Effects of rearing system and narasin on growth performance, gastro-intestinal development and gut microbiota of broilers

Abstract

BackgroundThis study was conducted to evaluate the effects of three rearing systems (FL: flooring litter rearing, MC: multilayer cage rearing, PN: plastic net rearing) and narasin inclusion or not on growth performance, gastro-intestine development and health of broilers. A total of 2400 one-day-old Ross 308 mixed-sex broilers (1:1 ratio of males and females) were used in a completely randomized design utilizing a 3 × 2 factorial arrangement of treatments, with 12 replicates per treatment. In each replicate for FL, MC and PN consisted of: 34 birds per pen, 30 birds per cage, and 36 birds per pen, respectively, ensuring that the density of each rearing system was the same (12 birds/m2).ResultsLower ADG (average daily gain), ADFI (average daily feed intake) and FCR (feed conversation ratio) observed in MC group than those of the other two systems from 1 to 36 days of age (P < 0.05). Narasin inclusion in diets decreased ADFI and FCR significantly (P < 0.05). MC and PN rearing systems reduced the relative weight of the gizzard significantly (P < 0.05). Compared with FL rearing, MC reduced the relative weight of the duodenum, jejunum and ileum (P < 0.05). The mRNA expression levels of the ileal IL-1β and IFN-γ in FL was higher than those in PN and MC groups (P < 0.05). Narasin decreased the mRNA expressions of TNF-α in the ileum (P < 0.05). Different rearing systems changed the ileal microflora structure of broilers. The FL system increased ileal microbial diversity of broilers and relative abundance of Actinobacteria. Narasin combined with MC increased the relative abundance Proteobacteria of broilers. Conclusionbirds reared in PN had higher body weight. MC birds had poorer intestinal development and health condition, higher abundance of Proteobacteria, but better FCR. FL rearing appeared to be propitious for gastro-intestinal development and health. Narasin inclusion in diets improved FCR and changed the relative abundance Proteobacteria of broilers.