Effect of shearing on growth performance, water balance, thyroid activity and heat production of crossbred rams

M. A. Dollah

Abstract

The effect of shearing on the growth performance of F₁ DH and ISM crossbreds was studied on two groups of growing rams. The sheep were released or grazing in the open pasture during the day (0800-1500h ) and kept in the shade at night. In one of the groups, the rams were shorn after they had reached the age of 8 months. and then at 6 months intervals. Body weight and growth rate of shorn rams up to the age of 16 months were significantly higher (p <0.05) than unshorn rams with the respective value of 36.7 kg and 50.7 g/day; and 34.4 kg and 44.0 g/day. The water turnover rate of the shorn rams (108 mL/day/kg ^0.82) was higher (p <0.05) compared to the unshorn rams (87.1 mL/day/kg ^0.82).The shorn rams also had significantly higher (p <0.05) plasma triiodothyronine and thyroxine (0.80-1.08 ng/mL and 49.60-56.10 ng/mL respectively) compared to unshorn rams (0.62-0.82 and 39.8-42.00 ng/ml respectively). The mean values of heat production were similarly higher (p <0.05) in shorn rams (3.77-6.58 kcal/h/kg ^0.82) than the unshorn rams (3.38-5.38 kcal/h/kg ^0.82). The study concluded that shearing increased the growth performance of growing rams. The shearing had improved the heat and thyroid hormone balance which then improved the metabolic processes. It is therefore recommended that shearing should be practised as part of management system of F₁ crossbreds especially when they are managed under open grazing system.

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