A team of researchers from Kentucky State University and the US Department of Agriculture’s (USDA) Agricultural Research Service (ARS) examined the use of black solider fly larva meal (BSFLM) in the diets of farmed Pacific white shrimp. The group published its findings in the journal Aquaculture.
The meal was examined because plant-based protein alternatives have not been completely successful in replacing fishmeal (FM) in shrimp diets, the researchers said. The insect meal also has generated promising results in other crustacean diets.
It is important to research more efficient ways to produce food in a space, said Carl Webster, director and research leader at the Harry K Dupree Stuttgart National Aquaculture Research Center and corresponding author. “Since the amount of land on Earth isn’t increasing, it will be important to maximize production on available land,” he added.
Research into agriculture is one way to improve food production and food security, he said. In the US, it has been found that for every $1 spent on research by the USDA’s ARS, about $17 has been generated for the economy.
“I have always seen a need for evaluating alternative protein ingredients in aquaculture diets – I was one of the first researchers to systematically evaluate distiller’s dried grains with solubles (DDGS) in fish diets almost 30 years ago,” he told FeedNavigator. “Since fishmeal (FM) is the most nutritious ingredient in an aquaculture diet, but is also the most expensive macro ingredient, it is important to reduce or eliminate its inclusion in fish/shrimp diets.”
The group saw shrimp production and body composition supported with the alternative protein ingredient, when it was used at or below certain levels, said the researchers.
“The current results give insight into current limitations of using black solder fly larvae meal in white shrimp and possible avenues of expanding insect meal replacement of fishmeal in aquaculture diets,” said the researchers. “With judicious modifications to diet formulations which include BSFL meal, increased inclusion levels may be possible in diets for Pacific white shrimp.”
Why black solider fly larva meal?
Looking forward, aquaculture will be one way to address the protein needs of an increased global population, but there also are obstacles that remain to widespread production, said Webster. “One of these is to formulate economical, nutritious, environmentally-responsible diets to feed cultured organisms,” he added.
Additionally, it is unlikely that the amount of fishmeal produced will increase, so other protein sources need to be considered, he said.
Soybean meal is a widely-used protein in aquaculture diets, but there are some challenges to extensive use of that ingredient, he said. It has reduced amounts of methionine and lysine, contains anti-nutritional factors, like trypsin inhibitors and phytic acid, and can make a diet less palatable, he said. Other plant-based proteins, such as cottonseed meal, canola meal and mustard seed cake, also present challenges when used as the only protein source, he said.
“Animal-source ingredients (meat meal, poultry by-product meal, porcine meal) offer more flexibility and higher inclusion levels in diets for many fish species, and can be used with plant-protein ingredients to compliment the nutrient composition of a diet formulated with FM,” said Webster. “However, it is important to evaluate new protein ingredients since commodity prices can increase.”
If products become too expensive, producers need to have alternative ingredients readily available, he said. “Thus, the impetus for our feeding trial using black soldier fly larval meal in diets for white shrimp; no one had previously evaluated the ingredient for use in shrimp diets.”
The ingredient is high in protein, has a good amino acid balance and, if defatted, a lower lipid level at about 6-15% instead of the 25-35% of unprocessed BSFLM, he said.
In the study, six diets were fed to shrimp for a period of 63 days, said the researchers. The diets included a control made with fishmeal and soybean meal, and that diet with increasing amounts of BSFLM, replacing fishmeal at 20%, 40%, 60%, 80% and 100%.
Shrimp were collected on day 63 and evaluated for final weight, weight gain, specific growth rate, feed intake, feed conversion ratio and percent survival, said the researchers. Dietary amino acid profile also was assessed.
If the amount of BSFLM was kept below 25% of the diet, then 95-100% of the growth responses including final weight, weight gain, specific growth rate (SGR) and food conversion could be maintained, said the researchers. “Similarly, 95% or greater of maximum whole-body protein and lipid content could be achieved when BSFL inclusion was restricted to [less than] 29% and 15%, respectively,” they said.
BSFLM had a higher lipid and moisture content, but reduced levels of protein and ash compared to fishmeal, they said. Most essential amino acids also were lower, except for Histidine and Tyrosine.
Shrimp survival and feed intake was similar for all diets, they said. However, shrimp final weight, percent weight gain, SGR and feed conversion declined as more fishmeal was replaced.
“As this was the first study to evaluate BSFLM in white shrimp diets, the downward growth trend with increasing BSFLM addition did not disappoint me,” said Webster. “The diets were formulated to meet the essential amino acid requirements of shrimp, but there is not any digestibility data for BSFLM in shrimp so the results were not necessarily unexpected.”
The feeding trial was just an initial step in the ongoing evaluation, he said. “Our next step is to utilize the data obtained from this study and refine the diet formulations,” he added.
“Data from the second study should build upon the results from the first,” he said. “This should give a more clear picture of the suitability for BSFLM in shrimp diets, and possibly diets for other aquaculture species, especially carnivorous fish species such as salmon, bass, and marine species.”
Title: Evaluation of black soldier fly (Hermetia illucens) larvae meal as partial or total replacement of marine fish meal in practical diets for Pacific white shrimp (Litopenaeus vannamei)
Authors: V. Cummins Jr, S. Rawlesb, K. R. Thompsona, A. Velasqueza, Y Kobayashia, J Hagera, C D. Websterb