This is a much too short non-fiction 1977 book from Scholastic. I'm not sure how I missed this when I was a horse book collector since I was about eight. I just found it up on the Internet Archive. Who knows how much longer it'll stay up?
Anyway, the photographer was damn lucky to find a mare foaling in daylight. The vast majority of mares foal in darkness. The mare, stallion and foal are Welsh Mountain ponies. Although the adorable foal is given the equally adorable name Fizz, the names of the stallion and mare are not mentioned.
The author also got the color wrong for the mare. She says the mare is grey, but she's clearly a roan. She's even pictured on the cover, where it's GODDAMN CLEAR that she's not a grey.
This kind of book was ambitious, and did have a few good photos, such as Fizz standing under her mother's belly. However, a book like this really needs to be done in color, not in black and white. Many of the pictures are difficult to make out details.