Effects of mimosine and 2,3-dihydroxypyridine on fiber shedding in Angora goats
P. J. Reis, R. Puchala, T. Sahlu, and A. L. GoetschJournal of Animal Science 77:1224-1229. 1999.
Leucaena (Leucaena leucocephala) is widely used as a forage for livestock in tropical and subtropical regions. However, seeds and leaves are high in mimosine, a toxic, nonprotein amino acid-like compound, which causes alopecia in various species and fiber shedding in sheep. Mimosine has been extensively studied in Merino sheep as a potential chemical defleecing agent. Though mimosine is rapidly removed from the body, intravenous infusion for 2 d at 80 to 100 mg/(kg body weight · d) has consistently caused fiber shedding 7 to 10 d after treatment commenced. This level of infusion yielded a plasma mimosine concentration of approximately 100 mol/L. Sheep can also be defleeced by single oral doses of 400 to 600 mg/kg body weight of mimosine, raising plasma mimosine concentration to greater than 100 mol/L 24 h after dosing. In the rumen, mimosine is converted to 3-hydroxy-4(1H)-pyridone (DHP), which is not depilatory in sheep. Some 3,4-DHP may be further converted to 2,3-DHP, and depilatory properties of 2,3-DHP have not been examined. Mimosine, or other defleecing agents such as epidermal growth factor, may be useful for removing fiber of Angora goats as well as of sheep. In this regard, in an experiment at the E (Kika) de la Garza Institute for Goat Research, five Angora goats were intravenously infused with mimosine for 2 d at 75 mg/(kg body weight · d), which is slightly less than the level commonly used for sheep. Fiber growth was unaffected in two goats, but there was partial or complete alopecia within 10 d in the other three goats. In another Institute study, mohair fiber growth was not affected and defleecing was not induced by 3-d perfusion of a local area of skin of Angora goats with mimosine at 20% of a whole animal defleecing dose for sheep. Objectives of the present study were to determine efficacy for removing fiber of Angora goats by 2-d intravenous infusion of different levels of mimosine or one level of 2,3-DHP. Effects of two levels of an oral dose of mimosine were also investigated. Based on results of this experiment, mimosine is a depilatory agent for Angora goats. Two-day infusion of Angora goats with levels of mimosine similar to those effective for defleecing in sheep were effective in removing Angora fiber. However, mimosine may not remove all Angora fibers, particularly primary fibers, when in a temporary resting phase. Oral mimosine administration at doses effective to defleece sheep may be less efficacious with Angora goats. Further research is required to fully characterize seasonality of follicle activity for Angora goats in the United States to most effectively use compounds such as mimosine to defleece, and to develop practical means of mimosine delivery, such as feeding of Leucaena leucocephala.
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