Dietary substitution effect of Undaria pinnatifida with onion extract by-product on growth, chemical composition and air exposure stress of juvenile abalone (Haliotis discus, Reeve 1846)

Abstract

Effect of dietary substitution of Undaria pinnatifida with onion extract by-product (OEB) on growth, body composition and air exposure stress of juvenile abalone was determined. One thousand and eighty juvenile abalone were randomly distributed into 18,100 L net cages (sixty per cage). Five formulated diets were prepared. Twenty percent U. pinnatifida was included into the control (Con) diet. Twenty five, 50, 75 and 100% U. pinnatifida were substituted with an equal amount of OEB, referred to as the OEB25, OEB50, OEB75 and OEB100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare formulated diets on growth performance of abalone, referred to as the Undaria. Each diet were randomly assigned to triplicate groups of abalone and fed to abalone once a day to satiety with little leftover for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure for 24 h and survival was monitored for the next 4 days. Weight gain and specific growth rate (SGR) of abalone fed all formulated diets were greater than those of abalone fed the Undaria. The greatest weight gain and SGR were obtained in abalone fed the OEB50 diet, followed by the OEB75, OEB25, Con and OEB100 diets, in that order. Weight gain and SGR of abalone fed the OEB100 diet were lower than those of abalone fed the Con diet. Shell length, width and height and soft body weight of abalone tended to agree with growth rate of abalone. No difference in the chemical composition of the soft body of abalone was observed. The survival of abalone fed the OEB25, OEB50, OEB75 and OEB100 diets was higher than that of abalone fed the Undaria and Con diet at the end of 4-day post observation after 24-h air exposure. In conclusion, U. pinnatifida up to 75% could be replaced with OEB in abalone feed when 20% U. pinnatifida was included. The greatest growth performance was obtained in abalone fed the OEB50 diet.