The effect of breeding strategy on liveweight and fibre production in mature Cashmere and Angora does.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 19 THE EFFECT OF BREEDING STRATEGY ON LIVEWEIGHT AND FIBRE PRODUCTION IN MATURE CASHMERE AND ANGORA DOES J. A. ROBERTSONAB, A. J. RITARA, P. D. BALLA and G. EVANS B *Tasmanian Dept of Primary Industry, P.O. Box 180, Kings Meadows Tas. 7250. BDept of Animal Science, University of Sydney, N.S.W. 2006. SUMMARY Mature cashmere and Angora does were mated annually early (February) or late (May) in the breeding season or at 8-monthly intervals commencing in May 1989. Pregnancy and lactation affected liveweight and fibre production in both breeds. Weight loss during lactation could be minimised by kidding at times of high pasture availability in the spring. Fibre production decreased when the last 2 months of pregnancy and the first month of lactation coincided with the fibre growth cycle. Keywords: breeding strategy, cashmere, Angora, fibre, liveweight. INTRODUCTION The productivity of a cashmere or Angora enterprise may be affected by the time of year of mating and reproductive rate (Ritar 1990). Improvement in the annual reproductive rate of goats may be achieved by reducing the interval between kiddings, but the physiological cost of any breeding strategy affects liveweight and fibre growth (Norton 1991). This study examined the effects of mating once per year in February (EM) or May (LM) or mating every 8 months (EW) on these production parameters in cashmere and Angora does. MATERIALS AND METHODS The study was carried out over a period of 3 years. Mixed-age cashmere (n=121) and Angora (n=89) does were randomly allocated to 3 breeding strategies (Table 1) on the basis of stratified liveweight in February 1989 before natural mating, and were artificially inseminated in 1990 and 199 1. Liveweights were recorded at kidding and weaning. Table 1. Breeding strategy, time of mating and duration of suckling In the week prior to the annual shearing of the cashmeres on 6 July 1989, 8 August 1990 and 20 August 199 1, secondary fibres (down) and guard hair lengths were measured on the neck, midside and hip of each goat (Pattie et al. 1984). Midside samples of fibre were collected and fleeces were weighed at shearing. Samples were tested by the Australian Wool Testing Authority (AWTA) for down yield. Down production was estimated by the regression equations of Winter et al. (1985) and McDonald (1988) but were not suited to our AWA results. Therefore, we developed a regression equation based on a subset of 26 midside samples randomly selected on stratified fleeceweights for each group at shearing in August 1990, excluding those shedding. The regression was intended to provide an index of fibre production with which to compare animals from 1 breeding strategy to another within this trial. Where secondary fibres easily pulled out at measuring, animals were deemed to be shedding and down weights were not calculated due to inaccurate estimated yield caused by the loss of some of the secondary fibre. Regression analysis of data from 26 cashmere midside samples showed that down production (D) in grams can be estimated from the average secondary fibres (down) (C) and guard hair (G) lengths (mm) and fleeceweight (FWT) by the following equation: Angoras were shorn each year in February and July-August (as for cashmeres) and fleeces were weighed. The effect of breeding strategy on mohair weights was examined within each shearing and 269 Proc. Aust. Sot. Anim. Prod. Vol. 19 included lactational status if animals within breeding strategy were at their peak of lactation during the previous 6 months. Liveweight and fleece data were analysed by analysis of variance. RESULTS The liveweight change between kidding and weaning was affected by breeding strategy (P<O.OOl), but there were no significant breed differences. Therefore data for cashmeres and Angoras were pooled and are presented in Table 2. There were interactions between breeding strategy and lactational status (P<O.OOl), between breeding strategy and year (P<O.Ol) and between lactational status and year (PcO.05). Within each group, the dry animals lost less weight or gained more weight than lactating does during the period up to weaning although the difference between breeding strategies and between lactational states varied over the 3 years. Table 2. Effect of breeding strategy and lactational status on liveweight difference (kg) (mean + s.e.) between kidding and weaning, 1989-91 Number of does are in parentheses Table 3. Effect of breeding strategy and lactational status on estimated mean (& s.e.) down weights (g), 1989-91 Number of cashmere does shorn and shedding in parentheses Estimated down production was affected by breeding strategy (P < 0.001) and lactational status of animals (P < 0.01, Table 3). Dry does mostly produced more down than lactating does. For lactating does, the down production of the EM females was similar over the 3 years. In 1991, 39% of lactating does shed fibre, and 21% of dry does also shed fibre. The estimated down production of LM females was similar in 1989 and 1990 but was significantly higher in 1991 (P < 0.05). No LM does were recorded as shedding during the trial. For lactating EW does (kidding October), fibre production was similar to the EM and LM does in 1989 (kidding October). However, production decreased markedly 270 Proc. Aust. Sot. Anim. Prod. Vol. 19 for all EW does in 1990 (kidding June), and shedding occurred in 55% of lactating does and 50% of the dry does. Fibre production in 1991 (kidded February) increased again but was less for lactating than dry does. Table 4. Effect of breeding strategy and lactational status weights (g) (mean2s.e.) 5 shearings times Number of Angora does shorn in parentheses Data for mohair weights are presented in Table 4. For the July 1989 shearing, no does were lactating and mohair weights were similar between breeding strategies. Similarly, for the February 1990 shearing, mohair weights were comparable between breeding strategies, but were lower for lactating than for dry does (PcO.001). No does were at the peak of lactation before the August 1990 shearing and mohair weights were similar for the 3 breeding strategies. Some animals in all breeding strategies were at peak lactation before February 199 1. There was an interaction between breeding strategy and lactational status (P<O.Ol) at this shearing. Dry does in the EM and EW groups produced similar or higher mohair weights than the lactating does, but the LM dry does produced less mohair than the lactating does. The EW does were the only group to reach peak lactation by the August 1991 shearing and there was no difference in mohair weight between dry and lactating females. However, the EW and LM does produced more mohair at this shearing than the EM does. DISCUSSION Kidding and lactation influenced liveweight and fibre production in lactating cashmere and Angora does but the magnitude of the effect depended on breeding strategy and the time of year of kidding and lactation. Most pasture growth in Tasmania occurs between September and December and there is little pasture growth during the winter months due to low soil temperature (J. Carpenter unpublished data). For the EM group kidding in August when pasture growth was just recommencing, lactating does consistently lost weight, whereas dry does maintained or gained weight. For does which kidded in October (LM each year and EW 1989), when availability of vegetative pasture is high, liveweight increased or only slightly declined for both lactating and dry animals. EW does kidding in June and February lost weight regardless of lactational status due to the unavailability of pasture. Time of year of kidding influences the production of down in cashmeres. The growth of cashmere down occurs between December and June (McDonald 1987). Kloren (1991) demonstrated that where the fibre growth cycle coincided with the last 2 months of pregnancy and the first month of lactation, down growth was inhibited. Our study showed that when does were pregnant and lactating during the fibre growth cycle (e.g. the EW in April-June 1990), down production was significantly reduced. Shedding in pregnant does at this time may have been due to the early cessation of the down growth cycle as a result of reproductive stress. EW does were mated out-of-season in October 1990 but few became pregnant. Therefore, since pregnancy and lactation (December-February 199 1) coincided with the fibre growth cycle in 1991, total production of this group was not decreased, although production of the pregnant does was only 67% that of the dry does. The fibre production of the LM does was never compromised due to late pregnancy and lactation (August-October) being out of phase with the fibre growth cycle. 271 Proc. Aust. Sot. Anim. Prod. Vol. 19 Angoras exhibit a fibre growth cycle which peaks in the spring (September to November) and is reduced to a minimum (but does not cease) in the winter (June-August) (Stapleton 1975). We found that mohair weights mostly followed this fibre growth cycle with heavier fleeceweights at the February than at the August shearings. However, where the peaks in the fibre growth cycle coincided with late pregnancy and early lactation, mohair production in lactating does was decreased (e.g. EW and LM in Feb 1990 and LM in Feb 1991) which appears to be due to the marked effect of pregnancy and lactational stress as suggested by McDonald (1987). ACKNOWLEDGMENTS We gratefully acknowledge the farm staff at Cressy Research Station for the management of the animals and experimental assistance. This research was supported by the Rural Industries Research and Development Corporation. REFERENCES IUOREN, W. R. L. (1991). Ph.D. Thesis, Univ. Qld cited by Norton B.W. (1991) in Cashmere Research Seminar Proceedings, N.S.W Agriculture and Fisheries. pp. 9-25. MCDONALD, B. J. (1987). SCA Information Series QI 89012 Qld. DPI. Chapter 6,9 pp. M CDONALD, B. J. (1988). Aust. J. Exp. Agric. 28: 37-9. NORTON, B. W. (1991). Cashmere Research Seminar Proceedings, N.S.W. Agriculture and Fisheries. pp. 9-25. PATTIE, W. A., RESTALL, B. J. and SMITH, G. A. (1984). Proc. Aust. Sot. Anim. Prod. 15: 525-8. RITAR, A. J. (1990). Proc. Aust. Assoc. Anim. Breed. Gen. 8: 545-6. STAPLETON, D. L. (1975). Angora Breeding and Mohair Production Seminar, Western Victoria Angora Club. WINTER, J. D., RESTALL, B. J. and DE' ATH, G. (1985). Proc. 1st International Cashmere Seminar, A.N.U., Canberra pp. 225-8. 272