At birth, a calf’s rumen is not fully functional, and milk bypasses the rumen via the esophageal groove to be digested in the abomasum. As the calf grows, a healthy, active rumen becomes more and more essential for its long-term success. The transition from a nonfunctional to a fully functional rumen is heavily diet-dependent. Offering starter feed early on encourages rumen fermentation, which produces butyrate, a vital compound for developing the rumen’s lining and papillae. The earlier you provide access to a clean, dry starter, the sooner you can supply the rumen with all the essential compounds it needs for a smooth weaning.
Diet is a very important factor for the care of any livestock, and dairy calves in particular are very reliant on proper nutrition to develop a healthy rumen.
This article from OSU Graduate Research Associate Elizabeth Plunkett provides details on best management practices for providing starter feed to dairy calves. https://dairy.osu.edu/newsletter/buckeye-dairy-news/volume-26-issue-6/starter-success-dairy-calves