Abstract
The increasing demand for natural products is reshaping meat consumption, with grass-fed and grass-finished beef emerging as a lucrative option. However, shifting from conventional grain-fed style to grass-fed systems necessitates numerous adjustments in management decision-making and practical operations. To meet the knowledge gap, our study delved into various OMIC data, including growth performance, microbiome, metabolites, and epigenetics in a closed Wye Angus herd. Our findings revealed no difference in meat tenderness between the two treatments (P = 0.25), but significant diet effects on epigenetics with a substantial number of DNA methylation marks, which are of paramount importance. Moreover, we ascertained the microbiome in intestinal and rumen after weaning. Grass-fed cattle exhibited a significantly greater level of microbial diversity. The top 20 essential genera identified with random forest analysis could serve as microbial biomarkers and associate with the components of bile acids. Notably, the metabolomic analysis unveiled changes in glucose availability and utilization, variations in free fatty acids and carnitine-conjugated lipids, and altered β-oxidation, which influence complex lipid hydrolysis, contributing to the accumulation of anti-inflammatory n3 polyunsaturated fatty acids in grass-finished cattle. At the same time, greater concentrations of n6 PUFAs in grain-finished animals could promote inflammation and oxidative stress. With the discovery of low cortisol levels in grass-fed cattle, the cattle have health and welfare benefits in a grass-fed manner. Most importantly, they also provide fresh insights into microbial interactions in the rumen under different feed schemes and their ecophysiological implications, further aiding in developing rumen manipulation strategies to enhance feed conversion ratios and methane emission.