Effects of black soldier fly (Hermetia illucens) larvae oil and meal on growth performance, cecal microflora, and meat quality in broiler

Abstract

As the needs for animal-origin food have soared with population growth, it became increasingly difficult to secure enough feed resources while food losses have been intensifying in developed countries. Black soldier fly larvae (BSFL) can produce high-quality proteins and fats sustainably, and better yet, convert organic wastes as their diets into feeds. Due to this recycling capability, BSFL have attracted attention as a critical player in the circular economy. The BSFL-derived ingredients can supply macro-nutrients and physiologically active compounds to animals. However, an effective use of BSFL-derived protein and fat as a feed ingredient requires scientific data in target animal species. The present study aimed to address the impact of BSFL oil (BSFLO) and meal (BSFLM) on growth performance, intestinal health issue, and meat quality in broilers. The first feeding trial evaluated the effects of BSFLO as a partial or total replacement of soybean oil (SBO) on the growth performance and the fatty acid (FA) profile and meat quality of broiler chickens from 1 to 5 week of age. A total of 210 male broiler chickens (Ross 308) at one day of age were randomly allotted to 3 dietary treatments (10 replicates and 7 birds/group): a basal control diet (CON), and two diets in which the soybean oil was replaced by 50% (50 BSFLO) or 100% (100 BSFLO) of BSFLO in the basal diet. The inclusion of BSFLO in diets did not influence the growth performance, physical measurements and chemical traits of leg meat, and sensory analysis of breast meat. However, the relative weight (g/kg) of the gizzard was reduced by dietary BSFLO at the expense of SBO (14.9, 12.5, and 13.0 for CON, 50 BSFLO, and 100 BSFLO, respectively; p < 0.05) The saturated fatty acid proportion (% of total FAME, fatty acid methyl ester) of SFA was increased (27.2%, 27.6%, and 28.7% for CON, 50 BSFLO, and 100 BSFLO, respectively; p < 0.05) by BSFLO inclusion and the percentage (% of total fat) of monounsaturated fatty acids was also increased (43.4%, 44.6%, and 48.6% for CON, 50 BSFLO, and 100 BSFLO, respectively; p < 0.001). On the contrary, the proportion (% of total FAME) of polyunsaturated fatty acids was decreased (29.5%, 27.8%, and 22.7% for CON, 50 BSFLO, and 100 BSFLO, respectively; p < 0.001). The first study confirmed that the replacement of SBO with BSFLO did not have any adverse effect on broilers' growth performance and that BSFLO can be used as a dietary fat source in broiler diets. The second experiment was performed to examine the effect of BSFLO as an alternative to SBO on the cecal microbiota in broilers. A total of 210 male broiler chickens (Ross 308) at one day of age were randomly allotted to 3 dietary treatments (10 replicates and 7 birds/group) that were same as in the first feeding trial. At the end of the study (d 35), 18 birds (6 broilers/treatment) were randomly selected and slaughtered. The cecal digesta samples were collected to measure the cecal microbiota population. Overall, 235,978 gene sequences were generated, and a total of 4,398 operational taxonomic units were identified in the three groups. At the phylum level, Firmicutes were the dominant phylum in all three groups. At the genus level, Faecalibacterium was the dominant genera in all treatments. There were no significant differences in relative abundances of all genera between the BSFLO groups and CON. However, genus Erysipelatoclostridium was more abundant in the 50 BSFLO than in the CON (p < 0.05). It was concluded that the substitution of the SBO with the BSFLO in broiler diets had no adverse effect on cecal microbiota in broilers. In the last experiment, the effects of microwave-dried BSFLM on carcass traits, meat quality, FA profiles of abdominal fat and meat, and heavy metal residues in the broilers meats. A total of 126 male broilers were randomly assigned to three dietary treatment groups (6 replicates and 7 birds/pen): a control diet and two experimental diets in which soybean meal was replaced with 25 or 50% BSFLM. The broilers were slaughtered at day 35; the carcasses were weighed, and breast and leg meats were excised from 12 birds per treatment (2 birds/pen) for meat analysis. For the higher BSFLM diet, the content of saturated FA in the abdominal fat was increased and that of polyunsaturated FA was decreased (p < 0.001); the FA profile of leg meat did not differ between groups. The concentrations of undesirable heavy metals in the BSFLM and leg meat were below maximum permissible levels. However, the carcass weight was decreased (p < 0.001) in the 50% BSFLM group. Microwave-dried BSFLM is a potential ingredient for broiler diets, with up to 25% inclusion showing no detrimental effects on carcass traits, meat quality, FA profiles, and heavy metal residues in the meat. It was confirmed that BSFLO could be used as an energy source in broilers by replacing SBO without negative impact on their productivity and meat quality. However, even though BSFLO contains a large amount of lauric acid, its effect on the intestinal microflora was not found. In conclusion, BSFLO can replace the existing energy feed source such as soybean oil with no adverse effects on growth performance, meat quality and health of broilers. On the other hand, BSFLM, microwave-dried and press-defatted, could not fully substitute SBM so its evaluation as a feed ingredient must be preceded to use BSFLM as a feed ingredient. Collectively, the results from the present studies demonstrated that BSFLO and microwaved defatted BSFLM could be an alternative to conventional ingredients such as SBO and SBM in broiler's diet.