Effects of ovariohysterectomy in dogs and cats on adrenocortical, haematological and behavioural parameters

Background: Ovariohysterectomy is considered a prophylactic and therapeutic effect on average better health and reduced mortality rate than intact. Measurement of endocrine, haematological and behavioural responses have been used to evaluate the animal companion response to stressful events. The purpose of this study was to identify the effect of ovariohysterectomy on routinely measures of cortisol response and haematological variables in clinically healthy adult dogs and cats, and to determine whether these parameters could be used to identify a stress response and/or an adaptation to this commonly performed surgery. Materials, Methods & Results: The study was carried out on 12 clinically healthy female dogs (6 control group and 6 experimental group), Beagle, English Setter, Alsatian breeds, aged 2-4 years, with a mean (sd) weight of 16 (2) kg, and 12 clinically healthy mixed-breed domestic female cats (6 control group and 6 experimental group), aged 2-3 years, with a mean (sd) weight of 4 (1) kg. Sexually intact bitches and cats were randomly assigned to control groups; at the same time, bitches and cats of experimental groups were randomly submitted to ovariohysterectomy, within 2 months after an estrous cycle. Blood samples of experimental groups were taken from a cephalic vein, and only occasionally from a jugular vein in the morning (09:00 a.m.), immediately before ovariohysterectomy and one hour after. Baseline blood samples of control groups were taken in the morning (09:00 a.m.). Owners were interviewed via questionnaire at the time the female dogs and cats were spayed and 2 months later. Dogs and cats showed only slightly decrease of cortisol concentrations after surgery compared to pre-ovariohysterectomy values. In addition, baseline cortisol values of control dog and cat groups were superimposable to pre-ovariohysterectomy values. Related to haematological variables no significant differences between pre-ovariohysterectomy and baseline values were observed in both species. No significant behavioural changes were observed within 2 months after surgical sterilization. Cortisol concentrations, haematological variables and behaviour are not significantly affected by ovariohysterectomy in clinical healthy adult companion animals. Discussion: The results obtained are in line with what it would have been extrapolated from laboratory studies on the effects of gonadectomy on physical, physiological and behavioural problems. The reason why we did not observe any significant differences of cortisol concentrations between control and experimental groups in our study might be that pure-breed dogs and middle-breed cats used were very homogenous for gender (only females), age (adult subjects), clinically healthy status, and body weight. No significant changes of haematological variables between pre- and post-ovariohysterectomy were supported by successful ovariohysterectomized animals, without complications. Moreover, increases of WBC and PLT count after ovariohysterectomy, in bitches and cats, confirmed data observed in male cats after castration under general anaesthesia with or without local anaesthesia. From the findings obtained in this study we can conclude that cortisol concentrations and haematological variables, body weight and behaviour are not significantly affected by ovariohysterectomy in clinical healthy adult companion animals.