Author
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AIKEN, GLEN |
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Submitted to: Cow Country News
Publication Type: Popular Publication Publication Acceptance Date: 5/11/2017 Publication Date: N/A Citation: N/A Interpretive Summary: An emphasis is typically placed on the crude protein of forages when assessing their nutritive value, but meeting the protein requirement will not have much value if the requirement for digestible energy is not met. A forage with crude protein of less than 9 percent will possibly meet the protein needs of dry, non-pregnant cows, but there is a good chance the low-energy value, or total digestible nutrients (TDN), of the forage will cause the cow to lose body condition. Total digestible nutrients equals the addition of digestible simple carbohydrates, digestible fiber, crude protein and lipids. It can be time consuming and expensive to determine the digestibility of each of these components; therefore, most forage quality service labs use formulas to estimate TDN for use in formulating rations. Previously published research, done in Arkansas, daily fed 0, 1, 3, or 5 pounds of ground corn per steer on pastures of bermudagrass that was fertilized with nitrogen to maintain crude protein values above cattle requirements. Compared to the control treatment (0 corn), daily weight gains per steer averaged over the two years was increased 15 percent by feeding 1 pound of corn per steer a day, 41 percent by feeding 3 pounds per steer a day, and 39 percent by feeding 5 pounds per steer a day. The energy supplementation clearly boosted steer weight gain efficiency with the 3 pound rate being optimum among the three rates. Cattle producers that are maintaining productive herds will be interested in assessing both crude protein and digestible energy of their forages. Technical Abstract: An article was written to discuss digestible energy of forages and their importance. Is it typical to rate a forage’s nutritive value based on its crude protein content? A forage with crude protein of less than 9 percent will possibly meet the protein needs of dry, non-pregnant cows, but there is a good chance the low-energy value, or total digestible nutrients (TDN), of forage will cause the cow to lose body condition. Total digestible nutrients equals the addition of digestible simple carbohydrates, digestible fiber, crude protein and lipids. It can be time consuming and expensive to determine the digestibility of each of these components; therefore, most forage quality service labs use formulas to estimate TDN. Although TDN is not an actual energy measure, it is closely related to the energy value of the forage and will continue to serve as an estimate of forage energy for formulating rations and meeting cattle requirements for energy for commercial cattle operations. It is important to know the crude protein and digestible energy of the forages fed to cattle because meeting the requirements of one will not matter if the requirements of the other are not met. |
