Comparison of cecal microbiota composition in a three-way cross model in two hybrid pigs

30 Objectives: The intestinal microbiota plays an important role in host physiology, metabolism, 31 immunity, and behavior. And host genetics could influence the gut microbiota of hybrid 32 animals. The three-way cross model is commonly utilized in commercial pig production; 33 however, the effects of this model on the gut microbial composition are rarely reported. 34 Methods: Two three-way hybrid pigs were selected, with Saba pigs as the starting maternal 35 pig: Duroc × (Berkshire × Saba) (DBS) pig, Berkshire × (Duroc × Saba) (BDS) pig. One 36 hundred pigs of each model were reared from 35 days (d) to 210 d. The body weight or feed 37 consumption of all pigs were recorded and their feed/gain (F/G) ratio was calculated. On day 38 210, 10 pigs were selected for slaughter, and cecal chyme samples were collected for 16S 39 rRNA gene sequencing. 40 Results: The final body weight (FBW) and average daily gain (ADG) of DBS pigs were 41 significantly higher than those of BDS pigs (p<0.05), while the F/G ratios of DBS pigs were 42 significantly lower than those of BDS pigs (p<0.05). The dominant phyla in DBS and BDS 43 pigs were Bacteroidetes (55.23% vs 59%, respectively) and Firmicutes (36.65% vs 34.86%, 44 respectively) (p>0.05). At the genus level, the abundance of Prevotella, Roseburia, and 45 Anaerovibrio in DBS pigs was significantly lower than in BDS pigs (p<0.01). The abundance 46 of Eubacterium, Clostridium XI, Bacteroides, Methanomassiliicoccus, and Parabacteroides in 47 DBS pigs was significantly higher than in BDS pigs (p<0.05). The FBWs and ADGs were 48 positively correlated with Bacteroides, ClostridiumXI, and Parabacteroides but negatively 49 correlated with the Prevotella, Prevotella/Bacteroides (P/B) ratio, Roseburia, and 50 Anaerovibrio. 51 Ac ce pt ed A rti cle