Differences in productive performance and intestinal transcriptomic profile in two modern fast-growing chicken hybrids.

This study aimed to characterize growth performance and ileum transcriptomic profile of two fast-growing chicken hybrids (HA and HB). A total of 1,170 one-day-old female chicks (n = 585 per genotype) were weighed and randomly divided into 18 pens (9 replications/group). Both the groups received the same commercial diet (starter, 0-9 days; grower I, 10-21 days; grower II, 22-34 days; and finisher, 35-43 days). Body weight (BW), daily feed intake (DFI) and feed conversion ratio (FCR) were determined on a pen basis at the end of each feeding phase. At the processing (43 days), incidence of footpad dermatitis (FPD) was evaluated on all the birds and ileum mucosa was collected from 1 bird/replication. Total mRNA was extracted to perform microarray analysis (Chicken Gene 1.1 Array Strip), and an exploratory pathway analysis was then conducted (Gene Set Enrichment Analysis software). The two genotypes showed different growth patterns throughout the study. HA birds exhibited higher BW and better FCR than HB after 9 days (228 vs. 217 g and 1.352 vs. 1.419, respectively, p < 0.05). At 21, 34 and 43 days, HB birds reported higher BW (807 vs. 772 g; 1,930 vs. 1,857 g and 2,734 vs. 2,607 g, respectively; p < 0.01), DFI (74.9 vs. 70.6 g bird  day , p < 0.01; 144.4 vs. 139.6 g bird  day , p = 0.06; and 196.5 vs. 182.4 g bird  day , p < 0.01) and similar FCR compared to HA ones. HB group showed a higher percentage of birds with no FPD (75% vs. 48%; p < 0.001). Transcriptomic analysis revealed enriched gene sets for mitochondria, cellular energy metabolism, and cell structure and integrity in ileum mucosa of HA broilers and enriched gene sets for immune system activation, cell signalling and inflammation in HB ones. In conclusion, these results indicated that the two chicken genotypes are characterized by different growth patterns, feeding behaviour and gene expression profiles in the intestinal mucosa.