Substitution effect of Saccharina japonica with beet leaf by-product in feed on the growth and chemical composition of the soft body of juvenile abalone (Haliotis discus hannai Ino 1952) subjected to air exposure

Abstract

Dietary substitution effect of beet leaf by-product (BLB) for Saccharina japonica on the growth and soft body composition of abalone (Haliotis discus hannai) subjected to air exposure was determined. A total of 1260 juvenile abalone was randomly distributed into 18 containers. Five experimental diets were prepared. The control (Con) diet contained 20% S. japonica. Twenty five percent, 50%, 75% and 100% S. japonica were substituted with equal amount of BLB, referred to as the BLB25, BLB50, BLB75 and BLB100 diets, respectively. The dry S. japonica was also prepared to compare effect of formulated diets on growth of abalone. The experimental diets were fed to triplicate groups of abalone for 16 weeks, and then exposed to air for 24 h. Survival of abalone was monitored for the next 6-day post observation period after the 24-h air exposure. Weight gain and specific growth rate (SGR) of abalone fed with formulated diets were greater than those of abalone fed with the S. japonica. The greatest weight gain and SGR were obtained in abalone fed the BLB25 diet, followed by the BLB50, BLB75, BLB100 and Con diets, in that order. The maximum values of weight gain, SGR, shell length and shell width of abalone were estimated to be approximately 42.3%, 43.5%, 39.8% and 33.7% of substitution level of BLB for S. japonica in abalone feed. The chemical composition of abalone soft body was not affected by the experimental diets. Survival of abalone fed with formulated diets was higher than that of abalone fed with the S. japonica at the end of the 6-day post observation period. In conclusion, S. japonica could be completely replaced with BLB in abalone feed without retardation of growth and survival of abalone subjected to the 24-h air exposure. The greatest weight gain and SGR were obtained in abalone fed the BLB25 diet.