Reference material specific to the digestive tract of piscivores is scant, and knowledge of the gastrointestinal tract of a normal penguin is based on information from other fish-eating birds. The purpose of this study is to determine the normal gross anatomy, transit time, and histopathologic structures of the penguin gastrointestinal tract.
Twelve clinically normal penguins were selected from the colony at the Maryland Zoo in Baltimore, which on average consists of 55 birds. Complete blood work, malaria screening, and fecal pathogen screening were performed to ensure a healthy population. All birds underwent a barium contrast study, and radiographic images were obtained until the entire gastrointestinal tract was empty. Approximately 2 wk later, each penguin was anesthetized using isoflurane, and an endoscopic evaluation of the anterior gastrointestinal tract was performed. Fluid from the ventriculus was collected for pH determination and parasite evaluation, and three representative biopsy samples from the ventriculus, proventriculus, and esophagus (for a total of nine samples) were obtained for histopathology, koilin thickness determination, and electron microscopy. Time from barium ingestion to defecation ranged from 17–70 min, and most penguins required 24–30 hr for the barium to clear the gastrointestinal tract completely. During endoscopy, koilin was not observed grossly in several birds; however, it was present on biopsy samples. Fluid from the ventriculus had an average pH of 2.75 and contained a mixed bacterial population. Several birds also had yeast or pollen present. The results of this study provide a comparative baseline to use during diagnostic workups and help guide treatment decisions.
The authors thank the animal care and veterinary technician staff at the Maryland Zoo in Baltimore for their assistance in gathering historical and research data.