Effects in livestock
Deoxynivalenol exerts various adverse health effects in farm animals. The reaction of animals to acute intoxication with DON resembles the well-known reaction of the human body to spoiled food. The typical symptoms include vomiting (therefore DON also bears the name “vomitoxin”), diarrhea, loss of appetite, changes in body temperature and a decrease in movement and social activity. Animals may also develop an aversion to the taste of DON-contaminated food. DON is furthermore harmful to the gut tissue, increases the gut’s susceptibility to pathogenic bacteria and impairs the uptake of nutrients.
Figure 1: A strain of Fusarium (Fusarium culmorum). Source: BIOMIN
Given the frequent contamination of feedstuffs with low levels of mycotoxins, chronic exposure of farm animals to lower doses of DON may be more common than exposure to a high toxin load. Chronic low level DON exposure primarily causes a decrease in appetite that results in reduced growth or weight loss. The reasons for a decreased appetite upon DON exposure have been investigated in mice and rats as model animals.
Reasons for lower feed intake
It was shown that a decrease in appetite triggered by deoxynivalenol is mediated by changes in certain areas of the brain. How DON elicits these changes is currently under investigation. On the one hand, recent scientific evidence indicates that DON interacts directly with brain cells. On the other hand, it was shown that animals react to DON exposure with a premature release of satiety hormones in the gut. During normal digestion, satiety hormones known as peptide YY (PYY) and cholecystokinin (CKK) are released from the gut to signal to the brain that the digestive system is full and the intake of feed should be finalized. If the feed is contaminated with DON, the release of these hormones occurs earlier and consequently the intake of feed is stopped earlier as well, thus resulting in a reduction of meal size.
Reduced weight gain
A decrease in feed intake is not the only reason for reduced growth induced by deoxynivalenol. It was shown that DON interferes with growth hormone signaling which leads to a reduced weight gain independent of the decrease in appetite. In animals fed a DON-contaminated diet, the levels of certain proteins in the blood are decreased. However, sufficiently high levels of these proteins are required to enable growth hormones that govern weight gain to take full effect. Therefore, animals exposed to DON gain less weight than they otherwise would.
In conclusion, the presence of DON in feedstuffs –even at low doses– compromises the health, wellbeing and development of farm animals. Good practices in feed storage and implementation of suitable mycotoxin decontamination strategies can assure that animals stay healthy and well nourished.