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This study evaluated the effects of calcium butyrate (CB) and bacitracin methylene disalicylate 50 (BMD) combined with different phytase concentrations on broiler intestinal health and physiology. Day-old YPM x Ross 708 male broilers (2,880) were distributed in 72 floor pens and assigned to 1 of 9 treatments (8 replicates/treatment). This experiment was a factorial arrangement including 2 phytase concentrations (500 or 1,500 FTU/kg) and 4 microbiota modulating feed additive levels (MMFA; (1) none, (2) only CB (0.5 g/kg of diet), (3) only BMD (55 mg/kg of diet), or (4) both CB and BMD). Additionally, a negative control without phytase and MMFA was included. Intestinal permeability was assessed on d 27. Jejunum wall and cecal content samples were collected on d 28 and 42 to assess jejunum villus height (VH), crypt depth, tight-junction and mucin gene expression, cecal microbiome diversity, and predicted bacterial metabolic pathways. Phytase and MMFA did not influence intestinal permeability (P > 0.05). Combining both CB and BMD with 1,500 FTU/kg of phytase compared to 500 FTU/kg lowered d 28 VH (P ≤ 0.05). Jejunal expression of CL-1, CL-4, CL-5, and ZO-2 on d 28 as well as CL-2 on d 42 changed between MMFA when combined with 1,500 FTU/kg of phytase but not 500 FTU/kg (P ≤ 0.05). Day 42 Pielou's evenness increased when 1,500 FTU/kg of phytase was combined with both CB and BMD compared to no MMFA (P ≤ 0.05). The cecal microbial beta diversity was not influenced by phytase, MMFA, or their interaction (P > 0.05). Overall, broiler intestinal health and physiology were influenced by CB and BMD depending on phytase concentration, demonstrating the complex interactions between these feed additives.

ABSTRACT: A study was conducted to assess the effects of a dietary yeast cell wall (YCW) with and without a Campylobacter jejuni (CJ) challenge. A total of 2,240-day-old Ross 708 males were randomly assigned within 8 treatments with a 4 × 2 factorial design, with 4 diets (negative control, positive control, YCW constant dose (400 g/ton), and YCW step-down dose (800/400/200 g/ton in the starter/grower/finisher diets, respectively) and with and without d 21 CJ oral gavage challenge at 5.2 × 107 CFU/mL. At d 0, 14, 28, and 41 body weights and feed consumption were measured to determine performance. At d 14, 28, and 42, 8 jejunal and ileal histology samples per treatment were collected for villi morphology measurements. At d 22 and 28 (1- and 7-days postinoculation), 24 ileal tissue samples per treatment were collected for relative gene expression analysis. At d 42, 24 cecal content samples per treatment were collected for CJ enumeration. Finally, on d 44, 96 birds per treatment were processed to determine carcass yield and 16 carcass rinses per treatment were collected to determine CJ prevalence after processing. Diet or inoculation did not impact broiler performance (P > 0.05). Limited differences were observed in intestinal morphology, and villus height and crypt depth were different only in the ileum at d 42 (P = 0.0280 and P = 0.0162, respectively). At d 1 postinoculation, differences between treatments inoculated with CJ and PBS were observed in the expression of avian beta defensin 10 (AvBD10), interleukin 1ß (IL-1ß), and interleukin 10 (IL-10) (P < 0.05). At d 7 postinoculation, expression of AvBD10, IL-1ß, and IL-10 was similar among all treatments (P > 0.05). At d 42, all birds, regardless the inoculation, had similar levels of CJ recovered from cecal contents (P > 0.05). After processing, carcass yield and CJ prevalence postchilling was similar in all treatments (P > 0.05). Overall, under the conditions of this study, the addition of YCW during a CJ challenge did not have an impact in growth performance, innate immune response, cecal colonization, carcass yield, or CJ prevalence after processing.