A survey attempted to determine the extent to which cows are being inseminated when not in oestrus. The method used to check the farmers' diagnoses of oestrus was based on peripheral plasma progesterone concentrations analysed by radioimmunoassay. Of 141 cows examined in this way, a total of 30 (21-28 per cent) showed abnormalities of the progesterone levels. The fertility within this group was very poor with only two of the cows being known to have conceived to the service in question.
Attempts were made to transmit Chlamydia psittaci, the causal agent of enzootic abortion of ewes, in three different ways. Ten ewes were inseminated artificially with freshly collected semen containing 10(5) CELD50 chlamydia. Serological evidence of infection was found two weeks before parturition in nine ewes and the organism was recovered from three of them. By six weeks post partum antibody titres had fallen and were negative in six ewes. Twenty-four hours after service two groups of 10 ewes were infected intravaginally with 10(8) CELD50 and 10(3) CELD50 chlamydia respectively. Positive complement fixation titres were present in the first half of pregnancy in all the ewes in the high dose group but not the low dose group. None of the ewes showed evidence of infection at parturition. Fourteen ewes were served by four rams which had been intravenously infected with 10(8) CELD50 chlamydia four to six days earlier. Following service seroconversion occurred but titres became negative again by late pregnancy. No microbiological evidence of infection was detected in any of the ewes at parturition but complement fixation titres were positive in 12 of 14 ewes sampled six weeks post partum. The 14 ewes were sampled during their pregnancies the next year and none showed any evidence of chlamydial infection. It is concluded that venereal transmission of C psittaci is biologically feasible in sheep, but that under normal systems of flock management in Britain it is unlikely to contribute greatly to the epidemiology of enzootic abortion of ewes.
Eleven out of 36 suckler cows, all in late pregnancy, aborted seven to 10 days following introduction to a rye grass pasture heavily infested with ergot. On the basis of known heavy exposure to ergot infested grass and negative findings in a range of other investigations, details of which are given, a diagnosis of ergotism was made.
A progesterone-releasing intravaginal device (PRID) was inserted for 14 days into 10 lactating dairy cows at least 50 days after calving. Synchronization of oestrus was good and 5 of the cows conceived to a double insemination 48 and 72 h after PRID removal. In 9 cows vaginal infection was present when the PRID was removed but resolved spontaneously. The level of progesterone in the milk and the milk yield were similar to those in the 10 control animals. PRID treatment of 9 cows whose ovaries had remained inactive for at least 50 days after calving was followed by ovulation, as judged by the milk progesterone profile, in 8 animals after removal of the device.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.