Publication Date
1993
Description
Advances have been achieved in the diagnosis of chronic intoxications caused by poisonous plants in which the pathological changes present In the affected animals are not definitive, by the chemical identification of toxin adducts in their tissues. This has been demonstrated for pyrrolizidine alkaloids which are of global significance as plant poisons and has resulted on occasion in more determined efforts in eliminating the plants responsible. Many plant toxins need to be metabolised for toxicity within the animal's tissues in order to result in disease, and the furanoterpenes found mainly in myoporaceous plants are e,rnmples, Dietary regimes that lend lo promote low levels of hepatic microsomal mixed function oxygenases tend to be protective against intoxication after consumption of such plants. Many plants on the other hand contain essential oils which can enhance the activity of these enzymes, and this also can have an impact on the effects of subsequent diet and drug treatment on the well-being of the animal. Metabolism of plant toxins by ruminal micro-organisms is central to the roles that compounds such as cyanogenic glycosides, nitrates, oxalates and isoflavones, for example, play in ruminant intoxication. The most notable advance in this area is the part that specific micro-organisms can play in the prevention of toxicity owing to the non-protein amino acid mimosine which is contained in Lencaena leucacepliafa. Protection against this intoxication (mainly hypothyroidism) is achieved by inoculation of the rumen with cultures of the organism. This leads to the possibility that genes coding for enzymes which can break down specific plant organic toxicants can be inserted into rumen microflora and lead to prevention of specific toxicities. Attempts at the prevention of higher plant intoxications by immunisation has not in general been successful. Such an approach is being explored with some optimism in relation to the prevention of lupinosis. With changing climatic conditions, pasture-derived intoxications of grazing animals occasionally appear which have never been recognised before in the particular pastures involved. Poisoning by tunicaminyluracil antibiotics derived from bacteria introduced into grass infloresences by nematodes is well known as "annual ryegrass toxicity". This kind of toxicity has lately been recognised in relation to other grasses and no effective prevention or control is so far available for it. Finally, an issue that will need lo be addressed in relation to the effect of ingestion of higher plant toxins on animal production and economics is the existence in meat and milk of toxic chemical residues derived from the plants.
Citation
Seawright, A A. and Hegarty, M P., "Recent Developments in Higher Plant Toxin Research of Relevance to Animal Production" (2024). IGC Proceedings (1993-2023). 1.
https://uknowledge.uky.edu/igc/1993/session39/1
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Recent Developments in Higher Plant Toxin Research of Relevance to Animal Production
Advances have been achieved in the diagnosis of chronic intoxications caused by poisonous plants in which the pathological changes present In the affected animals are not definitive, by the chemical identification of toxin adducts in their tissues. This has been demonstrated for pyrrolizidine alkaloids which are of global significance as plant poisons and has resulted on occasion in more determined efforts in eliminating the plants responsible. Many plant toxins need to be metabolised for toxicity within the animal's tissues in order to result in disease, and the furanoterpenes found mainly in myoporaceous plants are e,rnmples, Dietary regimes that lend lo promote low levels of hepatic microsomal mixed function oxygenases tend to be protective against intoxication after consumption of such plants. Many plants on the other hand contain essential oils which can enhance the activity of these enzymes, and this also can have an impact on the effects of subsequent diet and drug treatment on the well-being of the animal. Metabolism of plant toxins by ruminal micro-organisms is central to the roles that compounds such as cyanogenic glycosides, nitrates, oxalates and isoflavones, for example, play in ruminant intoxication. The most notable advance in this area is the part that specific micro-organisms can play in the prevention of toxicity owing to the non-protein amino acid mimosine which is contained in Lencaena leucacepliafa. Protection against this intoxication (mainly hypothyroidism) is achieved by inoculation of the rumen with cultures of the organism. This leads to the possibility that genes coding for enzymes which can break down specific plant organic toxicants can be inserted into rumen microflora and lead to prevention of specific toxicities. Attempts at the prevention of higher plant intoxications by immunisation has not in general been successful. Such an approach is being explored with some optimism in relation to the prevention of lupinosis. With changing climatic conditions, pasture-derived intoxications of grazing animals occasionally appear which have never been recognised before in the particular pastures involved. Poisoning by tunicaminyluracil antibiotics derived from bacteria introduced into grass infloresences by nematodes is well known as "annual ryegrass toxicity". This kind of toxicity has lately been recognised in relation to other grasses and no effective prevention or control is so far available for it. Finally, an issue that will need lo be addressed in relation to the effect of ingestion of higher plant toxins on animal production and economics is the existence in meat and milk of toxic chemical residues derived from the plants.
