It should be bearably warm. Place the nipple in the foal's mouth and move it back and forth gently to encourage the foal to suckle. Let the foal do the work. Never, ever squeeze the milk bottle. Always keep the foal's nose below its ears.
Foals can easily aspirate milk into their lungs, setting up a severe pneumonia.
Once the foal has finished, record how much milk the foal drank. Clean the bottle and nipple for the next use. If the foal wants more milk, won't drink any milk, or if its belly stays distended after feeding, let the foal technician know.