Abstract:

The aim of this study is to investigate the effects of three rearing systems on the growth performance, immune function, intestinal morphology, and cecal microbiota of Lueyang black-bone chickens. In this study, ninety 70-day-old healthy Lueyang black-bone chickens from the same batch of chicken flocks were randomly divided into 3 groups: cage rearing (CR), net-flat rearing (NF), and free-range rearing (FR) groups, each group had 5 replicates with 6 chickens per replicate (half of male and female). A one-week pre-experiment was conducted, and all experimental chickens were fed the same basic diet and had free access to feed and water. The body weight was collected every 7 days, the experimental chickens were raised to 119 days old, total feed consumption was recorded to calculate the average daily feed intake (ADFI), average daily gain (ADG) and feed to gain raito (F/G). Samples including serum, small intestine and intestinal mucosa (duodenum, jejunum, and ileum), and cecal contents were collected. The results showed that the average body weight of male and female chickens in NF and CR groups was significantly higher than FR groups (P < 0.01), the body weight of CR hens in the later stage of the experiment (105 to 119 day-old) was significantly higher than NF and FR groups (P < 0.01). The average daily feed intake (ADFI) and average daily gain (ADG) of NF and CR chickens were higher than FR chickens (P < 0.001, P=0.005), and the ratio of feed to gain (F/G) of FR chickens is significantly higher than CR and NF groups (P=0.002). The results of immune performance testing using ELISA kits showed that there was no significant difference in immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin G (IgG) and secretory immunoglobulin A (sIgA) among the roosters under the three rearing systems (P>0.05), while serum IgA of NF hens was significantly higher than CR and FR hens (P < 0.05). The results of intestinal morphology showed that the villus height of duodenum, jejunum, and ileum, as well as the ratio of villus height to crypt depth, were significantly higher in the NF and CR groups than FR group (P < 0.05). The 16S sequencing results of cecal contents indicated that the FR group increased the relative abundance of Proteobacteria, Epsilonbacteraeota, and Spirochaetes and decreased Bacteroidetes and Firmicutes at the phylum level. The NF group increased the relative abundance of Actinobacteria, Verrucomicrobia, and Chloroflexi. The CR group increased the relative abundance of Bacteroidetes and Firmicutes. At the genus level, the relative abundance of Escherichia-Shigella, Helicobacter, Enterococcus and Campylobacter increased, while Faecalibacterium, Bacteroides, and Akkermansia decreased in the FR group. The CR group increased the relative abundance of Bacteroides and Rikenellaceae_RC9_gut_group. In summary, the growth performance and intestine of Lueyang black-bone chickens were better under cage rearing and net-flat rearing, and net-flat rearing can improve immune performance. Therefore, net-flat rearing is a more proper rearing system for Lueyang black-bone chickens.

Key words: Lueyang black-bone chicken, rearing systems, growth performance, immune, cecal microbiota