Colonic impaction in guinea pigs fed a chemically defined diet: a case report.

Pathogen-free female Hartley guinea pigs were divided into four diet groups to determine optimal nitrogen requirements for growth, pregnancy and lactation. Three chemically defined test diets varying in total nitrogen were compared with commercial guinea pig feed. Within 13 days, 24 of 78 animals from the three test diet groups died or required euthanasia. Affected guinea pigs were depressed, lost weight and had distended abdomens. Distension, impaction and, in most cases, rupture of the spiral of the ascending colon and subsequent peritonitis were observed at necropsy. Husbandry changes which resulted in a decreased incidence of impactions included increased acclimatization time on commercial feed post-shipping, decreased animal density per cage and cessation of water medication with oxytetracycline.