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 times 10⁶ 315.6 times 10⁶/mL, total sperm per ejaculate 4041 times 10⁶ 4657 times 10⁶ 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 times 10⁸ 2.8 times 10⁶ 2.3 times 10⁸ 2.0 times 10⁶. 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.     

Prevalence of Escherichia coli O157:H7 in white-tailed deer sharing rangeland with cattle.

OBJECTIVE: To determine the prevalence of fecal shedding of Escherichia coli O157:H7 in white-tailed deer (Odocoileus virginianus) with access to cattle pastures. DESIGN: Survey study. SAMPLE POPULATION: 212 fecal samples from free ranging white-tailed deer. PROCEDURE: Fresh feces were collected on multiple pastures from 2 farms in north central Kansas between September 1997 and April 1998. Escherichia coli O157:H7 was identified by bacterial culture and DNA-based methods. RESULTS: Escherichia coli O157:H7 was identified in 2.4% (5/212) of white-tailed deer fecal samples. CONCLUSIONS AND CLINICAL RELEVANCE: There is considerable interest in the beef industry in on-farm control of E coli O157:H7 to reduce the risk of this pathogen entering the human food chain. Results of our study suggest that the design of programs for E coli O157:H7 control in domestic livestock on pasture will need to account for fecal shedding in free-ranging deer. In addition, the results have implications for hunters, people consuming venison, and deer-farming enterprises.     

Over representation of Burmese cats with diabetes mellitus

Objective To determine if Burmese cats in Queensland have an increased risk of diabetes mellitus.
Design A retrospective study of diabetic and nondiabetic cats that had blood submitted to a veterinary clinical laboratory over a 22 month study period.
Sample population 4402 cats
Procedure Cats were considered diabetic if blood glucose concentration was > 11 mmol/L and fructosamine was > 406 μmol/L or hydroxybutyrate was >1 mmol/L. Cats were grouped into Burmese and non-Burmese. Adjusted odds ratios of diabetes were calculated for breed, gender and age group amongst cats with blood glucose > 11 mmol/L.
Results Burmese cats comprised 20% of 45 diabetic cats of known breed, which was higher (P < 0.001) than among the normoglycemic reference population of 2203 cats (7% Burmese). There were more females among the diabetic Burmese (62%), but this did not differ (P > 0.05) from the Burmese reference population (45% females). In contrast, males seemed to predominate among diabetic non-Burmese (63%), although this also did not differ (P > 0.05) from the reference population (55%) or from diabetic Burmese (38% males). The majority (90%) of diabetic cats were older than 6 years, irrespective of breed (median age 12 years, interquartile range 10 to 13 years). This was higher (χ²= 8.13, P < 0.005) than among the normoglycaemic reference population, where 69% were older than 6 years.
Conclusions Burmese cats were significantly over represented among cats with diabetes mellitus. Irrespective of breed, the risk of diabetes in the study population increased with age.     

Optical porosity and windspeed reduction by coniferous windbreaks in Southern Ontario

Relative windspeed reduction was measured behind nine relatively narrow, homogeneous windbreaks in southern Ontario, Canada to assess whether any characteristics of the windspeed reduction curve could be predicted from optical porosity. The latter was determined for each windbreak using high contrast black and white photographic silhouettes on a computer digitizing system. Minimum windspeeds behind the windbreaks ranged from 29 to 71% of open windspeed; these minima were located 2 to 6 multiples of windbreak height away from the windbreak. Optical porosities of the bottom half of the windbreak ranged from 0 to 31%. Multiple regression of the shelter parameters (location and value of minimum relative windspeed) on the independent variables (optical porosity, open windspeed, surface roughness, approaching wind direction relative to the windbreak, average tree diameter and average tree spacing) showed that the minimum relative windspeed could be predicted from the optical porosity of the bottom half of the windbreak. The results suggest that optical porosity can be used to predict minimum relative windspeeds and may therefore be useful as a guide in the field evaluation of windbreaks.