The potential of calcium thioglycollate and fibre protectants for use in chemical shearing

Abstract

The wool-severing properties of 2-8% aqueous solution of calcium thioglycollate were increased by 76% by dissolving the depilatory agent in a KCl-NaOH buffer of pH 12-5. The optimum Ca-thioglycollate concentration for defleecing was 3-6%. One ml of this solution defleeced an area of 12-1 cm a .A comparison of five buffers and water as solvents for 3-6% Ca-thioglycollate indicated that the area of skin defleeced was directly related to solution pH and the stubble remaining appeared to be inversely related to solution pH. A KCl-NaOH buffer of pH 12-0 provided the optimum relationship between area defleeced (10-2 cm 2 / ml applied) and stubble (ca. 2 mm wool) remaining.Single site applications of 0-1-1-0 ml of defleecing agent at skin level were compared and it was shown that the application of 0-1 ml aliquots would require 320 ml solution to defleece an average-sized sheep.Preliminary evaluation of 6 % formaldehyde buffered to pH 6 and a carbowax-citric acid solution of pH 2 showed that protection of fibres against dissolution by Cathioglycollate solutions can be sustained for 21 days. Pre-treatment with these compounds could therefore produce a protected band of wool immediately above the proposed site of wool dissolution.The practical implications of these findings are discussed with regard to a wool harvesting programme. reviewed work demonstrating that 4-6 % formaldehyde solutions in the pH range of 3-7 produce new An aqueous solution of 4-5 % Ca-thioglycollate cross-links in wool which provide stability to concontaining 0-3 % surfactant was shown to be an traction in bisulphite and greatly reduce the alkali effective defleecing agent when applied externally solubility of wool. This effect offered a potential to the skin of Merino sheep (McDonald et al. 1980). method of protecting wool fibres from the woolIt was also demonstrated that the addition of 1 % dissolving properties of Oa-thioglycollate solutions. KOH to solutions of 2-8% Ca-thioglycollate in-This potential could be exploited if previous treatcreased the area defleeced by 94-3%. However, this ment with formaldehyde produced a protected resulted in the loss of wool cover remaining band of wool immediately above the proposed site (stubble) on the sheep following wool harvesting of wool dissolution. The use of a non-volatile thereby predisposing the animal to climatic stress, organic acid to neutralize Ca-thioglycollate also One aspect of this research programme investigated offers a method of wool protection if long-term methods of increasing the defleecing effectiveness adherence to fibres can be achieved. Both treatof solutions of Ca-thioglycpllate with an emphasis ments were evaluated in this study, on maintaining the wool cover on sheep following fleece removal thus providing some protection MATERIALS AND METHODS against effects of climate.As wool removal without fleece damage is a preChemicals requisite of chemical defleecing, a preliminary AR grade reagents and distilled water were investigation of methods of fibre protection was used in the prepa...