Nutrient concentration varies considerably in hay. Why does this happen? Well, there are many causes. For example, leafiness of the hay, or maturity of the plant when your hay was cut, or even how you handled the hay during raking and baling all can affect its feed value.
This year, weather conditions have made things more complicated. This spring’s wet weather in many areas caused many folks to delay first cutting. Leaf diseases, mature plants, and other factors made much alfalfa lower in quality. But some fields had the second growth already growing when first cut was taken, keeping feed value relatively high. And this summer we have had periods of very hot weather that often causes plants to burn off their easily digested nutrients at night, leaving us with hay that looks really good but is high in fiber and low in energy.
Grass hay might be even more difficult to predict. Some fields have fewer seedheads than normal. This might give higher-quality hay, but if harvest was delayed in hopes of increasing yield or if the heat affected grass quality like it affects alfalfa, grass hay quality might actually be lower. And when growth is stimulated by extra rain, many nutrients are used for tonnage instead of quality. So you see, this year, maybe more than ever, forage testing is important. It is the only way that you can find out for sure ahead of time what the feed value is of your hay.
So gather samples now for testing, before feeding your animals and before it's too late. The internet can provide you with a list of the certified labs. Just go to http://www.foragetesting.org.