Laboratory Animals

A haemagglutination inhibition test, developed specifically for primates, diagnoses early pregnancy in the chimpanzee, gorilla, orang-utan and baboon. The test was sensitive and reacted positively when the concentration of gonadotrophin in urine was equivalent to 0·03 i.u. human chorionic gonadotrophin per ml. This degree of sensitivity and the certitude that it cross-reacts with primate luteinizing hormone probably accounts for most of the false positive results.

Some common laboratory species are now considered unsuitable for the study of the toxicity of inhalants because of the natural incidence of abnormal respiratory histology. Levels of ammonia commonly encountered in animal boxes and cages have been shown to cause histopathological changes in the tracheal epithelium of rats, and it is suggested that 'abnormal respiratory histology' could be a reflection of the standard of husbandry employed before and during an experiment.

Keratitis was noted in mice which were splenectomized and subsequently treated with immunosuppressive drugs. It was found that anaesthesia was the cause of the lesion and not the azathioprine or meticorten administration.

The qualitative and quantitative evolution of the digestive microflora of SPF inbred mice (C57BL/RhoIco strain), barrier-maintained since 1970, is described. Some 'contaminants' appeared spontaneously during the period 1971-1973, but microorganisms belonging to the genera Lactobacillus Streptococcus, Enterobacteria, Escherichia and Bacillus remained stable. The methods of investigation used were not suitable for the assessment of strictly anaerobic strains. The stability of the digestive microflora during the last 2 years of this study is believed to be related to the skill and conscientiousness of the technicians responsible for the daily care of these mice.

Processing may result in losses approaching 20% of the added vitamin C. The extent of these losses depends upon the process and is apparently related to temperature and moisture. Storage losses are also related to processing conditions, and no more than 50% of the vitamin C present in the diet immediately after processing may remain after 6 weeks. These results indicate that the current practice of including 1000 mg/kg of vitamin C in pelleted guinea-pig diets should be satisfactory, provided such diets are used within 6 weeks of manufacture and are stored during this period in conditions conducive to stability, that is dry, not exposed to direct sunlight and, preferably, with an even cool temperature.

Vaginal smear cyclicity was used as a physiological test to compare the response of rats to the new 'silent' fire alarm developed by the Laboratory Animals Centre with a conventional fire bell.

The fire bell had a highly significant effect on the vaginal smear cyclicity whereas the rats exposed to the 'silent' fire alarm showed no significant changes from the control animals in quiet conditions.

Mortality and hence the proportion of young weaned was markedly affected by the type of nesting material but not by maternal age or parity. With paper tissues for nesting purposes 476/791 (60%) young were lost compared with 216/1182 (18%) with woodwool. Similar results were obtained in 2 additional series. The proportion of young weaned was also affected by litter size; in general, pup mortality was heavier and took place earlier in the large litters (more than 9 young).