4 steps for fighting Salmonella in animal feed

Salmonella contamination remains a problem that can be addressed partially by measures taken through the feed we offer to animals. Use this four-step approach to fight Salmonella in feed.

It is unrealistic to expect complete elimination of Salmonella from animal feed. dustin day | freeimages.com
It is unrealistic to expect complete elimination of Salmonella from animal feed. dustin day | freeimages.com

Salmonella is one of the most frequent foodborne diseases, with poultry and pork being a potential source for humans in many countries. Live animals can be infected sub-clinically, leading to mild diarrhea and depressed growth performance, whereas acute infection can bring about septicemia and death. Nevertheless, the most prevalent form of Salmonellosis is that of a sub-clinical infection.

Current regulations in many countries have a very strict approach to Salmonella tolerance in human foods. Nevertheless, in practical terms, it is rather unrealistic to expect complete elimination of Salmonella from animal feed, especially at the point when the animal actually consumes feed. Fortunately, current technology and know-how can reduce Salmonella contamination to insignificant levels. From an animal feed standpoint, there are four aspects that can be controlled to ensure minimal risk of Salmonella contamination.

1. Formulation

We can reduce or avoid ingredients that are known to harbor high(er) levels of Salmonella, especially if they are of suspect quality and (or) without microbiological guarantees. Such are fishmeal, meat meal, blood-derived products, and some milk products. However, such ingredients offer certain benefits (low cost and/or high protein quality) that eliminating them from formulas can be problematic. Thus, it is best to implement a quality control program that includes Salmonella monitoring. To the same effect, it pays to purchase sensitive ingredients from sources known to monitor their products for Salmonella levels offering guarantees.

2. Organic acids

Certain organic acids used at the correct dosage are known to be quite effective against Salmonella in animal feed. There is a great amount of literature on this topic, but the most important aspect is that the required dosage is rather higher than currently practiced (for cost saving reasons). It is best to use organic acids that remain active in the stomach so as to eliminate Salmonella as soon as it enters the gut. Fortunately, most antibiotic-free diets contain at least some moderate levels of organic acids. Care should be taken their acidity is not buffered by other ingredients in the diet.

3. Thermal processing

Steam heating, pelleting, extrusion and expansion all can reduce the Salmonella load in ingredients and complete feeds, but the required temperatures to achieve zero Salmonella concentrations usually end up being destructive to the nutritive value of the heated feedstuff. For example, regulations in some countries call for certain feeds to be heated at 90 C. In such cases, feed-grade amino acids are expected to suffer considerable loses and thus, over-supplementation is warranted, albeit at the detriment of feed cost. The same problem exists with certain heat sensitive vitamins, and even other additives that can be destroyed by excessive heating.

4. Storage

Although feed can be treated one way or the other so that it is largely Salmonella-free, Salmonella is bound to reenter the feed system through some point. Examples abound and include an unclean truck, a half-filled silo or unclean feeders. To this end, it is best to pay attention to what happens to feed after it leaves the feed plant. In general, the shorter the route and time from production to consumption, the less the chances for any significant growth of Salmonella to happen. If Salmonella is found to be a problem, feed samples should be collected at feed manufacturing point (just before being bagged) and at feeding point (feeders). This will provide a first indication where Salmonella first enters the system.


A review 

A comprehensive review on practical control measures against Salmonella in animal feed was prepared by Jones in 2011 (Journal of Applied Poultry Research, 20:102-113). This is highly recommended reading. In brief, it clearly indicates that thermal treatment (usually pelleting) alone is not enough to eliminate Salmonella. Additions of chemical products (such as certain organic acids and/or formaldehyde) are also recommended in combination or alone. Other measures are also proposed to (a) reduce the chances of Salmonella entering the feed plant, and (b) once unavoidably there, ways to reduce its multiplication rate.


Clays fight Salmonella in broilers

Although clay products are frequently used against feed mycotoxins, a recent study indicated they can be also effective against Salmonella. When two clay products were included in feeds offered to healthy and Salmonella-challenged broilers (Salmonella enterica serovar Typhimurium), growth depression was restored indicating that clays can be part of Salmonella control program. Interestingly, goblet cell function (part of the immune system) may have contributed to the benefits observed.

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