MOLDY GRAINS, MYCOTOXINS AND FEEDING

PROBLEMSDr.KEDAR KARKI

Introduction

• Fungi produce an array of chemical products known as secondary metabolites.

Introduction

• Penicillin is an example of a secondary metabolite with medicinal applications.

Introduction

• Unfortunately, not all secondary metabolites are as useful as penicillin.

Introduction

• Mycotoxins are secondary metabolites of fungal origin that are toxic to animals and humans.

Introduction

• Disease that results from ingestion of mycotoxin-contaminated feed or food by animals or humans is called mycotoxicosis.

Introduction

Introduction

• Common examples of mycotoxicosis are mushroom poisoning and ergotism.

Introduction

• Among the thousands of species of fungi, only about 100 are known to produce mycotoxins. Under favorable environmental conditions, some toxigenic molds can produce mycotoxins on agricultural commodities during plant growth, or after harvest in storage and shipment. Some of the agricultural commodities affected are cereal grains, soybeans, peanuts and forage crops. Mycotoxin-contaminated feeds are of critical importance due to their potential hazard to livestock and poultry. Additionally, contaminated food grains can affect human health.

Introduction

• , the most common feed sources with mycotoxin contamination problems are corn, wheat, forage and silage crops. However, producers should be aware that mycotoxin problems can be associated with grains and grain products purchased off the farm or mixed in feed rations. Mycotoxin problems are often aggravated by poor storage conditions

symptoms of mycotoxicosis

• General symptoms of mycotoxicosis in domestic animals are: loss of appetite, poor weight gain, feed refusal, diarrhea, bleeding and unthriftiness.

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Mycotoxicosis

• Mycotoxicosis is generally characterized by the following features:

• The disease is not contagious • Antibiotics and drugs have little effect in

controlling the disease • Outbreaks are often seasonal • The problem is associated with a specific feed • Analytic assay of the feed indicates the

presence of toxic metabolites

PREVENTIVE PRACTICES

• Prevention is the best method to control mold growth and possible toxin formation. The following practices can help minimize mold growth and subsequent toxin production in storage

Preharvest

• Clean inside and outside of grain bins and dryers.

• Prior to storage, check the condition of the bin for possible water leaks, and clean it properly by removing dust, dirt, leftover grain and other foreign material.  

• Crop rotation in many regions or tillage can reduce the risk of Gibberella ear rot in corn and Fusarium head blight of wheat. These practices have little effect on other corn ear rots.

Post harvest 

• The crops should be allowed to mature in the field to the following moisture contents: shelled corn, 23-25%; ear corn, 20-25%; small grain, 12-17%; and soybeans, 11-15%.

• Upon storage, dry the grain to 13-14%, if possible, within 48 hours. Long-term storage can be achieved at a uniform moisture of 18% for ear corn; 13% for sorghum, wheat and shelled corn; and 11% for soybeans.  

• After drying, store under cool temperatures (36-44° F).  

• Every few weeks check the condition of the grain for temperature, wet spots and insects.  

Grain treatments

• Antifungal treatments can be applied to grain to reduce mold growth in storage. These products, such as proprionic acid, do not kill the mold already present nor do they reduce toxins already present in the grain. Do not use antifungal agents on stored grain unless you are certain the grain can be marketed after treatment.

Grain treatments

• Hydrated sodium calcium aluminosilicate (HSCAS) (Novasil) can reduce the effects of aflatoxins when fed to swine, cattle, or poultry. HSCAS at 10 lb./ton provides substantial protection against dietary aflatoxins.

Common mycotoxins important for Livestock

• AFLATOXINS   • Toxin Characteristics • Aflatoxins,  secondary metabolites produced by

some strains of Aspergillus flavus and A. parasiticus, are the most commonly occurring mycotoxins in feedstuffs worldwide.  

• Aflatoxins are a group of highly toxic metabolites that includes specific forms designated as B1, B2, G1, G2, M1 and M2.