Is excess protein available as an energy source?
COWBYTES does not calculate the energy equivalent of excess protein after deamination and its entry into the Krebs cycle. We do know that excess protein can be deaminated and used for energy, but it is a very inefficient use of protein. Similarly, COWBYTES does not penalize energy utilization when protein is low or deficient. Cattle will normally eat 10 to 20% LESS dry matter if protein is low or deficient compared to cattle with the correct levels of protein. So if protein is low, you can reduce DMI by 10 to 20% to account for less efficient use of energy. The reduction in intake associated with low protein diets can be related to a longer retention time due to a slower rate of digestion in the rumen. Note that animals on low protein diets tend to have large guts. COWBYTES assumes that the dry matter intake and gain will be met ONLY if ALL other nutrients are met.
