Nutritional strategies can help control salmonella in pigs

Nutritional strategies to combat salmonella in pigs are a key component in producing safer food for consumers, according to vet Catharina Berge, speaking at the Society of Feed Technologists and Home Grown Cereal Authority’s conference on pigs, last week.

“With 10.3% of pigs going in to slaughterhouses across the EU testing positive for salmonella, it is important to look at ways of preventing salmonella being introduced on to farms through feed,” she said.

Ms Berge discussed different ways feed could be treated prior to entering the farm to prevent salmonella. “There are various ways feed can be treated and heat treatment and acidification are just two controls that have been used.”

The role feed plays in a control programme is two-fold, she added. “First, feed is a potential vector to introduce salmonella in to the farm. Proper control measures must therefore been in place at any feed manufacturing site as well as on farm to avoid feeding pigs salmonella,” she said.

Nutritional salmonella intervention methods can be made through general diet formulation or the addition of additives. Through diet formulation, the availability of fermentable substrate and the buffering capacity can be influenced, she added.

Heat treatment can reduce microbial loads in feed materials and compound feed, she said. “Heat treatment for more than 30 seconds at more than 75C can achieve a 1000 fold reduction of salmonella. However, the risk of recontamination is substantial and using acidification in combination achieved higher salmonella risk reduction.”

Organic acids, such as formic, acetic and propionic acids have also been shown to have an inhibitory effect on salmonella growth, explained Ms Berge.

However, more interestingly the physical property of feed could have an effect. “Research in Denmark and Greece has shown there is less salmonella in herds using a home-mixed, non-pelleted wet feed than those feeding a ready-mixed pelleted dry feed.”

There is also evidence course ground meal fed to pigs changed the microbial contents of the pigs’ stomach and reduced salmonella. “But the challenge is to maintain growth performance on these coarse ground diets compared to pelleted diets,” she said.

Other techniques being trialled to reduce salmonella including feeding probiotics such as lactic acid which has been shown to decrease salmonella infection. A competitive exclusion culture (a kind of probiotic culture) has also been shown to reduce salmonella shedding in pigs and contact pigs during the pre-weaning and weaning periods.

“However, although there are various nutritional interventions with potential to control salmonella in the pre-harvest stage of pork production, it is important nutritional intervention is only viewed as one of the tool to decrease salmonella on farm,” she said.