Do newborn puppies have their own microbiota at birth? Influence of type of birth on newborn puppy microbiota.

With recent research in humans, a hypothesis known as the sterile womb paradigm has been challenged. The objectives of this study were to determine the presence of placental and fetal microbiomes in dogs, the effect of different types of parturition on the fetal microbiome, and the effect that the fetal microbiome has on early puppy development. A total of 96 newborn puppies from 17 dams were included in the study. Puppies were divided into two groups depending on the type of parturition (vaginal birth (VB) or cesarean section (CS)). Immediately after birth, swabs of the placenta and meconium were taken. Swabs of the oral and vaginal mucosa of the dam were taken in the second half of the pregnancy and just before parturition. All samples were analyzed with a classical bacteriological examination, and bacterial colonies were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The weight gain of each puppy was tracked daily in the first 7 days postpartum. Bacteria from several different genera were isolated from 86.5% of meconium samples and 57% of placenta samples. While the meconium microbiota resembled bacteria from the maternal vagina in VB puppies, the meconium microbiota of puppies born by CS indicated a relative resemblance to maternal oral and vaginal microbiota. A statistically significant difference in the relative growth rate between puppies born by VB and CS was found (p < 0.05), with puppies born by VB gaining weight faster compared to the CS group. This difference was even more noticeable when VB puppies were compared to puppies born by elective CS. Puppies born without a detectable meconium or placental microbiota showed a slower growth rate than those with a meconium microbiota, regardless of the type of parturition (p < 0.05). The findings of this study provide new information about the placental microbiome in healthy pregnant dams and suggest intrauterine colonization of the fetus in dogs. It seems that the type of delivery and bacterial colonization might be an important consideration for the weight gain in puppies in the first few days of life. Published by Elsevier Inc.