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Non-nutritive feed additives: To add or not to add

By Tracy Meyer, nutritionist, Advit
The Merriam-Webster dictionary defines the word non-nutritive as “not relating to or providing nutrition”. In other words, these are additives included in pig diets that are not providing a nutritive benefit but otherwise aiding in the growth of the animal.
There are numerous products on the market and one can get overwhelmed with choice. In this article I will highlight the more common additives and provide a basic description of each so as to help make an educated decision when choosing additional feed additives.

Antimicrobial agents
Antimicrobial agents destroy or inhibit the growth of microorganisms. The mode of action of antimicrobials is still not fully understood. Reports have shown a disease-reducing effect due to improving the immunity and controlling pathogens in the intestine.  The energy and nutrient digestibility of feeds has also been seen to improve and this may be attributed to changes in the intestinal microbial population.
Also known as dewormers, anthelmintics play an important role in herd health. Internal parasites may reduce the growth rate of the pig, which will have significant economic losses.  Carcasses may also be condemned if infestation is extreme. Common internal parasites are roundworm, kidney worm, lungworm, whipworm and threadworm.
Acidifiers include organic acids, inorganic acids and acid salts. Again, the mode of action has varying explanations. Acidifiers are said to reduce the gastric pH which aids in digestion of nutrients as well as reduces the survival of pathogens in the stomach. The low pH is also said to directly kill any bacteria ingested.
Direct-fed microbials
Probiotics can be divided into three categories: bacillus, lactic-acid producing bacteria and yeast. These micro-organisms colonise the intestinal tract and prevent intestinal pathogens from colonising. Yeast cultures may be added as live or dried yeast, and can contain vitamins, minerals, saccharides, ensymes, amino acids, nucleotides and other metabolites.
Non-digestible oligosaccharides
These additives are also known as nutraceuticals or prebiotics. The oligosaccharides stimulate the growth of Bfidobacteria in the large intestine, thereby increasing the lactic acid concentration and in turn, reducing the pH. They are also believed to stimulate the growth of other beneficial bacteria in the large intestine and improve the health of the intestine itself.
Plant Extracts
Throughout history herbs and spices have been shown to have antimicrobial properties. The most common herbs and spices used are carvacrol, thymol, oregano and garlic. Mixtures of plant extracts have been proposed as alternatives to antibiotics for pigs.
Fibre digestibility in diets containing wheat, oats or barley may be improved by adding carbohydrate-digesting enzymes. This however does not always affect growth performance.
The effect of adding phytase to pig diets has been well documented. These enzymes hydrolyse phosphorus from phytate and therefore make it available for the animal. There is an increase in total tract digestibility of phosphorus as well as a reduction in phosphorus excretion.
The magnitude of the response is dependent on the raw materials in the diet being fed. Phytases have also shown a positive effect on the digestibility of amino acids, minerals and energy.
Feed flavours
In order to improve palatability, flavours, sweeteners, aromas and combinations of these can be added to the diet.  These can also be used to initiate intake or to mask flavours that may affect intake.  It has been shown that pigs have a preference for a sweet rather than a sour taste.
Mycotoxin binders
The most common mycotoxins found in diets fed to pigs are aflatoxin B1, zearalenone, deoxynivalenol (DON), T-2, fumonisin B1 and oxchratoxin. Each mycotoxin will illicit a specific response in the pig, but in general, feed refusal, reduced weight gain, immune suppression, poor feed conversion, poor reproduction and residues in the final product are general symptoms of a mycotoxin contamination.
Mycotoxin binders are added to the feed to reduce or inhibit the absorption of mycotoxins as well as to increase exrection of these mycotoxins. The general mode of action is to bind to or detoxify the particular mycotoxin.
Oxidation of fats and vitamins can cause feed and feed ingredients to become rancid and destroy fat-soluble vitamins. Vitamin E, vitamin C and selenium are efficient antioxidants but often the level included is not enough to provide a sufficient antioxidant role and therefore commercial antioxidants may be added. It is recommended that antioxidants to diets are added to diets or feed ingredients that contain unsaturated fatty acids and/or stored under hot conditions.
Pellet binders
These are feed additives used to improve the pellet durability and in turn decrease the number of feed fines incurred during manufacturing and transport. The binders improve adhesion and cohesion between the feed particles.
Flow agents
Flow agents and anti-caking agents prevent caking and help improve flowability of granular/powdered ingredients and meals during handling, storing and processing.

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