Alfalfa is a legume, not a hay. It is commonly referred to as a hay because it is harvested similarly to how grass hay is harvested. Hays are fescue, timothy, orchard, Bermuda, etc.
Straw is the stalks leftover from harvesting wheat, barley, and oats. There will be some seeds left in the straw after bailing, because it is nearly impossible to make sure all of the grain has been harvested. There just will not be as many seeds left over as there are in hay. Also note that horse manure should be composted before using in any areas where you do not want hay seeds to sprout. Most of the seeds survive the digestion process in a horse, however I am not sure about cattle, since they have multiple stomachs.
Alfalfa is a legume, not a hay. It is commonly referred to as a hay because it is harvested similarly to how grass hay is harvested. Hays are fescue, timothy, orchard, Bermuda, etc.
Straw is the stalks leftover from harvesting wheat, barley, and oats. There will be some seeds left in the straw after bailing, because it is nearly impossible to make sure all of the grain has been harvested. There just will not be as many seeds left over as there are in hay. Also note that horse manure should be composted before using in any areas where you do not want hay seeds to sprout. Most of the seeds survive the digestion process in a horse, however I am not sure about cattle, since they have multiple stomachs.