Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 18 CASHMERE GROWTH IN AUSTRALIAN GOAT DOES IMMUNISED AGAINST MELATONIN S.R.D. SUTHERLAND*, HENNIAWATI*, B.J. RESTALL* and R.M. HOSKINSON** SUMMARY The growth of cashmere and guard hair was measured in Australian goat does which were either entire, ovariectomised, or ovariectomised and immunised Entire and ovariectomised does grew cashmere between against melatonin. December and June and shed it in September. Immunisation appeared to alter the pattern of cashmere growth such that immunised does grew cashmere in the spring In these does down was and early summer as well as the normal growing period. The data are consistent with continuous shed between January and March. Immunisation had no production of down through overlapping growth cycles. effect on the growth of guard hair. There was a decline in live weight between March and June each year, which may have been modified by immunisation in 1989. INTRODUCTION The annual cycle of cashmere growth in Australian Goats was described by Under natural light growth of cashmere began in late McDonald et al. (1987). Cashmere fibres were shed December and continued until June, July or August. from the coat after July and there was no further growth until the following December. Exposure to continuous light accelerated this cycle of cashmere growth, resulting in three cycles in two years. The circadian rhythm of melatonin secretion, believed to be responsible for translating photoperiod effects into a physiological response, is abolished in sheep by exposure to continuous light (Rollag and Niswender 1976). Immunisation against melatonin may also be expected to abolish the circadian rhythm of melatonin secretion, and thereby mimic the effect of exposure to continuous light. This paper reports the effect of immunisation against melatonin on the growth of cashmere in Australian Goats, MATERIALS ANDMETHODS The observations on cashmere growth were made incidentally during the course of an experiment designed to study various aspects of reproduction. The offspring of domesticated feral goats, whose origin, experimental environment and management have been described by Restall and Pattie (1989) were used. Fifteen 2 year old does (1985 drop) were randomly selected from 209 females and randomly assigned to three treatment groups. The groups were 1) entire, 2) ovariectomised, and 3) ovariectomised and immunised against melatonin. The antigen used in the immunised group was a melatonin-HSA conjugate made up in Freund's complete adjuvant, and was injected intramuscularly on the 29th The anti-melatonin titres of the third May I 29th June and 29th July, 1987. group were measured in April 1988, by a method similar to that of Abraham (1974) and were in the range of 1:91,000 to 1:500,000. These animals could be described as 'highly immune' to melatonin. The does were grazed on available pasture and fed supplements of oat grain and lucerne or pasture hay at times of declining pasture quality. The does were shorn regularly in July of each year except 1989 and the production parameters for the three treatment groups in July 1987 are given in Table 1. Fleece -differences were apparent shortly after immunisation and it was decided to The Goat Research and Development Centre, N.S.W. Agriculture and Fisheries, North Coast Agricultural Institute, Wollongbar, N.S.W. 2480. ** CSIRO, Division of Animal Production, Prospect, N.S.W. 214% 380 * Proc. Aust. Soc, Anim. Prod- Vol. 18 measure the fleece lengths and liveweight at weekly intervals commencing in November 1987.. The fibre lengths were measured to the nearest centimetre, using a short ruler held next to the skin at the neck, shoulder and rump. The average of the three site measurements was calculated for each animal. Only fibres apparently attached to the skin were measured, but the presence of shed fibres in the fleece was recorded. The last monthly length measures and live weight for each goat were subjected to analyses of variance using the appropriate error term variances for repeated measures. Table 1 Production parameters of experimental does at two years of age There was an annual cycle of cashmere growth in the entire and ovariectomised does and as there was no significant difference between these two groups their data were pooled (Fig. 1). Most of these does had no cashmere visible in November and December and growth of cashmere began between December and January, continuing in a linear fashion until June in both years, Between August and October 1988 (after shearing) there was a short length of cashmere visible which had fallen out by November. Between August and October 1989 381 Proc- Aust. Soc. Anim. Prod. Vol. 18 there was a rapid decline in the average length of cashmere. Signif icant differences in cashmere length between the immunised does and others were evident