Abstract:
Animal Production in Australia 1998 Vol. 22 EFFICIENCY OF CONVERSION OF PASTURE TO WOOL IN MERINO STRAINS M.A. FRIENDA, G.E. ROBARDSB and J.P. KENNEDYB A B School of Agriculture, Charles Sturt University, Wagga Wagga, NSW 2678 Dept of Wool and Animal Science, University of New South Wales, Sydney, NSW 2052 The efficiency with which sheep convert feed into wool is a major determinant of the profitability of a wool growing enterprise. Both Weston (1959) and Dunlop et al. (1966) have compared the efficiency of wool growth from different strains of Merinos, and observed significant differences in efficiency between strains. The aim of this study was to determine the efficiency with which fine, medium and strong wool sheep converted pasture to wool. Five of each of fine, medium and strong wool two year old Merino wethers were randomly allocated to high, low or control grazing regimes. These grazing regimes were described in detail by Friend et al. (1995). Pasture intake was measured in both summer and winter, using slow release alkanes (Dove and Mayes 1991). Alkane dosing occurred on 14 February and 23 June 1994, and subsequent daily faeces samples were collected between 21 to 24 February and 30 June to 3 July 1994 respectively. Wool growth was measured on midside patches between January 27 to April 26 1994, and April 27 to July 26 1996, for the summer and winter intake estimates respectively. Efficiency of wool growth was calculated as the weight of clean wool produced per day per kilogram of organic matter intake (OMI). Results were analysed using the GLM procedure of SAS (SAS Institute 1985). Problems were encountered in obtaining representative herbage samples, hence intake data for each strain and grazing regime should be interpreted with caution (Friend et al. 1995). However, assuming strain differences in species selectivity are negligible, we believe relative efficiency comparisons between strains are valid (Table 1). Table 1. Mean liveweight and mean efficiency of wool growth (� s.e.) of Merino strains across grazing regimes and seasons Fine wool Liveweight (kg) Clean wool, g/day, per kg OMI a,b,c. Medium wool 50.8 11.2 b b Strong wool 52.1 10.0 b c 42.7 � 0.80 a 6. 9 � 0.38 a � 0.75 � 0.34 � 0.77 � 0.35 Means in the same row with different superscripts are significantly different (P<0.05) The results support Dunlop et al. (1966), who observed both strong and medium wool sheep converted feed to wool more efficiently than fine wool sheep. The results also support the work of Weston (1959), who observed strong wool sheep converted feed to wool more efficiently than fine wool sheep. However, the results are at variance with Dunlop et al. (1966), who observed no difference between medium and strong wool sheep in the efficiency of wool growth. Such conflicting results may be due to differences in experimental design and/or the sheep used. In this study, fine and strong wool wethers were from commercial flocks, while the medium wool wethers were the progeny of sire evaluation rams. DOVE, H. and MAYES, R.W. (1991). Aust. J. Agric.Res. 42, 913-52. DUNLOP, A.A., DOLLING, C.H.S. and CARPENTER, M.T. (1966). Aust. J. Agric. Res. 17, 81-9. FRIEND, M.A., ROBARDS, G.E., LINDSAY, A.R. and CHAMPION, S.C. (1995). Proc. NZ Soc. Anim. Prod. 55, 127-29. SAS INSTITUTE (1985). SAS Users Guide. (SAS Institute Inc.: North Carolina). WESTON, R.H. (1959). Aust. J. Agric. Res. 10, 865-85. 306