Estimation of dietary protein and energy requirements of doctor fish, Garra rufa, using a bioenergetic factorial approach

The use of doctor fish, Garra rufa, is widening in the treatment of psoriasis and in recreational spas all over the world. The increasing demand for the fish has created pressure on its wild stocks, making its rearing in captivity necessary. However, there is no specifically formulated diet meeting the dietary nutrient requirements of doctor fish at different developmental stages. The present study was planned to estimate the dietary protein and energy requirements of doctor fish based on a factorial approach. Two growth experiments were conducted using fish with initial mean weights of 0.46 g (small) and 0.84 g (large) at various feeding levels to estimate the maintenance requirements of energy and protein and their utilization efficiencies. Metabolic body weight (BW) exponents for energy and protein were estimated from a starvation study as 0.81 and 0.67, not significantly different from the largely accepted values of 0.80 and 0.70, respectively (P > 0.05). The maintenance requirements of digestible energy (DE) and digestible protein (DP) were 55.5 (kJ/kg BW0.80/day) and 0.49 DP g/kg BW0.70/day, and the utilization efficiencies of DE and DP were 0.61 and 0.35, respectively. Dietary DP:DE demands decreased as fish size increased. The key sizes of fish for changing DP:DE requirements were estimated with one and two-break point analysis. Based on those estimated critical sizes, two hypothetical diet specifications were provided for doctor fish weighing between 0.1 g and 5.0 g. A video shooting study carried out to measure the fish's nibbling behavior showed a strong influence of feeding level (P < 0.05) where the lowest feeding level (21 kJ/kg BW0.80/day) induced fish to longer skin feeding behavior. The findings of the study allow the creation of specific doctor fish diet formulations for their culti-vation and maintenance in spas and health centers.