Feeding a High-Concentrate Corn Straw Diet Induced Epigenetic Alterations in the Mammary Tissue of Dairy Cows

PURPOSE The objective of this study was to investigate the effects of feeding a high-concentrate corn straw (HCS) diet (65% concentrate+35% corn straw) on the epigenetic changes in the mammary tissue of dairy cows in comparison with a low-concentrate corn straw (LCS) diet (46% concentrate+54% corn straw) and with a low-concentrate mixed forage (LMF) diet (46% concentrate+54% mixed forage). EXPERIMENTAL DESIGN Multiparous mid-lactation Chinese Holstein cows were fed one of these three diets for 6 weeks, at which time blood samples and mammary tissue samples were collected. Mammary arterial and venous blood samples were analyzed for lipopolysaccharide (LPS) concentrations while mammary tissue samples were assayed for histone H3 acetylation and the methylation of specific genes associated with fat and protein synthesis. RESULTS Extraction of histones and quantification of histone H3 acetylation revealed that acetylation was significantly reduced in cows fed the HCS diet, as compared with cows fed the LCS diet. Cows fed the HCS diet had significantly higher LPS concentrations in the mammary arterial blood, as compared with cows fed the LCS diet. We found that the extent of histone H3 acetylation was negatively correlated with LPS concentrations. The methylation of the stearoyl-coenzyme A desaturase gene associated with milk fat synthesis was increased in cows fed the HCS diet. By contrast, methylation of the gene encoding the signal transducer and activator of transcription 5A was reduced in cows fed the HCS diet, suggesting that feeding a high-concentrate corn straw diet may alter the methylation of specific genes involved in fat and protein synthesis in the mammary tissue of dairy cows. CONCLUSIONS Feeding the high-concentrate diet induced epigenetic changes in the mammary tissues of dairy cows, possibly through effecting the release of differing amounts of LPS into the mammary blood.