Correlation between lambing performance and incidence of cystic endometrium in ewes.

Abstract

CORRELATION BETWEEN LAMBING PERFORMANCE AND INCIDENCE OF CYSTIC ENDOMETRIUM IN EWES H. LLOYD DAVIES* and M. NAIRN I. INTRODUCTION A high incidence of cystic glandular hyperplasia of the endometrium of ewes grazing on subterranean clover (Trifolium subterraneum, L.) (variety Dwalganup) was first shown to be associated with infertility by Bennetts, Underwood and Shier (1946), but there is little published information relating incidence of cystic endometrium to reproductive performance of sheep. II. EXPERIMENTA L The ewes in this study were some of those included in the experiment described by Davies (1962); they were medium woolled Merinos from the Experiment Station' flock, three to five years old in 1959, and had successfully reared s a lamb in 1959. In September 1959 they were placed on the experimental plots also described by Davies (1962). Previously, they had grazed on pastures containing some subterranean clover. The ewes grazed on the plots continuously for three years until October 1962. The botanical composition of the plots varied from mainly grass to mainly capeweed (Cryptostemma calendula) and geranium (Erodium botrys); there was never more than 35% of subterranean clover. Sixty-six of the ewes from the experiment were culled for age in October 1962 and slaughtered. Their uteri were examined macroscopically and the severity of visible cystic endometrium was rated as shown in Table 1. TABLE 1 . 'C.S.I.R.O., Division of Plant Industry, W.A. Regional Laboratory, Nedlands. I- Western Australian Department of Agriculture, South Perth. 62 Some uteri of each class were examined microscopically to check the classification procedure. There was agreement between macroscopic and microscopic methods. The association between cystic endometrium score and the number of years (1960, ` 1 or ` 6 62) in which the ewes failed to produce a lamb is shown in Table 1. Using the rank correlation method (Kendall 1955), there was a significant (P<O.O02) association between increasing score and decreasing fertility. The damage rarely extended past the superficial layers of the endometrium and there was little fibrous and cellular reaction. These observations suggest that the hypertrophy may have been of short duration and reversible. The significant association between increasing cystic endometrium and reduced fertility suggests that this condition could interfere with fertilization of the ovum or with implantation of the embryo. III. ACKNOWLEDGMENTS Mr. D. Roberts assisted with the recovery of reproductive tracts and in macroscopic scoring. Thanks are due to the officers of the Division of Mathematical Statistics (Perth) for advice. IV. REFERENCES B ENNETTS H. W., U NDERWOOD , E. J., and S HIER , F. L. (1946). A specific problem of sheep on subterranean clover pastures in Western Australia. The Australian Journal oj Veterinary , .DAVIES, K H. L LOYD (1962). Studies on time of lambing in relation to stocking rate in SouthWestern Australia. Proceedings Australian Society of Animal Production 4: 113. ENDALL , M. G. (1955). 'Rank Correlation Methods.' 2nd Edition. (Griffin: London.) Science 22: 2. 63