The efficiency with which fish can convert dietary macronutrients and energy into bodily growth (feed conversion ratio; FCR) is one of the most important economic considerations for finfish production. Two important factors that influence this process are the amount of food provided and the timing of feeding events. Studies over the last 40 years have suggested that restricting feeding rates below satiation levels can improve FCR values, and that recurrent short-duration fasting events (intermittent fasting) can improve FCR and greatly increase appetite. This investigation examined the culture performance and expression of appetite control markers in rainbow trout fed to apparent satiation, on a restrictive feeding regime, or on a restrictive feeding regime with partial weekend fasting.
Rainbow trout (48.9±1.3g) were randomly distributed to nine 100-L tanks within a recirculating aquaculture system (9 L/min inflow in tanks) with an initial stocking density of 30 fish/tank. Tanks were fed three times per day either to apparent satiation or on a restricted feeding regime (75-85% of satiation feeding rate; NRC 2011). A third experimental group was included that was fed on the restricted feeding regime with partial fasting two days per week (1 feeding/day, 33% of recommended feeding rate). Fish were weighted every 14 days for the 70-day experiment, and feeding rates were adjusted based on fish size.
The mean weight (p=0.008), specific growth rate (p=0.007), and FCR (p=0.040) of fish were significantly different between diet groups (122-163g/fish final weight; Figure). Initial results suggest that growth is maximized when feeding fish to satiation, but that restrictive feeding and partial fasting on weekends can greatly improve FCR. The expression of appetite controlling hormones CCK, GRP, ghrelin, and leptin in intestinal tissues, as well as histological analysis of distil intestines, will be evaluated for this presentation.