There is a diverse population of microorganisms in the intestine, and numerous studies have demonstrated the significant regulatory impact of the intestinal flora on the reproductive performance of animals. In this study, we analyzed the relationship between the composition of the intestinal flora and the reproductive performance of Yorkshire sows during late pregnancy under different feeding patterns and explored the effects of different feeding patterns on reproductive performance from the perspective of the intestinal flora.
The results of this study indicate that different feeding methods have a significant impact on reproductive performance indicators such as the TNB and NBA in the same breed of pigs. SM effectively enhanced reproductive performance indicators such as TNB and NBA in Yorkshire pigs compared to AM. Furthermore, analysis of the intestinal microbial composition revealed that regardless of the feeding mode, the intestinal microbiota of Yorkshire pigs is composed mainly of Firmicutes and Bacteroidetes, but the abundance of different microbial communities varies to some extent[17, 18]. A previous study revealed that Firmicutes and Bacteroidetes are the dominant phyla in the gut microbiota of healthy individuals. However, substantial variations in their abundance exist among individuals[19]. These findings align with those of a prior study conducted on pigs, further validating the results obtained in this study[11]. The present study demonstrated that the abundance of Bacteroidota in the SM group was significantly lower than that in the AM group, while the abundance of Firmicutes was significantly greater in the SM group than in the AM group. (P < 0.05). In Shin et al.'s study, a correlation was observed between the abundance of Bacteroidota and Firmicutes and the level of estradiol. Specifically, the group with high estradiol levels exhibited a greater abundance of Bacteroidota and a lower abundance of Firmicutes[20]. Research on estradiol indicates its role in promoting endometrial proliferation and repair, exerting a broad impact on the uterus, and being closely associated with the reproductive performance of female animals. However, elevated estradiol levels may diminish the reproductive performance of female animals and increase their susceptibility to disease[21–23]. This may be an important reason for the differences in the reproductive performance of Yorkshire pigs among the different breeding modes.
At the genus level, research has demonstrated that the effects of diet-induced gut microbiota dysbiosis extend beyond the gut. Zhang et al. showed that a decrease in the abundance of Ruminococcaceae_NK4A214_group in the gut can lead to abnormal metabolism of vitamin A in the gut, thereby causing abnormal sperm production and impacting the reproductive performance of the host[24]. Moreover, considering maternal microbial transfer, the gut microbiota is significantly linked to the reproductive performance of the host. Studies indicate that during fetal development, compounds produced by the maternal microbiota are transferred to the fetus and offspring[25]. This transfer enhances the generation of fetal innate immune cells, thereby contributing to the reproductive performance of the host, with Escherichia coli playing a significant role in this process. Hence, the genus-level microbial community plays a pivotal role in the host reproductive process[25, 26]. Consequently, we analyzed the variations in the genus-level gut microbiota of Yorkshire pigs during late pregnancy under different feeding regimens. At the genus level, there were significant differences in the abundances of 106 bacterial taxa between the AM and SM groups (P < 0.05). The AM group exhibited significantly greater abundances of Corynebacterium and Parabacteroides than did the SM group (P < 0.05). Previous research has indicated a correlation between Corynebacterium and Parabacteroides and decreased levels of follicular estradiol and luteinizing hormone, suggesting that these hormones may impact the reproductive performance of Yorkshire pigs by influencing their levels[27]. The findings of pig research suggest that reducing the abundance of Fusobacterium can enhance sows' immune performance and, to some degree, improve their reproductive performance. Moreover, their research findings indicate that the proliferation of beneficial bacteria, including Lachnospiraceae_XPB1014_group and Roseburia, can notably enhance the daily feed intake of pregnant sows, promote the growth rate of weaned piglets, lower the fecal moisture content of sows, decrease the incidence of constipation in sows, and elevate the levels of anti-inflammatory factors in the sows' intestines[28, 29]. In this study, Yorkshire sows in the SM group demonstrated superior reproductive performance. Additionally, the analysis of intestinal flora diversity revealed a significantly greater abundance of beneficial bacteria, including Lachnospiraceae_FCS020_group, Lachnospiraceae_XPB1014_group, Lachnospiraceae_AC2044_group, Lachnospiraceae_NK4A136_group, Lachnospiraceae_UCG_007 and Roseburia, in the sows' intestines than in those of the AM group. These results align with those of prior research[15, 30]. Overall, the aforementioned research results demonstrated that the feeding method impacts the composition of the sow's intestinal microbiota. These variations in the gut microbiota can regulate the host's reproductive performance by influencing hormone levels and nutrient absorption[31]. Additionally, probiotics can enhance the immune indices of weaned piglets through probiotic transfer, thereby improving piglet survival rates[32].
To elucidate the impacts of different feeding methods on the reproductive performance of Yorkshire pigs from a microbiota perspective, we conducted GO and KEGG enrichment analyses to identify the pathways and functions associated with different microbiota resulting from various feeding methods[33, 34]. The findings demonstrated that the functional categories and pathways enriched in the gut microbiota of late-pregnancy Yorkshire sows exhibited remarkable similarities, with predominant enrichment observed in the global and overview maps, carbohydrate metabolism, amino acid metabolism, metabolism of cofactors and vitamins, nucleotide metabolism, and translation. The functional enrichment terms were enriched in general function prediction only; amino acid transport and metabolism; translation, ribosomal structure and biogenesis; transcription, carbohydrate transport and metabolism; cell wall/membrane/envelope biogenesis; replication, recombination and repair; and energy production and conversion. Specifically, the transcription, carbohydrate transport and metabolism, signal transduction mechanism, general function prediction only, cell motility, and defense mechanism categories exhibited significantly lower expression in the AM group than in the SM group (P < 0.05). These findings indicate that while artificial feeding allows precise control of the feeding amount and duration based on animal needs and conditions, it also introduces additional pathogenic bacteria. Artificial feeding increases the diversity and richness of the intestinal flora in late pregnant sows but diminishes energy metabolism and immune capacity, consequently affecting reproductive performance. Pathway enrichment analysis of the AM group revealed a significantly greater enrichment of infectious diseases, cardiovascular diseases, and neurodegenerative diseases than that of the SM group, further confirming our hypothesis.