Comparative analysis of testicular development, production performance, and the fecal microbiota in boars with different testicular indices

A healthy gut microbiota is essential for the host's absorption and utilization of nutrients, providing necessary nutritional support for growth. Conversely, an imbalance in the gut microbiota can lead to poor nutrient absorption, which may indirectly affect production performance and testicular function. In this study, we observed that 170-day-old Junmu No. 1 white boars (JN1WBs) with a high testicular index (HT) presented superior testicular development and production performance indices compared with those with a low testicular index (LT). Fecal 16S rRNA gene sequencing revealed that Lactobacillus and Anaerovibrio sp. were significantly more abundant, whereas the abundances of Campilobacterota and Streptococcus were significantly lower in HT boars than in LT boars. Spearman's correlation coefficients revealed that the abundance of Streptococcus was negatively correlated with the testicular index (TI), lean meat percentage (LMP), testicular testosterone level, total testicular volume, and Anaerovibrio sp. abundance but was positively correlated with Campilobacterota abundance. Anaerovibrio sp. abundance was positively associated with testicular weight (TW), TI, and Lactobacillus abundance but negatively correlated with Campilobacterota abundance. Moreover, prediction of fecal microbiota function revealed that compared with those in the LT group, the expression of genes associated with nutrient metabolic pathways was significantly upregulated, but the expression of genes related to chromosomes and associated proteins, adenosine triphosphate (ATP) hydrolysis, ATP synthase-binding cassette (ABC) transporters, peptidoglycan biosynthesis, and nucleotide metabolism was downregulated in the HT boars. Taken together, the results of the present study indicate a significant correlation between the gut microbiota of boars and their testicular development, as well as production performance. These findings provide important fundamental information for improving the breeding efficiency of breeding boars.