Digestive enzymes of a small avian herbivore, the Rufous-tailed Plantcutter

Abstract

We studied the activity of three intestinal membrane-bound digestive enzymes in the Rufous-tailed Plantcutter (Phytotoma rara), one of the smallest species of avian herbivores. We selected the disaccharidases (sucrase and maltase) as indicators of a bird's capability to assimilate carbohydrate, and the oligopeptidase (aminopeptidase-N) as an indicator of a bird's ability to digest protein. Small intestine length was 44.6% shorter than expected based on body mass. Sucrase, maltase, and aminopeptidase-N activities did not differ along the first 80% of the proximal portion of the intestine. Activities of sucrase, maltase, and aminopeptidase-N are probably matching the higher carbohydrate and lower protein concentrations of P. rara's herbivorous diet. The higher and nearly constant enzyme hydrolysis observed along the intestine axis may allow the Rufous-tailed Plantcutter to compensate for and to exploit the abundant and highly diluted plant material, without sacrificing digestive efficiency and nutritional balance.