Rumen Development in Dairy Calves

Nutrition : Calf & Heifer

Katie Bradley, Ph.D.

Dairy Research Scientist

The calf is born with a small, underdeveloped rumen compared to its other stomach compartments.

The substrate or diet provided to the young, growing calf directly impacts the progress of rumen development.

Therefore, not only is the calf feeding program critical to provide the nutrients needed to achieve the calf’s full potential for growth (weight and frame), it also is an important aspect in the transition of the calf from a pre-ruminant to a ruminant animal.

Calves fed a milk-only diet, which is primarily shunted to the abomasum by the reflexive closure of the reticular groove (Ørskov et al., 1970), have shown to have more limited rumen development since nutrients bypass the rumen. Therefore, the abomasum increases in size and the rumen remains, small with restricted development of the rumen wall and papillae. A study by Tamate et al. (1962) showed that by infusing milk directly into the rumen, growth of the rumen papillae could be stimulated due to the production of volatile fatty acids (VFA) by rumen fermentation. It is known that the production of VFAs is essential to the development of the rumen papillae (Flatt et al., 1958).

Calves fed forages early in life (prior to weaning) will begin to ruminate and have greater flow of saliva into the rumen (Hodgson, 1971) along with greater muscle development of the rumen wall (Tamate et al., 1962). However, this dietary program does not provide sufficient concentrations of VFAs — especially butyrate — to promote rumen papillae development. This development is a key component to a functioning rumen (Coverdale et al., 2004). A study by Heinrichs and Lesmeister demonstrated that calves fed milk and high-quality alfalfa hay diets over a 12-week period had high growth rates, but minimal papillae development compared to calves fed milk only.

The forage-based diets resulted in the primary production of acetic acid rather than butyric acid. (Butyrate, or butyric acid, is believed to stimulate papillae growth in the rumen as the primary substrate for energy to the rumen wall.)

A key element to a calf’s rumen development is the ingestion of grain. Grain is necessary for sufficient VFA production, which results from microbial digestion and therefore supports papillae growth. When calves were fed milk and free-choice grain over a 12-week period, the papillae were larger and the rumen wall was thicker and more developed (Heinrichs and Lesmeister). Additionally, the rumens of grain fed calves were darker in color due to greater vascularization or blood capillary growth, which allows for more absorption of VFA into the blood stream.

During this period of time, it also is critical that adequate water be fed, along with the grain, to create the correct rumen environment that will support fermentation and production of VFAs, which will in turn stimulate rumen development.

Research has helped make progress on understanding the role of the calf’s diet through the first 12 weeks of life, to support growth and rumen development. And yet, the optimal nutritional program during the phase of 12-to-24 weeks of age is not as well defined. At this time the calf is still undergoing significant growth in structure (frame) and body weight, along with additional, important rumen development. Traditionally, calves have been feed high amounts of hay or forage with limited grain during this period. However, the heifer is still in a critical growth stage and needs adequate nutrient supply to meet these demands. Identifying the grain and hay balance of a nutritional program should continue to develop her structurally, and to potentially improve her later success during lactating and for longevity in the herd.

Recent studies at Purina Animal Nutrition Center (2010-2011 unpublished) indicated that during this growing phase, calves fed higher amounts of grain with ad libitum hay (10 pounds per head per day versus 4 pounds per head per day) demonstrated optimized growth in weight and frame, as well as beneficial rumen growth and development. Proper rumen development at this time supports the calf’s transition into a fully functional ruminant, able to utilize higher forage-based diets. A well-developed and fully functional rumen may efficiently utilize forage for continual growth during the next stage of the heifer’s life. Continuing this research will continue to expand insights and the ability to supply value-added nutritional programs to growing calves. In doing so, calf feeding programs will have an increasingly important role in influencing the calf’s lifetime productivity potential as a more profitable dairy cow.