Abstract:
Animal Production in Australia Vol. I5 THE EFFECT OF PROTEIN AND ENERGY INTAKE ON CASHMERE AND BODY GROWTH OF AUSTRALIAN CASHMERE GOATS A.J. ASH* and B.W. NORTON* SUMMARY The dry matter intake, body growth and fleece growth of Australian cashmere goats, initially weighing 13.6kg, were measured over 10 weeks when pelleted diets of different protein content were offered either ad lib or 75% ad lib to males and females. Animals offered the high protein diet (20,5%CP) consumed significantly more (Pc.05) and grew significantly better (Pc.05) than goats offered the medium (l5.5%CP) or low (lO.5%CP) protein diets. Males grew better than females although their intakes were similar. Fleece (cashmere + hair) growth rate and cashmere fibre diameter (mean, 14.Opm) was not affected by the level of protein or energy offered in the diet. It was concluded that fleece growth was not a competitor with body growth for protein or energy at the levels offered in this experiment. INTRODUCTION The presence of cashmere in the fleece of Australian feral goats was first reported by Smith et al. (1973) and since that time considerable interest has developed in the potential of these goats for commercial cashmere production (Restall 1982). Improvement of cashmere production on a flock basis will be best achieved by selection of superior animals and most research to date on cashmere has been aimed at improvement through genetic gain. Cashmere is produced from secondary hair follicles in the skin and is characterised by a fibre diameter ranging from 11 to 25pm (mean diameter 16pm). Cashmere growth on goats differs from wool growth in sheep because growth is distinctlyseasonaland the fleece is shed annually. This suggests that for a short period of the year nutrition may be critical in determining growth rates. Howeverthere is no information presently available on the effects of nutrition on cashmere growth. Studies with Angora goats (Throckmorton et al. 1982) demonstrated that growth rates of mohair could be significantly increased with the addition of bypass protein to the diet indicating that protein nutrition was important for fibre growth. The following experiment was designed to study the effects of both protein and energy intake on the body and cashmere growth and follicle development of male and female goats in the postweaning period. MATERIALS AND *METHODS Animals and their management The experiment was conducted at the University of Queensland's research farm at Mt. Cotton in south-eastern Queensland. Thirty-six goats (18 males and 18 females) were randomly selected from a group of single birth kids at weaning and placed in metabolism cages for the 13 week experimental period. Goats were stratified according to live weight (initial mean live weight, 13.6kg) and randomly allocated to 12 treatment groups. All kids were initially treated for intestinal parasites (Rametin H., Bayer), coccidiosis (Sulphadimidine, Dimivec), and injected with vitamins A, D, and E. A three week adaptation period was allowed for the goats to acclimatize to the environment and the diets before entering the 10 week measurement period. Goats were weighed at fortnightly intervals during this 10 week period. * Department of Agriculture, University of Queensland, St.Lucia, Qld 4067. 247 Animal Production in Australia Vol. I5 Experimental design and treatments The experiment inclorporated a 3 x 2 x 2 factorial design comparing protein level (10.5%, 15.5% and 20.5% crude protein), energy level (ad lib (high) and 75% ad lib (low)) and sex type. Diets were offered in pelleted form and contained 30% barley straw, 1.4% CaC03, 0.1% chromic oxide, and varying proportions of cottonseed meal and grain sorghum to give the different protein levels. The 75% restriction level was based on ad lib intakes per unit of live weight with weekly corrections being made to accommodate changes in live weight. Fleece and skin sampling fter the three weiek adaptation period both left and right mid-side areas 3 (250cm ) were shorn and skin biopsies performed with a surgical trephine (lcm diameter) for measurement of follicle numbers and distribution. At the conclusion of the 10 week measureme~nt period, skin section were again taken and mid-side 3 patches were shorn over la measured area (~1OOcm > to provide a measure of fleece growth rate per unit arela of skin. Total fleece growth (cashmere + hair) during the experimental period was predicted using the relationship between live weight and skin area reported by Couchman and McGregor (1980). Fibre diameter was estimated from 100 fibre samples from each patch. Analytical and statistical methods Dry matter in feed offered and refused was determined by drying at 80�C in a forced draught oven. Secondary and primary follicle numbers and distribution were determined by counting prepared sections of skin samples collected (Winter and Restall, unpublished). The significance of differences between treatments for food intakes, body growth rates and fleece characteristics were determined by analysis of variance (Steel and Torrie 1960). Interactions between treatments were analysed but not reported in this paper, RESULTS Table 1 shows the main effects of protein level, energy level and sex type on feed intake and growth rate of the kids during the experimental period. There was a significant difference (Pc.05) between the high protein diet and the low and medium protein diets for both dry matter intake and growth rate. The difference between groups in energy intake was also significant, with