Hay vs. Straw

I just never paid much attention – what’s straw versus hay?  It seems I need to know this to keep goats: 

Straw  

First of all, straw is the leftover stalk of plants, like wheat or oats, which have had the seeds removed.  Because the seed part of the plant is removed, it lacks nutritional value and is typically used as bedding.  Even as bedding, the goats seem to think that any grains the harvester missed are good for munching.      

Hay  

Hay is comprised primarily of grasses which still have the seed or grain attached at the time of harvest, and is used as feed.  However, the grass making up the hay might be timothy, alfalfa, clover, rye, orchard grass, Bermuda grass, tall fescue, or any combination of these.  The legume grasses (such as clover or alfalfa) are much higher in protein and nutrient content than grass hays (timothy, orchard grass, Bermuda grass), and within each grass type, the biggest factor affecting nutrient content is maturity at harvest.  The digestible nutrient and protein content of the hay decreases with each subsequent cutting (increase in maturity).  

Regardless of the type of grass making up the hay, the most important factor stressed is that the hay should be clean.  Hay that is moldy or dusty should never be fed.   Also, it’s important that a goat’s diet be changed very gradually.  In our case, the goats were being fed 2^nd cutting orchard grass hay, but we bought 4^th cutting alfalfa hay.  So, we got some of the orchard grass hay too, and are gradually mixing in the alfalfa.   So now I’m wondering, is 4^th cut alfalfa or 2^nd cut orchard grass a more appropriate hay for growing goats?   Got right to the bottom of this one didn’t I?  For now, I’m just going to delude myself; the hay we got is clean, so it’ll be fine.