Blocks and tubs can remain with the cows whereas a bag supplement must be transported to the cows on a fairly regular basis. Supplements developed by feed companies often will contain additional minerals, vitamins, and selected feed additives. Simply calculating cost per unit of a single nutrient fails to take into account the benefits of these added products. In many cases, our forages may be adequate in protein to meet the requirements of gestating cows but may lack sufficient energy. Price per unit of nutrient will vary within the same feed depending upon the unit you use for comparison.
Grain usually contains a readily available starch.
Grain sugar and starch ferments rapidly in the rumen and may lower rumen pH, resulting in reduced feed intake and digestibility of forages. It is therefore recommended that the amount of grain be limited when used in a forage-based diet. Certain feeds such as soybean hulls, corn gluten feed, beet pulp, and brewers grains are satisfactory energy sources, but the starch is more slowly degraded and does not alter rumen pH to the same degree as grain sources such as corn. Comparing the cost of TDN, we can estimate the cost of energy supplements as we have done for protein supplements in the previous example. TDN Like protein sources, energy sources also vary amounts of mineral and vitamin available.