Several toxic substances can be present in feed, with the most common being molds, mycotoxins, fat rancidity, chemical residues and pathogenic microorganisms.
Controlling mold growth and mycotoxins production can generally be achieved by keeping moisture low, keeping feed fresh, keeping equipment clean and using mold inhibitors.
Moisture determines if and how fast molds will grow in feeds. Moisture control in feed ingredients, feed milling processes and feed storage are essential if one is to control the moisture level in feeds.
Chemical mold inhibitors are useful in controlling the growth of molds, but they should not be relied upon exclusively.
Certain feed ingredients such as soymeal, fishmeal and limestone may also affect mold inhibitor performance.
Oxidative rancidity of feed fats can reduce metabolisable energy, destroy fat-soluble vitamins and reduce palatability. In severe cases, rancidity can cause muscular degeneration or dead tissue in various organs. Five steps can be taken to prevent oxidative rancidity in feed fats:
1. Establish specifications with fat or ingredient suppliers.
2. Collect fat samples at delivery and have the samples analysed by a reputable lab.
3. Avoid fat suppliers who have supplied sub par quality fats in the past.
4. Store liquid fats in clean tanks.
5. Do not expose liquid fats to pipes or fittings containing copper.
Two main types of chemical residues in feed are antibiotics and industrial chemicals, which include pesticides. Chemical residues can cause many problems, such as a mass recall or even ordered destruction of products, extensive damage to the feed as well as possible hazardous effects of the chemicals on animal health.
Chemical residue avoidance program in feed involve two steps:
1. Regular testing
2. Sample retention
Contamination of feed can come from two sources - the sample feed and from the person collecting the sample. However, which source the contamination came from can be questionable, and methods have been created to deal with the issue of cross contamination.
Control of microbial pathogens in feeds and feed mills involves procedures to,
1. exclude pathogens from the feed
2. prevent multiplication of the organism in the feed
3. kill pathogens within the feed and prevent recontamination
However, feed milling processes are incapable of killing certain pathogens so these pathogens must be excluded for control. In addition, even when feed mill processes destroy pathogens, high numbers of these pathogens in feeds require even harsher treatments, which could cause nutritional damage to the feed as well as costing more. Therefore, each of the control procedures is interdependent and must be implemented simultaneously.
There are six basic steps to exclude pathogens from feed,
1. Obtain clean ingredients
2. Verify ingredient quality
3. Maintain a clean receiving area
4. Adequate dust control
5. Clean up feed spills
6. Proper feed storage
Lack of moisture is also essential to prevent pathogen multiplication therefore great care must be taken to eliminate moisture in facilities. High heat can also be used to kill pathogens, although only pelleting and chemical treatment can reliably eliminate pathogens in feed.