Dietary insect meal inclusion in chickens: preliminary results about anatomopathological investigations.

Insects are being considered as a novel protein source for poultry feed, because they have high quality and quantity of protein, show low competitiveness with human feed and reduce the environmental contamination (1, 2). Previous studies found that chickens fed diets containing insect meal can improve growth performances in terms of feed intake, body weight gain and feed conversion efficiency (2), but limited anatomopathological data are available. The present study aims to investigate the anatomopathological findings in different chickens strains fed with standard or experimental diets including insect meal. 160 male broiler (group 1) and 100 female medium-growing hybrid chickens (group 2) were divided in 4 (basic feed, 5%, 10% and 15% Tenebrio molitor inclusion) and 2 (basic feed and 7.5% Tenebrio molitor inclusion) dietary treatments, respectively. For each experiment birds were distributed over 5 replicates for each dietary treatment. Diets were isoenergetic and isonitrogenous. At the age of 53 (male) and 100 (female) days the animals were slaughtered and 2 birds for each replicate were taken for analysis. 5 animals for each dietary treatment in the group 1 and 10 animals for each dietary treatment in the group 2 were submitted to anatomopathological investigations. Samples of liver, spleen, thymus, bursa of Fabricius, kidney, heart, glandular stomach and intestine (4 standardized segments of duodenum, jejunum, ileum and caecum) were collected, fixed in 10% buffered formalin solution and paraffin embedded to obtain 5μm histological sections stained with Haematoxylin & Eosin. Histopathological lesions were scored using a semiquantitative scoring system as follows: absent or minimal (score 0), mild (score 1) and severe (score 2). Data were compared by Kruskal-Wallis and Mann-Whitney U tests (GraphPad Prism R software, P value < 0.05). Histopathological findings were similar in both groups and were not significantly different (P > 0.05) between broilers fed with standard diet and with dietary insect meal inclusion. Spleen, thymus, bursa of Fabricius, liver and glandular stomach were the most frequently affected organs, while heart and kidney showed no significant alterations. Spleen showed white pulp hyperplasia or depletion. In thymus there was cortical depletion. Bursa of Fabricius showed follicular depletion with or without intrafollicular cysts. In liver there was lymphoid tissue activation. The etiopathogenesis of the lymphoid tissue activation and/or depletion remains to be elucidated. Glandular stomach showed lymphoplasmacytic flogosis with lymphoid tissue activation and epithelial squamous metaplasia. Interestingly, glandular stomach of medium-growing hybrids was affected by more severe alterations (P = 0.0008) than broilers. This finding could be related to the free range farming of this group. These preliminary results suggest how insect meal could be included in chickens diet without inducing histopathological changes. Studies are in progress to evaluate the effects of dietary insect meal inclusion on intestinal mucin composition and morphometry.