Metabolism of toxic pyrrolizidine alkaloids from tansy ragwort (Senecio jacobaea) in ovine ruminal fluid under anaerobic conditions

Abstract

The ability of ovine ruminal fluid to metabolize pyrrolizidine alkaloid (PA) from Senecio jacobaea under anaerobic conditions was evaluated. Four fistulated sheep fed PA served as individual sources of ruminal fluid, which was incubated in a defined minimal salts medium under two different anaerobic conditions, denitrifying and methanogenic. Anaerobic cultures amended with ovine ruminal fluids (20%), PA (100 ,ug/ml), and a defined minimal salts medium were monitored for a period of several days. These cultures revealed that while PA was not depleted in sterile, autoclaved controls or under denitrifying conditions, it was metabolized during periods of active methanogenesis under methanogenic conditions. In addition, samples of ruminal fluid were separated by differential centrifugation under anaerobic conditions, and the resultant supernatants were tested for their ability to metabolize PA as compared with those of the respective uncentrifuged control fluids. Uncentrifuged controls exhibited a PA depletion rate of-4.04 0.17 ,ug of PA per ml per h. Supernatants 1 (centrifuged at 41 x g for 2 min), 2 (centrifuged at 166 x g for 5 min), and 3 (centrifuged at 1,500 x g for 10 min) exhibited significantly slower depletion rates, with slopes of data representing-1.64 0.16,-1.44

Toxin Degradation by Rumen Microorganisms: A Review

“…Resistance to PA poisoning was previously reported in sheep where the detoxification was hypothesised to occur in the rumen, suggesting that sheep rumen microorganisms have the ability to metabolise PAs and render them non-toxic [ 74 , 172 ]. Resistance against PA poisoning was reported to only occur in animals that were previously exposed to the toxin allowing rumen microbes to adapt to metabolise PAs.…”

“…A later study showed the synergistic relationship of ruminal microorganisms in metabolising S. jacobaea PAs. It was reported that a group of unidentified ruminal bacteria were responsible for PA metabolism while ruminal protozoa may have been involved in increasing the rate of degradation [ 172 ]. This could be due to the presence of protozoa and certain bacteria that could be responsible for the adsorption or adherence of PA-degrading bacteria to plant particles thus allowing the metabolising bacteria to utilise PAs [ 172 ].…”

In vitro ovicidal effect of a Senecio brasiliensis extract and its fractions on Haemonchus contortus

“…The pyrroles originating from dehydrogenation of PAs can bind with the hepatocyte DNA, inhibiting cellular mitosis and thereby causing hepatic dysfunction [46, 47]. However, it is known that sheep, the targets of our study, are more resistant to Senecio intoxication than cattle due to their ruminal microbiota [48] and liver metabolization system [49].…”

Effects of antibacterial agents on in vitro ovine ruminal biotransformation of the hepatotoxic pyrrolizidine alkaloid jacobine

“…Some PA cause cirrhosis of the liver and some cause lung damage, leading to death (32). In the western United States, multimillion dollar livestock losses result from the poisoning of cattle and horses because of ingestion of tansy ragwort, Senecio jacobaea (10,11,34). Ingestion of plants which contain PA is also a worldwide problem, affecting animal and human populations, because of PA in various weeds, herbal remedies, and contaminated food and feed (17).…”