It’s difficult to imagine modern pig production without antibiotics. At the same time it’s not only fashionable but also scandalous topic nowadays. There are many reasons for this. To understand why it’s needed to get to know this phenomenon better.

Antibiotics vs Antimicrobials

The term «antibiotic» (derived from the Greek words αντι — «against» and βίος — «life») belongs to Zelman Vaksman, a Jewish who lived in the USA, although he was born in Ukraine (town Nova Pryluka of Vinnytsia region) and finished Gymnasium in Odessa. In simple words antibiotics are substances produced by microorganisms that act against another microorganism: inhibit or kill them. For example, Penicillium spp. produces penicillin; Cephalosporium spp. cephalosporin; Streptomyces spp. — lincomycin, erythromycin, tylosin, tetracycline, tetracycline etc. All antibiotics are mostly of natural origin, although today there are also synthetic antibiotics — they are chemically related to their natural grand-parents. The main disadvantage of antibiotics is that pathogens develop resistance.

In contrast, the term «antimicrobials» include all agents that act against all types of microorganisms — bacteria (antibacterial), viruses (antiviral), fungi (antifungal) and protozoa (antiprotozoal). They are are synthetic (sulfonamides and quinolones), or semisynthetic (methicillin and amoxicillin), or those which come from plants (quercetin and alkaloids) or animals (lysozyme). Antimicrobals kill or inhibit the growth of microorganisms but causes little or no damage to the host. All antibiotics are antimicrobials, but not all antimicrobials are antibiotics.

Usage of Antibiotics in Pig Production

The use of antimicrobials in animals closely parallels their discovery and usage in humans. Sulfonamide was the first antimicrobial to be introduced to food animal medicine in the 1940s. The subsequent discoveries and availabilities of newer antibiotics in the early 50’s quickly led to their widespread therapeutic usage for a multitude of infectious diseases in virtually all food animal species. Antibiotics are also given to food animals for growth promotion and prophylactic medication.

Therapeutic Use of Antibiotics. Choosing an antibiotic one should consider the following aspects:

Pathogen: identification, susceptability, site of infection, extra- or intracellular, pathogenesis, virulence factors.

Drug: pharmacodynamics/ physicochemical properties, distribution, elimination, dosage, route,duration half-life, clearance, solubility, drug interaction.

Hosts: toxicity, allergic reactions, pregnancy, presence of other diseases, immunocompetence.

Public health: build-up of resistence, environmental contamination, residues in food animals.

Other concerns: price of treatment, animal value.

Non-Therapuetic use. It’s not a secret that antibiotics are often used for non-theraupuetic perposes, although in many countries, including EU, it is forbidden.

Antibiotics as growth promotant was discovered in the 1940s, when it was observed that chicks improve in growth when fed bacterial shells of Streptomyces aureofaciens from which antibiotics had been extracted. At rhat time it was considered a very useful discovery.

Although repeatedly proven in various studies, the mechanism of action for the enhancement of growth of subtherapeutic levels of antibiotics remains unclear. Among the hypotheses tested are the following (Giguere et al., 2006):

• Stimulation of intestinal synthesis of vitamins by bacteria.
• Reduction in total numbers of bacteria in the intestinal tract with a lowering of competition between microorganisms and host animals for nutrients.
• Inhibition of harmful bacteria which may be mildly pathogenic or toxin-producing.
• Inhibition of bacterial urease.
• Improved energy efficiency of the gut.
• Inhibition of bacterial cholytaurin hydrolase activity.
• Nutrient sparing.
• Improved nutrient absorption from morphological changes to small intestinal epithelium.
• Modification of intestinal enzyme activity.
• Reduced immune stimulation.
• Modification of rumen microbial metabolism.

It is not uncommon for veterinarians to give antibiotics to animals that are not currently ill with a particular disease, but are at high risk of acquiring an infection. For example, an animal may be treated with antibiotics after having undergone surgery or injurious trauma or herds are at risk of suffering an outbreak of infectious disease due to exposure to disease agents. Mass administration of antibiotics is often practiced when transporting or moving young animals or when animals have been subjected to severely stressful conditions. In all this cases antibiotics are an efficient tool for maintaining pig health, although it shouldn’t replace good management practices.

1) What antibiotics are better upon certain condition?

2) What are the main routes of managing antibiotics in pigs (their advantages and disadvantages)?

3) Why is MIC deceptive?

4) How long to treat animals for?

You can find answers for these and other questions in the full version of the interview in the magazine “Profitable Pig Production”, №3 (15) 2013.