When disease problems were first identified they were treated with antibiotics, then antibiotics were used to keep the diseases away until eventually the bacteria became resistant to the antibiotics. The world responded by banning antibiotics in animal feed too late and now we need an alternative.
In Figure 1 we can see high levels of antibiotic resistance in pigs and significant resistance in poultry but low levels in feed. This confirms that feed is not the source of infection. There are more bacterial cells in the intestine of a healthy animal than there are cells in the animal. It therefore means that you need a microbiological solution to keep the animals healthy.
What are the alternatives?
Probiotics are a source of healthy lactic acid producing bacteria, such as the Lactic Acid Bacteria (LAB), and can compete with potential pathogens to physically or chemically exclude the enteropathogens. However, probiotics are not always 100% effective. In poultry the stomach or crop/proventriculus has a low pH, which is used as a natural defence mechanism, and this area is colonised by acid tolerant probiotics, but at a low density. However, the enteropathogens that we need to control do not normally colonise this area of the intestine. In monogastrics the more neutral large intestine, colon and rectum are more suited to potential enteropathogen colonisation.
Probiotics require an acid pH for optimum colonisation. Under disease situations or high calcium diets like lactation or layer/breeder rations the pH will not support acid-loving bacteria and probiotics will not be fully effective.It is important to remember that all bacteria require four things to grow:
• Temperature - The body temperature of pigs and chickens are ideal.
• Nutrients - The gut of any commercial animal is full of nutrients.
• Water - All animals drink.
• pH - The pH of the small intestine is perfect for E. coli.
The pH of the hindgut is ideal for salmonella. High calcium rations result in a high pH, about 8.0 – ideal for salmonella.Therefore, probiotics will not work in the large intestine, colon or rectum of pigs without some assistance.