Performance response of broiler chickens fed diets containing dehydrated microalgae meal as partial replacement for soybean until 22 days of age

Microalgae meal (MM) could represent a sustainable alternative to soybean meal as protein ingredient for broiler diets. The aim of this study was to investigate the effects of the dietary substitution of soybean with MM (Arthrospira spp.) during the first stages of the rearing cycle on the growth performance of broiler chickens. A total of 1 000 one-day-old Ross 308 male chicks were divided into 4 experimental groups (10 replicate pens/group with 25 birds each) receiving, during the starter (0–12 days) and grower (13–22 days) phases, either a conventional soybean-based diet (CON group) or the same diet including MM at low (LM group: 50 g/kg in both phases), intermediate (IM group: 100 and 90 g/kg, respectively), or high dosages (HM group: 150 and 140 g/kg, respectively). From 23 days onwards, all groups received the same conventional soybean-based diet up to slaughter age (47 days). All diets were formulated to be iso-energetic and with a similar amino acid profile. Productive parameters were recorded on a pen basis at housing (0 day), at 22 days, and at slaughter. At 22 days, body weight was linearly reduced and feed conversion ratio significantly worsened as the dietary inclusion of MM increased (931 vs. 850 vs. 709 vs. 462 g, and 1.539 vs. 1.656 vs. 1.783 vs. 2.312 for CON, LM, IM and HM groups, respectively; P < 0.001). CON and LM groups presented similar feed intake from 0 to 22 days, which was significantly higher if compared to IM and HM (1.367 vs. 1.333 vs. 1.184 vs. 0.964 kg/bird, respectively; P < 0.001). At 47 days, CON and LM groups exhibited comparable body weight, while IM and HM showed lower values (3455 vs. 3446 vs. 3221 vs. 2802 g, respectively; P < 0.001). No significant difference in FCR was observed in the overall period of trial (0–47 days). Similarly, liveability was not substantially affected by the treatments. Overall, these results indicate that the dietary administration of MM during the first 22 days of life significantly impaired broiler growth performance regardless of the dosage. However, by re-feeding a conventional soybean-based diet up to slaughter (47 days), broilers receiving 50 g/kg of MM up to 22 days achieved similar growth performance and productive efficiency to those fed a conventional soybean-based diet in all feeding phases.