Background last update:6 Aug 2012

Mycotoxins in ruminants

The effects of mycotoxins in cattle may vary from reduced weight gains or milk production, according to information from the Canadian Ministry of Agriculture, Food and Rural affairs.

Performance losses of 5 - 10% are typical with moldy feeds even in the absence of mycotoxins. Mycotoxin contamination increases production losses, even when mold is not readily visible. It can also lead to mycotic abortions and respiratory disease Ketosis and displaced abomasum problems may increase significantly with the consumptions of mycotoxins.
Some animals develop diarrhoea or have signs of haemorrhaging. Estrogenic effects, swollen vulvas and nipples; vaginal or rectal prolapse may occur. Reduced fertility / conception rates or abortions may also be evidence of mycotoxin consumption. The effects of mycotoxins are amplified by production stress. High producing dairy cows and rapidly growing feedlot cattle are more susceptible to the effects of mycotoxins than low producing animals.
Effect of the rumen
Ruminants are uniquely equipped to protect themselves from the harmful effects of mycotoxins. It is assumed that sufficient degradation of the mycotoxins has taken place before absorption into the blood and vital organs to protect the animals. Mycotoxins are detoxified or altered in the rumen. but: The rate of detoxification differs for the different types of mycotoxins and the extent of detoxification of any particular mycotoxin depends on the rate of passage of feed. Rumen turnover rates are about 8 times longer in beef cows than lactating dairy cows.
The extent of detoxification also depends on the original dose level. Five and 10 ppm DON were completely transformed to the reportedly less toxic deepoxy DON or DOM-1 within 24 hours when incubated in rumen fluid. More than half of the DON remained from the 50 and 100 ppm DON treatments at 24 hours incubation. The altered metabolite(s) may be more toxic than the original mycotoxin. Work in sheep had Zearalenone transformed into the reportedly more toxic Zearalenol.

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