Impact of dietary lipid source on fecal microbiota composition in dairy cows

The degree of saturation of the dietary lipid sources could affect the microbiota of the animal digestive tract. Aim of this experiment was to evaluate the influence of two different lipid sources, one saturated (hydrogenated fatty-Megafat 88; FAT), and one unsaturated (soybean full-fat flaked; SOY) on fecal microbiota composition of high-producing dairy cows fed hay – based ration. The study involved 8 Italian Friesian dairy cows and pH, rumination time, rumen and feces microbiota composition (bacteria and protozoa) were determined. DNA from rumen contents was extracted, purified, and sequenced to quantify bacteria populations. Sequencing was performed on Illumina MiSeq. Data were analyzed with JMP pro v 17.1. For the statistical analysis, a linear mixed model was used with a fixed effect: Saturated Fat vs Unsaturated fat. The different lipid sources significantly influenced bacteria community in feces. Ruminococcaceae family showed a tendency (p=0.06) being higher in FAT compared to SOY (27.9% vs. 24.5%), while Peptostreptococcaceae were higher in SOY compared to FAT (3% vs. 1.95%). Rikenellaceae were significantly higher in SOY (21.8% vs 19.7%), while Prevotellaceae did not differ, as well as Fibrobacteriaceae, Lachnospiraceae, Christensellaceae and Veilonellaceae. Moreover, within the same treatment group, the cited families were significantly different among animals for both SOY and FAT, with the exception of Rikenellaceae, which did not differ in SOY treatment. Since this part of the study followed a similar analysis of the rumen microbiota of the same animals, it was possible to observe substantial differences among the two. Surprisingly, Proevotellaceae, the most abundant family in the rumen, showed a decreased abundance (11% on average), while Rikenellaceae, which are not so represented in the rumen, increased their relative abundance in feces. Ruminococcaceae were more abundant in feces compared to the rumen, and even the family composition, in terms of genera, was different. In conclusion, the lipid source affected fecal microbiota, showing differences in families that are not abundant in the rumen, but highly represented in the intestinal tract of different mammalian species, including cows, buffaloes, and humans. At the same time, data underlined the individual response even when animals are fed the same lipid source, and the unicity of the intestinal environment compared to the ruminal one.