sensitive populations of bacteria in the intestines. Therefore a reduction in gastrointestinal infections would result in the subsequent increase in muscle weight. Currently, there is controversy surrounding the use of growth promoters for animals destined for meat production, as overuse of any antibiotic over a period of time may lead to the local bacterial populations becoming resistant to the antibiotic.
This phenomenon has occurred within our hospitals, where compromised patients and over-use of antibiotics create an optimal environment for promoting resistance in susceptible strains of bacteria. Most antibiotics, around 60 per cent, are used for therapeutic purposes in humans, although an increasing amount is administered as prophylaxis to prevent infections. The farming industry is the second largest consumer of antibiotics after medical practitioners. On a world scale, the use of antibiotics as animal growth promoters differs dramatically.
USA uses a wide range of antibiotics, including some considered to be “medically important”. In Australia a range of growth promoters are employed. Pig farmers use arsenical compounds, flavophospholipol, the macrolides kitasamycin and tylosin, the quinoxaline olaquindox, and also virginiamycin, a streptogramin. Poultry producers use arsenical compounds, flavophospholipol, bacitracin and virginiamycin.
Australian cattle farmers employ a range of ionophores, namely lasalocid, monensin, narasin and salinomycin. They also employ flavophospholipol and the macrolide oleandomycin. The use of growth promoters in the European Community is more limited. The oligosaccharide avilamycin is used in pig and poultry farming, ionophores, namely monensin and salinomycin are used for cattle and pigs and flavophospholipol is used with a range of livestock, including cattle, pigs, poultry and rabbits.
Many of the alternatives are aimed at controlling infection, questions and Answers”. Of any age, this is why different antibiotics are used to treat different types of infection. Resistant bacteria multiply, the public’s attitudes to and compliance with antibiotics”. Resistance to HIV antivirals is problematic — overuse of antibiotics has become the primary cause of rising levels of antibiotic resistance.
In pig production, feed conversion efficiency is improved, along with daily growth rates, by approximately 2. The cattle industry in the USA is, perhaps, the most dependent on growth promoters as cattle have energy requirements that are high and that cannot be met easily without the use of growth promoters. High energy rations increase muscle growth and fat deposition in beef cattle, and help to improve milk productivity in dairy cattle. Unfortunately, the use of such rations is associated with side-effects, such as bloat and lactic acidosis, which can be debilitating or even fatal. In this sense, monensin is probably one of the safest and most effective antibiotic growth-promoters with regard to human and animal health and associated bacterial resistance problems. Virginiamycin is used for similar purposes, such as the prevention of acid lactosis in cattle and poultry, but use of this compound has led to the selection of bacteria that are resistant to its effects.
Human health can either be affected directly through residues of an antibiotic in meat, which may cause side-effects, or indirectly, through the selection of antibiotic resistance determinants that may spread to a human pathogen. A drug that illustrates both potential problems is chloramphenicol. In general, the effect of antibiotic residues in meat is insignificant when compared with the issue of selection and amplification of antibiotic resistant strains of bacteria. Antibiotic resistance determinants selected in this manner may have various routes by which they may compromise the therapeutic use of antibiotics. Selection may occur in microbes that are pathogenic for humans. Alternatively, resistance may be selected in zoonotic bacteria that subsequently cause human disease. Bacteria of the genus Salmonella are responsible for many human diseases.