This Is AuburnElectronic Theses and Dissertations

Effects of dietary protein intake on fecal and milk microbiota




Warren, Matthew

Type of Degree

Master's Thesis


Biological Sciences


Microorganisms in milk have traditionally been assumed to be contaminants, but recent data suggest that these microbial communities naturally reside in milk and may contribute to vital maternal effects. Investigators have speculated that microorganisms are derived, at least in part, from populations of microorganisms found in a mother’s gut. Milk microorganisms are ingested by offspring gut and contribute to the microbial populations that colonize the offspring gut. Thus, factors that impact the population of microorganisms in milk have implications for advancing knowledge of how mothers influence offspring development. In this case, females are likely preparing offspring for a similar dietary environment at independence. To characterize the relationship between milk microbial diversity and maternal protein intake, a pilot study was conducted to characterize impact of maternal protein intake on gut microbial diversity in rats. Based on this preliminary analysis, diets with 10% and 20% protein were selected to determine impact of protein intake on milk microbial diversity. Milk was collected from Sprague-Dawley rat dams at 14 days post-partum. No differences were observed for dry matter or crude protein content of milk between treatment groups. Alpha diversity of milk microbiota from high protein fed rats was greater than low protein fed rats. Staphylococcus spp. taxa relative abundance was higher in LP milk samples compared to HP samples and Lactobacillus spp. taxa had higher relative abundance in HP milk samples compared to LP samples. The results of this investigation indicates that dietary protein intake affects gastrointestinal microbial diversity and suggests that protein content of a mother’s diet impacts relative abundance of milk microorganisms. This study highlights the importance of dietary protein intake on composition of rat fecal and milk microbiota, with higher protein intake favoring potentially beneficial Lactobacillus populations in milk and reducing the relative abundance of potential pathogens like Staphylococcus taxa. Proteus mirabilis and Enterococcus faecalis were cultured from rat milk and are likely natural occurring bacteria found in rat milk. Future work with milk microorganisms involves examining possible interactions between beneficial bacteria like Lactobacillus and potential pathogenic bacteria like Staphylococcus to examine how maternal diet can affect offspring development.