Studies in the wool production of grazing sheep. 3. Changes in efficiency of production

Abstract

Data from an experiment described by Arnold, McManus and Bush (1964) were used to examine the efficiency of wool production of sheep grazing at different stocking rates. Large differences were found between seasons and between stocking rates in the gross efficiency of wool production (GE), in estimated maintenance requirements (MR), and in an activity index (a). The seasonal pattern for GE, MR, and a was for highest GE and lowest MR and a to occur in late spring. MR and a rose in summer, declined in autumn, and rose in winter following shearing. The maximum value of MR was nearly twice the minimum value. With increased stocking rate the mean annual GE decreased and MR and a increased. The maximum effect recorded was a 34 per cent decrease in GE and a 50 per cent increase in MR for the year. The relations between GE and MR was curvilinear. Possible causes of changes in MR are discussed and the paucity of evidence on stress mechanisms in grazing sheep is pointed out. The use of production data for evaluating pastures is discussed in the light of these results.