Welfare implications of teeth clipping, tail docking, and permanent identification of piglets

Literature Review

July 15, 2014

This peer-reviewed summary has been prepared by the American Veterinary Medical Association Animal Welfare Division. While principally a review of the scientific literature, it may also include information gleaned from proprietary data, legislative and regulatory review, market conditions, and scholarly ethical assessments. It is provided as information and its contents should not be construed as official AVMA policy. Mention of trade names, products, commercial practices or organizations does not imply endorsement by the American Veterinary Medical Association.

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Introductory statement

Piglets may undergo a battery of procedures during the first few days or weeks of life, potentially including tooth-clipping, tail docking, castration, and ear-notching or another identification method such as tagging or tattooing.¹ Each of these procedures involves a degree of tissue damage potentially resulting in the piglet experiencing pain. As it is generally accepted that pigs experience pain, and pain compromises welfare, it would be desirable for these procedures to be refined or replaced with practical alternatives, so long as this results in a net benefit to the animal. The corresponding background information of teeth clipping, tail docking and identification is grouped together because strategies such as reduced invasiveness, analgesia and anesthesia, and replacement are common themes requiring consideration for each procedure. While some procedures (such as identification techniques) have received relatively little research attention, general findings, such as which analgesics are safe and effective for use with unweaned piglets, may be broadly applicable.

Piglet teeth clipping

The Practice
Piglets are born with outwardly projecting canine or “needle” teeth used in competition with littermates for teat access. These teeth can be blunted or shortened during the first week of life by grinding the tip, clipping the tip, or clipping the tooth at the gum line.

Benefits
Litters of piglets with intact needle teeth suffer more facial lacerations,^{2,3,4,5,6,7,8} and their sows may have more lacerations on their udder^4,8 and may shield their teats by spending more time lying on their bellies.⁴ Piglets whose teeth have not been clipped may sometimes suffer higher rates of mortality due to increased overlying and crushing by the sow; it has been suggested this might be due to sows being injured and becoming more restless. ⁴ However increased udder injury is not always found when piglets are left intact,⁸ and it has also been suggested that piglets whose teeth have not been clipped are less competitive and so lie closer to the sow thus increasing their risk of being crushed.⁸ Recently, a study found that unclipped teeth and undocked tails did not have significant negative effects on average daily gain (ADG), gain to feed ratio (G:F), serum immunoglobulin G (IgG) concentrations, mortality rates, wound severity/incidence, post-weaning behavior of piglets or carcass composition.⁹ These studies could suggest that there is little to no significant advantage to the clipping of teeth.

Detriments
Clipping has been shown to increase behaviors suggestive of discomfort such as “chomping.”⁵ Piglets whose teeth have been clipped may experience more gum and tongue injuries^4,8 and potentially painful inflammation or abscesses of the teeth.^10,11 These injuries may lead to infections and increased time spent sleeping⁴ (seen as an indicator for infection).

Refinements
Reduced Severity—Clipping off the tip of the tooth has similar benefits to clipping to the gum line.¹²

Technique—Some studies find that grinding causes more damage⁸ and distress¹³than clipping, while others found clipping to be more damaging.⁶ Equipment maintenance and staff proficiency may be more important than the type of equipment used.

Alternatives
Clipping is now often carried out selectively on individuals or litters demonstrating or predisposed to injuries. Clipping only as required can save time and labor costs, but involves clipping some teeth at a later age.^1,14 Routine clipping may be easier to forego when working with more placid breeds¹⁴ and when larger litter sizes are avoided.^14,15

Summary
Clipping, properly performed, rarely produces significant changes in growth rate,^4,7 weaning weight^8,7 or mortality.^4,7 It is performed primarily to reduce animal discomfort and poor appearance due to lesions; however, tooth resection also causes discomfort and potential infection due to opening of the pulp cavity. Routine preventive teeth clipping is reportedly becoming less common.^1,16

Piglet tail docking

The Practice
Tail biting causes physical damage and fear in recipient animals.²² Tail-bitten pigs are also more likely to exhibit pleuritis (inflammation) and lung abscesses¹⁷ and their carcasses are more likely to require trimming.¹⁷ Tail injury may^18,19or may not^20,22 effect growth or mortality depending upon severity.

Tail docking reduces the incidence and severity of tail injury. Tail docking also helps control tail biting behavior, though it does not treat the underlying causes. The incidence of preventive tail docking is hard to establish. A survey of supermarkets conducted in the UK in 2007 provided an estimate that 88% of pigs were tail docked—although tail docking is permitted in the UK only when tail biting is a problem and not as a routine precaution.²¹

Benefits
Tail-docked pigs have been found to have fewer tail injuries^22,23 and indications of better immune function.²²

Detriments
Tail docking causes physiological and behavioral responses indicating acute stress when performed on six-day-old pigs.²⁴ These include increased blood cortisol concentrations, reduced white blood cell count and increased sitting and scooting behavior. The cortisol response does not occur when tail docking is performed with a cautery iron.^24,25 Docked tails may develop neuromas, which are associated with increased sensitivity to pain.²⁶

Considerations: Causal Factors
Outbreaks of tail-biting behavior are complex, with many contributing factors. There is an inherited component in some breeds associated with lean carcass traits.²⁷ Pigs are more likely to be bitten if they have an undocked tail,²⁸ hold their tail between their legs,²⁹ or are male.^17,30 Males may be more frequently bitten when housed with females,³¹ but other studies suggest that mixed-sex housing reduces the incidence of biting overall.²⁸

Although tail biting does occur in outdoor systems,³¹ it is generally less common in outdoor housing²² or indoor housing with natural ventilation.²⁸ Provision of solid floors³⁵ and straw^28,35,32,33 reduces the incidence of tail biting.

