Effects on growth, survival, body composition, processing traits and water quality when feeding a diet without vitamin and mineral supplements to Australian red claw crayfish (Cherax quadricarinatus) grown in ponds

To be profitable, producers must reduce diet costs, which can be as high as 80% of the variable costs of an aquaculture expense. As vitamin and mineral premixes represent a significant cost, eliminating addition of these premixes could reduce diet costs if no adverse effects were observed for growth and production parameters. A 105-day feeding trial was conducted with juvenile Australian red claw crayfish (Cherax quadricarinatus) to evaluate the effects of growth, survival, body composition, processing traits and water quality when red claw were fed a supplemental diet containing 28% crude protein (CP) without vitamin and mineral premixes (and supplemented alfalfa hay) compared with red claw fed a diet (control diet) containing 42% CP, vitamin and mineral premixes, and with supplemented alfalfa hay, and compared with red claw only fed alfalfa hay when grown in ponds. Juvenile red claw (mean weight of 15.7±1.0g) were randomly stocked into nine 0.02-ha ponds at a rate of 640 per pond (3.2 perm2), and each treatment was used in three ponds. There were two feedings per day, each consisting of one-half of the total daily ration. At harvest, individual weight, percentage weight gain, specific growth rate, survival and total yield of red claw fed a control diet was significantly higher (P<0.05) (83.0g, 398%, 1.53%day-1, 65.1%,and 1708kgha-1 respectively) compared with red claw only fed alfalfa hay (44.9g, 202%, 1.04%day-1, 30.3% and 431kgha-1, respectively), but not different (P>0.05) from red claw fed the supplemental diet without vitamin and mineral premixes (76.2g, 367%, 1.47%day-1, 57.2% and 1378kgha-1). There were no significant differences (P>0.05) in feed conversion ratio (FCR) among treatments, which averaged 5.0 (based on prepared diet input). These results indicate that vitamin and mineral supplementation in a diet is not necessary when diet containing 28% CP and alfalfa hay are used in combination for pond grown red claw. These results may help reduce diet costs and possibly increase producers' profits which might allow for industry expansion.