Positive affective state induced by opioid analgesia in laying hens with bone fractures
Laying hens with keel fractures (n = 35) and control hens with no fractures (n = 12) were trained to associate the colour and position of an environment with the effects of either a subcutaneous injection of an opioid analgesic drug (butorphanol) or a subcutaneous injection of saline in a conditioned place preference experiment. Each […]