Feeding birds bacterial product could help egg producers in fight against salmonella

Giving layers a complex mixture of bacteria can help eradicate salmonella from the bird’s environment.

This year sees new salmonella sampling and testing rules for UK laying flocks, and failure to get on top of any infection could result in units going out of business next year.

The stark warning made by poultry vet David Parsons of the Poultry Health Centre came at a recent Schering Plough Animal Health seminar at Sparsholt College in Hampshire.

He was referring to the requirement for producers to heat treat eggs from 1 January 2009 when a flock tests positive for S enteritidis or typhimurium, as he doubts whether any processor would actually take these eggs. “Potentially, you are out of business if you don’t get it right.”

He highlighted that the bacterium is very resilient. “It can survive 7-16 months in litter at 20-25C, so if there is a trace of litter left in a crevice, it can then survive between flocks.

In preventing infection, he outlined three key considerations. “Firstly, appreciate how the organism can enter your site, ensure suppliers are following preventative measures and thirdly, consider how to stop it getting in birds if it does get on-site.

Routes on to farm include used pallets and keyes trays. He cited an example where a pallet arrived on a layer unit covered in old egg shells and was salmonella positive, having previously been at a breaking plant. Then there are the chicks themselves. Hatcheries will have their own measures in place, but don’t forget some birds are hatched outside UK, so ask for salmonella-free chicks.

Another route is wild birds. While many focus on game and sea gulls, Mr Parsons stressed that salmonella infected wild finches had recently been blamed for increased deaths in domestic cats.

One novel approach could be to modify the make-up of bacteria in the bird’s environment. As Sue Reynolds of Microbial Developments explained, the new salmonella testing is of the environment, not eggs.

“Salmonella control is like a jigsaw puzzle, with lots of different elements and all of these must fit together to be effective. Elements include salmonella-free feed, good biosecurity and hygiene, rodent control, using certified salmonella-free stock and vaccination.” She believes another element of this is the use of the competitive exclusion product – Aviguard – a freeze dried preparation of normal gut bacteria from healthy birds.

She explained that in nature, a chick picks up flora from its mother and the environment. But this cannot happen in a modern sterile hatchery environment and this is where the product comes in. These good bacteria colonise the bird’s gut and prevent bad bacteria, such as salmonella, E coli and clostridium perfringens, from becoming established in the gut.

Aviguard contains over 200 types of bacteria, which colonise the gut. Each batch is tested for efficacy and is only sold if it results in at least a 100,000-fold reduction in a test strain of salmonella, when tested in young chicks.

In the past, producers have either adopted competitive exclusion or vaccination as their chosen method of salmonella control. However, new research results suggest there are benefits of combining both approaches, particularly when faced with a heavy challenge and considering the greater consequences of finding a positive result, she said.

“Trial results from the Institute of Animal Health, Compton, show a complementary effect. Results show that combining both strategies gives added protection at heavy exposure (see graph).”

This has also proved to be the case with live oral vaccines, but she adds that timing is crucial, vaccinate with live oral vaccine first and then use Aviguard or the vaccine will be excluded by the Aviguard

Of greater interest to producers facing the new salmonella testing regime is that Aviguard can also be used to change the environmental flora, as it is excreted by birds.

“Even after thorough cleaning and disinfection, you are left with residual bacteria in the shed. So it’s better to leave behind good bacteria instead of bad.

“However, experience with broilers shows that to get the full effect you need repeated applications over time, as the Aviguard bacteria build up in the environment and you get recycling through the bird.”

“Ideally, you need three crop cycles to get environmental flora change, but in layers, since the flock cycle is much longer, this would take years. So to speed it up, producers are advised to give the first flock a repeated application, then it’s one dose for each subsequent flock (see panel).”