Additives to Improve Manufacture and/or Properties of Feed
Three classes of feed additives added to feeds to improve the manufacture
and/or properties of the feed are antifungal agents, antioxidants, and
pellet binders.
Antifungal agents prevent the growth of fungi in feeds. Fungi may be referred
to as molds. All feedstuffs are susceptible to fungal growth given appropriate
conditions (i.e. warm, moist, and aerobic). The critical moisture content
for growth is 12%. Fungal growth may occur in the field prior to harvest
and during storage. Feeds may be contaminated during feed processing,
storage, and feeding. Fungi cause issues via the production of toxins,
alteration of the chemical composition of the feedstuff, and/or alteration
of the metabolism of the animal. Fungi reduce the palatability of a feedstuff
and are detrimental to the health and productivity of the animal. Effect
on the animal varies with species and physiological state. Propionic acid,
sodium propionate, calcium propionate, sodium diacetate, sorbic acid,
ammonia, and phosphoric acid are effective antifungal agents. Propionic
acid is a common antifungal agent. Propionic acid is economical, safe,
and is available in liquid and dry forms.
Various feedstuffs such as lipids, fish-based products, animal-based products,
and vitamins are susceptible to oxidation. Feedstuffs high in unsaturated
fatty acids are especially susceptible to oxidation and subsequent rancidity.
Oxidation and rancidity decrease the palatability and the nutritional
value of a feedstuff via the destruction of nutrients. Antioxidants are
added to feedstuffs to minimize the oxidation of polyunsaturated fatty
acids of various nutrients within feedstuffs. In general, antioxidants
function via provision of the unsaturated fatty acid with hydrogen. Various
antioxidants also have the ability to function as antioxidants in the
cells of the animal. Synthetic antioxidants added to feedstuffs to minimize
oxidation include ethoxyquin, butylated hydroxytoluene (BHT), and butylated
hydroxyanisole (BHA). Synthetic antioxidants also have the ability to
minimize the detrimental effects of peroxides. Vitamin E is a natural
antioxidant. Vitamin C and selenium are also natural antioxidants. In
addition to use of antioxidants, oxidation may also be minimized by refrigeration,
exclusion of light, exclusion of oxygen, and destruction of enzymes.
Pellets are a physical form of feed; dense particles of various feedstuffs.
Feedstuffs may be pelleted to improve characteristics of processing and
feeding. Depending on the feedstuffs in the pellet, pellets may crumble.
In addition, fines may be present in the resultant product. Fines are
small feed particles. Pellet binders enhance the firmness and strength
of pellets, thus reducing the tendency to crumble. Feed additives added
as pellet binders include bentonites (i.e. clays), cellulose- and hemicellulose-based
products of the wood industry, lignin derivatives, and by-products of
the grain industry. Bentonites are the most common pellet binders. The
presence of steam improves the efficacy of bentonite. In general, bentonite
is added at 2-3% of the ration. Additionally, bentonite may also function
to improve the utilization of NPN compounds in ruminants via interaction
with ammonia and also absorbs and faciliates the excretion of mycotoxins.
Molasses and lipids may also be added to the ration to improve pelleting.
Natural feedstuffs in the ration such as wheat may also function as pellet
binders.
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