Effect of environmental stress and immobilization on stress physiological variables in farmed mink

The effect of cage size and nest box environment on plasma cortisol, number of eosinophil leucocytes, and on frequency of leucocyte groups was measured on 132 farmed mink. The experiment included three cage sizes (0.10 m(2), 0.27 m(2), and 1.1 m(2)) and cages with and without nest boxes. Furthermore, the effect of daily immobilization a mink trap for 5 or 30 min. over periods of 10 days was demonstrated. The effect of daily immobilization for 5 min. was an unchanged cortisol response to immobilization from day 1 to day 10, no effect on eosinophil leucocyte level, and a decrease of H/L-ratio from day 1 to day 10. After 30 min. daily immobilization the cortisol response decreased from day 1 to day 10, the eosinophil leucocyte level decreased, and the H/L-ratio increased from day 1 to day 10. Mink females in cages without nest boxes had a higher plasma cortisol level, a lower level of eosinophil leucogytes, and a higher H/L-ratio than mink in cages with nest boxes. No effect of cage sizes was seen on the physiological variables used. A pronounced seasonal variation has been shown in the physiological variables used. The results made it possible to conclude that the duration of individual immobility sessions is of consequence to the physiological effect of immobilization. The physiological stress level increased when farmed mink were deprived of the use of nest boxes. The effect of keeping mink in cages without nest boxes was similar to daily immobilization for 30 min. with regard to both the level of eosinophil leucocytes, the relative distribution of leucocyte types, and the H/L-ratio.