the low energy group receiving 77% of that given to the high energy group. Growth rates of males and females were significantly different (Pc.05) although there was no difference in dry matter intake between the two groups. Table 1 Effect of protein level, energy level and sex type on dry matter intake and growth rate of cashmere bearing goats 248 Animal Production in Australia Vol. 15 Table .2 shows mean values for follicle numbers and distribution at the beginning and end of the experiment together with the main treatment effects on fleece growth rate and fibre diameter. Analysis of variance indicated that at the beginning of the experimental period there were no significant differences between groups of kids (Px.05) for secondary, primary and total follicle density or secondary/primary (S/P) follicle ratio. At the end of the experiment there were again no significant differences between treatments although there was a 30% decrease in follicle density. Secondary/primary follicle ratio remained relatively constant during the measurement period. There was a signifi ant difference (Pc.05) between males and females in 5 fleece growth rate (pg/mm /day) although when fleece growth rate was expressed as pg/follicle, the difference between males and females was not significant. Protein and energy intakes had no significant effect on either mean follicle density or fleece growth rate. Differences in fleece growth rate between left and right sides of the animals were not significant (Px.05). Mean cashmere fibre diameter was l@m (range 8-23pm) and there was no significant effect of protein, energy or sex on fibre diameter. Approximately 90% of the fibres counted were of cashmere type with the other 10% being coarse hairs derived from primary follicles. Table 2 Mean values and standard deviations for follicle densities, S/P follicle ratios, fleece (cashmere + hair) growth rates in cashmere bearing goats $= Values within a column with different subscripts differ significantly (Px.05) DISCUSSION Kids offered the high protein diets consumed significantly greater amounts and grew better than those offered the two lower protein diets with goats receiving the high protein diet requiring 8.7g of food per g of gain in body weight compared with 9.1 and 9.9g eaten/g gain for the medium and low protein diets. Comparable studies with sheep given pelleted diets (Weston 1971) show similar trends where the intake of high protein diets was significantly greater than that ' of lambs given low protein diets. However, lambs grew faster and utilized feed more efficiently than did the goats used in the present study requiring only 6.2, 4.7 and 4.3g food/g live weight gain for low, medium and high protein diets 249 Animal Production in Australia Vol. 15 respectively. Males grew significantly faster than females although their intakes were similar indicating a higher efficiency of feed utilization for growth by males. This difference in growth rate between males and females was greatest at the low protein level (48% difference) and least at the high protein level (11%). Louca and Hancock (1977) have also reported a difference in feed efficiency between young male and female goats (Damascus) with the difference also being greatest at low protein intakes. The results from the fleece growth studies suggested that there was little nutritional effect on fleece growth rate or cashmere fibre diameter. Total fleece growth over the 10 week experimental period was calculated to be approximately 70-100 grams (l-1.5g protein/day) and at this low rate of accretion of fleece protein, even the lowest protein intake would provide sufficient protein to meet all fleece growth requirements. When total fleece growth was related to live weight gain, there was no significant correlation lending further support to the concept that fleece growth was not an important competitor with body growth for energy or protein. However, Weston (1971) reported a significant increase in wool growth with increased protein intake suggesting that the nutritional demands of wool growth are greater than those of cashmere growth. Weston's study also showed an increase in fibre diameter with increased protein intake but this was not apparent in the present experiment. Mean cashmere fibre diameter of 14pm was somewhat finer than has been reported for other cashmere bearing goats (Shelton 1981) but this may be attributed to the young age of the goats. It may be concluded that increasing the protein and energy level of the diet significantly increased body growth rate but the nutritional demands of fleece growth were not great enough to record a response in growth rate at the protein and energy levels fed. ACKNOWLEDGEMENTS The authors wish to thank Mr. Doug Winter and MS Althea Lambert for the processing and counting of skin sections, the CSIRO for use of feed preparation facilities at Samford Research Station, and the Manager, Mr. Jim Hales, and staff of the MtXotton Research Farm for assistance during the experiment. REFERENCES COUCHMAN, R.C., and MCGREGOR, B.A. (1983). Anim. Prod. 36: 317. LOUCA, A.I and HANCOCK, J. (1977). J, Anim. Science 44:727. RESTALL, B.J. (1982). Proc. Aust. Soc. Anim. Prod. lr 130. SHELTON, M. (1981). In 'Goat Production', p-386, EdTor C. Gall. (Academic Press). SMITH, I.D., CLARKE, W.H., and TURNER, Helen Newton (1973). J. Aust. Inst. Agric. Sci. 39: 128. THROCKMORTON, J.C.,FFOULKES, D., LENG, R.A., and EVANS, J.V. (1982). Proc. Aust. Soc. Anim. Prod. 14: 661. WESTON, R.H. (1971). AGt. J. Agric. Res. E 307. 22: 250