Effect of the Shearing Date on Wool Growth on Native Pasture in Merino Sheep

Wool growth rate has been studied in 30 Merino Australian adult wethers divided into three groups according to shearing dates: September, October and November. Differences in fleece weight were observed between shearing dates with heavier weight in October and November (5.50; 5.60 Kg) respect to September (4.95 Kg). Marked seasonal rate in wool growth was observed, reached its maximum in summer and minimum in winter. Annual wool growth average was 11.8g day-1 for September and 13.1g day-1 for October-November (p<0.05). Annual variation of pasture production explains wool growth determining changes in body weight and its interaction with shearing date. The maximum percent clean wool yield was found in summer and minimum in winter. Staple length follows the same tendency as wool growth, whereas the diameter was independent and same in the three groups (20.18; 20.42 and 20.57 micron, September, October and November, respectively). Wool growth is affected by nutrition, photoperiod and temperature, wherever in our conditions the major factor is the quality and quantity of native pasture is very important to know wool growth rate as well as the best shearing moment in order to improve wool production.