Influence of different dietary calcium levels on the digestibility of Ca, Mg and P in Hermann's tortoises
Calcium and phosphorus are very important minerals in reptile nutrition, but many diets are still not balanced. To achieve optimal growth, including a healthy skeleton and a strong shell, a well-balanced supply with these minerals is prerequisite.
The purpose of this study was to evaluate the apparent digestibility in Hermann's tortoises (Testudo hermanni) of diets with different calcium levels with special emphasis on the digestibility of minerals. Eight adult Hermann's tortoises of the veterinary faculty in Zurich were used. The animals were housed indoors at a mean temperature between 23 °C and 26 °C. The animals were fed a diet, which consisted of vegetables, herbs and different supplementation of calcium carbonate. Daily faecal samples of all tortoises were collected from day 8 to day 12. A proximate analysis was performed and the HCl-insoluble ash was used as an indigestible natural indicator (marker) for the determination of the apparent digestibility of minerals. The calcium content of the mixed feedstuffs of diet I was 0.64% on a dry matter basis, and the Ca:P ratio in the food was 3:1. In diet II the Ca content was 1.29% on a dry matter basis, and the Ca:P ratio in the food was 6:1. The digestibility of Ca in diet I was 57%. The other examined minerals, Mg and P, had a digestibility of 46% and 58% respectively. In diet II the digestibility of Ca was 79%, of Mg 52% and of P 52%. The results of this study indicated, that higher Ca concentrations in the diet led to an increased apparent digestibility of Ca and Mg.
Title: Influence of different dietary calcium levels on the digestibility of Ca, Mg and P in Hermann's tortoises (Testudo hermanni)
Authors: A. Liesegang, J.-M. Hatt and M. Wanner