|It is a well-known that fish meal supplies will not increase as most fisheries are beyond sustainable limits. If aquaculture and shrimp production in particular is expected to expand, the industry must move away from fish meal as a primary protein source, particularly in the production diets. As shrimp are a major aquaculture product and a primary use of fish meal it is critical that we expand our knowledge of novel protein source which could be used to reduce fish meal levels in production diets. Towards this goal the present study was dedicated to explore the potential of novel ingredients (flash dried yeast, non-genetically modified soy cultivars, bacterial biomass, fish meal analogue, and Ulva meal) as protein sources in practical diets for Pacific white shrimp, L. vannamei.
The first study was design to evaluate the potential of a novel yeast product flash dried yeast produced by low pH fermentation of Saccharomyces Pombe as a feed supplement in practical shrimp feed. Under the conditions of this study, the energy and protein digestibility of flash dried yeast are significantly lower than FM and SBM. Amino acids digestibility of FDY was lowest among the three ingredients tested. The use of FDY at 60 g kg-1 caused significant negative impacts on growth, feed conversion ratio and protein retention. Dietary flash dried yeast supplementation in the practical diets for Pacific white shrimp had no effects on the proximate composition of the whole shrimp body. Based on these results, further research regarding the effects of the low levels (< 40 g kg-1) inclusion of FDY in practical diets on immune responses of Pacific white shrimp is warranted.
The second study explored non-genetically modified soy cultivars as protein sources in commercial type shrimp feed formulations. The results indicate that breeding technology and novel soy processing has the potential to increase the nutritional values of SBM for shrimp feeds. Observed trends on immune indicators of shrimp to both independent and combined effects of soy ingredients and fermented yeast were not easily discernible. The variable response may be related to the difficult in working with shrimp or a suboptimal exposure period.
The third study investigated the effects of a dried fermented biomass as alternative ingredients for fish meal or soy protein concentrate. Under the reported conditions of the study, the use of dried fermented biomass can partially replace fish meal up to 50 g kg-1 without causing negative effects on the growth performance of Pacific white shrimp. However, completely replacement of fish meal (100 g kg-1) by dried fermented biomass resulted in growth depression. These results were confirmed in a second trial, which replaced soy protein concentrate with fermented biomass dried under two methods. The granular dried fermented biomass worked well as a substitution for soy protein concentrate, however, the inclusion of spray dried dry fermented biomass at 60 and 120 g kg-1 decreased the growth of shrimp. This data demonstrates that granular dried fermented biomass is a good nutrient sources and can be incorporated in practical shrimp feed formulations.
The aim of the fifth study was to evaluate a novel bacterial biomass as a replacement for soybean meal in practical shrimp feeds. Under the conditions of the present study bacterial biomass can be utilized up to 4% in shrimp feed without causing growth depression. However, supplementations (≥ 6%) of bacterial biomass can result in negative effects on growth response, FCR, and protein as well as amino acids retention efficiency. Negative result of dry matter digestibility as well as no improvements in the treatments balanced on digestible protein basis infers that something other than protein is influencing performance. Given that this is a new technology, there is a need to evaluate BB in term of possible immune stimulation as well as a nutrient source.
The sixth study was designed to evaluate a fish meal analogue as a replacement for fish meal in practical shrimp feed. Results indicated that in a practical diet containing 20% fish meal, fish meal analogue can replace all of the fish meal as long as the diets are supplemented with inorganic phosphorus without compromising the growth of shrimp. The improvement of growth when fish meal analogue was incorporated at 4.95% across three trials was not able to be defined. Given the good growth across the range of inclusion without any indication of a growth depression, the digestibility of the protein of fish meal analogue would be similar to that of the fish meal for which it was substituted. Hence, the low nutrient digestibility of fish meal analogue may due to an atypical response or the product simply does not work with the testing technique.
The seventh study evaluated the potential of Ulva meal Ulva sp. as an alternative protein source to fish meal and soybean meal in practical shrimp feed. Results demonstrated a clear depressing in growth as fishmeal was replaced. This data also demonstrated significant difference between batches of Ulva with the second batch producing the poorest results. To elucidate if digestible protein was limiting growth, a trial was initiated for which feeds were formulated on a digestible protein basis. In this trial, growth and survival were significantly reduced as the level of Ulva meal (Batch 2) was increased. Although, growth and survival was depressed this was less than that of previous trials, indicating that protein quality may be part of the problem. However, given the level of protein replacement other components of Ulva meal are likely to be causing poor performance. To survey possible problems caused by high levels of minerals the meals and select diets were analyzed for mineral content. Clearly there are shifts in mineral profiles; however, there is no obvious correlation to a mineral and this research team feels that it is unlikely a mineral toxicity. Other possible reasons which are beyond the scope of this project but would include anti-nutrients present in the algae. If Ulva meals are to be use to their full potential, e.g. as a primary protein source, the anti-nutritional components will need to be identified, specific lines of plants with enhanced nutrient value need to be developed and of course processing technologies evaluated to produce a high quality commercial product.
There is a clear need to develop sustainable ingredient sources for aquaculture, the use of soybean meal is clearly a viable option. Besides soybean meal, there are abundant alternative sustainable ingredients such as yeast, bacterial biomass, seaweed meals, and etc, which exhibited great potential as both immune enhancer and protein source. Therefore, it is vital for us to evaluate these potential alternative ingredients and promote a sustainable, environmentally friendly, and economical aquaculture.