Physical characteristics of eggs from Hy-line Brown layers fed with Hermetia illucens larvae meal.

A total of 162, sixteen-week-old hens (average live weight 1.41 kg ± 0.13) were divided into 3 groups: the control was fed a corn-soybean meal-based diet (SBM) covering the hens' requirements according to the Hy-line Brown commercial line management guide (2016). In the diets of the treated groups (HI25 and HI50), the soybean meal was partially replaced by an insect meal from Hermetia illucens (HI) larvae, in order to develop 3 isoprotein and isoenergetic diets. In the HI25 and HI50 groups, 25 and 50% of the diet protein were replaced by the HI protein, reaching an inclusion level of 7.3 and 14.6%, respectively. The hens were housed for 20 weeks in the same building in modified cages (800 cm2/hen), under controlled environmental conditions. For each group, the hens were distributed into three cages (18 hens/cage), each of them was divided by two internal transects into 3 equal areas in order to obtain nine replicates of six hens per group. Feed and water were manually distributed. The dark:light cycle was 9:15 h. Six eggs per group and per week were weighed, and the weights and percentages of shell, yolk and albumen were recorded. The shell thickness was measured using an appropriate calliper. The yolk colour measurement was performed with a Konica Minolta colorimeter, according to the CIE system and expressed as lightness (L*), redness index (a*) and yellowness index (b*). The albumen pH was measured using a pH-meter. The eggs from the insect groups were heavier than those of the control (61.10 and 60.82 vs. 57.56 g, respectively for HI25, HI50 and SBM groups; p<.05) and the SBM group had a shell thicker than that of the HI50 group (541.9 vs. 476.3 µm; p<.05). The yolk weight of the insect groups was higher (p<.01) than that of the control (14.30 and 14.33 vs. 12.93 g, respectively for HI25, HI50 and SBM groups). Nevertheless, the albumen and yolk did not show significantly different incidences on the whole egg weight. The yolk of the eggs did not differ for L* values among groups, but the a* index of the eggs obtained from the control was markedly higher (p<.01) than that of the insect groups (6.01 vs. 0.67 and 0.80, respectively for SBM, HI25 and HI50 groups). Furthermore the b* index of the HI25 group was higher (p<.05) than that of HI50 (33.01 vs. 27.39). Both levels of H. illucens larva meal used in this trial modified the physical properties of the eggs inducing a heavier weight and a lower redness index of yolk and25% of the diet protein content replaced by the HI protein seems to be more appropriate than 50% level of replacement as it did not modify the shell thickness.