Biomedical subjects
Publications and source records attributed to J W Plant.
A total of 1823 ewes in three flocks was examined for pregnancy using a rectal-abdominal palpation technique. A correct diagnosis was made in 97 per cent of ewes with no evidence of ewe mortality or abortion. Ewes can be examined at the rate of 120 or more per hour. It is concluded that the technique is a simple, safe and reliable method of pregnancy diagnosis in sheep from 70 days of gestation.
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Injection of 0.25 ml of a solution of 3.6% formaldehyde in 90% ethanol direct into the caudae epididymides caused sterility in the rams treated. No live sperm were seen in ejaculates collected 35, 57, 91 and 196 days post-injection. The rams retained their libido and were mated to ewes between 2 and 3 months post-injection with no pregnancy ensuing. The technique offers a simple, safe, quick and effective method of sterilising rams. Attempts to produce sterilisation by injection of the sclerosing agent into the vas deferens were not successful.
An investigation into causes of low lamb marking percentages was made on a property in north-west New South Wales from 1971 to 1975. Investigations revealed that from 11 to 70% of the ewes in lamb were losing all their lambs. Observations suggested that feral pig predation was a factor in the perinatal loss. In 1975, 2 groups of ewes were placed in adjoining paddocks prior to lambing. Feral pigs were excluded from one paddock for most of lambing by means of an electric fence. In this paddock, 117% of lambs were marked compared with 80% in the adjoining paddock. It was estimated that in 1975 over 600 lambs were killed by feral pigs from 1,422 ewes lambing in paddocks with feral pigs. The problems involved in the diagnosis of feral pig predation are discussed.
The transmission of mucosal disease virus (MDV) from infected ewes and their lambs to susceptible sheep was investigated. MDV was recovered from the amniotic fluid of an infected pregnant ewe and from the blood, nasal swabs and urine of hairy lambs. MDV infection was transmitted either at lambing, from infective foetal fluids or lambs, or later as a result of contact with a surviving with a hairy lamb and either aborted or gave birth to an infected hairy lamb. Adult sheep and 12-months-old sheep were less readily infected than were newborn lambs. Pregnant ewes were infected by contact with a hairy lamb and either aborted or gave birth to an infected hairy lamb. A method to minimise spread of the infection in the field is suggested.
An experiment was designed to investigate whether a condition in Australian sheep with clinical and pathological similarites to Border Disease was caused by the infection of the pregnant ewe with a Mucosal Disease virus (MDV). Forty ewes, at 58 to 63 days after mating, were inoculated with material from lambs in which all, some or none of the tissues examined contained MDV. The clinical condition was observed only in lambs born to ewes inoculated with MDV-positive material and then only to ewes in the group which had serological evidence of MDV infection. It is concluded that the Border Disease-like condition in Australian sheep is caused by the infection of the pregnant ewe with a Mucosal Disease virus.
Observations on 2 bulls from a brucella-infected property are reported. Bull 1 gave serological reactions to Br. abortus in both the SAT and CFT from day 0 to day 141. Br. abortus was not recovered from semen and the bull remained clinically normal. The serological status of bull 2 changed from negative to positive to negative over a 203 day period and remained negative for a further 74 days. Semen agglutinins were only detected on one occasion (20 iu). The first clinical sign observed was epididymitis followed by orchitis, which became apparent on day 122. Br. abortus was not recovered from semen but at autopsy, on day 363, Br. abortus biotype 1 was isolated from the right seminal vesicle and ampulla. The histology of the lesion is described. The literature relating to Br. abortus infection in the bull is discussed. Recommendations are made regarding the diagnosis of Br. abortus infection in bulls.
A condition resembling border disease has been transmitted by the inoculation of pregnant ewes with material from affected lambs. Forty-nine merino ewes, mated to merino rams 7 to 87 days previously, were inoculated with an homogenate of brain, spinal cord and spleen from affected lambs. Mummified foetuses, abortions and stillbirths were observed, and lambs with hairy birth coats were born to ewes inoculated between days 12 to 70 of gestation. A mucosal disease virus (MDV), present in the original material, was recovered from the aborted foetuses and lambs. Attempts to induce passive protection using bovine anti-serum to the C24V strain of MDV were not successful. The condition was also transmitted by inoculation of pregnant ewes with a cell culture supernatant prepared from tissue cultures that had been inoculated with an organ homogenate pool. MDV was present in the supernatant and was recovered from aborted foetuses and lambs. It is suggested that a condition in sheep in Australia resembling border disease is due to the infection of the pregnant ewe by a mucosal disease virus.
A condition in Australian sheep resembling border disease was transmitted by the inoculation of pregnant ewes with material from affected lambs. This material contained mucosal disease virus (MDV). Twenty-two lambs comprising 6 from uninoculated control ewes, together with 11 with hairy coats and 5 with normal coats from inoculated ewes, were observed from 7 to 182 days after birth. Nine of the lambs from inoculated ewes died during the experiment from a variety of causes. Glial cell abnormalities were observed in control and affected lambs, but only 4 of the 11 hairy lambs were judged to have abnormal glial cells. There were no consistent histopathological findings indicative of MDV infection. MDV was recovered from tissues of all 11 hairy lambs, but not from any of the lambs with normal coats. The hairy lambs appeared to be immunologically tolerant to the virus. Susceptible sheep in contact with the hairy lambs were infected with MDV. It is suggested that a condition in Australian lambs characterised by hairiness of the birth coat and poor viability is due to foetal infection with a mucosal disease virus.
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