Effects of Alternative Administration Programs of a Synbiotic Supplement on Broiler Performance, Foot Pad Dermatitis, Caecal Microbiota, and Blood Metabolites

SIMPLE SUMMARY: Banning antibiotics as feed additives has brought out the impelling necessity to develop reliable and cost-effective alternatives to improve livestock performance without undermining public health. Synbiotic supplements enhance poultry gut health, which in turn affects productivity and general well-being. Synbiotics have been traditionally supplemented in-feed or via drinking water. However, in-ovo injection and spraying aqueous suspensions on feathering of newly hatched chicks were proposed to allow desirable strains to early colonize the gut and hinder harmful microorganisms more effectively. The aim of this study was to investigate the effects of alternative administration programs of a synbiotic on broiler’s productive performance, foot pad dermatitis, caecal microbiota, and plasma metabolites. Favorable effects on feed efficiency and foot pad conditions were observed when the synbiotic was -delivered as gel droplets at the hatchery combined to in-feed supplementation during the entire growing cycle. Such improvements can be ascribed to the potential modulatory effect of the synbiotic towards gastro-intestinal microbial community. Significant differences of plasma ascorbic acid and propylene-glycol levels were also observed in treated animals. ABSTRACT: This research investigated the effects of different synbiotic administration programs on broiler productive performance and foot pad dermatitis (FPD). Molecular insights on caecal microbiota and plasma metabolomics were also performed. - A total of 1000 one-day-old male chicks were grouped by the synbiotic treatment. The synbiotic was either sprayed as gel droplets onto newly hatched chicks at the hatchery (100 g/10,000 birds) or supplemented in-feed during the entire rearing period (1000, 500, and 250 g/ton according to feeding phase), or both. Only the treatments’ combination produced significant results in comparison with the control group (untreated), improving feed conversion ratio from 14 to 29 d and in the overall period of the trial (1.570 vs. 1.509 and 1.643 vs. 1.596, respectively; p < 0.05) while lowering FPD occurrence at slaughter (17% vs. 5%; p < 0.05). These findings can be related to significant variations of caecal microbiota, like higher Firmicutes to Bacteroidetes ratio (with favorable implications for host’s energy-harvesting potential from the diet) and more beneficial microbial consortium presumably sustaining eubiosis. Overall, these results indicate that administering synbiotics through gel droplets at the hatchery combined to in-feed supplementation for the whole growing cycle positively affects broiler feed efficiency and welfare.