Use of Organically Certified Yeast in the Diet of Juvenile Rainbow Trout (Oncorhynchus mykiss): Growth Performance, Nutrient Utilization, and Fatty Acid Composition

This study evaluated the effects of the dietary organically-certified yeast, NuPro™, used as a replacement for fishmeal, on growth performance, nutrient utilization, and fatty acid composition in juvenile rainbow trout, Oncorhynchus mykiss. Two reference diets (conventional and organic) and three experimental diets (including 10%, 20%, or 30% NuPro™) were formulated. Diets were assigned to triplicate groups of 20 fish (4.0 g) for 12 weeks. There were no differences in growth performance or feed conversion ratio (FCR) between the two reference groups and growth responses were similar among experimental groups (p>0.05). Fish fed the 20% diet grew significantly better than the conventional group (p0.05). The highest n-3/n-6 ratio was obtained in fish fed the organic diet and the lowest in fish fed the 30% diet. Results show that organically certified yeast can contribute be an effective alternative to plant proteins in organic trout feed

Assessment of Chlorogloeopsis as a novel microbial dietary supplement for red tilapia (Oreochromis niloticus)

A 9week study was conducted to assess the effect of incorporating dietary Chlorogloeopsis on the growth performance, feed utilisation, body composition, haematology and gut microbiota of red tilapia (Oreochromis niloticus). Chlorogloeopsis cells were supplemented to the diet at 0.25%, 0.50% and 1.00%. Compared to the control group, no significant differences of growth parameters or body composition were observed in the Chlorogloeopsis fed fish. However, haematological and gut microbial load appeared to be more sensitive to dietary Chlorogloeopsis. Haematocrit levels increased from 31.0±2.9% in the control group to 32.8±4.2 and 33.3±5.0 in the 0.50% and 1.00% Chlorogloeopsis groups, respectively. The total allochthonous microbial load and lactic acid bacteria levels were elevated but the microbial groups identified and microbial diversity did not differ between the dietary groups. PCR-DGGE fingerprints of the microbial profiles supported this finding but revealed clear differences between the allochthonous and autochthonous communities. Sequence analysis from DGGE fingerprints identified several bacterial clones closely related to bacteria previously isolated from the digestive tract of fish and revealed a Lactobacillus spp. found in all groups was present only as part of the allochthonous communities. Low level dietary applications of Chlorogloeopsis for tilapia aquaculture seem limited but further evaluation is required