Along with showing other signs, pigs that are eating moldy feed may vomit. The pigs in the image on your screen show classic signs of mold consumption. They are showing an uneven growth rate, swollen vulvas and vomiting. Another cause of vomiting is gastric ulcers. Pigs that are pale and have obvious blood loss from a bleeding gastric ulcer should be moved to the hospital pen and treated for gastric ulcers.
Treatment: Ensure feed is mold-free. Treat vomiting caused by gastric ulcers in a hospital pen. There is no specific treatment for ulcers, but pigs do better if fed a high milk diet such as a first stage nursery feed. If ulcers are more than an occasional occurrence, it may be useful to increase the particle size of feed given to the herd. Adding fiber to feed may help prevent ulcers too. Also, make sure that feed intake is adequate and uninterrupted.