All hay is not created equal. Two major values we often judge hay quality on are protein and energy, both of which vary from year to year and between crops. So how do we use these values when deciding what and how much hay to feed?
Protein values in hay tests are typically reported as percent crude protein (CP). This measures the nitrogen portion of the hay. Not only is this protein important for rumen microbes, it is also important for animal maintenance and growth.
When looking at hay energy values, one common measure often used is TDN, or total digestible nutrients. TDN is the sum of the digestible fiber, protein, lipid and carbohydrate components of a feedstuff.
Knowing TDN is useful, especially for diets that are primarily forage. Without consideration, diets may be lacking energy as much or more than CP. Low-energy diets can be as impactful to animal condition and performance as those lacking in protein.
Being familiar with how animal requirements for protein and energy change between animal class and with demands like pregnancy or lactation can help with decisions about how hay is fed. Keep in mind that in addition to these base demands, environmental conditions like temperature can impact animal needs in the short term as well.
With this knowledge, we can feed lower-quality hay to dry cows and save high-quality hay for pairs at peak lactation or growing animals. This not only ensures animals are properly fed, but can also help control feed costs. — Ben Beckman, Nebraska Extension educator
