The effects of shearing on the heat production and activity of sheep receiving dried grass or ground hay

Abstract

SUMMARY: 1. Oxygen consumption was measured in two experiments using castrated Romney male sheep both shorn and unshorn. The sheep were fed either ground hay or dried grass. An ambient temperature of 13°C ± 1°C was maintained at all times. In Experiment 1, oxygen consumption was measured with eight sheep using a respiration chamber and in Experiment 2, oxygen consumption was measured with four sheep using a ventilated hood. The times spent standing, lying, eating and ruminating were measured in Experiment 2. Heat production was calculated from the measured values for oxygen consumption.2. Heat production increased following shearing in both experiments. In Experiment 1, heat production of the sheep receiving dried grass was significantly greater (P<0·05) on days 1, 8 and 16 following shearing, compared with pre-shearing values. For sheep receiving ground hay, heat production was greater on day 1 (P<0·05) and day 8 (P<0·01) following shearing, compared with pre-shearing values. The mean maximum increase in heat production following shearing was 2·3 MJ/24 hr (25% increase) for sheep receiving dried grass and 1·2 MJ (17%) for those receiving ground hay.3. The patterns of change in heat production following shearing in Experiment 2 were similar to those observed in Experiment 1 although the maximum increases were smaller: 21% for the sheep receiving dried grass and 13% for those receiving ground hay.4. The time spent standing increased considerably after shearing and this change in behaviour made a large contribution to the increase in energy expenditure after the sheep were shorn.