Cow, yak, and camel milk diets differentially modulated the systemic immunity and fecal microbiota of rats

Cow milk is most widely consumed; however, non-cattle milk has gained increasing interest because of added nutritive values. We compared the health effects of yak, cow, and camel milk in rats. By measuring several plasma immune factors, significantly more interferon-γ was detected in the camel than the yak (P = 0.0020) or cow (P = 0.0062) milk group. Significantly more IgM was detected in the yak milk than the control group (P = 0.0071). The control group had significantly less interleukin 6 than the yak (P = 0.0499) and cow (P = 0.0248) milk groups. The fecal microbiota of the 144 samples comprised mainly of the Firmicutes (76.70 ± 11.03%), Bacteroidetes (15.27 ± 7.79%), Proteobacteria (3.61 ± 4.34%), and Tenericutes (2.61 ± 2.53%) phyla. Multivariate analyses revealed a mild shift in the fecal microbiota along the milk treatment. We further identified the differential microbes across the four groups. At day 14, 22 and 28 differential genera and species were identified (P = 0.0000-0.0462), while 8 and 11 differential genera and species (P = 0.0000-0.0013) were found at day 28. Some short-chain fatty acid and succinate producers increased, while certain health-concerned bacteria (Prevotella copri, Phascolarctobacterium faecium, and Bacteroides uniformis) decreased after 14 days of yak or camel milk treatment. We demonstrated that different animal milk could confer distinctive nutritive value to the host.