Effect of nutrition, body condition and liveweight change on efficacy of biological wool harvesting with epidermal growth factor (Bioclip)

Abstract

This study investigated the effect of nutrition on wool harvesting efficiency of a biological wool harvesting system (Bioclip) utilising epidermal growth factor (EGF) to induce shedding of the fleece. The experiment had nine groups, each representing a different growth path based on a 3 by 3 design with three levels of nutrition (low, medium and high) fed during two periods, specifically the pre-injection period (4-weeks leading up to EGF injection) and post-injection period (4 weeks between EGF injection and wool harvesting). Sheep weight and body condition score were measured at the start and end of each period. Wool harvesting efficiency, fleece weight and body wrinkle were assessed at wool harvesting. Continuous data were analysed using general linear models and linear regression. Bivariate categorical data were analysed using Chi-squared tests and odds ratios. Wool harvesting efficiency was reduced in sheep with greater skin wrinkle (P < 0.001), poorer body condition (P < 0.001) and poorer nutrition in both pre- and post-injection periods (P < 0.001). Sheep that gained 1 kg bodyweight or 0.5 body condition score either pre- or post-injection had improved wool harvestability (P < 0.05). Sheep that lost weight post-injection were 10.2 (95% confidence interval 4.0, 25.5) times and 4 times (2.4, 6.7) more likely to have very poor harvestability compared with sheep that gained or maintained weight respectively (P < 0.001). Sheep with greater body wrinkle were 6.6 (4.1, 10.7) times more likely to have very poor harvestability than plain-bodied sheep (P < 0.001). Nutrition that ensures modest weight gain during the pre- and post-injection periods can partially overcome poorer harvestability in wrinkly sheep.