Poultry meat and eggs are important food products and the poultry-related industry is an economically important component of the agro-industry in the EU. Unfortunately, poultry eggs and meat are one of the major sources of food borne bacterial infections in humans.
In this respect, salmonella (mainly salmonella enteritidis) and campylobacter are of particular importance, since these pathogens can colonise the chicken host without causing discernible illness in the infected chickens.
Since poultry meat will, due to EU legislation, not be allowed as fresh poultry meat on the market from Dec 12, 2010, if salmonella is detected, the broiler industry needs to take measures to decrease the colonisation of the animals and their environment.
These include pre-harvest, harvest and post-harvest measures. All of these are equally important and each type of measure has a more or less important effect on reducing salmonella incidence, but no measure is successful on its own.
Since antibiotics are not the method of choice to control salmonella and since vaccination cannot be applied in broilers due to the short life span of the animals, the use of feed additives is increasingly accepted as a valuable way to combat bacterial gut infections.
Medium chain fatty acids (C6 to C12; caproic, caprylic, capric and lauric acid) appear to be much more effective against salmonella than short-chain fatty acids (formic, acetic, propionic and butyric acid).
Poultry feed is a major source for salmonella introduction to the farm. When chickens are given artificially contaminated feed, the gut is colonised and salmonella are shed into the environment. The original concept of incorporating acids into feed was based on the notion that the acids would decontaminate the feed itself and prevent salmonella uptake by the chickens.
The antibacterial activities of organic acids were dependent on the temperature and moisture. Since the water content of poultry feed is generally low, the action of the acids is not always optimal, and it is unclear whether effects of the acids in the feed itself or effects of the acids in the animals' gastrointestinal tracts were the major reason for protection.
In the 1980s, it became clear that the acid concentrations were also increased in the crop, and this antibacterial action could aid in controlling infection caused by horizontal transmission. Indeed, when chickens eat the acid-treated feed, it is both warmed and moistened and the activity of short chain fatty acids should increase. It appears that supplemental acids are most apt to affect in the crop and gizzard rather than in the intestine.
It has been shown in various animal species that salmonella colonisation of the gut is decreased when the bifidobacterial population is increased, either by administration of bifidobacteria as probiotic strains, or by addition of certain types of oligosaccharides that stimulate proliferation of these bacteria in the gut (Asahara et al., 2001; Buddington et al., 2002; Bovee-Oudenhoven et al., 2003; Silva et al., 2004; Thitaram et al., 2005).
Increasing the concentration of butyrate producers in poultry caeca using nutritional strategies and addition of pro- or prebiotics would be an efficient way to combat salmonella infections.
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Article made possible through the contribution of Lohmann Animal Health.