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Impact of complete replacement of soybean meal with black soldier larvae meal on plasma amino acid concentrations, enzymes, and other biochemical constituents in broiler chickens

Facey, H., M. Kithama, M. Mohammadigheisar, L. Huber, A. Shoveller and E. Kiarie

There is growing interest for the use of black soldier fly larvae meal (BSFLM) as a more sustainable, and functional protein ingredient. However, consistent with literature, we previously reported growth depression in broilers fed higher levels of BSFLM. Therefore, we examined plasma constituents as indicators for metabolic responses of complete replacement of soybean meal (SBM) with BSFLM in broiler diets. A total of 1,152-d-old male Ross × Ross 708 chicks were placed in 48 floor pens and assigned to six diets in a completely randomized block design. Diets were: a corn-SBM diet (A), four BSFLM diets formulated to replace SBM by 12.5% (B), 25% (C), 50% (D), and 100% (E) and diet (F), including Monteban and Bacitracin Methylene Disalicylate to diet A. The diets were isocaloric, prepared as mash in a three-phase program (starter: d 0-10, grower: d 11-24, finisher: d 25-49). On d 24 and 49, cardiac blood samples were taken from 2 random birds per pen for plasma amino acids (AA), enzymes, and other biochemical constituents. Data were subjected to Proc Glimmix procedures of SAS with a fixed effect of diet and random effect of block. A Tukey’s test and contrast statements were used for analyzing LSMeans between diets. On d 24, BSFLM linearly (P<0.05) increased plasma concentration of His, Ser, Thr, Lys, Val and Tyr. Likewise, on d 49, BSFLM linearly (P<0.05) increased plasma Thr, Lys, Met, Ala, Pro, Tyr, Phe and uric acid (PUA) concentrations. On d 24, plasma gamma-glutamyltransferase (GGT) and creatine kinase (CK) concentrations increased linearly (P≤0.05) with BSFLM and GGT quadratically (P<0.05) on d 49. Diet had no effects on plasma concentration of glucose and cholesterol (P<0.05). On d 24, BSFLM increased plasma Ca linearly (P=0.014) and Na quadratically (P=0.012) but reduced P quadratically (P=0.012). On d 49, BSFLM linearly (P≤0.01) reduced plasma K and Cl.

In conclusion, high circulating plasma AA combined with elevated uric acid and altered mineral metabolism suggested reduced protein synthesis likely due to AA unavailability/imbalance. This may explain previously observed depression in growth in broilers fed diets high in BSFLM. Further research is required to unravel post-absorptive AA availability and utilization of BSFLM.