Tail biting is a vice of hogs. Docking tails helps reduce the problem, but this practice is increasingly looked upon critically as an animal welfare issue. Tail biting as well as ear biting and flank biting affect group-raised hogs of all ages. Any number of factors have been associated with causing and/or inciting pigs to bite, such as genetics, high-fat diets, crowding, disease, ventilation issues and malnutrition.
When there is only a hammer in the toolbox, every problem looks like a nail. Being a nutritionist, I tend to worry about what can be done from a feed perspective to address the vice of tail biting. Sometimes tweaking the feed helps; other times it has no effect or seems to worsen the problem.
Ration factors that have been considered include:
Protein-amino acid balance: There are questions about whether too much or too little protein may be part of the problem. Excess protein stresses electrolyte balance, and animal proteins have been implicated. If pigs are biting and there are no animal proteins in the diet, try adding an animal protein source. If there is animal protein in the ration, remove it. We do not have a good idea of the effect, so the recommendation is “whatever you are doing, do something different.”
Calcium level: Verify the calcium level in hogs’ diet. It is often excessive.
Fat content: High-fat diets have been associated with tail biting, but there is not a consensus on what constitutes “high” fat. The immediate response is to remove added fat in the diet.
Salt level: Be sure there is adequate salt in the diet. If not, feed more electrolytes and provide more potassium and sodium as mineral. Some nutritionists will also include or increase the level of magnesium oxide. Adding more salts is probably the most common first tweak.
Fiber: Increasing the amount of fiber in the diet sometimes reduces the incidence of biting. For animals that cannot eat up to their energy need, such as wet sows or nursery pigs, the diet will usually have either an energy minimum or fiber maximum specification. Typical corn-soy swine diets will be about 3-percent crude fiber. Common things to feed are alfalfa meal, soyhulls and distiller’s dried grains with solubles.
Water: Ensure that water is adequate in quality and availability.
Tail biting does not appear to be solely caused by nutrition, so expecting a ration tweak to stop the problem may be expecting too much. Uncomfortable, over-crowded and bored pigs tend to bite more. From an environmental perspective, tail biting is more likely when temperature and humidity are high or the pen is cold, especially when it is cold and damp. Large temperature variations, significant drafts and poor air quality are also linked to increased tail biting. If the pen layout forces active pigs to walk through resting areas or the resting area is inadequate, there seems to be more tail-biting incidents. And having varied tail lengths with a mix of docked-undocked tails can also aggravate a biting problem.
It will likely be helpful to mark suspected biters. With group-housed hogs, it is often a smaller, less dominant animal that is biting. Remove bitten pigs from the group. Leaving victims in their initial pen tends to increase biting.
Provide alternative things for hogs to bite and play with. Hang chains or a hose they can chew on. Some people like to use bowling pins and bowling balls in the pens for enrichment. Auto tires are also used, but they shouldn’t be steel-belted radials. They have metal bits that scratch. I am not a big fan of tires because they can be troublesome in the pens. I also dislike using pallets. Pigs can chew on them, and they are cheap, but the nails and large size can cause issues. Make sure objects provided for enrichment stay clean to encourage pigs to bite them rather than each other.