Brisket Disease Is Associated with Lower Volatile Fatty Acid Production and Altered Rumen Microbiome in Holstein Heifers

SIMPLE SUMMARY: Development of the dairy industry in the high-altitude plateau environment through incorporation of Holstein cows is complicated by the risk of brisket disease. While the physiological effects of brisket disease are well-studied, its effects on rumen function and microbial community composition are not. There are clear shifts in volatile fatty acids production and rumen microbial community composition in Holstein heifers suffering from brisket disease. Observed shifts reveal key genera associated with healthy and disease states and suggest that bovine brisket disease is associated with impaired rumen functioning. This work supports further understanding of the roles of key rumen taxa in bovine brisket disease, with particular focus on candidate rumen biomarkers in healthy animals that may be able to reduce economic losses for farmers. ABSTRACT: Brisket disease is heritable but is also associated with non-genetic risk factors and effects of the disease on the rumen microbiome are unknown. Ten Holstein heifers were exposed to the plateau environment for three months and divided into two groups according to the index of brisket disease, the mean pulmonary arterial pressure (mPAP): brisket disease group (BD, n = 5, mPAP > 63 mmHg) and healthy heifer group (HH, n = 5, mPAP < 41 mmHg). Rumen fluid was collected for analysis of the concentrations of volatile fatty acids (VFAs). Extracted DNA from rumen contents was analyzed using Illumina MiSeq 16S rRNA sequencing technology. The concentration of total VFA and alpha-diversity metrics were significantly lower in BD group (p < 0.05). Ruminococcus and Treponema were significantly decreased in BD heifers (p < 0.05). Correlation analysis indicated that 10 genera were related to the mPAP (p < 0.05). Genera of Anaerofustis, Campylobacter, and Catonella were negatively correlated with total VFA and acetic acid (R < −0.7, p < 0.05), while genera of Blautia, YRC22, Ruminococcus, and Treponema were positively related to total VFA and acetic acid (R > 0.7; p < 0.05). Our findings may be a useful biomarker in future brisket disease work.