Flatpea intoxication in sheep and indications of ruminal adaptation

This paper describes the signs of toxicity when seed-bearing flatpea (Lathyrus sylvestris L) hay is fed to sheep. Signs of intoxication (including seizure, muscular trembling and spasmotic torticollis) are similar to those observed for ammonia toxicity in ruminants. Accumulation of ammonia may be a direct consequence of flatpea ingestion, given that 2,4-diaminobutyric acid (DABA, a toxic constituent of flatpea) is known to inhibit hepatic urea synthesis. However, other modes of toxicity for DABA as well as other flatpea toxins may also contribute to this process of intoxication. Our evidence suggests that ruminal microbes are responsible for flatpea detoxification and host animal protection. The adaptation of sheep to flatpea may be a consequence of enhanced ruminal detoxification activity. Ruminal protective functions can be disrupted, however, through abrupt monensin feeding or the replacement of nonadapted for adapted rumen contents. This disruption temporarily suppresses mechanisms of ruminal detoxification. As a consequence sheep can again be made vulnerable to flatpea intoxication.