General effects of mycotoxins
Long term exposure to mycotoxins often contributes to chronic problems which result in higher incidence of disease, poor reproductive performance and/or lower milk yields. Effects of mycotoxins are often compounded by the presence of other metabolic and environmental stressors, which can lead to difficulties in diagnosis.
Feeding mycotoxin contaminated feedstuffs will negatively impact animal performance, especially animals under stress and/or immune-compromised. Transition cows are generally the first to exhibit signs of mycotoxicosis.
Degradation of mycotoxins by rumen microbes can provide some protection against acute toxicity from mycotoxins in feedstuffs. However, rumen degradation may lead to the production of toxic metabolites, resulting in cows exhibiting a wide range in severity of symptoms. Refer to Table 1 for a summary of effects of common mycotoxins.
Table 1: Effects of Common Mycotoxinsa
a Whitlow, L.W., and W.M. Hagler, Jr. 2008. Mold and mycotoxin issues in dairy cattle.
Effects, prevention and treatment. Pp 80-89. Proc. Southeast Dairy Herd Mgmt. Conf.,
Mycotoxin sequestering agents
The most common classes of mycotoxin sequestering agents include: hydrated sodium calcium aluminosilicate (HSCAS) and silicate minerals. In addition, other types include activated charcoal, cholestyramine, chlorophyllin and yeast cell wall-derived agents.
Research data on the impact of mycotoxin sequestering agents on trace minerals is limited (see Table 2) and virtually no published data are available in dairy cattle at this time.
About Hydrated Sodium Calcium Aluminosiliate (HSCAS)
HSCAS from natural zeolite functions to sequester positively charged (cationic) compounds, mainly aflatoxins.
Results from Chung et al. indicated young broiler chicks fed HSCAS in mycotoxin-free diets supplemented with inorganic minerals lead to a decrease in tibia zinc.
Results from Chestnut et al. found HSCAS impaired zinc absorption in sheep while also reducing the absorption of magnesium and manganese.
Mineral nutrition considerations:
Zinc plays a critical role in carbohydrate and energy metabolism, protein synthesis, epithelial tissue integrity, cell repair and division and vitamin A and E absorption and transport, all of which affect immune function. Therefore, based on these studies, livestock diets fed diets containing HSCAS may benefit from supplementation with highly available forms of trace minerals including complex forms of zinc and manganese.
About Silicate minerals:
Largest class of mycotoxin sequestering agents and consists of phyllosilicate (mineral clays such as montmorillonite/bentonite) and tectosilicate (zeolites) subclasses. The bentonites largely are used as a result of having a high degree of ion exchange capabilities and are primarily effective against aflatoxins.
Research from Schell et al. in weanling and growing pigs found that:
Feeding aflatoxin contaminated feed increased phosphorus, sodium and zinc absorption and retention suggesting a possible increased metabolic demand for these minerals when aflatoxin is present. Feeding sodium bentonite decreased magnesium absorption regardless of the presence of aflatoxin. The addition of bentonite clay also decreased calcium and sodium absorption and retention in aflatoxin contaminated diets and decreased sodium concentration when the feed was free of aflatoxin. Similar to the effects of HSCAS, zinc absorption and retention was decreased in diets supplemented with sodium bentonite. Research by Ivan et al. found that silicates decreased copper bioavailability in sheep fed no supplemental trace minerals. Bentonite also decreased the ruminal solubility of zinc, copper and magnesium and led to significant decreases in copper in both plasma and liver.
Mineral Nutrition Considerations:
Utilizing silicate minerals as mycotoxin sequestering agents could lead to decreases in both zinc and copper status.
The interaction between complex trace minerals and mycotoxin sequestering agents has not been researched. However, providing a portion of supplemental zinc and copper as amino acid complexes may be warranted to improve the likelihood of maintaining optimal trace mineral status when diets contain silicate-based mycotoxin sequestering agents.
Table 2: Effects of Mycotoxin Sequestering Agents On Mineral Nutritiona
a Chestnut, A.B., P.D. Anderson, M.A. Cochran, H.A. Fribourg, and K.D. Gwinn. 1992.
J. Anim. Sci. 70:2838-2846; Chung, T.K., J.W. Erdman, Jr., and D.H. Baker. 1990.
Poultry Sci. 69:1364-1370; Schell, T.C., M.D. Lindemann, E.T. Kornegay,
and D.J. Blodgett. 1993. J. Anim. Sci. 71:1209-1218
b Hydrated sodium calcium aluminosilicate
What potential solutions exist for dealing with mycotoxin contaminated feeds?
Regardless of the type of mycotoxin(s) present, consider the following:
Eliminate or reduce the feeding rate of the contaminated feed.
Provide additional dietary protein, energy, fiber/buffer/additives which enhance rumen function.
Incorporate a research proven mycotoxin sequestering agent to aid in decontaminating the feed.
Based on limited data, some classes of mycotoxin sequestering agents may render some minerals and vitamins unavailable for absorption and metabolism. Therefore, it is important to provide a highly bioavailable source of trace minerals. Research has demonstrated the critical role that highly-available forms of complex trace minerals play in improving animal performance.