Development of Potential Substitute of Fouling Macroalgae, Ulva australis, Sargassum horneri and Their Combination for Undaria pinnatifida in Juvenile Abalone (Haliotis discus, Reeve 1846) Feed

Abstract

1. Dietary Substitution Effect of Ulva australis for Undaria pinnatifida on Growth, Body Composition and Air Exposure of Juvenile Abalone (Haliotis discus, Reeve 1846)

Substitution effect of Undaria pinnatifida with Ulva australis in formulated diet on growth, body composition and air exposure of abalone (Haliotis discus) was investigated. A total of 1260 juvenile abalone were distributed into 21 cages. Six formulated diets and dry U. pinnatifida were prepared. The control (UA0) diet contained 20% U. pinnatifida. Twenty, 40, 60, 80 and 100% U. pinnatifida were substituted with the same amount of U. australis, referred to as the UA20, UA40, UA60, UA80 and UA100 diets, respectively. U. pinnatifida was prepared to compare effect of formulated diet on performance of abalone. Abalone were fed with one of the experimental diets for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure for 24 h and then cumulative mortality was monitored for the next 4 days. Higher survival, weight gain and specific growth rate (SGR) were observed in abalone fed all formulated diets than the U. pinnatifida. Abalone fed the UA60 diet produced the greatest weight gain and SGR. No difference in proximate compositions of the soft body of abalone was observed. The cumulative mortality of abalone fed the U. pinnatifida was higher than all formulated diets at 84 h until the end of the 4-day post observation after 24-h air exposure. Abalone fed the UA0 diet showed higher mortality than other formulated diets at 84 h until the end of the 4-day post observation. In conclusion, U. pinnatifida could be completely replaced with U. australis in abalone feed. The best growth was obtained in abalone fed the UA60 diet.

Keywords: Abalone (Haliotis discus), air exposure, dietary substitution, formulated diets, Ulva australis, Undaria pinnatifida

2. Substitution effect of Undaria pinnatifida with Sargassum horneri in formulated diet on growth performance, body composition and air exposure stress of juvenile abalone (Haliotis discus, Reeve 1846)

Dietary substitution effect of Undaria pinnatifida with Sargassum horneri on growth performance, proximate composition and air exposure stress on juvenile abalone was investigated. A total of 1260 juvenile abalone were randomly distributed in 21, 100-L net cages (60 per cage). Six formulated diets were prepared. Twenty percent U. pinnatifida powder was included in the control (SH0) diet. The U. pinnatifida component of the experimental diets was substituted with S. horneri at the rates of 20, 40, 60, 80, and 100%, referred to as the SH20, SH40, SH60, SH80, and SH100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare effect of the formulated diet on abalone. Abalone were fed with one of the experimental diets once a day for 16 weeks. Water stability of nutrient content in all formulated diets was changed with time. Survival of abalone fed all formulated diets was higher than that of abalone fed the U. pinnatifida. Abalone fed the SH0, SH20, SH40, SH60, and SH80 diets achieved greater weight gain and specific growth rate (SGR) than those of abalone fed the SH100 diet and U. pinnatifida. The greatest weight gain and SGR were obtained in abalone fed the SH60 diet. The proximate composition of the soft body of abalone, except for crude protein, was not affected by the experimental diets. Higher cumulative mortality was observed in abalone fed the U. pinnatifida than that of abalone fed the all formulated diets, except for SH0 diet at 84 h until the end of the 4-day post observation after 24-h air exposure. In conclusion, U. pinnatifida up to 80% could be substituted with S. horneri when 20% U. pinnatifida was included in formulated abalone feed. The SH60 diet achieved the best growth performance of abalone.

Keywords: Abalone (Haliotis discus), air exposure, phaeophyta, Sargassum horneri, substitution effect, Undaria pinnatifida

3. Substitution effect of the combined fouling macroalgae, Ulva australis and Sargassum horneri for Undaria pinnatifida in formulated diets on growth and body composition of juvenile abalone (Haliotis discus, Reeve 1846) subjected to air exposure stressor

The effect of substituting the combined macroalgae Ulva australis and Sargassum horneri for Undaria pinnatifida in formulated diets on growth and body composition of abalone subjected to air exposure stressor was investigated. A total of 1260 juvenile abalone were distributed into 21 cages. Six formulated diets were prepared. The control (CUS0) diet contained 20% U. pinnatifida. Twenty, 40, 60, 80 and 100% of U. pinnatifida were substituted with an equal amount of the combined U. australis and S. horneri, referred to as the CUS20, CUS40, CUS60, CUS80 and CUS100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare the growth performance of abalone. Abalone were fed with one of the experimental diets once a day for 16 weeks and then subjected to air stressor for 24 h. The cumulative mortality of abalone was monitored for the following 4 days after 24 h of air exposure. Abalone fed all formulated diets attained higher survival, weight gain and specific growth rate (SGR) than U. pinnatifida. Abalone fed the CUS100 diet achieved the greatest weight gain and SGR, followed by the CUS80 and CUS60 diets. The greatest shell growth and heaviest soft body weight were obtained in abalone fed the CUS100 diet. Proximate composition of the soft body of abalone, except for moisture content was not affected by the experimental diets. The cumulative mortality of abalone fed the U. pinnatifida was higher than that of abalone fed all formulated diets at 84 h until the end of the 4-day post observation. The lowest cumulative mortality was obtained in abalone fed the CUS80 diet at the end of the 4-day post observation. Therefore, U. pinnatifida could be completely replaced with the combined U. australis and S. horneri in abalone (H. discus) feed.

Keywords: Abalone (Haliotis discus), air exposure stressor, Sargassum horneri, substitution effect, Ulva australis, Undaria pinnatifida