The rumen is the largest digestive organ in adult ruminants, where feed is digested into volatile fatty acids (VFAs) and where most VFAs are absorbed and metabolized. However, ruminants are not born with a large, functional rumen. The rumen undergoes significant growth and functional changes from birth to adulthood. In this study, we aimed to identify the cellular and molecular mechanisms that guide these changes in the bovine rumen. We have found that the rumen grows by increasing the number rather than the size of individual cells from birth to adulthood. Nearly 3,000 genes are differentially expressed in the rumen between neonatal calves and adult cattle, and the bovine rumen gains the absorptive, metabolic, motility, and immune functions with minimal structural change from birth to adulthood. We have also discovered that many transcription factors (TFs), including the serum response factor and TCF 4, along with multiple signaling pathways, including the peroxisome proliferator-activated receptors pathway and the Wnt/β-catenin pathway, mediate changes in gene expression, growth, and maturation of the rumen from neonatal calves to adult cattle.

Read the full article in the Journal of Animal Science.