Abstract:
Proc. Amt. Sot. Anim. Prod. 1994 Vol. 20 SEASONAL FLEECE PRODUCTION IN TUKIDALE SHEEP M. ESLAMI and G.E. ROBARDS Dept of Wool and Animal Science, University of New South Wales, PO Box 1, Kensington, N.S.W. 2033 Seasonal fluctuations in wool growth by Merino sheep are mainly attributed to variations in quality and/or quantity of feed (Ryder and Stephenson 1968). However, Sumner (1983) has shown that in New 0 Zealand coarse wool producin, Cheviots and Romneys, and carpet wool producing Drysdales, grow more and coarser wool in summer than winter. There are strong indications that this difference is due to a natural seasonal rhythm rather than primarily to nutrition. The study reported here was established to compare the seasonal productivity of Merinos, and carpet wool producing Tukidales, grazing at 3 grazing pressures at Wellington in central-western New South Wales between 21 April 1992 and 20 May 1993. A group of 51 Tukidale and 30 Merino wethers aged 12 months were randomly allocated to 6 paddocks in 2 blocks : 1 of 3, 0.5 ha paddocks and 1 of 3, 1.0 ha paddocks. Grazing pressures of low (L), medium (M) and high (H) were each applied to 1 small and 1 large paddock by allocating Tukidales:Merinos as L = 2:4 and 8:4; M = 5:4 and 12:6; and H = 8:4 and 16%. Results (Table 1) are means for the 3 grazing pressures. Within breeds, the individual grazing groups 0 followed the expected pattern of those at higher stockin, intensity having lower wool growths and liveweights. However, the differences between breeds, particularly for wool growth rate, were nearly alwavs ereater than the differences between grazing pressures within breeds. Table 1. Wool growth (mg/cm2.day) and liveweight (kg) of Tukidales (T) and Merinos (M) at Wellington* Tukidales grew increasingly more wool/unit area than Merinos as the year proceeded (Table 1). Tukidales maintained a peak throughout spring and summer, whereas the wool growth of Merinos peaked in spring and then declined as pasture quality declined in late spring and through summer. During autumn 1993 pasture was restricted, but of good quality, and although liveweights may have declined a few kilograms the decline would not account for the large decrease in wool growth of Tukidales in autumn. Indications from this study are that Tukidales grazing at Wellington, NSW, have a marked seasonal rhythm of wool production with a peak in summer and trough in winter. The short peak of wool growth by Merinos in late spring indicates strongly that while Tukidale wool growth in spring may have a nutritional component, high growth during summer is more likely to be a photoperiodic effect. RYDER, M-L. and STEPHENSON, SK (1968). 'Wool Growth', (Academic Press: London). SUMNER, R.M.W. (1983). Proc. N.Z. Sot. Anim. Prod. 43: 79-82. 450