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- Energy values of feed are calculated based on the fibre content of the feed. Digestible energy (DE), metabolic energy (ME), total digestible nutrients (TDN), gross energy (GE), net energy - maintenance (NE m) net energy - gain, (NE g), net energy - lactation (NE l) are different methods of describing energy content. Forages increase fiber content and drop energy content as they mature.
- Ruminants digest roughage and grain in the rumen. Energy is released either as carbohydrates or fats. Carbohydrates are converted to glucose and further digested into acetic, propionic, and butyric acids by rumen bacteria and protozoa. The short chain fatty acids are then absorbed into the blood stream as useful energy sources.
- The amount of forage and grain fed influences the amount and type of short chain fatty acids produced in the rumen. Bacterial and protozoa populations change depending on the cellulose, hemicellulose and starch concentration in the feedstuffs. Starch digesting bacteria produce more propionic acid relative to acetic acid than cellulose digesters.
- When rations are rich in starch (high grain), lactic acid accumulates in the rumen. The amount of propionic acid increases while acetic and butyric acid levels drop. Rumen pH drops, predisposing the animal to acidosis and possibly bloat.
- The digestibility of forage is affected by the cellulose, hemicellulose and lignin found in cell walls. Feeds high in crude fibre usually take longer to digest and are less digestible than those high in starches and sugars. As a plant matures, lignin increases making other nutrients less digestible. Lignin is the "glue" that holds the fibre components together, and reduces the digestibility of nutrients.
- When feed is digested, heat is produced and is called the total or gross energy content of the feed.
- Energy requirements of cattle increase when temperatures decrease, body condition is poor, cows are lactating, or if animals are growing. Small animals have a higher energy requirement because of a high body surface to weight ratio. These animals loose more heat on a weight basis compared to larger animals.
- Excess dietary protein can be partially converted into energy. The process is less efficient than the use of carbohydrate or fat sources. If the amount of energy obtained from protein is more than 25 % of total energy requirements, an accumulation of blood urea and ketosis can occur.
- When the initial digestion of starch is low in the rumen, efficiency of use is decreased. The "bypass" energy (sugars and starches) that enters the small intestine provides an energy source for undesirable bacteria that can cause scours.
Cattle Feeding Strategies to Cope with High Priced Corn
Cold Weather Adjustments for Beef Cows
Feeding Wheat to Beef Cattle - available in PDF format only
Feeding Barley to Beef Cattle
Nutrients for Cattle
Oats as a Feed for Beef Cattle
Use of Energy Values in Ration Formulation
Using the Net Energy (NE) System to Improve Body Condition Score - available in PDF format only
Using NDF and ADF To Balance Diets
Effect of feeding different sources of fat during gestation and lactation on reproduction of beef cows and calf performance - available in PDF format only
Evaluation of NRC (2000) model energy requirement and DMI equation accuracy and precision for wintering beef cows in western Canada - available in PDF format only
Strategicially Feeding Protein And Energy During Wintering And Managing Cow Condition - available in PDF format only