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Research articles

ScienceAsia 42(2016): 237-246 |doi: 10.2306/scienceasia1513-1874.2016.42.237

Faecal characteristics as markers of Chelonia mydas feeding

Karun Thongprajukaewa,b,*, Hirun Kanghaec, Kongkiat Kittiwattanawongc

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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a Department of Applied Science, Faculty of Science, Prince of Songkla University, Songkhla 90112 Thailand
b Biochemical Research Unit for Feed Utilization Assessment, Faculty of Science, Kasetsart University, Bangkok 10900 Thailand
c Phuket Marine Biological Centre, Phuket 83000 Thailand

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

Received 23 Feb 2015, Accepted 13 Jul 2016