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Field Investigation of Chemical Defleecing of Sheep^{1, 2,}

Oregon State University, Corvallis, 97331³

Abstract

One-hundred-twenty-one yearling or mature ewes of three breeds and three crossbred groups were administered cyclo-phosphamide and defleeced. Three dose levels were employed. No overt reactions to the chemical between dosing and defleecing were noted. The lowest dose tested (6.8 mg/lb of body weight) (15 mg/kg of body weight) was not satisfactory for the population and management conditions under investigation. While doses of 9.0 and 11.4 mg/lb (20 and 25 mg/kg) did allow defleecing in most ewes, several did not respond sufficiently to be defleeced without retreatment. For both levels, there was a wide range in number of days from dosing to defleecing. Higher level ewes could be defleeced sooner than lower level ewes (15 vs. 25 days and 12 vs. 22 days for two trials in which the two levels were compared). Breed groups did not influence days from dosing to defleecing but did influence days from dosing to .24 in. (0.6 cm) wool regrowth (P<.05). Dose level did not influence rate of regrowth. There was a high frequency of black wool in initial regrowth from Hampshires, Suffolks, and Hampshire x Suffolks. Wide variability in ease of fleece removal between parts of the fleece within sheep was noted. Ewes defleeced within 18 days of dosing were quite bare and unprotected from the elements but did not suffer from this stress under the conditions of the experiment. Constraints to commercial application of chemical defleecing are discussed.

¹ Technical paper No. 3228, Oregon Agricultural Experiment Station.

² Cyclophosphamide was furnished by Dr. H. Leo Dickison, Bristol Laboratories, Syracuse, New York. Mr. Lloyd Westcott, Oregon State University staff, and Mr. Dan Lowrie, Oregon State University student, were instrumental in observation and data collection. Mr. Chris Kirby, Oregon State University student, prepared the photomicrographs.

³ Department of Animal Science.