Feed calves concentrate, forage for healthy rumens
November 5, 2015
Proper nutritional management of weaned calves is critical in ensuring optimal health and performance.
"It is important to develop weaning rations that will adequately prepare calves for efficient growth and profitability in backgrounding and finishing programs or for a lifetime of productivity in the cow herd," explained Janna Kincheloe, SDSU Extension Research Associate II.
Understanding the digestive physiology of a ruminant animal can provide cattle producers with some insight into how various feedstuffs and rations may impact future production potential.
Cattle Physiology 101
“Both hay and grain are important for production of VFAs and rumen development. Fermentation of starch in grain produces high amounts of the VFA butyrate, which has been shown to play a critical role in formation of papillae, while forage intake promotes muscle development in the rumen and stimulates rumination and saliva production.” Janna Kincheloe, SDSU Extension research associate II
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Cattle have four compartments in their stomach; a rumen, a reticulum, an omasum and an abomasum. These compartments allow for efficient digestion of fibrous feeds.
The rumen is the largest compartment and is where the majority of fermentation takes place with the assistance of billions of bacteria, fungi, and protozoa. Its microbial population digests fiber components such as cellulose to yield by-products such as microbial protein and volatile fatty acids (VFA's). Protein that is digested in the rumen is used to support microbial function and growth, while VFA's are primarily absorbed and utilized as energy by the animal.
When calves are born, their initial digestive processes are similar to simple-stomached animals (monogastrics) such as pigs in order to maximize digestion of milk proteins, fats, and simple sugars, explained Kincheloe. "Rumen development begins within the first several days to weeks after birth, and it is advanced by exposure to bacteria from the environment and consumption of solid feed."
She explained that there are essentially two layers in the rumen; a muscular layer that assists in contraction and mixing of feed, and an epithelial layer that functions in absorption of nutrients. The production of VFA's from solid feed stimulates development of the epithelium, which increases surface area in the rumen. The epithelium elongates into small projections called papillae that increase the absorptive ability of the rumen.
"Both hay and grain are important for production of VFA's and rumen development. Fermentation of starch in grain produces high amounts of the VFA butyrate, which has been shown to play a critical role in formation of papillae, while forage intake promotes muscle development in the rumen and stimulates rumination and saliva production," Kincheloe said.
Researchers at Penn State fed calves various diets based on combinations of milk, hay, and grain, and then harvested calves to evaluate rumen development. A healthy rumen has a dark coloration due to large blood vessels and greater tissue mass. Papillae should be numerous and able to be observed without a microscope. Although producers obviously can't evaluate rumen development in a production setting, the results of this study provide visible evidence of differences due to feeding various types of diets. "It is important to note that forage intake alone will also result in normal papillae development over time; however, concentrates may stimulate papillae growth to a greater degree than forages early in life," Kincheloe said. "Utilizing a mix of forage and concentrate will stimulate rumen capacity and development, resulting in a healthy microbial population and optimizing health and performance of weaned calves."
There are a variety of options available for weaning rations depending on the marketing plan and production goals.
For normally weaned calves, receiving programs may be based on either forage or concentrate depending on available resources. "If forage quality and availability is high, turning calves back onto pasture several days after weaning is a good option," she said. "Other programs may utilize a forage-based diet with supplement."
Concentrates that are high in digestible fiber and moderate to low in starch such as distiller's grains, wheat middlings and soybean hulls have been shown to provide adequate gain without the potential management issues associated with starch-based concentrates.
A 50-60 percent concentrate ration is typically recommended for normally weaned calves. Good quality grass hay or medium quality alfalfa hay should be fed for the first several days at around 2 percent of body weight, followed by the introduction of concentrate.
To learn more about weaning rations, visit iGrow.org or contact your area SDSU Extension Field Specialist. A complete listing of specialists can be found at iGrow.org.