I've been making yogurt lately.
I started using pasteurized whole milk, the kind where the cream rises to the top. It made good yogurt.
I've tried goat's milk. It made thin, sour yogurt, but it was really yummy in its own way.
I've tried raw milk. I tried it the normal way, heating the milk to 180 degrees then cooling to 100 before adding the culture. Then I wondered if that wasn't wasting the rawness by cooking it so I tried heating it to 115 and putting the culture in. This did not make good yogurt. It was wet and not well-set and a lot of whey would form each day.
One thing that bothered me was how the heat seemed to ruin the cream. It turned yellow and oily. I'd try to skim off as much as I could before heating and put it back in with the culture after the milk cooled. The cream would rise to the top of the yogurt. Sometimes it did not taste very good, like the culture didn't eat it and it went bad. I also tried adding more cream since I've been adding cream to it anyway when I'm ready to eat it. It didn't make very good yogurt to add more cream during the culture stage.
I'm thinking now that maybe the best formula would be to use low-fat pasteurized milk to make the yogurt and then when it's time to eat it, mix in the cream. I may try that next.