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Biomedical subjects

B L Clark

Publications and source records attributed to B L Clark.

At least 55 records · Page 3Linked to original sources
PubMed1977

Incidence of Tritrichomonas foetus in young replacement bulls following introduction into an infected herd.

Three hundred 8-year-old Shorthorn and Santa Gertrudis bulls, with a 47% incidence of Tritrichomonas foetus infection in the 30 surveyed, were removed from a herd of approximately 6000 cows and replaced by 325 two-year-old Brahman bulls. A sample of 50 of the replacement bulls was examined at introduction and found to be uninfected. After 2 years, the incidence of infection in a sample of 80 of the replacement bulls was 4%. The results suggests that a major reduction in incidence of infection in extensively managed herds might be achieved by the exclusive use of young bulls for mating.

Age Factors↗
PubMed1977

Studies on the transmission of Tritrichomonas foetus.

Although 2 experiments showed that non-infected bulls can passively transmit Tritrichomonas foestus from infected to non-infected cows during mating, the rates of transmission were low. The results of the second experiment, in which time intervals between services were recorded, suggested that T. foetus was most likely to become established in previously non-infected cows when the interval was less than 20 minutes. Application of 2 X 10(6) active cells of T. foetus to the vulva failed to cause genital infection in 10 cows.

Animals↗
PubMed1977

A dual vaccine for the immunisation of cattle against vibriosis.

Single subcutaneous injections of a mineral oil adjuvant vaccine containing 20 mg dry weight of Campylobacter fetus subsp fetus biotype venerealis cells and 20 mg dry weight of C. fetus subsp fetus biotype intermedius cells per 5 mil dose protected 2- and 3-year-old heifers and 3- and 4-year-old cows against genital infection with either organism.

Animals↗
PubMed1975

Studies on veneral transmission of Campylobacter fetus by immunised bulls.

Temporary contamination of the penis and prepuce with Campylobacter fetus subsp. venerealis and Campylobacter fetus subsp. venerealis biotype intermedius may occur when immunised bulls mate with infected heifers. However, 2 experiments showed that this contamination was not a significant cause of genital infection in susceptible heifers that subsequently mated with bulls.

Animals↗
PubMed1975

The influence of age on the susceptibility of bulls to Campylobacter fetus subsp venerealis.

Observations were carried out on 22 Hereford bulls to determine the age at which they bacame carriers of C. fetus. During preliminary investigations, 5 bulbs were repeatedly exposed to the organism by artificial or natural means from the age of 18 months. All animals became longterm carriers on reaching an age of between 40 and 70 months. Prior to this, a temporary carrier state lasting from 4 to 29 days was produced in 4 bulls. In a subsequent experiment, 17 bulls of 3 different age groups were artificially exposed to C. fetus on 5 occasions over a 2-year period. Thirteen bulls became long-term carriers, including 9 (53%) when less than 4 years old. A transient carrier state occurred in 4 bulls, 2 of which subsequently became long-term carriers. It usually lasted 1-2 weeks, although in 1 animal the organism persisted for 11 weeks. These results are discussed in relation to the findings of other workers and it is concluded that the use of young bulls to limit the spread of C. fetus in infected herds is of dubious value.

Age Factors↗
PubMed1975

Immunisation of cattle against vibriosis with vaccines prepared from Campylobacter fetus subsp fetus.

Subcutaneous administration of vaccines prepared from cells of Campylobacter fetus subsp fetus strain A28 to heifers gave substantial protection against infertility due to C. fetus subsp venerealis strain B6. Strains A28 and B6 had different heat-stable antigens and conformed respectively to serotype B and serotype A of Berg et al (1971). The results suggested that the protective antigens were heat-labile antigens common to both strains. Although vaccines prepared from serotype B strains of C. fetus subsp fetus could be used to immunise cattle against vibriosis, the results did not suggest that their use in preference to those prepared from C. fetus subsp venerealis would offer any advantages.

Abortion, Veterinary↗