Abstract:
Proc. Aust, Soc. Anim. Prod. Vol. 18 THE RELATIONSHIP BETWEEN THE PROPORTIONS OF ORTHO-, MESO- AND PARACORTEX AND THE FIBRE DIAMETER AND STAPLE STRENGTH OF MERINO WOOL K.A. HANSFORD*+ and J.P, KENNEDY* In non-Merino breeds, Bigham et al. (1983) proposed that the diminution of fibre diameter (FD) along the staple was related to increased tenderness while Orwin et al. (1980) reported relationships between the proportions of ortho-, The meso- and paracortex (OMP) and both wool strength and fibre diameter. present study examined these issues in Merino sheep. Groups of 6 or 7 Merino ewes housed for 12 months were treated as follows: Control, a constant plane of nutrition; Pregnant/Lactating, fed requirements estimated to maintain maternal live weight; Drought, decline in nutrition then wheat grain followed by maintenance then ad libitum levels of high quality roughage, and High/-w, similar to Drought but without change in feed type. Measurements on midside staples of each sheep were: strength and position of break (POB); FD at specific points along the staple (Hansford et al. 1985); and proportions of OMP (Orwin et al. 1984) on 100 fibres at the POB. Table 1 Treatment group means (+ 8-e-m.) for staple strength (SS), fibre diameter (FD) and the proportions of ortho-, meso-, and paracortex Treatment means for each character (columns) followed by a common superscript were not significantly different, P<O.O5 (1.8-d.) Table 2 Correlation coefficients (r) among staple strength (SS), fibre diameter (FD) and the proportions of ortho-, meso-, and paracortex As shown in Table 1 there were significant differences and FD, but not in the proportions of OMP. Since cortical components were not highly correlated with (Table 2) it was concluded that variation in these is to SS in Merino sheep. between treatments in SS the proportions of the SS or the FD at the POB not a major contributor Proc. Breed. Text. 37: 237. BIGHAM, M-L., SUMNER, R.M.W., HAWKER, H. and FITZGERALD, J.M. (1983). N.Z. Soc. Anim. Prod, 43: 73. HANSFORD, K-A., EMERY, G-B. and TEASDALE, DC. (1985). Wool Tech. Sheep 33: 25. ORWIN, D-G-F., WOODS, J.L. and ELLIOT, K.H. (1980). Proc. 6th Int. Wool Res. Conf. 2: 193. ORWIN, D.G.F., WOODS, J-L. and RANFORD, S-L. (1984). Aust. J. Biol. Sci. * Dept Wool and Animal Science, University of N-S, W,, Kensington, N.S.W, 2033. + Current address: CSIRO Division of Wool Technology, Ryde, N.S.W. 2112, 484