What can a feed mill do to overcome the withdrawal of Antibiotic Growth Promoters
First thing to realize is that we want to take AGP's out of the animal production chain because of the risk in human health. We want to raise animals in a healthy way and therefore a healthy and safe feed is required. As a feed mill we are making feed for food.
To guaranty better the safety of the feed we have several quality management systems implemented. The most well-known are the ISO, HACCP and GMP+ certifications. These systems are control mechanisms and support programs but still do no guarantee an good quality and safe feed.
These quality control systems mean in practice that we try to optimize working procedure, storage, transport and tracking and tracing, by checking all incoming samples and taking appropriate measure in case a raw material is not according standards. Also during the production process the quality of the finished product can deviate from the set standards. With these quality control systems in place we reduce the risk of, among others, microbial and bacterial contaminations. And therefore also the need of AGP's to kill or reduce these possible bacterial contaminations.
As we all know AGP's are working very well to reduce harmful bacteria in the animals, hence having healthier animals and therefore better growth. As we are taking out these AGP's we are looking for alternatives to replace them. But unfortunately there is not a "AGP-out-product-B-in" principle. We need complete new feeding concepts. There is done over the last 20 years done a lot of research, mainly in Europe to find alternatives for AGP's. This research resulted in a long list of alternatives that have proven an anti-microbial effect. ( see my las article). Our job as feed millers is to choose the best alternatives given the circumstances, climate, animal species, used raw materials, and of course price.
Of course good balanced feed, and in particular the protein and amino acid balance is extremely important to reduce the not digested protein and amino acids in the end gut. Restricting the nutrients that might promote the growth of pathogenic bacteria and restricting the anti-nutritional ingredients such as lectin, tannins and protease inhibitors can inhibit the proliferation of pathogens, especially in the end gut. Coarse grinding improves the structure of the feed. Bigger particles stimulate stomach and intestines which will develop better this way and keep animals healthy. However, to coarse grinding means incomplete digestion: the whole grain kernel is difficult to digest for younger animals and will be excreted almost undigested.
As a feed company we see it also as our task to advice customers on farm management. Good ventilation, farm design, all-in-all-out, vaccination schedules, supply of clean water, disinfection and hygiene are things that definitely can reduce health problems. We consider it as out task to help customers to get the maximum performance from a good quality feed.
Salmonella is one of the bacteria that can come into the animal through the feed and this bacteria can cause health issues in the animals as well as in human, as it can pass through eggs or meat. Most important to reduce risk is of course prevention. As a feed mill we check potential hazardous raw materials on the presence of Salmonella. First problem is the sampling as the bacteria very possible is not evenly distributed through the ingredients, resulting in a risk that negative sample still has Salmonella in the delivered batch of raw material. Important is that raw materials have a low moisture level as moisture promotes multiplication of the bacteria. For example proper dried corn and selecting reliable suppliers for us is course very important.
As dust is the major source of Salmonella contamination in feed mills (Butcher and Miles, 1995) it is extremely important to control dust. Most dust is generated at the receiving pit and a good dust collection system is a must for a good feed mill. Although more dust is produced in the raw ingredient receiving area than at any other point in the feed mill, dust may also be produced by hammer mills, roller mills, crumblers, mixing systems, elevator legs, distributors, conveyors, at bagging, pellet coolers and at the finished feed bins. Clearly, dust control is a broad, continuing, daunting, necessary task in Salmonella control within all feed manufacturing facilities.
Sampling at these dust collection points as well as sampling of spilled feed and debris in the processing area can give an excellent overview of hazard points and the Salmonella risks in the feed factory. Another measure to reduce Salmonella is to avoid flow of human from the raw material receiving area to the production area. Also air flow from receiving to production should be reduced to a minimum.
Fats and oils are protecting Salmonella from destruction by environmental conditions (Morita, 2006). Therefore it is important to reduce fat and oil accumulation and protect oil and fat storage and dosing equipment from entering dust. Also fats and oils for greasing of machines should be taken into account and excess of grease should be avoided.
Controls of vectors such a rodents and wild birds who can bring Salmonella into the feed mill but also spread it through the mill, is one of the measures to reduce Salmonella. Vectors such as vehicles should be cleaned and disinfected and only be used exclusively for transport of feed or exclusively for raw materials.
Low moisture conditions does not allow microbiological growth. Wet spots in the production area, such as at post pellet spraying equipment, and condensation spots, for example at pellet coolers, bags stored on the floor instead of pellets should be avoided at all times.
Thermal processing of the feed, by conditioner (mixing with steam), and pelleting (pressing through the metal die) which increases the temperature another couple of degrees due to the friction is another method of elimination of bacteria in the feed. Minimum temperature that kills Salmonella is 71 degrees (Stodt and Hodgson, 1975) but depends highly on formulations, equipment design, pelleting conditions, particle size, steam quality, air flow in the cooler, etc.
Salmonella can also be killed by chemicals such as organic acids. Propionic acid and formic acid are the most common used. The efficacy of organic acids against Salmonella in feed varies widely, being influenced by the level of contamination, the type of acid or blend of acids, the physical form, inclusion rate, the diet composition, moisture in the feed, and the chemical form of the product (i.e., free acid or acid salt). (European Food Safety Authority, 2008) Superior decontamination of feed by formaldehyde, compared with acid products, has been demonstrated (Duncan and Adams, 1972.) However, formaldehyde is a volatile substance that may evaporate in open systems and workers must be protected from overexposure. Note that in many countries formaldehyde is forbidden due to carcinogenic properties.
Resuming it can be said that a feed mill can have a very important role by reducing the risk of introduction of bacteria, in particular Salmonella, into farms which in return have less need to use antibiotics.
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Article made possible through the contribution of Jan Cortenbach, MSc. and De Heus Animal Nutrition B.V.