Effects of dietary sulfur amino acid levels on growth performance and intestinal immunity in broilers vaccinated and subsequently infected with coccidiosis

Coccidia vaccination is a common prac-tice in the poultry industry. However, research is lacking regarding the optimal nutritional support for coccidia vaccinated broilers. In this study, broilers were vacci-nated with coccidia oocyst at hatch and were fed with a common starter diet from 1 to 10 d. On d 11, the broilers were randomly assigned to groups in a 4 pound 2 factorial arrangement. Briefly, the broilers were fed one of four diets containing 0.6, 0.8, 0.9, and 1.0% of standardized ileal digestible methionine plus cysteine (SID M+C), respectively, from 11 to 21 d. On d 14, the broilers from each diet group were orally gavaged with either PBS (Mock challenge) or Eimeria oocysts. Compared to PBS-gavaged broilers and regardless of dietary SID M +C levels, the Eimeria-gavaged broilers had 1) decreased gain-to-feed ratio (15-21 d, P = 0.002; 11-21 d, P = 0.011); 2) increased fecal oocysts (P < 0.001); 3) increased plasma anti-Eimeria IgY (P = 0.033); and 4) increased intestinal luminal interleukin-10 (IL-10; duo- denum, P = 0.039; jejunum, P = 0.018) and gamma interferon (IFN-g; duodenum, P < 0.001; jejunum, P = 0.017). Regardless of Eimeria gavage, broilers fed 0.6% SID M+C had decreased (P<0.001) body weight gain (15-21 and 11-21 d) and gain-to-feed ratio (11-14, 15-21, and 11-21 d) when compared to those fed >= 0.8% SID M+C. Eimeria challenge increased (P < 0.001) duo-denum lesions when the broilers were fed with 0.6, 0.8, and 1.0% SID M+C, and increased (P = 0.014) mid -intestine lesions when the broilers were fed with 0.6 and 1.0% SID M+C. An interaction between the two experi-mental factors was detected on plasma anti-Eimeria IgY titers (P = 0.022), as coccidiosis challenge increased plasma anti-Eimeria IgY titers only when the broilers were fed with 0.9% SID M+C. In summary, the dietary SID M+C requirement for grower (11-21 d) broilers vaccinated with coccidiosis was ranged from 0.8 to 1.0% for optimal growth performance and intestinal immu-nity, regardless of coccidiosis challenge.