Effects of immune stress on growth performance, immunity, and cecal microflora in chickens

Immune stress is the loss of immune homeostasis by external forces. This study investigated the effects of different types of immune stress on growth performance, immunity, and the distribution of cecal microflora in broiler chickens. In total, 540 one-day-old Cobb 500 broilers were randomly assigned to receive 1 of 5 (n = 108 birds/group) treatments: 1) no vaccination; 2) simplified vaccination, which included the infectious bronchitis vaccine (H120), the inactivated avian influenza vaccine (AI), the live vaccine strain Clone-30 of the Newcastle disease virus (NDV), and the combined inactive vaccine for infectious bursal diseases and the Newcastle disease vaccine (ND-IB); 3) normal vaccination (simplified vaccination + second dose of ND-IB, H120, and AI); 4) lipopolysaccharide (LPS) stress (normal vaccination + LPS); or 5) cyclophosphamide (CPM) stress (normal vaccination+ CPM). The results showed that the average BW and average feed intake decreased significantly after treatment with LPS or CPM (P < 0.05). Chickens that were challenged by LPS or CPM had a lower ileal CP digestibility than that of the control group (P < 0.01). Compared with the control group, the levels of secreted IgA decreased significantly at 42 d of age in the chickens that were treated with LPS or CPM (P < 0.01). The proliferation of the peripheral blood mononuclear cell and the levels of serum IgG in the LPS-challenged chickens were higher than those in the control group chickens at 21 and 42 d of age, respectively (P < 0.05). Six clusters were identified at 21 d of age, but cluster 6 was a single sample. Only 5 clusters were identified at 42 d of age. The enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprints of the cecal samples from the no vaccination and the simplified vaccination groups clustered together with high coefficients. The ERIC-PCR fingerprints of the 3 cecal samples from the CPM and LPS treatment groups clustered together with high coefficients among them. The ERIC-PCR fingerprints of the microbial flora of the cecal contents revealed the potential effects of immune stress on the microbial populations of treated birds. These data suggest that broilers with simplified vaccinations or without vaccinations can achieve the same growth performance as broilers with general vaccinations, but immune stress can break the homeostasis of cecal microflora and impair intestinal mucosal immune function.