Managing broilers gut health with antibiotic-free diets during subclinical necrotic enteritis.

Necrotic enteritis (NE) caused by Clostridium perfringens is among the most important enteric diseases in poultry production. This study examined the effects of 2 probiotics (Prob) and a synbiotic (Synb) during a naturally occurring NE challenge. On the day of hatch, 1200 Cobb male broilers were randomly allocated to 5 groups (8 pens/treatment, 30 birds/pen) including 1) negative control (NC): corn-soybean meal diet; 2) positive control (PC): NC + 453 g Stafac20/907 kg feed; 3) Prob 1: NC + 453 g Prob 1/907 kg feed; 4) Prob 2: NC + 453 g Prob 2/907 kg feed; and 5) Synb: NC + 453 g Synb/907 kg feed. One day after placement, birds were challenged by a coccidia vaccine to induce NE. Feed intake and body weights were measured on day 8 (NE onset) and end of starter (day 14) and grower (28) periods. On day 8, the small intestines of 3 birds/pen were examined for NE lesions. Ileal mucosal scrapings from one bird/pen were collected on day 8 and day 28 to profile the microbiota using 16S rRNA sequencing. Data were analyzed in JMP or QIIME 2 and significance between treatments identified by LSD or linear discriminant analysis effect size (P < 0.05). The Synb group significantly lowered NE lesion scores on day 8 and reduced day 0-14 mortality by 50% compared with NC. FCR was significantly better in all the groups, whereas ADG was higher in PC, Synb, and Prob 2 groups compared with NC from day 0 to day 28. Lower lesion scores in the Synb group were accompanied by lower relative abundance of Alistipes, ASF356, Faecalibaculum, Lachnospiraceae UCG-001, Muribaculum, Oscillibacter, Parabacteroides, Rikenellaceae RC9 gut group, Ruminococcaceae UCG-014, and Ruminiclostridium 9 compared with NC on day 8. On day 28, relative abundance of Lactobacillus was lower, whereas abundance of Bacteroides, Barnesiella, Butyricicoccus, CHKCI001, Eisenbergiella, Eubacterium hallii group, Helicobacter, Ruminococcaceae UCG-005, Ruminococcus torques group, and Sellimonas was significantly higher in the NC birds than in the Synb and Prob 2 groups. Collectively, these data indicate that during a subclinical naturally occurring NE, supplementation of specific additives could be effective in reducing intestinal lesions and mortality, and improving performance potentially through developing a signature microbial profile in the intestinal mucosal layer.