Abstract: This experiment aimed to study the effects of starch supplementation on milk fat and rumen bacterial flora of dairy cows. Four Chinese Holstein cows with similar body conditions and healthy lactation were selected. At the first stage of 7 days, cows were fed by basic diet to be control group. After the second stage of 15 days, cows were fed by basic diet supplemented with an additional 1.5 kg of corn starch per day per head to be experimental group. The results showed that milk fat percentage of dairy cows decreased significantly after starch supplementation (P<0.01). At the phylum level, 28 phyla of rumen bacteria were detected, the richness of Gemmatimonadetes and Tenericutes decreased significantly (P<0.01), Armatimonadetes, Acidobacteria and Cyanobacteria decreased significantly (P<0.05), Firmicutes increased significantly (P<0.05). At the level of genus, 383 genera were detected, 90 of which changed significantly. At the genus level, the abundance of Acetobacter, Lactobacillus, Pediococcus, Leuconostoc, Lachnoclostridium-1, Ruminococcus-1 and Prevotella-7 increased significantly (P<0.01), Anaerovibrio, Enterococcus and Enhydrobacter decreased significantly (P<0.01). In the experiment, flora diversity and distribution uniformity of rumen bacteria in daily cows were not different after adding starch in diet, while proliferation of most acid-producing bacteria was promoted.

Key words: dairy cow, rumen, 16S high-throughput sequencing technology, rumen bacteria