Interaction between feeding regimen, NSPase enzyme and extent of grinding of barley-based pelleted diets on the performance, nutrient digestibility and ileal microbiota of broiler chickens

1. The effects of feeding regimen, NSPase, extent of grinding and their interaction on the performance, digestive tract characteristics and ileal microbiota were studied. Eleven-day-old Ross 308 male broilers were given <i>ad libitum</i> (ADL) or intermittent (INT) access to finely (FG) or coarsely (CG) ground barley-based pelleted diets, with or without NSPase in a replicated pen trial. All birds had 4 h darkness separated with 1 h light periods with feed access. In addition, INT birds had access to feed through three 1 h feeding periods and one 2 h feeding period, with 3 h feed restriction periods in between.2. The INT feeding decreased weight gain (<i>p</i> < 0.001) but did not affect FCR. Supplementation with NSPase increased (<i>p</i> = 0.018) weight gain, but there was a tendency (<i>p</i> = 0.063) for it to be improved in INT-fed birds only. Including NSPase improved FCR, but only with FG diets (<i>p</i> = 0.037) and in INT group (<i>p</i> = 0.033).3. The CG diet significantly reduced (<i>p</i> = 0.044) pH of the gizzard contents and increased (<i>p</i> = 0.035) gizzard relative weight compared to FG. Addition of NSPase (<i>p</i> < 0.001) or FG (<i>p</i> = 0.049) reduced jejunal digesta viscosity. The FG diet improved (<i>p</i> = 0.019) starch digestibility compared to CG. In NSPase-supplemented diets, CG increased ileal protein digestibility compared to FG in birds fed ADL only, resulting in a three-way interaction(<i>p</i> = 0.012).4. The FG diet increased ileal concentration of total eubacteria and <i>Lactobacillus</i> spp. (<i>p</i> = 0.049), whilst INT feeding increased ileal concentration of S<i>treptococcus</i> spp. (<i>p</i> = 0.001). In NSPase-containing diets, FG increased ileal density of <i>Enterococcus</i> spp. in INT-fed birds (<i>p</i> = 0.027).5. In conclusion, finely-ground barley in pelleted diets responded better to NSPase enzymes than coarsely ground, particularly under INT feeding.