Determination of the passage rate in saltwater crocodiles (C. porosus) using beads, flagging tape and fluorescent pigment as digestive markers

Abstract

The saltwater crocodile (Crocodylus porosus) is extensively farmed for their skin and meat. In order to optimise growth rates and production crocodiles need to be fed an optimal diet, based on their nutritional physiology. In this study two experiments were conducted to determine the passage rate of food in juvenile and sub-adult crocodiles. Plastic beads, pieces of flagging tape and a fluorescent pigment were used as digestive markers, to evaluate whether these markers are suitable as digestive markers in C. porosus. Results showed differences in excretion patterns between the type of markers. Large percentages of beads and pieces of flagging were retained in the stomach, not passing the digestive system. The fluorescent pigment was excreted by juvenile crocodiles almost continuously during the experiment. Despite the fact that the fluorescent pigment did pass the digestive tract, the obtained data is inaccurate. It can be concluded that the used markers are not useable as digestive markers in crocodiles, since they were not successful in determining the passage rate in juvenile and sub-adult C. porosus. More precise markers need to be used as digestive markers in crocodilians to achieve more accurate knowledge about the crocodile digestive system to eventually improve crocodile nutrition.