A comparison of the productivity of Corriedale and Polwarth sheep.

Abstract

A COMPARISON OF THE PRODUCTIVITY OF CORRIEDALE AND POLWARTH SHEEP B. J. McGUIRK* and E. C. SCARLETT Summary Flocks of Corriedale and Polwarth sheep have been compared for two years at Temora, New South Wales. Corriedale produced significantly more clean wool when shorn at 18 months of age but the wool had fewer crimps per centimetre. There were significantly more lactating ewes, multiple births, and fewer lamb deaths in the Corriedale flock while Corriedale lambs had higher growth rates and weaning weights than Polwarth lambs. I. INTRODUCTION Corriedales and Polwarths are regarded as dual-purpose sheep suited to mixed farming areas. This paper presents some early results of an experiment comparing the productivity of these two breeds. II. MATERIALS AND METHODS Flocks of Corriedale and Polwarth sheep were compared in 1963 and 1964 at Temora Agricultural Research Station, New South Wales. Polwarth ewes were obtained from a stud nominated by the Polwarth Sheepbreeders ' Association, while three studs supplied the Corriedale ewes. Until 1962 there were 220 ewes in each flock. This was reduced to 100 ewes in 1963 when three additional breeds were added to the experiment. Rams have been purchased from a number of studs. The Corriedale and Polwarth flocks did not become fully comparable until 1963 when they were similar in age structure and all of the ewes in the trial had been bred and reared together. At 13 years of age ewes are culled for major faults and sufficient replacements are randomly chosen to maintain flock size. The ewes are joined with five rams for five weeks following shearing in February. After four joinings all ewes are cast for age. Each year, standard fleece measurements on 12 months' wool are made when the 13 year old ewes are shorn. The greasy fleece weights and reproductive performance of all ewes are recorded together with the birth weights and weaning weights of their lambs. Weaning weights were corrected for age by interpolation to the average age each year (98 days in 1963 and 91 days in 1964). The percentages of wet ewes, multiple births and lambs lost were transformed to angles and then examined by analysis of variance. \.*` l Fleece measurements of the 13 year old ewes were classified according to breed, year and age of dam. The lamb weights were arranged in the sa me * New South Wales Department of Agriculture, Agricultural Research Station, Trangie. 'r New South Wales Department of Agriculture, Agricultural Research Station, Temora. 210 TABLE 1 The ~001 production of 11% year old Corriedale and Polwarth ewes way except that sex of lamb was included as another treatment. The greasy fleece weights of the mature ewes were classified according to breed, year and age of ewe. The data for these production characters were examined by analysis of variance of unweighted sub-class means. III. RESULTS The two breeds differed significantly in all hogget fleece masurements (Table 1) . The Corriedales had higher clean fleece weights and their wool had longer staples but fewer crimps per centimetre. Fleece weights and reproductive performance of ewes, and weights aad growth rates of Corriedale and Polwarth lambs TABLE 2 There were significant differences in favour of the Corriedales for greasy fleece weight, and percentages of lactating ewes and multiple births. Corriedale lambs had significantly higher birth weights, growth rates and weaning rates, and fewer deaths to weaning (Table 2). IV. DISCUSSION The base sheep for this comparison came from representative studs and were typical of good quality animals of their respective breeds. In addition, the ewes compared were grown together, as were their progeny. For these reasons this seems a realistic comparison of the two breeds and probably reflects their relative productivity when run under these conditions. Two-thirds of the Corriedales' 61% advantage in weight of lamb weaned was due to their higher reproductive performance. The remaining one-third was due to the higher individual weaning weights of the Corriedale lambs. Despite their higher reproductive performance, mature Corriedale ewes produced 13 % more greasy wool and their lambs were heavier at weaning. Thus, even allowing for the possibility that the differences in reproductive performance were due to chance, the Corriedales had a higher productivity per head. Gross economic returns per ewe from wool and lamb favoured the Corriedales by 22%. This was due entirely to the greater return from lamb for this breed, as return from wool did not differ in either year. This economic advantage could be reduced by the greater feed requirements of the Corriedales (P. A. McInnes, personal communication). V. ACKNOWLEDGMENTS Thanks are due to the Manager and staff of Temora Agricultural Research Station.