Effect of high moisture ear corn on lactation performance, serum metabolites, rumen fermentation parameters and microbiome community diversity in Holstein dairy cows

This study aimed to investigate the effects of feeding high moisture ear corn (HMEC) on milk yield, serum metabolites, rumen fermentation parameters, and rumen microbiome community of Holstein dairy cows. Thirty lactating Chinese Holstein dairy cattle were assigned to each of the two treatments in a completely randomized design: the SFC group (fed with steam-flaked corn) and the HMEC group (fed with HMEC replacing 2 kg steam-flaked corn on an equal dry matter basis). The experiment lasted for 74 d ( the pretrial period was 14 d and the trial period was 60 d). The results showed that: replacing SFC with HMEC significantly increased dry matter intake, milk yield and 4% milk fat corrected milk (P<0.05). There was also a tendency for an increase in milk protein (P=0.097). Serum oxide dismutase, glutathione peroxidase and immunoglobulin G, immunoglobulin M and immunoglobulin A were significantly higher in the HMEC group than those in the SFC group (P<0.05). However, creatinine and total cholesterol levels were significantly lower in the HMEC group than those in the SFC group (P<0.05). Substitution of SFC with HMEC significantly increased the total volatile fatty acid concentration (P<0.05) and acetate concentration (P<0.05) and a tendency to decrease the concentration of NH3-N (P=0.061). The dominant phyla of rumen bacteria in both treatment groups were Bacteroidota, Firmicutes, and Actinobacteriota, with Prevotella, NK4A214-group, and Succiniclasticum as the dominant genera, respectively. There were no significant differences in Alpha diversity indexes and beta diversity of the bacterial community between the two treatments. However, LEfSe analysis revealed that Mogibacterium, Eubacterium nodatum group, norank-f-Lachnospiraceae, and Eubacterium-brachy-group were significantly enriched in the rumen fluid of cows fed HMEC (P<0.05), while Aneurinibacillus, Denitrobacterium and Colidextribacter were significantly reduced (P<0.05). Tax4Fun analysis predicted that ruminal microbes in both groups of cows were mainly involved in carbohydrate metabolism, membrane transport, amino acid metabolism, and nucleotide metabolism. In conclusion, replacing SFC with HMEC improved lactation performance, antioxidant capacity, immune capacity, and regulated rumen fermentation and rumen microbiota in Holstein cows. This study provides new insights into the regulatory mechanism of rumen microbiota by HMEC and offers valuable information for the application of HMEC in dairy cows.