IMO and experience the one thing that horse do with easy and little to no complications 90+% of the time is foal. They don’t drag it out like humans.But I have only worked with TBs.
There are rules of thumb to follow but most mares don’t follow them. Some mares wax up some don’t. Some get huge bags early some don’t bag up until a few days before they foal. Some will roll a lot a few days before as the the foal moves into position. Maiden mares tend to be drama queens, up and down, walking their stall, etc. Keeps one on their toes when watching the foaling channel. If the mare develops “icicles” you’re pretty much guaranteed she will foal that night or the next IME.
Most foal at night but I have a number of them foal after being turned out in the morning. While my back was turned and closing the gate.
I don’t know anyone at TB breeding farms that use the milk testing method. I know ones that tried and said it wan’t worth the effort. No reliable. To each their own on this.
The best “tell tail” in my experience is knowing the look of your mare. They get bigger and wider/rounder. But when the foal moves into foaling position they tend to lose the “round” and their belly will drop a bit and develop more of an pointy or egg shape. The sides of their butt will lose its roundness and the sides will tend to be a bit concave. An old school test is to check the feel of their tail buy pulling it up. When close to foaling it will “soften” be loose instead of the mare being resistant. IME this is a pretty good “tell tail” about 60-80% of the time. (wonder if that is where the expression comes from).
Being a maiden breeder is pretty stressful.Much more than for the mare. Especially if they read a lot on the subject. Especially if they read the section in Blessed are the Broodmares that goes into all the things that can go wrong. IME 95% of the time everything goes perfect with little to no intervention. 4% may require a bit of intervention, mainly correcting leg position. 1% may require major intervention and or tragedy.
After the mare breaks water all I do is check for position. The 2 legs “palms” down, one leg a few inches “longer” then the other and the foals nose between. If one leg is sticking out much more then the other and or can barely be seen it maybe best to gently pull the “short” one out to straighten. If all is good I leave the mare alone and watch the rest on the stall cam. Once the foal is out it is normal for a bit of its hind legs to still be “in” the mare. This is the mare’s post foaling resting period. I do not go into the stall until she gets up. I generally wait until I can see that the umbilical cord has broken also.
IMO a stall foaling cam is god sent. A good wireless IR Cam with sender/receiver can be had for around $200. Our foaling stall are 14X14 when the cam is positioned correctly it covers the whole stall. The IR cam works great in a pitch dark stall, though it is in black and white. But because anything that is “hot” will “glow” on the stall floor like the “puddle” after water has broken and I missed seeing it. I have run down to the stall to check things only to find out it was a fresh warm turd.
I rarely worry about a mare that is going “long”. It only sucks if I miss judge the timing and spend countless nights watching the foaling channel in vain. Mares that bag up and or act the part several weeks early is stressful. We have foaled a lot of mares and though our vet is kept on call. We have only needed a vet on the rare occasion. Ours are pretty close by.
The book I recommend on the subject is The Complete Book of Foaling.