There are a variety of situations in which it is helpful to be able to milk a mare or strip a sample of milk from a mare’s udder.
The appearance of the milk as a mare nears foaling is a very good predictor of impending birth. In my vet practice, I sample the milk of mares nearing foaling and find it helpful for making more accurate predictions. The secretion turns from honey colored to white within 48 hours of foaling in most cases.
The other reason to be able to milk a mare is the rare situation in which a newborn foal cannot attach and nurse and you opt to bottle feed the foal. In most cases, your veterinarian will guide you in how to proceed.
Connect with the mare at the shoulder and move down her side to her flank. Ensure she is desensitized by maintaining contact and sliding your hand down slowly to her udder. If she resists, swishes her tail or kicks, keep your hand there until she stops, then remove it.
Bend down or kneel down on one knee. Put a teat between thumb and forefinger and pull them down toward the teat tip, repeat. Assess the color, amount and consistency of the milk.
The first milk (colostrum) should be sticky and more of a tan color. As the colostrum is exhausted after 12-24 hours post-foaling (or in cases in which there is no colostrum or it has been lost) the milk becomes a more classic white milk color.
Tips for safety & Success
The mare must be restrained properly by a knowledgeable horse handler in order for this skill to be safely performed.
For milking a mare, a "breast pump" can be made by cutting off the barrel of a 60cc plastic syringe with a sharp (serrated) knife. The plunger is removed and inserted reversed through the cut end. A small amount of sterile lubricant is placed on the udder end and it is placed over the teat. Gentle negative pressure on the plunger draws milk into the barrel. Once full, it can be dumped out into a clean container and collected.
In mares with less milk in the udder, it can be difficult to make a breast pump function properly, and hand milking may be preferable.