Phototropic bacteria as feed supplement for growth and survival of Malaysian mahseer fingerling, Tor tambroides

Abstract

This study was aimed to determine the growth and survival of fingerlings of Tor tambroides by using phototrophic bacteria. Phototrophic bacteria Marichromatium sp. (IIUM-JHM1 and IIUM-JHM2) were isolated from the mangrove sediments, Kuantan Pahang. While Rhodopseudomonas sp. (IIUM-JHR1 and IIUM-JHR2) were collected from fish rearing tanks INOCEM, IIUM. The bacteria were cultivated and monitored by using 112 media under anaerobic light conditions at 2500-lux light intensity of continuous illumination of 60-watt tungsten bulb at 30±2°C. Total carotenoid contents and dry cell weight of the bacterial cells were compared from day 0 to day 5 using UV-VIS spectrometer. The results showed that IIUM-JHR2 produced the highest total carotenoid content (4.08mg/g) at day 3 while IIUM-JHM 1 produced the highest dry cell weight (3.83 g/L) at day 2. Bacteriochlorophyll and carotenoid type were also determined using UV-VIS spectrometer and bacteriochlorophyll a and carotenoids of the spirilloxanthin series were detected as photosynthetic pigments in all isolates. Statistical analysis showed significant differences (P<0.05) in dry cell weight among the isolates but no significant differences (P>0.05) detected for total carotenoid contents among the isolates. IIUM-JHR2 and IIUM-JHM1 were mass cultured, centrifuged and the fresh biomass were incorporated into commercial pellet. Group of 10 fishes were kept in each of 9 aquarium filled with 40 liters of aerated tap water for 10 weeks. Diet 1 (commercial diet + IIUM-JHR2), diet 2 (commercial diet + IIUM-JHM1) and diet 3 was the commercial pellet alone without the bacteria supplementation. Growth responses of fingerlings fed with the experimental diets were presented as mean weight gain, length increment, survival rate and specific growth rate and showed that diet 2 exhibited the best growth among the diets. Diet 2 yielded 1.22 cm in length increment, 4.92 g in weight gain with 0.49 % specific growth rate and 100 % survival rate. Diet 2 also showed the best FCR and PER, which was 1.79 and 0.14 respectively followed by diet 3 and diet 1. There were significant differences (P<0.05) of weight and length gain observed among the days with different diets. The proximate compositions of the feed and fish carcass showed that diet 2 and the fingerlings fed with diet 2 has highest nutritive contents than other diets as shown by the trend of higher protein content, moisture content, crude lipid, and dry matter. The findings of the study revealed that phototrophic bacteria could be utilized as fish supplement to enhance growth and nutritional contents of Tor tambroides and other aquaculture potential fishes in Malaysia.