Feed refusal

Deoxynivalenol has not been known to produce deaths in humans, but has a significant impact on agriculture due to feed refusal. Pig and horse refusal of moldy grain was reported as early as 1928, and cases of complete refusal have been associated with wheat containing 34 mg per kg of deoxynivalenol (Moore et ah, 1985). 

Contamination occurs primarily in wheat, barley, rye, and maize. Type A trichothecenes include mainly T-2 toxin, HT-2, and diacetoxyscirpenol (DAS) mycotoxins of the group B include mainly 4-deoxynivalenol (DON), commonly known as vomitoxin, and nivalenol (NIV). Toxic effects include nausea, vomiting, visual disorder, vertigo, throat irritation, and feed refusal in farm animals. The most toxic is T-2, followed by DAS and NIV, with DON being the least toxic in acute toxicity studies but the most widespread in grains worldwide and therefore the most studied. Issues related to chemical and physical data, occurrence, toxicity, absorption, distribution, and metabolism of trichothecenes are reviewed in WHO (89) and IARC (34). Physicochemical data for some selected Fusarium toxins is given by Sydenham et al. (90). The molecular structures of the main trichothecenes are shown in Fig. 9. 

Whether due to reduction in TdO activity, reduced glyconeogenesis, or both, Weber et al. (1994) proposed that an initial increase in tryptophan levels result in some initial feed refusal, which in turn initiates the wasting of body mass and increases the supply of tryptophan with which the animals cannot deal. A vicious cycle develops which results in strongly elevated tryptophan levels and increased serotonin turnover, which acts as an appetite suppressant. 

Both slaframine and swainsonine were isolated from the fungus Rhizoctonia leguminicula. The fungal infection of red clover hay or pasture is associated with the occurrence of the slobbers syndrome in cattle and horses which consists of excessive salivation (slobbering), lacrimation, feed refusal, bloating, stiff joints, abortion, diarrhoea and/or violent behaviour. Some of these clinical symptoms are similar to loco-weed poisoning but the first two are not observed upon administration of swainsonine to animals [114]. 

Other mycotoxins, including DAS, DON, and ochratoxin, are not of major economic importance although they can be toxic to food-producing animals. DAS causes necrosis and erosion of the oral mucous membranes. Consequently, affected animals exhibit feed refusal and have impaired growth. DON (also called vomitoxin ) induces vomiting and feed... 

Trichothecences are a class of structurally similar mycotoxins produced principally by Fusarium molds. These cyclic compounds are of interest to feed manufacturers because they can cause feed refusal or reduced feed efficiencies in some animal species (1,2,3). Several approaches have been reported for the analysis of trichothecenes in feeds and feed ingredients. Trimethylsilyl derivatives of the trichothecenes have been formed and the derivatives measured by gas chromatography using a flame ionization detector (4,3,6,7). Other workers obtained improved... 

YoshizawaT, ShirotaT, Morooka NJ (1978) Toxic Substances in Infected Cereals, VI. Deoxynivalenol and Its Acetate as Feed Refusal Principles in Rice Cultured with Fusarium roseum No. 117 (ATCC 28114). J Food Hyg Soc Jpn 19 178... 

Essential oils can be used in feed as appetite stimulant, stimulant of saliva production, gastric and pancreatic juice production enhancer, and antimicrobial and antioxidant to improve broiler performance. Antimicrobial effects of essential oils are well documented. Essential oils due to their potent nature should be used as low as possible levels in animal nutrition. Otherwise, they can lead to feed intake reduction, gastrointestinal tract (GIT) micro ora disturbance, or accumulation in animal tissues and products. Odor and taste of essential oils may contribute to feed refusal however, encapsulation of essential oils could solve this problem (Gauthier, 2005). 

If ingested at a concentration of 0.15 mg/kg bw/day, DON is able to cause vomiting in swine, while it has been estimated that levels up to 1—2 mg/kg in the diet can cause partial feed refusal in livestock, mainly pigs. Unfortunately, an accurate acute dose—response evaluation in humans has not been reported so far. However, it has been possible to ascribe the induction of acute gastroenteritis to vomiting in both mammals and humans to... 

Regarding the well-described toxic activity of DON against the immune system, alterations of the immune cells could affect the intestinal and brain functions, as recently desciibed. In particular, the intestinal and systemic production of cytokines could participate in the growth retardation, feed refusal and emesis caused by DON on account of the effects on the neuroendocrine system. The consequent inflammation could lead to an increased permeability of the intestinal and blood barriers, thus affecting the xenobiotic absorption. 

In the first trial, purfled fibres were added to the control diet to determine any effect of overcoming toxin-induced feed refusal. Cellulose (United States Biochemical Corp., Cleveland, OH), hemicellulose (Masonite Corp., Laurel, MS), pectin (United States Chemical Corp., Cleveland, OH) and lignin (Reed Paper Co., Quebec, Quebec) were fed at 20% of the control diet by substitution for cellulose and a fraction of cornstarch. 

In the seventh trial, as little as 6.0% corn oil overcame the feed refusal and reduced body weight caused by T-2 toxin. 

Cellulose and hemicellulose were not found to overcome the growth depression and feed refusal associated with the consumption of T-2 toxin. This may be due to inability of cellulose to act as a binding agent in the gastrointestinal tract (Story and Kritchevsky, 1976). 

The ability of bentonite to effectively overcome feed refusal due to T-2 toxin is not likely due to ion exchange since this product is a colloidal hydrated aluminum silicate. It has the property, however, of forming highly viscous gels when mixed with water. Absorption of toxin may therefore be reduced as bentonite traps molecules. This property likely accounts for the observation that bentonite can bind aflatoxin in vitro (Masimango et al., 1979). 

The role of dietary fats in alleviation of T-2 toxicosis is not easily explained. No evidence was gathered to show that dietary fats altered T-2 metabolism. Hepatic esterase activities were unchanged and the degree of unsaturation of lipid had no effect on feed refusal. The fatty acid composition of dietary oils has been shown to alter mixed frunction oxidase activity in rats (Gefferth and Blakovits, 1977) and it was thought that this might influence T-2 toxin metabolism. 

It is unlikely that the reduced transit time seen when isoenergetic high fat diets were fed is of physiological significance since cellulose fed alone did not overcome T-2 induced feed refusal. 

D. I Toxidty. Voluntary feed refusal often prevents full expression of oral toxicosis from conta-minated feeds. Fiowever, iJosing studies using parenteral injection and oral administration reveal that trichothecenes are potent toxicants. 

Feed r sal is a learned response known as taste aversion tfierefore. Adoring agents do not prevent subsequent feed refusal. 

FIGUItE 29-4. Correlation between feed refusal and doxynivalenol (vomitoxin, DON) content of the feed in swine. 

Vomiting, feed refusal, weight loss, atxl normal kidney and liver fenction tests... 

Deoxynivalenol, also known as DON or vomitoxin, is a trichothecene mycotoxin that affects brain neurochemistry (e.g., dopamine and 5-hydroxyindolacetic acid), leading to nausea and appetite suppression. Feed refusal or decreased feed intake occurs through a learned response known as "taste aversion."... 

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