Most true "springs" are boxed in or protected, then water is piped to a trough or dirt tank which we call "drinkers". Ranchers generally try to protect the source of water if possible cause they know that cows trample everything they can get near, and they want good clean water for future generations of livestock. Many "drinkers" are just filled from snowmelt, rain or windmills. Cow tanks that are above ground (metal or plastic) just tend to get slimy and if there is no branch or ladder small critters drown, those are the worst, especially if that's your only source for the day. Not only do you need to look out for cow poop but cricket poop is also not good and they gather in dark places like spring boxes.
The last cow tank I had to use this past summer was filled with new rain water, but the oak leaves from the trees surrounding the water had leached tannin into the water, making it rather like dark tea. Lots of underwater bugs having a great time in there too! So I wet my bandanna, put it over the Sawyer bag and poked the fabric into the neck of the bottle a bit and poured water slowly from a cup into the bag, then filtered through the Sawyer into my 2 liter platy, and the water was still a bit colored, clear but like a weak tea, then I used the Aquatabs. The taste was not a problem. I was on the AZ trail and there is like NO water here for days and many miles and I was thankful to get what I had found at that tank.
JMHO by the way, I'm a retired rancher....I will also add that in the west, since 1970's I have seen a huge decline of available water as ranchers are edged out of business and the government stops maintaining the older wells, and the Nature Conservancy takes over old ranching grants, they destroy all water sources by the way....and other "signs of man"....much to my dismay as I'm a member. So there is a lot less water available for us when hiking the CDT than even 30 years ago. I know cause I did that trail in the 1980's and 1990's. So if you meet a rancher on your journey thank them for providing water for you, the wildlife and of course the cows.:-)