Toxicity
Toxicity is the ability of any chemical to produce adverse effects on a living being. All substances can be potentially toxic if they are consumed in a sufficient amount.
Many components of the diet, such as vitamins and minerals, can cause poisoning if they are given in excess.
Many drugs are also toxic if they are used above the recommended dose.
Another type of poisoning that may be relatively common is due to the consumption of rat poisons by pigs.
Some gases released from manure pits can also be toxic (as well for humans).
Another source are toxins produced by microorganisms such as fungi (mycotoxins in this case) that can grow in the feed under certain conditions.