Richard and I have yogurt smoothies most every morning.  The yogurt is homemade from my cows milk and very yummy.  You can make your own and I found a quick website to explain it.  I do it slightly different.  First I use a culture (purchased from any cheese supplier) or I use my own yogurt as the culture.  And I put the yogurt in a thermos to sit overnight.  That will hold the temperature and I have fabulous yogurt the next day.  If you buy yogurt to be your starter, make sure it is LIVE cultured.

http://www.makeyourownyogurt.com/