From what Ive heard, as stated in the earlier posts, pasty butts arent really a problem till they clog the vent, and then thats a big problem. Now, on the other hand, pasty butts can be a symptom of something. My chicks are going through a "pasty butt situation" right now, and I am trying to figure out what it is...I will give you my situation so that you can base yours off of it if needed:
Symptoms of chicks 4 days- 2 weeks: Chronic, reoccuring pasty butts (once I clean them within a few hours even with a bare butt they have it again). It is anywhere from a dark brown to a creamy brown to white, and it smells absolutely putrid...similar to the brown "ceacal" poops, but worse! Chicks become droopy and lethargic
Within a about 24 hours to around 3 days from coming down with these symptoms, they die.
Possible origination: outside, they were hatched under a broody hen
Treatment: I am still not entirely sure what it is, and I have contacted everyone I know including a licensed "chicken doctor", done tons of research, and depleted just about every source available except the vets, which I cannot afford. At first "we" thought it was cocci (even though no blood in stool, which i questioned that...), but they were on medicated food. I went ahead and treated them with Albon and Sulmet, but on the third day of treatment, 2 more died. After cocci was ruled out, I was told to go ahead and put them on antibiotics. I went ahead and did so, and so far I havent lost any (been 3 days). However, the real test is now because I have 3 chicks with the same thing and they are brand new, so we will see if it works. But to me it does sound like an infection of some sort, and these 3 days, the putrid smell stopped. So if you think you need to treat him and if he has similar symptoms, i suggest try antibiotics. I have them on 1/10 cc of oral Neomycin a day.
I also ordered some Oxine and have them on [3 cc per gal] of drinking water and I am spraying them with [6 1/2 oz per gal 3] times a day. So far, things seem to be working!!
Good luck!!