Variability of serum antibody responses of goat kids to a commercial Clostridium perfringens epsilon toxoid vaccine.

Twenty-nine Angora goats were used in a trial of a commercial enterotoxaemia (pulpy kidney disease) vaccine. The animals were allocated to four groups, of which three received an initial dose of vaccine, two also received a booster of the same vaccine either 28 or 42 days after the first vaccination, and the fourth remained as an unvaccinated control group. An indirect ELISA technique was used to measure the titres of Clostridium perfringens type D epsilon antitoxin in serum samples taken before vaccination and 17, 28, 42, 59, 70, 86, 98 and 128 days after vaccination. There was a wide range of antibody titres after vaccination, and the great majority of the vaccinated animals had titres below the protective level, arbitrarily set at 0.25 iu/ml, by day 98.

Suppression of testicular function using two dose rates of a reversible water soluble gonadotrophin releasing hormone (GnRH) vaccine in colts.

OBJECTIVE: To investigate the effect of two dose rates (200 and 400 ng) of a gonadotrophin releasing hormone (GnRH) vaccine on testicular function. DESIGN: A vaccination dose rate experiment. PROCEDURE: Two injections were administered 4 weeks apart to six colts in each treatment group. To maintain immunosuppression until the end of the breeding season, a third injection was given if antibody titres fell below 1000. RESULTS: Effective antibody titres were present for 12 to 27 weeks. Testosterone concentrations decreased from 2.22 to 0.31 nmol/L 6 weeks after primary vaccination. Androstenedione concentrations decreased from 1.78 to 0.28 nmol/L 5 weeks after vaccination. Testosterone and androstenedione concentrations above 0.69 and 0.87 nmol/L were attained 31 to 43 weeks after vaccination. Mean scrotal widths and lengths decreased over 29 weeks from 9.2 cm and 9.7 cm to 6.7 cm and 7.6 cm. At surgical castration these dimensions were 10.1 cm and 11.0 cm. Mean semen characteristics before vaccination and after recovery were: gel-free volume 16.5 and 13.5 mL, sperm concentration 295.5 x 10(6) and 315.6 x 10(6)/mL, total sperm per ejaculate 4041 x 10(6) and 4657 x 10(6) and live normal spermatozoa 32% and 60%. Histologically, the testes showed active spermatogenesis. The mean testicular parenchyma weights for the 200 and 400 mg groups were 129.0 g and 109.8 g. Daily sperm production per testis and per gram of testis for the 200 and 400 mg groups were 3.7 x 10(8) and 2.8 x 10(6), and 2.3 x 10(8) and 2.0 x 10(6). CONCLUSIONS: Both dose rates suppressed testicular function. Data showed that the vaccine effects were reversible. Individual immune response was less varied in the 200 mg group. Further work is necessary to achieve a less variable response in the immunosuppression of testicular function.

Seasonal variation in the estrous cycle of mares in the subtropics.

Data on the estrous cycles and sexual receptivity scores of 7 maiden Australian Stock Horse mares were used to study seasonal variation from December until the following November. Mares were grazed in paddocks containing both native and improved tropical pasture species. The study was conducted in South-East Queensland (27 degrees 27' South latitude). There were no differences between either the sexual receptivity or the lengths of natural (Mean=7.5 days, SEM=0.4) and PGF-induced estruses (Mean=7.6 days, SEM=0.4). Plasma estrogens were not related to differences in sexual receptivity scores between mares. The lowest incidence of estrus occurred at the time of the winter solstice (June 22) in the Southern Hemisphere. Winter estruses (Mean=9.3 days, SEM=0.8) were longer than those of summer (Mean=6.6 days, SEM=0.5) and autumn (Mean=6.6 days, SEM=0.9). Approximately 30% of estruses were anovulatory. Most of these occurred in autumn and winter (P<0.05). There was considerable variation in the occurrence of anovulatory estrus between mares. There were no differences between the lengths of ovulatory and anovulatory estruses. Ovulatory estruses were significantly longer in spring than in summer (P<0.05). There were no seasonal differences between the lengths of anovulatory estruses. The length of diestrus (Mean=16.6 days, SEM=0.3) was not affected by mare or season. Only 3 of the 7 mares did not cycle during winter (anestrus), as confirmed by progesterone concentrations of less than 1 ng/ml. Finally, there was no evidence of mares having 2 breeding seasons per year in this study.

A study of nonsurgical embryo transfer in the mare.

The success rate of nonsurgical embryo recovery was influenced neither by year nor by season within years. The preferred method of nonsurgical embryo transfer was by Cassou pistolette. From a total of 15 attempts to transfer embryos nonsurgically, 9 (60%) were successful. Of the five attempts during February through April 1982, only one was successful in producing a live foal. The degree of synchrony between the ovulations of the donors and recipients in these five attempts ranged from +3 to -3 d. The recipient of the successful transfer ovulated on the same day as the donor. Eight of the ten attempts during September through December 1982 produced live foals. Synchronization of ovulations between the donors and recipients in these transfers ranged from 0 to -2 d. Repeated attempts to recover embryos had no deleterious effects on fertility of the donors.