Effects of Eimeria maxima infection doses on growth performance and gut health in dual-infection model of necrotic enteritis in broiler chickens

Abstract

The objective of this study was to investigate the effects of the different doses of <i>Eimeria maxima</i> (<i>EM</i>) oocysts on growth performance and intestinal health in broiler chickens challenged with a dual infection model of necrotic enteritis (NE) using <i>EM</i> and NetB⁺ <i>Clostridium perfringens</i> (<i>CP</i>). A total of 432 fourteen-d-old male Cobb 500 broiler chickens were divided into 6 groups with 6 replicates each. The six different groups were as follows: Control, non-challenged; T0⁺, challenged with <i>CP</i> at 1 × 10⁹ colony forming unit; T5K⁺, T0⁺ + 5,000 <i>EM</i> oocysts; T10K⁺, T0⁺ + 10,000 <i>EM</i> oocysts; T20K⁺; T0⁺ + 20,000 <i>EM</i> oocysts; and T40K⁺; T0⁺ + 40,000 <i>EM</i> oocysts. The challenge groups were orally inoculated with <i>EM</i> strain 41A on d 14, followed by NetB⁺ <i>CP</i> strain Del-1 on 4 days post inoculation (dpi). Increasing <i>EM</i> oocysts decreased d 21 body weight, body weight gain, feed intake (linear and quadratic, <i>p</i> < 0.001), and feed efficiency (linear, <i>p</i> < 0.001) from 0 to 7 dpi. Increasing <i>EM</i> oocysts increased jejunal NE lesion score and intestinal permeability on 5, 6, and 7 dpi (linear, <i>p</i> < 0.05). On 7 dpi, increasing the infection doses of <i>EM</i> oocysts increased jejunal <i>CP</i> colony counts (linear, <i>p</i> < 0.05) and increased fecal <i>EM</i> oocyst output (linear and quadratic, <i>p</i> < 0.001). Furthermore, increasing the infection doses of <i>EM</i> oocysts decreased the villus height to crypt depth ratios and the goblet cell counts (linear, <i>p</i> < 0.05) on 6 dpi. Increasing <i>EM</i> oocysts downregulated the expression of MUC2, B⁰AT, B^0,+AT, PepT1, GLUT2, AvBD3 and 9, LEAP2, and TLR4, while upregulating CLDN1, CATHL3, IL-1β, IFN-γ, TNFSF15, TNF-α, IL-10, and Gam56 and 82 on 6 dpi (linear, <i>p</i> < 0.05). Additionally, increasing <i>EM</i> oocysts decreased Pielou's evenness and Shannon's entropy (linear, <i>p</i> < 0.01). In conclusion, increasing the infection doses of <i>EM</i> significantly aggravated the severity of NE and exerted negative impact on intestinal health from 5 to 7 dpi.