Abstract
BACKGROUND: Intensive swine breeding industry generates a complex environment where several microbial interactions occur and which constitutes a challenge for biosafety. Ad libitum feeding strategies and low levels of management contribute to residual and wasted feed for lactating sows, which provides a source of nutrients and microbial source for houseflies in warm climates. Due to the absence of the all-in/all-out system, the coexistence of sows of two production stages including gestating and lactating sows in the farrowing barn may have potential negative impacts. In this research, we evaluated the effects of lactating sow leftover on the environmental microbiota of the farrowing barn and the contribution of microbial environments to the gestating sow fecal bacterial structure with a 30-day-long treatment of timely removing lactating residual feed. RESULTS: Houseflies in the farrowing barn mediate the transmission of microorganisms from lactating sow leftover to multiple regions. Leuconostoc, Weissella, Lactobacillus and Pediococcus from the leftover which can produce exopolysaccharides, are more capable of environmental transmission than pathogenic microorganisms including Staphylococcus and Streptococcus and utilize houseflies to achieve spread in environmental regions of the farrowing barn. Leftover removal treatment blocked the microbial transmission chain mediated by houseflies, downregulated the relative abundance of pathogenic bacteria including Escherichia-Shigella and Streptococcus among houseflies, environmental regions and fecal bacteria of gestating sows in the farrowing barn and effectively attenuate the increment of Weissella and RF39 relative abundance in gestating sow feces due to the presence of lactating sows. CONCLUSIONS: Lactating sow leftover is a non-negligible microbial contributor of environment in farrowing barn whose transmission is mediated by houseflies. A 30-day-long treatment of removing lactating sow residual feed cause significant changes in the microbial structure of multiple environmental regions within the farrowing barn via altering the microbiota carried by houseflies. Meanwhile, lactating sow leftover affect the fecal microbial structure of gestating sows in the same farrowing barn, while removal of lactating sow leftover alleviates the contribution of microbial transmission.