Use of Antibiotic as Growth-Promoters in Animals: Livestock

April 26, 2013

A review

A review
A review

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. According to the National Office of Animal Health (NOAH, 2001), antibiotic growth promoters are used to “help growing animals digest their food more efficiently, get maximum benefit from it and allow them to develop into strong and healthy individuals”. Although the mechanism underpinning their action is unclear, it is believed that the antibiotics suppress sensitive populations of bacteria in the intestines.

Feighner, S. D. et al  (1987) stated that the mechanisms of growth promotion are still not exactly known. Experiments with germ-free chickens have seemed to indicate that the action of the growth promoters is mediated by their antibacterial effect. Four hypotheses have been proposed to explain their action: (i) nutrients may be protected against bacterial destruction; (ii) absorption of nutrients may improve because of a thinning of the small intestinal barrier; (iii) the antibiotics may decrease the production of toxins by intestinal bacteria; and (iv) there may be a reduction in the incidence of subclinical intestinal infections

Prescott & Baggot (1993), however, showed that the effects of growth promoters were much more noticeable in sick animals and those housed in cramped, unhygienic conditions.

W. N.Ewing, et al. (1994) reported that Several antibiotics have been in use as growth promoters of farm animals ever since. The introduction of these agents coincided with intensive animal rearing. These products improved feed conversion and animal growth and reduced morbidity and mortality due to clinical and subclinical diseases. The average growth improvement was estimated to be between 4 and 8%, and feed utilization was improved by 2 to 5%.

Homke & Elwinger (1998) hypothesize that cytokines released during the immune response may also stimulate the release of catabolic hormones, which would reduce muscle mass. Therefore a reduction in gastrointestinal infections would result in the subsequent increase in muscle weight. Whatever the mechanism of action, the result of the use of growth promoters is an improvement in daily growth rates between 1 and 10 per cent resulting in meat of a better quality, with less fat and increased protein content. There can be no doubt that growth promoters are effective;

Kim Klotins (2005) explained that continuous, low-dose administration of an antibiotic can increase the rate and efficiency of weight gain in healthy livestock. The presence of antibiotics likely changes the composition of the gut flora to favour growth. Debate is ongoing as to how that gut flora are changed; change may simply be a reduction in numbers, a change in species composition or a combination of the two. For example, a low, continuous dose of antibiotic may: eliminate bacteria that steal essential nutrients required by the animal for growth, reduce competition allowing beneficial bacteria that produce essential nutrients required by the animal for growth to multiply, control growth of bacteria that cause low-grade infections or produce toxins, both of which result in thick intestines that do not absorb nutrients well.Some antibiotics may also enhance feed consumption and growth by stimulating metabolic processes within the animal.

J. J. Dibner and J. D. (2005) Richards reported that orally ingested antibiotics promote growth and efficiency of poultry and other animals. The effect can include gain but often is limited to feed efficiency effects only.

Usage of antibiotics in farm animals is quite heavy and widespread, and has been a typical practice of farmers. This is a result of attempts to increase quality and quantity of output on farms. Consistently using drugs in farm animals raises concerns that this administering of antibiotics has caused an increase in the antibiotic-resistant bacteria that can be harmful to humans. Bacteria in the human microbiome can learn how to resist more drugs because humans are exposed to slight amounts of antibiotics in the meats that they eat. Antibiotics are used in animals and can help bacteria become resistant to the same or similar drugs used in humans. Antibiotics are naturally occurring, semi-synthetic and synthetic compounds of antimicrobial activity are used in human and veterinary medicine to treat and prevent disease, and for other purposes including growth promotion in food animals. Bacteria can spread via animals, which are turned into food, which are eaten by humans and can then cause human infection. This is a reason behind using antibiotics in farm animals, in addition to growth promotion. Antibiotic resistance occurs when “survival of the fittest” occurs with bacteria populations. When antibiotics do somehow not kill bacteria, these cells can multiply and pass on the genetic material that can resist drugs on to more bacteria. Thus, greater exposure to antibiotics, especially unnecessarily, will beget more resistance. Concern over antibiotic use in farm animals relates to the disadvantages to human and animal health that result from potential overexposure. The threat of antibiotic resistance is real, but some argue that the actual danger seems small: some question the quantified harm this process begets (drug companies, for instance, that have an economic stake in this issue). Growth promotion via antibiotics requires only small dosages. Some antibiotics are used both in animals and in humans but most of the resistance problems are from human use. While antibiotic use in farm animals is contributing to the problem of resistance, over prescription in humans is certainly a large factor as well. Animals, Livestock Farming,

Dr. Sajid Mahmood Sajid*, Dr. Muhammad Zubair** Dr. Abid Hussain*

*Lecturer, Faculty of Veterinary and Animal Sciences, the University of Poonch, Rawalakot

**Ph. D scholar, University of Agriculture. Faisalabad


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