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This article was published in 1947
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A Note on Infertility and other Phenomena in Merino Sheep Grazing on Pastures consisting mainly of Subterranean Clover

T. R. JONES, B.V.Sc., Inspector of Stock, Forbes.

In September, 1946, advice was received that a grazier was concerned with low lambing percentages and other phenomena in his merino flock. In the normal course of events the property was visited and the following information elicited.

The property concerned comprises some 1700 acres and is worked mainly as a merino stud. About 3500 sheep are carried normally, of which about 700 are merino stud ewes. Merino wethers, in addition to rams, make up the balance of the flock. The wethers are purchased occasionally and are run as wool cutters. The property lies in a fertile valley and the flats are rich. The slopes are regarded as good farming and grazing country. Rainfall normally would be about 24 inches per annum. In 1934 the owner commenced improving the pastures by sowing at the rate of 3lb. mid-season with ½lb. early subterranean clover, with 1lb. Wimmera rye. Superphosphate at the rate of about 90 lbs. was applied and this manuring was repeated about every three years. During the war years superphosphate was not obtainable. In some paddocks the clover has taken charge and there is little other pasture. In others the clover may make up 60% per cent. of the pasture. At inspection there were about 1000 acres of pasture, consisting mainly of clover, and about 300-400 acres of pasture showing about 60 per cent. clover. The rest of the land was farmed, with the exception of about 30 acres which was down to lucerne. The flock, with the exception of stud and show sheep which were mainly hand fed, was depastured chiefly on clover, and although some rotation was practised there was little variation in the diet.

Rams are joined about 1st October each year. During the past four or five years there has been a drop in lambing percentages from about 80 per cent. to about 30 per cent. The rams have worked well, indicating that the ewes have been in season. Rams sold to other properties have worked well and with satisfactory results. In order to improve the position the owner tried Autumn mating and he considers that the results were far better than those from early summer mating. The sheep which previously were referred to as being mainly hand fed bred normally. An inspection of the flock revealed that the sheep were in excellent condition and were carrying attractive fleeces. The pasture was dry and present in sufficient quantity. There was abundance of clover seed but little else.

Samples of sheep were caught and examined closely, when the following abnormalities were noted:—A number of ewe hoggets showed dark-stained breeches although they had been crutched about two months previously. There was not any offensive odour associated with these sheep and the discharge was tacky to the touch. Many showed precocious udder development and these udders contained appreciable quantities of fluid resembling milk or colostrum. Some had four or five teats, but only two were functioning. In some the vestibule contained a core or plug of friable, cheesy material which when removed left a raw bleeding surface.

A number of wether hoggets were caught and it was noticed that about 50 per cent. were affected with balanitis. This condition was not associated with any offensive odour. The prepuce frequently contained a core of material similar to that seen in the ewes. Rectal examination revealed that approximately 20 per cent. of the wethers showed enlargement of the bulbo-urethral glands. Maximum development would be to about the size of a pea. Udder development was seen in a fair percentage of cases and some of these had appreciable quantities of what appeared to be normal milk. Udder development was not noted in older wethers, but balanitis and some enlargement of the bulbo-urethral glands was seen.

The property was revisited towards the end of February, 1947, when larger samples of sheep were examined. It should be mentioned that there was little rain between the two examinations. Many of the sheep had been away on grass, although a number had remained on the property throughout the interval. A storm a week or so before the second visit had shot much of the clover but there had not been sufficient time for much growth.

Examination of the sheep showed a marked improvement. The ewes showed absence of breech staining and there were not any vestibular cores. In many of the younger sheep the vulva was scarred and leathery. This condition was associated often with misplacement and stricture. The constriction in some cases was continued to the vagina and it would seem that the ram would find penetration difficult, if not impossible. This unusual feature is emphasised lest the mechanical aspect of infertility is overlooked. Mammary development was normal and in odd cases only was it possible to extract small amounts of fluid from the teats. A similar improvement was noted amongst the wethers. The teats had returned to normal, and except in very few cases the mammary gland had disappeared, so far as could be determined by palpation. Balanitis, so prominent a feature on the previous visit, practically was absent, except for a few cases in which there was a small ulcer on the preputial opening. There was evidence of scar formation and stenosis in the region of the preputial opening in perhaps 40 per cent. of those examined. Except in a few cases in which the glands were very small, the bulbo-urethral glands could be palpated only by those gifted with a strong sense of imagination.

This case suggests that the changes mentioned above may be due to the absorption of an oestrogenic substance which is present in appreciable amounts in the green clover which forms so large a part of the pastures on this property. The rams were not affected, but they did not have access to these pastures to any great extent.

In Western Australia there is a similar problem, but the changes there are reported by Bennetts to be associated with dystokia and uterine inversion. These troubles were not noted in the case here recorded.

Reference: Bennetts, H.W., Journal of Agriculture. W.A., Vol. XXI No. 11.


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