Ruminants have some capacity to protect themselves against the harmful effects of mycotoxins due to certain detoxifying action of certain ruminal microorganisms. However, modern dairy cows have a much faster passage rate of feed through the rumen, leaving less time for microorganisms to detoxify. This, combined with higher feed intake, probably means that our cows’ natural defences cannot protect them as well as often assumed.
The harmful effects of mycotoxins do not begin with animal metabolism but with the ruminal microflora which affects the efficiency and productivity of ruminal fermentations. In fact, clinical symptoms may not manifest in most practical situations but performance will be subsequently compromised, resulting in decreased yield, poor reproduction and increased lameness or mastitis.
Most countries establish strict limits for aflatoxins in milk, but legislative attention is sometimes lacking for other important groups of mycotoxins that can greatly affect profitability and animal health and welfare. Some of the most important mycotoxin groups for ruminants are:
- Tricothecenes, including well-known mycotoxins such as DON (deoxynivalenol or vomitoxin)
- Ergot alkaloids