The haying situation this spring and early summer has been a little different than usual due to the prolonged and widespread rains. Historically, producers with winter annual forages to bale, like ryegrass and graze-out wheat, could compare the risk of cutting hay early and getting it rained on during hay curing versus the certainty of lower quality by waiting to cut it. However, this year, excessive rainfall has taken most of those decisions away and forced producers to just wait it out. With dry weather in the forecast and fields drying out, there will be many acres of very mature winter annual hay cut in the next few weeks, along with more mature first-cuttings of many warm season forages. The bright spot is that there should be plenty of hay available for purchase from now into summer. If that turns out to be the case, then you can and should be able to "shop" for the best hay available.
Regardless of the year, you should always get a composite sample from all individual lots of hay you are considering buying. Take cores or grab-samples from at least 12 to 15 individual bales (or 15 to 20 percent of the bales, whichever is more), then have it analyzed at least for crude protein and total digestible nutrients before you purchase it. Analysis is the only way to know the feed value of the hay. The cost of supplementing a cow through the winter on 6 percent protein hay versus 9 percent protein hay is huge. You can get results from most labs quickly enough to make timely buying decisions.
While collecting your sample, see if it has the general characteristics of quality hay. It should be leafy, fine-stemmed and green, with a good smell. You'll find few, if any, seed heads, blossoms, or weeds, and no foreign materials. Lower quality hay will have fewer leaves, coarser stems and more seed heads/blossoms, indicating more mature plants. It may be brown with a musty or moldy smell.
Pay special attention to wheat hay. There are many acres of wheat this year that were intended for grain harvest but will be hayed instead. Much of it will be from bearded varieties. The awns (beards) in these varieties can cause mouth injury and soreness when fed as hay to cattle. As you're pulling the sample for analysis, check for beards. Bearded wheat hay can be successfully fed with other hay or chopped to minimize problems, but you still need to be aware of what you're buying.
The phrase "rained-on hay" always bears caution in terms of decreased quality. However, the extent of damage on hay that was rained on after cutting but before baling depends on several things. Less than an inch of rain on freshly cut hay that did not had time to dry out much has been shown to have little to no effect on quality. However, even minimal rain on hay in the windrow that is nearly dry can cause significant losses in quality. Also, hay that is baled too wet can get hot and mold in the bale, which decreases nutritional value tremendously.
One last recommendation is to buy hay by the ton not by the bale. Once an analysis has helped you identify the hay you want, the final deal should be on weight. This will involve a scale at some point in the transaction.
Hopefully, this summer is a buyer's market for hay. If it is, then take your time and find the best value to provide your needs this fall and winter, and consider purchasing enough hay for an additional year or two if you have sufficient storage.