Cerebellar abiotrophy and segmental axonopathy: two syndromes of progressive ataxia of Merino sheep.

The results show that significant increases in salivary cortisol concentration can be caused by castration and that the level of this response may differ significantly between alternative castration procedures. Control values indicate that the saliva sampling procedure is not in itself stressful. The calves used in this trial were highly trained and accustomed to being handled in the race and to the saliva sampling. We have found much higher salivary cortisol levels in spot checks on untrained calves in a yard (unpublished). The calves in this trial reacted only to the castration operation, whereas, in other situations, it is likely that calves would react also to the handling and sampling procedures. Stephens and Toner (1975) found plasma corticosteroid levels rose from 7.7 ng/ ml to 28.8 ng/ml, simply due to restraint and blood sampling. The maximum cortisol levels following surgical castration were similar to those recorded in the same calves during transportation by cattle truck (unpublished). This is in general agreement with Johnston and Buckland (1976). who found plasma cortisol levels around 10 ng/ml after castration and 20 ng/ml after transportation, using relatively infrequent blood sampling. They concluded also that the animals’ behaviour was not an accurate indicator of the actual level of stress. Some mortality and weight losses after castration of calves were found by Lofgren et al(l978). but did not occur in our study. Measurement by others of plasma total cortisol in cattle have ranged from 4.4 to 7.6 pg/lOO ml before dehorning to 14.6 f 8.7 pg/lOO ml after dehorning (Carter et al 1983), and using earlier assay methodology, Robertson et al (1958) reported plasma corticosteroid levels of 5 pg/lOO ml in “normal” cows and 7 to 18 ml in cows after rumenotomy. It is concluded that while there was undoubtedly a physiological stress response to castration in calves, its magnitude These results, although clear-cut, measure only one indicator of physiological stress. There is a need to add to this information other physiological and behavioural indicators and other husbandry considerations in the continuing task of understanding stress in animals.