Abstract:
Animal Production in Australia Vol. 15 GROWTH AND CASHMERE PRODUCTION BY GOATS IN RELATION TO DIETARY PROTEIN SUPPLY T.J. JOHNSON* and J.B. ROWE* SUMMARY A trial was conducted to investigate the potential of the progeny of feral goats x selected, cashmere producing, bucks to utilize high levels of supplementary protein in order to increase cashmere yield. A basal diet (approx. 10 per cent crude protein (CP) and 12 MJ metabolisable energy (ME)) was fed on its own or supplemented in the following ways: urea (1.5 per cent), fishmeal (5, 10 and 15 per cent) or lupin seed (30 per cent). There were responses in growth rates and total fibre production with increasing levels of protein supplementation. However there was no increase in the amount of cashmere fibre produced in response to increased protein availability. It was concluded that cashmere production is probably strongly controlled by genotype or otherwise limited by a nutritional factor other than the amino acids provided by the protein supplements. INTRODUCTION Interest in the commercial production of cashmere fibre in Australia has increased in recent years as a result of high prices and a recognition of the gene pool for cashmere production in the feral goat population in this country. At present there are large numbers of first generation progeny from the mating of feral dams with bucks selected for their cashmere production. The feral goats have been confined to the arid pastoral area of central Australia and to the rugged mountainous terrain in the higher rainfall districts. The selected first generation progeny are currently being run under better grazing conditions, as an alternative to keeping sheep, however their true production potential under optimal conditions is not known. The production of cashmere down is seasonal. The fibre grows between February and July in the agricultural areas of Western Australia and begins to shed in August. Since there is a relatively short growing season and a high value of the fibre there appears to be potential for protein supplementation to increase cashmere production, based on the results of Throckmorton et al. (1982) for Angora goats. The objectives of the study reported here were to examine the ability of a group of first generation selected progeny to respond to improved protein nutrition in terms of cashmere production and liveweight gain. MATERIALS AND METHODS The animals used were selected from 117 wether weaners which were the progeny of unselected Western Australian feral does, and a group of five commercial cashmere bucks (Kinross Cashmere Company, Adelong, N.S.W.). Eighteen groups of six weaners were formed on the basis of similar liveweight. Within each group animals were assigned randomly to one of six dietary treatments described in Table 1. The eighteen animals assigned to each treatment group were randomly allocated to one of three pens (6 goats per pen). * Department of Agriculture, Jarrah Road, South Perth, W.A. 400 Animal Production in Australia Vol. I5 Table 1. . Composition of diets fed ad libitum to weaner goats All diets were pelleted and were designed to contain similar concentrations of metabolisable energy (ME). Apart from the basal diet, urea and inorganic sulphur were added to all diets where additional non-protein-N and S were potentially required for optimal microbial protein synthesis. Lupin seed was included in diet six to investigate the use of a commercial protein source in the event of a significant response to protein supplementation being established. It was included at a level which provided a similar quantity of protein to the highest level of fishmeal studied. Feed was available at all times and feed intake was measured on a per pen basis. Samples of feed were taken during the trial for analysis of dry matter and nitrogen content (Kjeldahl). Fibre production was estimated by two techniques. A midside patch (8 cm x 8 cm) was clipped from each animal one week before the start of the trial. Subsequent clippings were at six-weekly intervals. At the end of the trial each animal was totally shorn and measurements made of total fleece weight and cashmere content. Cashmere fibres were separated from the guard hair using a Shirley analyser (Australian Wool Testing Authority). The trial was conducted over a 126 day period between March and July and animals were weighed at fortnightly intervals. Rate of liveweight gain was estimated from the regression coefficient (liveweight vs time) for each animal individually. Statistical analysis was by analysis of variance. The pre-treatment patch weight was included as a covariate in the analysis of mid-side fibre production. RESULTS The results of measurements made of feed intake, liveweight gain, feed conversion efficiency and fibre production are summarized in Table 2. There were no significant differences as a result of dietary treatment on the level of feed intake or on the feed conversion efficiency. Liveweight gain was higher in all animals fed diets containing supplementary protein than in those receiving the basal diet. The animals given diets containing fishmeal grew 34 to 40 per cent faster than those receiving the control diet (10 per cent crude protein). 401 Animal Production in Australia Vol. 15 Table 2.. Feed intake, liveweight gain, feed conversion efficiency and fibre production measured in first cross cashmere goats fed diets containing different levels of protein + kg feed intake/kg liveweight gain a b c values in the same row with different superscripts are significantly (P < 0.05) different Estimates made by clipping the mid side patch indicated significant increases in response to the inclusion of fishmeal in the diet at either 10 or 15 per cent. The amount of fibre produced declined progressively during each successive six-week period between February and July. This rate of decline was apparently slower in the animals receiving higher levels of dietary protein. There was no significant effect of dietary treatment during the four-month trial on the total fleece weight (nine months growth), or on the cashmere content of the total fleece. 402 Animal Production in Australia Vol. 15 DISCUSSION The two sources of supplementary protein used in this trial, fishmeal and lupin seed, were estimated by Hume (1974) to be approximately 65 and 30 per cent degraded in the rumen respectively. When the additional dietary protein available to the animal is estimated, taking these measurements of rumen degradability into account, both mid-side fibre production and fleece weight appear to be related to the availability of protein. These responses would be expected from the relationship between protein intake and wool growth (see Hogan and Weston 1967) or mohair production (Throckmorton et al. 1982). It is surprising that cashmere production does not appear to be dependent on the supply of protein. The failure to respond to improved protein status suggests that the production of cashmere may possibly be controlled by genotype with little environmental influence. Alternatively a nutritional factor other than the amino acids supplied by these protein sources may be primarily responsible for limiting production. It appears that the protein requirement for liveweight gain in these young goats, growing from 14 to 30 kg, is approximately 15% (on a dry matter basis). It is also clear that there is a requirement for dietary protein supplementation over and above that provided by rumen micro-organisms when the diet contains adequate non-protein-nitrogen and S. The liveweight gain of lambs over a similar physiological stage (weaning to marketable weight) given a diet of approximately 12 MJ ME/kg DM would be expected to be over 200 g/d (Rowe et al, 1982) approximately twice that measured for goats in this study. ACKNOWLEDGEMENTS The skilled technical assistance of Mr P. Burgess is gratefully acknowledged. This work was partially funded by Kinross Cashmere Co. of Australia. REFERENCES HOGAN, J.P. and WESTON, R.H. (1967). Aust. J. Agric. Res. &8-:973. HUME, I.D. (1974). Aust. J. Agric. Res. 2:155. ROWE, J.B., OWEN, B., POTTS, H.C. and BROOME, A.W.J. (1982). Aust. 7:207. -s Proc. Nutr. Soc. Proc. THROCKMORTON, J-C., FFOULKES, D., LENG, R.A. and EVANS, J.V. (1982). Aust. Soc. Anim. Prod. 14:661. 403