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Boars play a critical role in pig production. Numerous studies have reported important effects of the gut microbiota on pig production traits. However, whether the gut microbiota is associated with reproduction traits in boars remains largely unknown. Understanding the gut microbial composition and its influencing factors in large-scale boar populations is an essential first step to investigate this association. In this study, shotgun metagenomic sequencing was performed on fecal samples of 1,651 commercial boars from three breeds raised in three pig farms to uncover their gut microbial structures. We observed significant differences in boar gut microbial compositions across three breeds, even when raised in the same farm. Permutational multivariate analysis of variance (PERMANOVA) within-farm breeds and with-age stages found that the effect size of each factor on boar gut microbial composition varied across farms and age stages. Breeds accounted for 2% ~ 9% of the variance of boar gut microbial compositions in different farms. We then identified gut microbial taxa enriched in each boar breed using MaAsLin2. Lactic acid and butyrate-producing taxa, such as Lactobacillus amylovorus and Faecalibacterium prausnitzii , were enriched in Duroc boars; Akkermansia muciniphila and Lactobacillus reuteri showed the enrichment in Landrace boars, accompanied by increased relative abundance of Enterobacteriaceae members. Meanwhile, the species from Bacteroides , Prevotella , and Treponema had higher abundances in the gut of Large White pigs than in the other two pig breeds. We also identified bacterial species enriched in each of the three age stages. These breed and age-associated microbial enrichment patterns might reflect the combined effects of long-term genetic selection of pig breeds, age, and differences in feeding diets. The results of this study provide important insights for further investigating the effects of gut microbiota on boar reproductive traits and for developing strategies to modulate the gut microbiota to improve boar health and production performance.
Hu et al. (Wed,) studied this question.