Offered Papers Theme A: Efficient Production from Grassland
Description
Improved pastures based on the leguminous shrub Leucaena leucocephala (leucaena) are the most productive, profitable and sustainable for beef cattle production in northern Australia. Leucaena forage contains the toxic, non-protein amino acid mimosine, which is rapidly converted to 3-hydroxy-4(1H)-pyridone (DHP) upon ingestion by grazing cattle. This is a potent goitrogen and appetite suppressant. Animals suffering severe DHP toxicity exhibit distinctive symptoms (e.g. hair loss, excessive salivation, goitre and weight loss), while subclinical DHP toxicity can suppress live weight gain by 30-50% without producing any obvious symptoms. Prior to the discovery and introduction of the DHP-degrading rumen bacteria Synergistes jonesii into Australia in 1982, DHP toxicity severely limited animal performance from leucaena pastures and was a major impediment to adoption. Initial rumen inoculation of cattle in Australia with S. jonesii successfully protected them against DHP toxicity and the bacterium appeared to be easily and rapidly transmitted between grazing animals. Consequently many scientists and graziers believed that a single inoculation of a herd with S. jonesii, combined with simple ongoing herd management, was sufficient to overcome the problem of DHP toxicity. However, during the 2003 drought there were several reports of severe leucaena toxicity (including animal deaths) in cattle grazing leucaena in Queensland. Toxicity was evident even in herds that had followed recommended control measures. Preliminary results are presented of a study, designed to ascertain the prevalence and possible causes of leucaena toxicity in Queensland cattle herds. Meat and Livestock Australia Limited funded this research (NBP.340).
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Toxicity in Beef Cattle Grazing Leucaena leucocephala in Queensland, Australia
Improved pastures based on the leguminous shrub Leucaena leucocephala (leucaena) are the most productive, profitable and sustainable for beef cattle production in northern Australia. Leucaena forage contains the toxic, non-protein amino acid mimosine, which is rapidly converted to 3-hydroxy-4(1H)-pyridone (DHP) upon ingestion by grazing cattle. This is a potent goitrogen and appetite suppressant. Animals suffering severe DHP toxicity exhibit distinctive symptoms (e.g. hair loss, excessive salivation, goitre and weight loss), while subclinical DHP toxicity can suppress live weight gain by 30-50% without producing any obvious symptoms. Prior to the discovery and introduction of the DHP-degrading rumen bacteria Synergistes jonesii into Australia in 1982, DHP toxicity severely limited animal performance from leucaena pastures and was a major impediment to adoption. Initial rumen inoculation of cattle in Australia with S. jonesii successfully protected them against DHP toxicity and the bacterium appeared to be easily and rapidly transmitted between grazing animals. Consequently many scientists and graziers believed that a single inoculation of a herd with S. jonesii, combined with simple ongoing herd management, was sufficient to overcome the problem of DHP toxicity. However, during the 2003 drought there were several reports of severe leucaena toxicity (including animal deaths) in cattle grazing leucaena in Queensland. Toxicity was evident even in herds that had followed recommended control measures. Preliminary results are presented of a study, designed to ascertain the prevalence and possible causes of leucaena toxicity in Queensland cattle herds. Meat and Livestock Australia Limited funded this research (NBP.340).
