Producers often estimate hay needs for their beef cowherd based on rules of thumb and neighbor's advice. This may not be accurate for their individual operation. One common approach is to allow two round rolls of hay for every cow to be supplemented during the winter. While this may get a producer started, it is not accurate and likely may result in not enough hay.
Likewise there can be extensive variability of conserved forage quality as a result of forage type, maturity, fertilization, growing conditions, and hay vs. balage.
From a practical standpoint, it is not feasible to consider and account for all of the possible variables that might affect the feeding value of particular forages. However, some factors are important.
To read the entire article, link here.