Effect of ketamine anesthesia on daily food intake in Macaca mulatta and Cercopithecus aethiops

Ketamine hydrochloride is frequently administered to non-human primates as a means of chemical restraint. This procedure can be a frequent source of stress to monkeys at research facilities, impacting animal health, well-being and research quality. This study was designed to measure ketamine's effect on daily food intake, a parameter that reflects and influences animal well-being and directly impacts research studies. On five occasions, baseline daily food intake was compared to daily food intake occurring 24, 48, 72, 96, and 120 h after an intramuscular injection of 10 mg/kg ketamine in male African green monkeys (AGMs) (Cercopithecus aethiops) and male and female rhesus macaques (Macaca mulatta). AGMs and female rhesus macaques had significantly reduced daily food intake during the first 4 days after receiving ketamine. The AGMs continued to display significantly reduced daily food intake on the fifth day after ketamine. The male rhesus macagues showed a trend toward reduced daily food intake, greatest during the first 2 days and remaining less than baseline intake through the fifth day following ketamine. The degree of observed food intake reduction was most severe at the 24 h (mean percent intake reduction: AGMs: 57%; rhesus males: 48%; rhesus females: 40%) and 48 h time points (AGMs: 24%; rhesus males: 14%; rhesus females: 13%). A subset of the AGMs that did not receive ketamine, but observed other animals in the room receive ketamine, showed reduced food intake at 24 and 48 h after ketamine, though not to the degree associated with ketamine administration. These results indicate that ketamine anesthesia is associated with a prolonged reduction in daily food intake in AGMs and rhesus macaques. Frequent use of ketamine in non-human primates may have a significant impact on animal health and well-being, and alternatives to its use warrant consideration.