An overview of dietary effects of Hermetia illucens meal in Muscovy duck.

Introduction. The research of alternative protein sources in poultry feeding is becoming really urgent, due to the future pressure on the already limited resources [1,2]. Thanks to their nutritional characteristics, insects represent a promising alternative protein source for monogastric animals [3,4]. Aim of the study is to provide a global overview on dietary inclusion of Hermetia illucens (HI) meal in Muscovy duck. Animals, material and methods. Females of Muscovy ducks (192, 3-day-old) were assigned to 4 experimental diets (6 replicate/treatment; 8 birds/pen) with increasing substitution levels of corn gluten with HI partially defatted meal (0, 3, 6, 9%; HI0, HI3, HI6, HI9, respectively). The nutrient composition of both 2 the test diets was the following: crude protein (CP) 60% on dry matter basis (DM) and ether extract (EE) 2% DM for corn gluten meal; CP 57% DM; EE 11% DM for HI meal. The diets were split in 3 feeding phases: starter (3-17d), grower (18-38d) and finisher (39-50d). Growing performance was assessed for the whole trial and diet digestibility was evaluated for each feeding phase (using titanium dioxide as inert marker 0.3 g/kg). At day 51, 12 birds/treatment were slaughtered, and blood samples were collected for further analysis (hematological and serum traits and plasma antioxidant status). Samples of spleen, liver and abdominal fat were weighed and collected for histopathological examination. In addition, histomorphological evaluation was assessed on gut samples (duodenum jejunum and ileum). The carcass, breast and thigh yields were then recorded, as well as the breast and thigh color, pH and proximate composition. Intestinal morphometric indices were analysed by general linear mixed model and Kruskal-Wallis test was used to evaluate the organs histopathological scores. The remained data were analysed by one-way ANOVA evaluating the effect of dietary HI inclusion level by polynomial contrasts. Significance was declared at p<0.05. Results and discussion. Growing performance were not affected by dietary treatments for the whole trial (p>0.05), showing a final live weight similar among groups (average: 2515.67±43.66) as well as the feed conversion ratio (average: 2.31±0.02). The apparent total tract diet digestibility was partially affected by dietary treatments, with a linear decrease in crude protein digestibility in starter period (p<0.05). Indeed, ether extract digestibility was always higher in insect-fed groups than HI0 (p<0.05). Among blood and serum parameters, a linear decrease was observed for cholesterol, triglycerides, alkaline phosphatase, with a minimum for HI9 group (p<0.05). The antioxidant status of birds resulted improved, with a linear decrease (minimum for HI9) of two oxidative metabolites: malondialdehyde and nitrotyrosine (p<0.05). Finally, organs yield and histopathological scores and gut histomorphometry were not affected by dietary treatments as well as carcass, breast and thigh yields, meat pH, color and proximate composition (p>0.05). Conclusion. The results show that the dietary inclusion up to 9% of HI partially defatted meal represent a promising feed ingredient in Muscovy duck nutrition from a productive and biological point of view. References: [1] Gariglio et al. (2019) J. Anim. Sci. Biotechnol. doi: 10.1186/s40104-019-0344-7; [2] Dabbou et al. (2018) J. Anim. Sci. Biotechnol. 9:49; [3] Cullere et al. (2016) Animal. 10: 1923-1930; [4] Cutrignelli et al. (2018) Res Vet Sci. 117: 209-215.