Infertility disease in sheep grazing on Subterranean Clover assumed some importance in the Wagga district during the years 1955 and 1956; reaching its peak of incidence at this time, due probably mainly to eminently suitable weather conditions for the growth of clover, but influenced, possibly, by other factors not so obvious.
It is proposed to illustrate the effects of the condition in the area by presenting a selection of field case history reports which appear to incorporate the main characteristics of the "disease".
Owner "H.Y." Yerong Creek, Wagga Wagga.
This owner first consulted the writer about his problem in June, 1955. In a Dorset Horn Stud of 260 ewes he had tagged 106 lambs after six weeks of lambing with 30 ewes yet to lamb. His final lambing percentage figure was 45% and this was supplemented by a further 10% of lambs in the spring. He had found in previous years that leaving the rams with the ewes to produce a spring drop was his only means of obtaining a reasonable percentage. Obviously, however, there was room for much improvement in his overall percentage; hence the consultation.
The ewes were aged from two to seven years and the loss of lambs was due to their miscarrying stillborn lambs two to four months advanced in pregnancy, and the failure to survive of small, weakly but live lambs. Dystocias accounted for only two lamb deaths and prolapses were rare. Lactation in wethers had not been seen. Lambing had commenced in mid-April under wet conditions.
In order to eliminate possible bacterial causes specimens were submitted to Glenfield Veterinary Research Station from a premature lamb but no organisms resembling Vibrio, Listeria or Brucella ovis were recovered.
Two per cent of rams had been used from November to April and the conception rate was satisfactory. The ewes were fat, carying nine months wool and had plenty of milk. The sheep had been run in an old cultivation paddock which had been sown down to Dwalganup-Mount Barker sub-clover and Wimmera Rye grass in 1951. Very little rye grass was discernible in this paddock in June, 1955; the clover being almost completely dominant. Clover growth on this property in 1955 was phenomenal and the best since the property was first sown in 1942; this being attributable to the late spring (November) rains in 1954 and the early autumn (February) rains of 1955. Clover growth had continued unrestrained throughout the spring summer and autumn and, apart from a few oats, supplementation of the feeding had not been considered necessary
The better soil type on the property was a red loam, top-dressed annually with 90 lbs. of superphosphate to the acre, on which the subject ewes were run, and paddocks of loam with granite. Only about 20% of the area of these latter paddocks was sown to clover-rye grass and they were stocked with 400 two-to-four years old comeback ewes, in lamb to Merino rams, and in only store condition. The lambing percentage with these ewes was 85%. which was considered by the owner to be satisfactory.
In 1956, 200 of the same Dorset Horn ewes, plus 20 two-tooth ewes, were mated with a satisfactory conception rate using similar methods of husbandry. Of the first twenty lambs born in the season twelve were born dead and eight alive, though one of the eight expired within a few hours of birth of the twelve born dead, six were obviously premature. However, despite this desperate start, the lambing improved as it progressed, and the 300 ewes produced 240 lambs in the autumn (80%) and a further 25 lambs in the spring: an overall 88% lambing percentage. The clover growth that year was not as spectacular as in 1955 and more skeleton weed and rough feed was available; although the ewes appeared to be in a similar physical condition. Acting upon the advice given in 1955, more hay and oats were fed. Dystocias and prolapses were uncommon.
The lambing season of 1957 appeared to progress favourably; with a similar conception rate, and with about 3% loss of lambs to the date of this report. Due to the drier summer, more dry feed was available and supplementary feeding was increased.
This owner is convinced that some hand feeding, even "in the midst of plenty" (of clover), is necessary in the interests of his lambing percentages.
Owner "J.T.," Brucedale, via Wagga Wagga.
This owner purchased 600 Corriedale ewes, aged 4-5 years, with the property in 1956. These sheep had been born on the property of about 900 acres, and run all their lives on pasture highly improved with Dwalganup, Bacchus Marsh and Mount Barker strains of sub-clover.
The ewes had been mated before they were purchased but the conception rate was so poor (about 20%) that the owner disgustedly sold them; retaining only 50 of their number which were obviously in lamb. The ewes were overfat at the time of mating but the property had a prior history of low lambing percentages; averaging about 50%.
Eight on the 50 ewes abovementioned failed to lamb naturally due to weak and ineffective labour, which, transient in its action, allowed the neck of the uterus to close; thus imprisoning the foetus which putrefied.
Prolapse also had been extremely common with these 600 ewes: occurring at all times of the year in both pregnant and non-pregnant animals.
Owner "G.M.," Illabo, via Wagga Wagga.
During 1957 the above reported the occurrence of abortions and still born lambs in a flock of 350 Merino two-tooth ewes on his property; situated in the central northern sector of the District; in a "dry" area which is not improved, nor capable of being improved, to the extent of the property mentioned in report number 1.
The subject ewes were in good store condition and at lambing time were grazing a stubble and grass-clover paddock where the feed was not abundant. One month before lambing was due to commence they were drenched with Phenothiazine and shifted from dry Dwalganup clover paddock to the area above-mentioned. This group of sheep had had excellent mixed clover and ryegrass pastures the previous year, which will be remembered as being a "bumper" year for clover all over the Wagga district.
Lambing was much earlier in this instance; being due to commence on 23rd March of the first 25 lambs to appear, 20 were aborted or still-born and only five were alive.
A comprehensive range of specimens was obtained from a still-born lamb; including the brain, foetal membranes and cotyledons, smears of uterine cotyledons, foetal stomach contents and spleen and the usual pipettes from cerebrum, spleen, heart blood, kidney and lung, but no significant bacteria were recovered at Glenfield and only scavenger polymorphs were present in the placenta.
In addition, a serum sample obtained from the ewe was negative to eight Leptospiral serotypes.
Dystocia, prolapse or lactation of wethers had not been observed previously on this property. The lambing improved as it progressed, but the final lambing numbers were down 10-20% on previous years.
Owner "P.P.," Coolamon Rd., via Wagga Wagga.
This property is of 700 acres, now all sown to Dwalganup strain of sub. clover; first laid down in 1950.
In 1955 it was partially stocked with 370 Corriedale one-year-old ewes; obtained from the Gundagai district the year previously as mixed-sex lambs. Two hundred lambs were produced from these 370 ewes at their maiden Lambing: the issue being small and miserable, and the final lambing percentage being 52. Premature births and prolapse were not uncommon.
The ewes had been fed 20 bales of clover hay per week during the month before lambing; approximately one half-pound per day per sheep.
Lactation was in evidence in the wether portion of these hoggets during the year.
The owner obtained a lambing of 50% from these same ewes one year later, in 1956, and then adopted the usual method of treatment of this disease; that of cashing them and purchasing replacement sheep.
It appears that he secured no bargain, because from 600 maiden Merino-Corriedale cross ewes, mated with Border Leicester rams in November, 1956, he had obtained 152 lambs as at the end of May, 1957; even though the ewes commenced to lamb, or rather mis-carry, in mid-March.