Abstract:
THE USE OF CRYOGENIC, IRRITANT, FIXATIVE AND PROTEIN DENATURIZING AGENTS FOR MULESING SHEEP M.S. PRATT* and P.S. HOPKINS* Summa t-y This study investigated the possibility of permanently defleecing those discreet areas of sheep which are predelection sites for blowfly strike. The use of cryogenic, irritant, fixative and protein denaturizing agents was studied. Painting the areas with 15-30 ml of 40% phenol or a mixture of 20% phenol and 50% orthocresol were the most successful treatments tested. A thick non-purulent encrustation of wool and cutaneous tissue formed within 10 days of treatment. This subsequently fell off leaving a bare area of healthy skin on the breech or belly regions of lambs and weaners 4-6 weeks after treatment. The low incidence (8%) of wool regrowth on the belly of male lambs and weaners suggests that this method may be of value in controlling blowfly strike in these animals. A higher incidence `of wool regrowth (26%) on the breech region would be a limitation to its use in female sheep. I. INTRODUCTION Husbandry measures aimed at preventing blowfly strike constitute a large proportion of the annual expenditure of Austral ian sheep producers. The removal of wool from those areas of the sheep which are predelection sites for blowfly strike is a generally accepted control method. This involves shearing of the breech (crutching) or belly (ringing) regions,. or the surgica.1 removal of skin folds from the breech (mulesing). A modified mules operation which involved the application of a caustic material was once used as an alternative to the conventional mu1esin.g p rocedu re. The main disadvantage of this method was the time taken for the subsequent healing of treated areas to occur.' This paper describes several variations of a simple technique using cryogenic, irritant, fixative and protein denaturizing agents to permanently defleece discreet areas of wool at the predelection sites of blowfly larvae strike without causing severe trauma. The techniques were adopted at the time of either lamb marking or weaning to enhance the practical feasibility of the procedure. The ultimate production objectives of the work were aimed at improving the efficiency of blowfly control and thereby increasing sheep and wool production in i ts broad context. II. . MATERIALS AND METHODS The materials used in these experiments were either cryogenic, irritant/fixative or protein denaturizing age'nts. All ,of the treatments were initially tested on clipped areas of the midside region of adult wethers. The more promising were then applied to the breech.or pizzle regions-of l-3 month old unshorn la.mbs. Treatment effects were recorded at weekly intervals. The- treatments used and the methods of administration are listed in tabular form in the results. J; Queensland Department of Primary Industries, 'Toorak' Research Station, Jul ia Creek, Queensland. 4823. \ 189 Ill. RESULTS (a) Cryogenic agents Table 1 shows that although these agents produced a fleece break, the subsequent wool regrowth after treatment rendered these methods unsat i sfactory . (b) Irritant and fixative agents These treatments almost invariably produced a break in the fleece (Table 2). The main ,disadvantage of using these chemicals,stemmed from the problems of administration, the often suppurative nature of autolysed cutaneous tissue and the unpredictable growth patterns of treated areas. TABLE 2 Numerous other agents including calcium and sodium hydroxide, sulphuric and boric acid, hydrogen peroxide, Bouin's and ammonia solutions were also tried unsuccessfully. Different concentrations of these were used with vehicle solutions (dimethyl sulphoxide) and surface active agents (tri ton). 190 Various combinations of treatments (a) and (b) were also tested. The most promising of these sprayed liquid propane and formaldehyde. (38%). A venturi system drew the fixative into the stream of liquid immediately before skin contact. A pressurized system of this nature (3,307 kPa) enhanced penetration. The resultant fleece break frequently left a discreet bare area around the breech and pizzle of lambs. In other instances this bare area was less discreet and diffuse areas of regrowth became apparent . When this occurred the wool from these regions (particularly the belly wool) grew at a slower rate than the remainder of the fleece and had a lower than normal crimp frequency. The unpredictable nature of the response was the main disadvantage of this method. (c) Protein denaturizing agents The results outlined in Table 3 indicate that these agents were the most successful used in this study. TABLE 3 The effects of protein denaturizing agents on wool growth Transverse sections of skin excised 5 weeks after treatment showed an almost complete rupture of all membranes in the epidermis and superficial layers of the dermis. Removal of the non-purulent encrustation exposed a completely denuded area of healthy skin. Suppression of subsequent regrowth was usually associated with a scaly appearance of this skin. The toxicity of these agents when painted on to young male sheep is shown' in Table 4. 191 TABLE 4 IV. DISCUSSION . These experiments have examined numerous attempts to ,permanently def leece discreet regions of sheep. The most encouraging results were obtained by painting the protein denaturizing agents phenol and/or its alkyl derivative ortho-cresol on to treated areas. These compounds rapidly penetrate the skin and act as protoplasmic poisons. The progressive denaturation of protein and paralysis of nerve endings produced an almost painless necrotizing effect. The potent bactericidal effect of these compounds prevented infection. It was possible to . produce the desirable defleecing by treating lambs at the time of marking or weaning (l-3 months) though the long term effects await evaluation. The trea'tment of wethers (pizzle) was more successful than the treatment of ewes (breech) since the wool follicles of the belly were apparently more susceptible to these chemicals. The disadvantages of using phenol or cresol for 'chemically mulesing' lambs arise from their toxic and irritant properties. Special precautions would need to be taken to prevent' injury to human operators.' Toxicity in lambs can result from excess absorption through the intact skin. The long term effects of this treatment on- meat contamination warrant consideration, though localized contamination would represent only a very minor portion of the carcase. The possibil ity of 'chemically mulesing' rams and wethers at lamb marking or weaning for an expenditure of l'ess than O.Q/head highlights the possible economical and practical advantages of this method as.a measure of blowfly control. The use of this type of technique to embrace the successful treatment of young ewes warrants further investigation. 192