I am very interested in pigs, and recently I read that some farmers will give pigs nose rings to prevent them from rooting. This seems cruel considering that the nose is a pig's primary means of interaction with the world. However, I've also seen some arguments that preventing pigs from rooting protects then from parasites and infections that might be in the soil.
Have there been any studies on the psychological and health effects of nose rings for pigs? I am having difficulty finding much information beyond basic pet care and enthusiast sites.