during the period November 1987 until February 1988 Thereafter cashmere lengths were similar in all groups (P<O.OOl, Fig. 1). Cashmere on the immunised does significantly increased until September 1988. in length over that observed in the other groups between August 1988 and All groups then showed similar length changes until February 1989 (P<O.OOl). September 1989 when decreases in cashmere length were observed. Shedding commenced in the immunised does between December and March and in 1989 this appeared to coincide with an apparent plateau in down growth (Fig. 1). In contrast shedding commenced in the non-immunised does between June and October 1989; the commencement of shedding was not observed in these does in 1988 as they were shorn in July. against There was no significant effect of ovariectomy or immunisation melatonin on the growth of guard hair (Fig. 2). Because of shearing in 1988 it was difficult to identify any annual cycle in the length of guard hair, but in both years the length was maximum in June and July, and in 1989 the average length began to decrease in September. Overall live weights were significantly lower (P~0.05) in the period March to June of each year (Fig, 2) and in 1989 the decline in live weight was less in the immunised.does than in the other groups (P=O.ll). Fig. 2. The mean live weight and the mean length of guard hair (2 s.e.m.), between November 1987 and October 1989, in entire or ovariectomised does (0, n=lO) and ovariectomised does immunised against melatonin (0, n=5). The does were shorn in July 1988. DISCUSSION The annual cycle of growth and shedding of cashmere in the non-immunised does was similar to that under natural light described by McDonald et al--( 1987). Immunisation against melatonin caused growth of cashmere at a time when no length changes were observed in the other groups, resulting in a continuous production of cashmere in the immunised animals. The commencement of shedding in these does in February each year may indicate that this continuous 382 Proc. Aust. Soc. Anim. Prod. Vol. 18 production results from overlapping fibre growth cycles. The average length of cashmere decreased in the immunised does after August 1989. This may be the end of the altered growth pattern of cashmere under the influence of perceived continuous light. McDonald et al. (1987) found the effect of continuous light to be lost after two years. The pattern of shedding in the normal does indicated synchrony in the activity of the secondary skin follicles producing the cashmere. The growth of cashmere In contrast, in the immunised does, was complete before the fleece was shed. length of cashmere was achieved. shedding began before the maimum The activation of follicles in these does may have been random or there may have been groups of follicles producing cashmere in overlapping cycles. All does showed a depression in live weight between April and July in both years. Walkden-Brown et al. (1990) demonstrated a depression in live weight in male goats at this time due to a depressed feed intake. Ash (1986) also observed a seasonal depression of growth rate in young goats due to a depressed feed intake which was modified by exposure to continuous light. The immunised does also showed the liveweight depression in 1988, but in 1989 it was not as marked as in the other groups. This may indicate modification of a photoperiod effect on voluntary feed intake by immunisation against melatonin. It is unclear whether the altered growth pattern induced by immunisation against melatonin would significantly affect annual production of cashmere. While the maximum length of cashmere fibre was no greater in the immunised animals than in the normal animals, it is possible that more cashmere may be harvested from them if they were to be shorn more frequently. This would avoid wastage of the cashmere which may otherwise be lost through shedding. ACKNOWLEDGEMENTS We gratefully acknowledge Mr Bruce Lewis for fleece measuring, Mr Bill Taylor for technical assistance, Mr Blair Harrison for measurement of anti-melatonin titres, and Messrs. Graeme Allen, Keith Frederiksen, Doug Wallace, Ken Watson and Barry Outerbridge for management of the animals and experimental assistance. This research was supported by a grant from the Rural Credits Development Fund and S. Sutherland was in receipt of a Charles and Annie Neumann Postdoctoral Fellowship from the University of Western Australia. REFERENCES ABRAHAM, G-E. (1974). Acta Endocr. (Copenh.) Suppl. 183: 1. ASH, A.J. (1986). Ph.D. Thesis, University of Queensland. MCDONALD, B.J., HOEY, W.A. and HOPKINS, P.S. (1987). Aust. J. Agric. Res. 38: 597. RESTALL, B-J. and PATTIE, W.A. (1989). Livest. Prod. Sci. 21: 157. ROLLAG, M.D. and NISWENDER, G.D. (1976). Endocr. 98:482WALKDEN-BROWN, S.W., NORTON, B.W. and RESTALL B.J. (1990). Proc. Aust. Soc. Anim. Prod. 18:564. 383