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Swine behavior studies: A close look at tail biting The University of Minnesota has a network of 10 Research and Outreach Centers across the state, with two of them hosting swine herds in research settings. The Southern Research and Outreach Center at Waseca houses an 800-sow commercial farm which allows for research in growth, development and nutrition, and reproduction. The West Central Research and Outreach Center 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 University of Minnesota 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 in pig populations 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 percent for pigs with docked tails, and 3 to 35 percent 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 pounds were used. Pigs were housed in a conventional barn for 16 weeks. There were four pens of docked pigs, and foure pens of undocked pigs, with each pen housing 30 pigs. Over the 16 weeks, 51.7 percent of undocked pigs and 7.5 percent 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 six 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 percent of undocked pigs and 5 percent of docked pigs were removed to hospital pens in this study. For pigs that were not
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SWINE &U
removed, growth performance when pigs are housed indoors and cannot perform was similar between docked pigs foraging behavior, either due to lack of suitable SWINE & U and undocked pigs. materials or space, they re-direct the foraging By Dr. Yuzhi Li behavior to rooting and chewing their pen mates. Results of this study suggest Usually, ears and tails become the major targets of that raising pigs without tail rooting and chewing because they are readily availdocking in a confinement housing system increases incidence of tail biting and tail damage, resulting in able for manipulation. As pigs grow, chewing can become biting, especially when triggered by stress. higher morbidity and compromised welfare of pigs. It seems that tail docking is still an efficient method Tail biting is usually worse than ear biting because victim pigs can protect their ears better than their to prevent tail biting in growing and finishing pigs tails. In this case, any pig can become a tail biter. under current commercial production conditions in Once a tail biter emerges, an outbreak of tail biting the United States. will occur. Tail biting details The second type of tail biting is believed another Tail biting is a behavioral problem that involves form of aggression. When pigs are restricted for both biters and victimized pigs. The biters are trigresources, such as too few feeders, drinkers, or limitgered by things such as genetics, physiology, or ed floor space, they try to displace other pigs from insufficient housing, nutrition or environmental enrichment needs. The victimized pigs, or those that the resources by biting their tails. In this case, usually the dominant pigs are tail biters and biting have their tails bit or even chewed off completely, usually occurs near the feeder or drinker. are attractive to biters because of their sex, body size or their insensitivity to being chewed. In a The third type of tail biting is assumed ‘obsessive’ recent PorkBridge webinar, Dr. Li offered tips to tail biting. For some reason, some pigs are geneticombat this problem. cally wired for tail biting. These pigs, so called ‘obsessive tail biters’, persistently go around and Research has shown that while biting happens in bite the tail from one pig to another in the pen once herds with both docked and undocked tails, it is triggered. These pigs are poorly understood. more prevalent in undocked herds. Not only is it painful for the victimized pigs and can lead to infec- However, it is usually relatively easy to identify the tion, the damage caused by biting and infection can obsessive tail biters at the early stage of an outbreak of tail biting because of their persistent tail lead to carcass trim loss, with more of the animal biting behavior. Once the obsessive tail biter is idenhaving to be trimmed away to remove the damaged tified and removed from the pen, the problem of tail area. If too severe, the pig may not even be able to biting can be solved. be sold at all. Pigs who are victimized generally weigh less than non-victim pigs. In a study (“Tail biting in growing-finishing pigs,” Tail biting is usually considered a negative conse- sponsored by the National Pork Board) which took quence of confinement housing systems, mainly due place in 2015 at the WCROC, researchers identified an obsessive tail biter. At 10 weeks old, the obsesto the barren environment of the fully slatted floor sive tail biter caused an outbreak of tail biting in a which cannot provide rooting materials for pigs to manipulate. However, in alternative production sys- pen of 30 pigs, with 28 pigs in the pen having injured tails. The tail biter was identified on the day tems where pigs are provided bedding (usually straw or corn stalks in the Midwest), tail biting can when an outbreak of tail biting was evident. After the tail biter was removed, all victim pigs with also become a problem. In fact, tail biting concerns alternative producers more than it concerns conven- injured tails were healed within three days. After that, no pigs had to be removed from the pen due to tional producers because alternative producers do tail biting over 14 weeks. This case demonstrated not dock tails. that it is possible to solve tail biting problems by Tail biting is a contemporary issue that challenges identifying tail biters at an early stage of an outboth alternative and conventional swine producers. break. Regardless of the causes, ultimately tail biting is an It is not an easy task to identify the real tail bitabnormal behavior. To tackle the problem, researchers, especially to identify the first two types of tail ers attempt to understand the development of the biters. In addition, as tail biting progresses, some behavior. pigs can become followers of the tail biter, and it is In general, three different types of tail biting are hard to differentiate the original tail biters from the proposed. The first type of tail biting is considered See SWINE & U, pg. 12 re-directed foraging behavior. It is suggested that
