In vivo performances, ileal digestibility, and physico-chemical characterisation of raw and boiled eggs as affected by Tenebrio molitor larvae meal at low inclusion rate in laying quail (Coturnix japonica) diet

A total of 120, 12 weeks old female Japanese quails were divided into 4 groups (6 replicates of 5 birds each). The control group (CON) fed a corn-soybean diet; in the other 3 groups, Tenebrio molitor larvae meal (TML) replaced 5, 10 and 20% of the soybean protein (T5, T10 and T20). The laying performance and egg quality were studied for 54 days. The data were processed by a one-way ANOVA; the orthogonal contrast analysis was performed to test the linear, quadratic and cubic effects among the means. The laying rate and egg mass linearly decreased (P < 0.01) as the TML inclusion level in the diet increased. The egg weight and feed conversion ratio linearly increased from the control to T20 diet (P < 0.01) while the digestibility of dry matter, organic matter and crude protein linearly decreased (P < 0.05). The albumen and yolk weight showed a linear increase (P < 0.01) due to dietary TML inclusion, while the eggshell weight showed the opposite (P < 0.05). The estimated activity of Δ9-desaturase (C16:0), Δ5+Δ6-desaturase on both polyunsaturated fatty acid n-6 and n-3 linearly increased (P < 0.05) as affected by dietary TML. The boiled yolk lightness (L*) showed higher values in T5 and T10 groups (quadratic contrast, P < 0.01). The yolk redness index (a*) showed lower values in T5 and T20 than control and T10 groups (cubic contrast, P < 0.01). The albumen L*, a*, and b* indexes showed a significant effect of the quadratic contrast (P < 0.05). In addition, the albumen b* index showed a significant effect of the cubic contrast (P < 0.01). The total lipids showed the highest values (cubic contrast, P < 0.05) in the T10 and T20 groups. The total monounsaturated fatty acids linearly increased (P < 0.05) according to the increase of dietary TML. The best inclusion level of defatted TML meal for laying quails seems to be 1.4% of diet, corresponding to the T5 diet.