We've kept up with her worming (did a fecal and worm by weight), trimming, vaccinations, etc. Feeding her has always been a bit mysterious to us. I've asked for help before from her veterinarians and from forums, but I've never received any definitive answers. When she was 7 months pregnant, the vet said she looked thin but not alarmingly so--that's when we added the pelleted hay, oil and supplements.
She looks to be in good weight, but is a bit thin on her top line, but this could be partially conformation and partially the baby pulling her belly down and thus drawing weight away from the top line.
Her current regime:
Unlimited Bermuda grass hay in the form of a round bale.
15lbs of soaked alfalfa/timothy pellets
1 liter of oil (currently soy)
2 oz of Vitamin E/Selenium/probiotic powder (Kaeco brand)