Skip to main content

Swine Behavior Studies: A Close Look at Tail Biting

By Dr. Yuzhi Li, Associate Professor of Swine Behavior and Alternative Production in the University of Minnesota Department of Animal Sciences.
Originally printed in The LAND – as April 30/May 7, 2021 Swine & U column

The University of Minnesota has a network of 10 Research & Outreach Centers (ROCs) across the state, with two of them hosting swine herds in research settings. The Southern Research & Outreach Center (SROC) at Waseca houses an 800-sow commercial farm which allows for research in growth, development and nutrition, and reproduction. The West Central Research & Outreach Center (WCROC) at Morris has long focused on conventional and organic agriculture, water quality, corn and soybean in addition to fruit and vegetable production, and renewable energy.

WCROC is home to an organic dairy herd and countless swine behavior and housing studies. Dr. Yuzhi Li, member of the UM Department of Animal Science’s swine faculty, focuses on swine behavior and welfare, and alternative swine production. One universal behavioral concern in swine farming has recently been addressed by Dr. Li’s research.

Tail biting is a common problem in growing-finishing pigs. Outbreaks of tail biting can cause major welfare complications of pigs with damaged tails, as well as considerable economic losses to pork producers. The prevalence of tail biting varies from farm to farm, ranging from 0% to 16% for pigs with docked tails, and 3% to 35% for pigs with whole tails. Although the incidence can be low on certain farms, outbreaks of tail biting are almost not predictable. Once an outbreak occurs, tail biting behavior can escalate rapidly, and it is difficult to prevent from further tail biting in the pen or room.

Preventions prior to an outbreak are common practices to avoid losses and implications caused by tail biting. Currently, the common prevention method for tail biting is tail docking which is usually performed when pigs are 1 to 7 days of age. Since tail docking can cause pain in pigs, performing tail docking on a routine basis is under scrutiny due to animal welfare concerns.

To re-evaluate consequences of raising pigs without tail docking, WCROC conducted a study to compare pigs with and without tail docking. Two hundred forty pigs with average body weight of 55 lb were used. Pigs were housed in a conventional barn for 16 weeks. There were 4 pens of docked pigs, and 4 pens of undocked pigs, with each pen housing 30 pigs. Over the 16 weeks, 51.7% of undocked pigs and 7.5% of docked pigs experienced moderate to severe tail damage, indicating that without tail docking more pigs were victimized by tail biting.

Undocked pigs experienced the first outbreak of tail biting 6 weeks earlier than docked pigs, suggesting that tail biting may start early and last longer when tail docking is not performed. As a consequence of tail damage, 18% of undocked pigs and 5% of docked pigs were removed to hospital pens in this study. For pigs that were not removed, growth performance was similar between docked pigs and undocked pigs.

Results of this study suggest that raising pigs without tail docking in a confinement housing system increases incidence of tail biting and tail damage, resulting in higher morbidity and compromised welfare of pigs. It seems that tail docking is still an efficient method to prevent tail biting in growing and finishing pigs under current commercial production conditions in the United States.

Tail biting is a behavioral problem that involves both biters and victimized pigs. The biters are triggered by things such as genetics, physiology, or insufficient housing, nutrition or environmental enrichment needs. The victimized pigs, or those that have their tails bit or even chewed off completely, are attractive to biters because of their sex, body size or their insensitivity to being chewed. In a recent PorkBridge webinar, Dr. Li offered tips to combat this problem.

Research has shown that while biting happens in herds with both docked and undocked tails, it is more prevalent in undocked herds. Not only is it painful for the victimized pigs and can lead to infection, the damage caused by biting and infection can lead to carcass trim loss, with more of the animal having to be trimmed away to remove the damaged area. If too severe, the pig may not even be able to be sold at all. Pigs who are victimized generally weigh less than non-victim pigs.

Tail biting is usually considered a negative consequence of confinement housing systems, mainly due to the barren environment of the fully slatted floor which cannot provide rooting materials for pigs to manipulate. However, in alternative production systems where pigs are provided bedding (usually straw or corn stalks in the Midwest), tail biting can also become a problem. In fact, tail biting concerns alternative producers more than it concerns conventional producers because alternative producers do not dock tails.

Tail biting is a contemporary issue that challenges both alternative and conventional swine producers. Regardless of the causes, ultimately tail biting is an abnormal behavior. To tackle the problem, researchers attempt to understand the development of the behavior.

In general, three different types of tail biting are proposed. The first type of tail biting is considered re-directed foraging behavior. It is suggested that when pigs are housed indoors and cannot perform foraging behavior, either due to lack of suitable materials or space, they re-direct the foraging behavior to rooting and chewing their pen mates. Usually, ears and tails become the major targets of rooting and chewing because they are readily available for manipulation. As pigs grow, chewing can become biting, especially when triggered by stress. Tail biting is usually worse than ear biting because victim pigs can protect their ears better than their tails. In this case, any pig can become a tail biter. Once a tail biter emerges, an outbreak of tail biting will occur.

The second type of tail biting is believed another form of aggression. When pigs are restricted for resources, such as too few feeders, drinkers, or limited floor space, they try to displace other pigs from the resources by biting their tails. In this case, usually the dominant pigs are tail biters and biting usually occurs near the feeder or drinker.

The third type of tail biting is assumed ‘obsessive’ tail biting. For some reason, some pigs are genetically wired for tail biting. These pigs, so called ‘obsessive tail biters’, persistently go around and bite the tail from one pig to another in the pen once triggered. These pigs are poorly understood. However, it is usually relatively easy to identify the obsessive tail biters at the early stage of an outbreak of tail biting because of their persistent tail biting behavior. Once the obsessive tail biter is identified and removed from the pen, the problem of tail biting can be solved.

In a study (Tail biting in growing-finishing pigs; sponsored by the National Pork Board) which took place in 2015 at the WCROC, researchers identified an obsessive tail biter. At 10 weeks old, the obsessive tail biter caused an outbreak of tail biting in a pen of 30 pigs, with 28 pigs in the pen having injured tails. The tail biter was identified on the day when an outbreak of tail biting was evident. After the tail biter was removed, all victim pigs with injured tails were healed within 3 days. After that, no pigs had to be removed from the pen due to tail biting over 14 weeks. This case demonstrated that it is possible to solve tail biting problems by identifying tail biters at an early stage of an outbreak.

It is not an easy task to identify the real tail biters, especially to identify the first two types of tail biters. In addition, as tail biting progresses, some pigs can become followers of the tail biter, and it is hard to differentiate the original tail biters from the followers.

Dr. Li suggests three things producers can do to reduce or prevent tail biting in the herd.
  1. Provide environmental enrichment. “Provide a small amount of substrate to pigs daily. It must be destroyable or easily manipulated, but the main thing is that it’s novel. If it’s not new, it won’t keep the pig’s interest,” Li says. The pigs can chew on that rather than each other.
  2. Observe the herd daily and catch any biting early. This will allow you to remove the tail biters promptly, Li says. There is usually an “indicator pig” that is the first pig to show signs of being bitten and indicates that there is a biter or biters in the pen. At the first sign of an indicator pig, it is time to find the tail biters and remove them from the pen. Catching the behavior at the first sign prevents it from spreading.
  3. Optimize the housing environment. Pigs are more likely to bite if there’s competition for resources in the pen. “Fighting for space at the feeder or drinker can lead to chewing on each other,” Li notes. “There should also be ample and comfortable laying areas, proper ventilation and lighting.”

Print Friendly and PDF