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Faecal characteristics as markers of Chelonia mydas feeding

Karun Thongprajukaew^a,b,*, Hirun Kanghae^c, Kongkiat Kittiwattanawong^c

 
ABSTRACT:     Faecal sampling can provide an unobtrusive monitoring of feed utilization. We demonstrate that faecal digestive enzymes and physicochemical characteristics correlate with the feed conversion efficiency in green turtle (Chelonia mydas). The 10-day-old juvenile turtles (25.4±1.3 g body weight) were fed with either fresh feed containing minced fresh fish and vegetable (diet 1); fresh feed containing minced fish fillet, vegetable and fish pellet diet (diet 2); or only fish pellet diet (diet 3) for four months in a completely randomized design (3 treatments ×  3 replicates × 10 subjects per replication). Analysis of faecal digestive enzymes (pepsin, trypsin, amylase, and activity ratio of amylase to trypsin) based on colorimetric determinations of specific activity suggested that carbohydrate digestion is a key indicator for feed utilization efficiency in terms of intake and conversion ratio. Physicochemical characteristics to enhance enzymatic hydrolysis, namely, microstructure (scanning electron microscope), thermal transition properties (differential scanning calorimeter), and relative crystallinity (X-ray diffractometer) indicate that the faeces of turtles fed with diet 3 provide a superior feed utilization efficiency. The observed faecal characteristics varied in response to different diets over the duration of the experiments. Thus analysis of faecal digestive enzymes and physicochemical characteristics appear to provide useful unobtrusively sampled indicators for determining feed utilization and can be applied in studies of nutritional status in endangered species without conflicting ethical standards.

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* Corresponding author, E-mail: karun.t@psu.ac.th

Received 23 Feb 2015, Accepted 0 0000