I have been trying various methods for hormone pregnancy testing using milk. I tried using Heataid milk progesterone ELISA test kit by Ridgeway Science and this was my result
http://youtu.be/UFpwE0NjsPY. The progesterone test is cumbersome and has to be carried out repeatedly over three weeks to ensure consistently high progesterone, rather than normal cycling, and the kit is not cheap at 44.00, but works out cheaper when testing multiple goats. Also progesterone does not differentiate between pseudo pregnancy and pregnancy.
The other
better option is more conclusive and is also cheaper on a single animal. It is Oestrone Sulphate detection in milk which is sent to a lab. I sent my two samples to Cambridge Specialist Laboratory Services who charged me 23.0 + vat per sample.
But the result is that the two girls who had consistently high progesterone over a three week period also have high levels of OES in their milk and so are quite conclusively pregnant!! RESULT!!

I don't keep a billy, so I took them both to a billy thirty miles up the road, one of my girls is really quiet about her in heat periods and so I decided to sync them both using progesterone sponges which it seems did the trick. Last year I went by behavioural changes and failed. This year I took a more scientific approach and succeeded.