Industrial production of black soldier fly larvae (BSFL) already offers a sustainable alternative to marine fish meal in diets for aquaculture species, particularly salmonids. BSFL meal and oil also may be attractive substitutes for vegetable proteins and fats in poultry. Recent research from China finds BSFL oil can replace 50% of soybean oil in broiler diets, yield comparable bird performance, and potentially improve gut health and immune function. Caveats include knowledge of the BSFL growth substrate (feed grade materials or not) and broiler performance potential (per genetics supplier).
Research and development of black soldier fly (Hermetia illucens) larvae in aquaculture diets goes back decades with the goal of replacing wild-caught ocean fish used for fish meal and oil. Advantages for industrial production of this high-protein, high-fat insect species include (1) breeding and feeding on organic waste materials, (2) relatively large and slow-moving adults and larvae, (3) adults that do not sting or bite, and (4) larvae with good amino acid and fatty acid profiles.
BSFL offer crude protein of 30-53g/100g of dry matter (DM) and crude fat of 20-41g/100g DM along with chitin, which functions like fiber in the poultry digestive system. Fat or oil from BSFL consists of palmitic, oleic and linoleic acids, but also contains high levels of lauric acid, like palm kernel oil and coconut oil.
The Association of American Feed Control Officials (AAFCO) recently updated its definition of "dried black soldier fly larvae" (T60.117) to cover use in salmonid, poultry, and swine feeds as well as adult dog and cat foods, specifying that the larvae must be "raised on feedstock composed exclusively of feed grade materials."
Importantly, nutrients in BSFL can vary according to that feedstock, as noted by
at team of researchers from the Wenzhou Academy of Agricultural Sciences and the Shanghai Veterinary Research Institute. These researchers also caution that "heavy metals and poisons can build when (larvae are) grown on polluted substrates...." So controlled, safe breeding and feeding of BSFL are paramount.
The researchers noted recent research in high-yielding hens showing that a BSFL-based diet can totally replace soy-based feeds, even in organic diets devoid of synthetic amino acids. They were encouraged by other work with broiler chickens suggesting that BSFL oil (BSO) might be a promising substitute for dietary fat.
"Nevertheless, knowledge about BSO as a feed ingredient is still lacking and requires further investigation into its effects on broiler's growth performance, immunity, and gut health."
In this study, the researchers obtained commercially available BSO in China with a fatty acid profile predominated by lauric (33.7% C12:0), linoleic (21.9% C:18:2), oleic (17.4% C:18:1), and palmitic (14.2% C16:0).
The researchers randomly divided 240 day-old Kebao broilers (China's leading white-feather broiler, comparable to Ross 308) into five groups. They fed conventional corn-soybean meal diets in two stages (high and low protein levels) with ad lib feed and water over the 28-day trial period. BSO replaced soybean oil at rates of 0% (control and basal diet), 25%, 50%, 75%, and 100%. All diets containing BSO were isonitrogenous and isoenergetic and all birds received vaccinations according to a typical immunization procedure.
Researchers measured:
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Broiler performance -- average daily feed intake, daily gain, and daily feed-to-gain ratio -- for potential economic and sustainability advantages of BSO over soybean oil
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Blood chemistry -- plasma levels of aminotransferase, alanine aminotransferase, albumin, globulin, immunoglobulin A, interleukin 2, tumor necrosis factor alpha, total protein, blood urea nitrogen, malondialdehyde, glutathione peroxidase, total superoxide dismutase, and total superoxide dismutase -- for immune and antioxidant function
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Small intestine morphology -- villi height and crypt depth changes based on samples from duodenum, jejunum, and ileum -- showing potential effects on digestion and gut health
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Ileal RNA extraction -- showing expression of mucin 2, junctional adhesion molecule 2, occludin, zona occludens-1, interleukin 2, interleukin 6, and tumor necrosis factor alpha -- for immune system changes including intestinal barrier function
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Ceca microbiota -- genomic DNA sequencing and analysis -- for changes in bacteria populations with potential effects on gut health and immunity
Generally, the researchers' results agreed with previous work using BSO in diets for poultry, including turkeys, layers, and broilers. However, they noted the possibility of differences in BSO nutrient composition given experiments with different sources of feedstock or growth substrate for the larvae. Also, they acknowledged possible differences in results based on different broiler genetics (for example, Kebao versus Ross 308).
The current study found that replacing soybean oil with BSO had no adverse effect on broiler growth performance. Moreover, the researchers suggested that BSO "could improve plasma immune and antioxidant function, intestinal morphology and barrier function of broilers."
However, they warned that, at higher levels (75-100% replacement), BSO impacted blood chemistry, increasing plasma levels of aminotransferase and blood urea nitrogen, which could have detrimental health effects.
"In this study," the researchers concluded, "50% substitution of soybean oil with BSO was preferred for the optimum production performance."
What does this study mean for producers?
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Black soldier fly larvae (BSFL) grown on non-feed grade materials are not approved for use in poultry diets in the U.S. and Canada
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BSFL oil (BSO) can replace soybean oil in broiler diets without hurting growth performance
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The 50% replacement level appears to optimize performance and potential health benefits
The full paper, titled "Effects of black soldier fly larvae oil on growth performance, immunity and antioxidant capacity, and intestinal function and microbiota of broilers" can be found in Applied Poultry Research and online here.
DOI: 10.1016/j.japr.2022.100292
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