I decided to have the vet out to check Dawn over. Although she's finishing her grain - balancer pellets plus Ultium - she isn't eating much of her hay at night and her water consumption and manure production at night are way down, although what manure there is seems normal. She doesn't seem to be having trouble chewing, as she eats her grain well and eats hay from the round bales in the pasture - I've seen her doing that. She doesn't act like a typical horse with ulcers - she's not ouchy or grouchy or reluctant to work, and she's happily eating grain but not much hay. She's been wormed and is on daily Strongid. She doesn't seem to be colicy. It's quite a mystery.
The vet checked her over and drew some blood for various tests, including basic blood panels as well as some metabolic checks. There's nothing obviously wrong with her - her vital signs are all normal, lungs are clear, mucus membranes and hydration are good and her teeth seem to be all right. The vet hypothesizes that the stress of the move and subsequent herd position struggles - Dawn's moved up enough that there are at least three horses I observed who move when she says so - have, together with my riding her, resulted in her moving a lot more and burning a lot more calories. She may be eating less hay since the Ultium is pretty calorie dense and filling. There is a possibility of ulcers, but I would have to trailer her to a clinic for scoping to determine that definitively.
So we're going to give her some corn oil with some electrolytes and probiotics in addition to her feed. I've also ordered some Ulcergard paste at the vet's instruction to see if it makes a difference over the next three weeks or so - if it's working I'll order more for a full 8 weeks.
One step at a time - she doesn't seem to be unhappy or in any pain, and is glad to work, but I'll feel better ruling some things out. She has been coughing a bit at the start of work, but that could be due to how hot and dusty and pollenish everything is now.
And tomorrow I'm off to see and ride the boys . . . can't wait!