As poultry producers face increasing pressure to cut their use of antibiotics, Rhian Price visits biotechnology company MDL to find out about an alternative solution

There’s no quick fix for reducing the therapeutic use of antibiotics in poultry flocks – it takes time and patience, with additional attention to detail where management practices are concerned.

But according to Sue Reynolds, director for microbial developments at MDL (Microbial Developments Ltd) in Malvern, using the competitive exclusion product Aviguard can help break the cycle of antibiotic use.

“Antimicrobial therapy plays a vital role in ensuring the health and welfare of birds when faced with a bacterial infection, and as an industry we need to ensure that we retain antibiotics for use when absolutely necessary,” she says.

“But we can minimise bacterial infection, and the use of antibiotics, by using best management practice and by taking advantage of a natural defence mechanism which has been lost due to modern production techniques.

“For many years microbiologists and veterinarians have concentrated on researching pathogenic bacteria, but there is growing interest in the role that gut flora plays in maintaining intestinal health.”

Developed by MDL, Aviguard is a freeze-dried preparation of intestinal bacteria from healthy, adult chickens, which acts by the process of “competitive exclusion” to prevent pathogenic bacteria from becoming established in the gut.

Through this process normal, healthy intestinal bacteria colonise the gut and prevent the colonisation by transient pathogenic bacteria.

“There are several theories. It works firstly by forming a physical barrier in the gut, preventing pathogens from locating onto receptor sites on the intestinal wall,” explains Mrs Reynolds. “The bacteria in Aviguard are anaerobic, which provides a low oxygen tension environment which is unfavourable to pathogens.”

The bacteria also produce volatile fatty acids which reduce the Ph of the gut, making the environment more acidic. And finally, they compete for nutrients in the gut.

“In the wild, chicks hatch with their mothers and naturally pick up their mothers’ gut flora. But because we hatch chicks in sterile hatchery conditions, they don’t get that opportunity and as a result they are susceptible to whatever pathogens may be present in the farm environment. By using Aviguard we are simply replacing the birds’ natural defence mechanism.”

The product was first developed for the control of salmonella. But since then, studies have indicated that it can help prevent other bacterial pathogens.

“It is unique because it contains more than 200 strains of gut bacteria and research has shown that only complex flora preparations effectively exclude pathogens.”

Efficacy tests show that the product is effective against all salmonella stereotypes, as well as E coli, Clostridium perfringens and enterococcus.

“Each batch is put through a live bird efficacy test prior to being released for sale. The minimum requirement for product release is at least a 500,000-fold reduction in salmonella in treated chicks compared to positive controls,” Mrs Reynolds explains.


How to administer correctly

Aviguard should be administered by coarse spray to day-old chicks in the hatchery at 0.2 to 0.25ml per bird in chlorine-free water. Alternatively it can be diluted into older birds’ drinking water and administered over four-to-six hours to re-establish healthy bacteria later on in life, after antibiotic application or at particularly stressful periods in the production cycle, such as prior to and following the transfer of point-of-lay pullets.

Timing is essential and the product must be administered before birds become exposed to pathogens in order for it to be effective, explains Mrs Reynolds.

“It is also important to remember that antibiotics will destroy all the good bacteria in the gut, as well as the pathogenic ones, and this makes them susceptible to re-infection from the environment.

“So by administering Aviguard 48 hours after the end of antibiotic treatment, you are replacing the gut bacteria and it gives the bird that barrier to prevent re-infection.”

It is equally important to get protection established within the house. “Aviguard colonises within the gut, but it also multiplies and gets passed out in the faeces. Over time the flora will build up in the litter and the house environment.

However it takes repeated applications over time to build up such an effect. “In broiler sheds it takes at least three repeated crop cycles to start getting the build-up in the environment.”

This is a long-term strategy, not a quick fix and producers shouldn’t be put off if they can’t see immediate effects, says Mrs Reynolds. “If you persist for three-to-five cycles you will really see the benefits.”