In a doctoral thesis entitled , we see clearly the benefits of fermentation. In this experiment, some pigs were fed a fermented liquid feed, some a non-fermented liquid feed, some a conventional pelleted dry feed and some were left to continue to suckle the dam for two weeks post weaning. Potential porcine pathogens were deliberately added to all four treatments.
The study concluded that no coliform bacteria were detected at the terminal ileum section of pigs fed fermented liquid feed, whereas all of the other treatments showed significant levels. “The main effect of feeding a fermented diet was to increase the lactobacilli numbers along the gut, with the greatest influence at the terminal ileum.” Compared to the other treatments, the ratio of lactobacilli to coliforms in fermented feed was “dramatically increased.” The study concluded that unfermented liquid feed “represents a risk to young piglets since there is a potential for pathogenic bacteria to grow in the feed and hence be ingested by the piglet.” For more on fermented liquid feed, see Fermented liquid feed for pigs: an ancient technique for the future.
Animal and fish feeds are often contaminated by multidrug-resistant salmonella and and Salmonella enteric in Commercial Swine Feed. Fermentation is an easy way to reduce counts of Salmonella and most other pathogens to safe levels.
We see in another doctoral thesis by Hoang Huong Giang that probiotics were added to the feed of growing pigs in Vietnam (Impact of bacteria and yeast with probiotic properties on performance, digestibility, health status and gut environment of growing pigs in Vietnam). “Giang ́s studies showed clearly that by combining suitable probiotic strains of Bacillus, Saccharomyces and LAB, positive effects on growth, feed conversion, and nutrient digestibility and a decrease in the occurrence and severity of diarrhea can be obtained, particularly in newly weaned pigs.” Her study showed that probiotic complexes “can be used as an alternative to antibiotic feed additives in pig production under conditions in Vietnam.” But rather than supplement pig feed with probiotics, why not ferment most feed? The pig feed itself serves as the substrate for the growth of probiotics.
In this review (The influence of probiotic use in sows and neonatal piglets on performance measures and diarrhea in suckling piglets), we see that if the feed of the sow is fermented, the health of her piglets is improved. If the sow receives fermented feed, the gut of the piglet has a much better chance of functioning correctly. If the sow receives fermented feed, there will be low coliform counts and high LAB counts in the feces of the piglet.
Since January 2006 the European Union has wisely banned the use of antibiotics as growth promoters in monogastrics. “In recent decades, organic acids (acidifiers) have been used as potential alternatives to antibiotics in monogastric animals’ diets in order to improve growth performance and prevent diseases” (The use of organic acids in monogastric animals – swine and rabbits)
But why add organic acids as external inputs? Instead the farmer has only to ferment feed.
Feed contaminated by salmonella bacteria is a familiar and costly problem for the animal feed industry all over the world. Some types of salmonella have succeeded in establishing themselves in feed and fish meal factories and have persisted there for several years because it has proved impossible to eradicate them.
In her doctoral thesis, Lene Karine Vestby therefore studied why it is so difficult to get rid of salmonella once they have managed to establish themselves in Norwegian feed and fish meal factories. She discovered that salmonella bacteria efficient at forming biofilm (bacteria coating) survived for longer in the factories than those that had a reduced ability to form this coating. The ability to survive in factories therefore appears to be connected with the ability to form a biofilm and it would seem that removing biofilm is a necessary step towards eradicating salmonella from the factories.
In a biofilm, bacteria are well protected by a slime (matrix) which they produce themselves. Vestby has studied the effect of the nine most frequently used disinfectants in the Norwegian animal feed industry and found that the efficiency of the disinfectants is substantially reduced if the salmonella has managed to form a biofilm. The effect of the majority of the disinfectants was then no longer satisfactory, but a product containing 70% ethanol was the most efficient, followed by one called Virkon S.
Cooperative behaviour between bacteria (quorum sensing) is an important factor in the ability to form biofilm. In recent years, so-called furanones have been developed, which are known to inhibit quorum sensing and thereby also the formation and maturation of biofilm. Vestby has shown that a furanone can be a useful tool in the fight against salmonella in factories. The furanone prevented the salmonella bacteria from forming an adequate biofilm and the bacteria were therefore more vulnerable to disinfectants, with the result that the disinfectants worked better.
The matrix produced by the salmonella bacteria in the biofilm consists of many different components, one of which is cellulose. A surprisingly large proportion of salmonella found in Norwegian feed and fish meal factories appeared not to produce cellulose. It has been claimed that cellulose is important for protecting bacteria in a biofilm, but Vestby’s laboratory tests have demonstrated that biofilm with or without cellulose respectively afforded the bacteria the same protection against disinfectants. On the other hand, it appeared that cellulose in the biofilm gave the bacteria better protection against dehydration over a period of several months.
MSc Lene Karine Vestby presented her doctoral thesis on 5th November 2009 at The Norwegian School of Veterinary Science. The thesis is entitled: “Biofilm formation by Salmonella from the Norwegian feed industry — with attention to potential persistence and eradication.”
Commercial feed appears to be a source of Salmonella contamination in commercial swine production units, according to a paper in the November 2010 issue of the journal Applied and Environmental Microbiology. Moreover, nearly half of isolates found in pigs were multidrug resistant. The findings suggest that pork could be a source of human infection. They also strongly question the conventional wisdom that processed feed is not a source of contamination. Heat treatment during processing has been thought to kill any bacterial contaminants.
The research team, led by Wondwossen A. Gebreyes of the College of Veterinary Medicine, The Ohio State University, tested samples collected from feed bins prior to exposure to the barn environment, as well as fecal samples and environmental samples from the barns. They found contaminated feed in eight of 36 barns tested, with a sample prevalence of 3.6%. These isolates fell into five different genotypes. In four of the five cases, they found that fecal samples they tested from a given barn and time point matched the feed samples from the same barn and time period, suggesting that the feed was indeed the contamination source.
“These genotypic clusters also shared similar antimicrobial resistance profiles and serogroups,” says Gebreyes. That provides additional support for both the genotypic findings, confirming the hypothesis that the contamination originated in the feed.
Gebreyes says that the source of feed contamination is most likely the feed ingredients, but that feed could be contaminated via handling, after processing.
“Although we cannot ascertain 100% that the feed was the source of contamination that was transmitted to the fecal samples, the findings strongly imply that fact,” says Gebreyes. “The other alternative is that the feed was contaminated after it was introduced into the barn. Regardless, the findings strongly imply that salmonella can be maintained and easily disseminated in a population of food animals.”]