Schmolke et al did not find that group size (10 to 80 pigs) affected rates of tail biting.³⁴ However, in general terms, tail biting is more likely to occur with high stocking densities and increased numbers of pigs per feeding space.^28,35

Once tail biting has begun to occur it may continue and intensify due to attraction of pigs to the smell and taste of blood.^36,37

Refinements
Tail docking with a hot iron was found to cause more distress and neuroma formation and so it is not an effective refinement of technique.¹³

Summary
Tail docking is performed to prevent peer-inflicted injury to the tail that can become severe. Because docking causes pain and stress, it should be performed as early as possible and/or in conjunction with appropriate analgesia.³⁸ The ideal welfare outcome would be for tail biting to be reduced to a level where tail docking need not be carried out routinely, if at all. Although tail biting has a complex etiologic basis some researchers believe that improved environmental design is the most promising approach to reduce biting and reduce or eliminate the need for docking.³⁹ Changes in the swine market, producer subsidies, and enrichment-material requirements could also encourage swine producers to explore and implement new practices to reach this goal.⁴⁰

Piglet identification methods

Pigs need to be individually identified throughout life for management and traceability of products for safety or assurance schemes.^41,42

Ear Notching
Ear notching is considered to be painful.⁴³ Due to the increased labor and time required to apply the ear notches and read them, this procedure is not commonly used in commercial settings. Ear notching is mostly used by small purebred breeders and 4-H pig breeders. Producers that do utilize ear notching, with or without tail docking, may limit resource expenditure by delaying these procedures briefly.⁴⁴ This may cause additional discomfort to the animals, but fewer animals of lower birth weight may survive to this point and fewer procedures would then need to be carried out.

Ear Tags
Ear tags may carry a visual number and/or and electronic transponder.⁴¹

Injected Transponders
Small transponders may be injected beneath the skin at the base of the ear^36,45,46 or intra-peritoneally. Injected transponders may result in inflammation or infection in some cases.⁴¹ Larger transponder size may cause more severe reactions.^41,47 Large transponders positioned at the base of the auricle also have a higher rate of loss, possibly because of inadequate application with insufficient needle penetration leading to a transponder that remains near the application point, facilitating its loss.^40,46,48

Tattoos
Pigs may be tattooed with an identifying number.⁴⁹Tattooing causes stress in pigs, which may be reduced by refinement of equipment and techniques.⁵⁰

Summary
Individual animal identification is desirable for tracking and ensuring good care. There has not been a comparison among identification systems on the basis or pain and other welfare parameters, and this should be included as part of an ongoing refinement process. Ultimately non-invasive methods such as biometric identifiers or DNA tracking may become available.^51,52

Concluding statement

Most invasive procedures performed on piglets are done to protect the welfare of the pigs rather than to improve production.⁵³ However, many of these procedures are widely considered to be painful for swine and the development of refinements and alternatives is desirable. Prophylactic removal of teeth, and to some extent tails, is becoming less common as less invasive alternatives become available. Where procedures that cause pain are still necessary, the use of analgesia and/or anesthesia should be encouraged wherever this is of net benefit to the animal.

REFERENCES
1. Widowski T, Torrey S. Neonatal Management practices. Swine Welfare Fact Sheet 2002;1:1-4.
2. Boyle LA, Boyle RM, Lynch PB. Effect of tooth clipping on piglet welfare. 2002 Available at: http://www.agresearchforum.com/publicationsarf/2002/page50.pdf Accessed May 5th, 2009.
3. Bates RO, Hoge MD, Edwards DB et al. The influence of canine teeth clipping on nursing and nursery pig performance. J Swine Health Prod 2002;11:75-79.
4. Lewis E, Boyle L. The pros and cons of teeth clipping. http://www.teagasc.ie/pigs/conf_proceedings/pigconferenceproceedings03… Accessed November 19, 2015.
5. Lewis E, Boyle LA, Lynch PB et al. The effect of two teeth resection procedures on the welfare of piglets in farrowing crates. Part 1. Appl Anim Behav Sci 2005;90:233-249.
6. Gallois M, Le Cozler Y, Prunier A. Influence of tooth resection in piglets on welfare and performance. Preventive Vet Med 2005;69:13-23.
7. Brown JME, Edwards SA, Smith WJ et al. Welfare and production implications of teeth clipping and iron injection of piglets in outdoor systems in Scotland. Preventive Vet Med 1996;27:95-105.
8. Holyoake PK, Broek DJ, Callinan APL. The effects of reducing the length of canine teeth in sucking pigs by clipping or grinding. Aust Vet J 2004;82:574-576.
9. Zhou B, Yang XJ, Zhao RQ et al. Effects of tail docking and teeth clipping on the physiological responses, wounds, behavior, growth, and backfat depth of pigs. Journal of Animal Science 2013;91:4908-4916.
10. Hay M, Rue J Sansac C et al. Long-term detrimental effects of tooth clipping or grinding in piglets: a histological approach. Anim Welf 2004;13:27-32.
11. Koller FL, Borowski FL, Asanome SM et al. Piglet teeth clipping: a review and new perspectives. A Hora Veterinaria 2005;25:40-44.
12. Weary DM, Fraser D. Partial tooth-clipping of suckling pigs: effects on neonatal competition and facial injuries. Appl Anim Behav Sci 1999;65:21-27.
13. Lay DC, Marchante-Ford JN. The impact of routine piglet processing on well-being. Pork Checkoff research report NPB# 04-043.
14. Ormond C. Teeth—to clip or not to clip. 6th Annual Red Deer Swine Technology Workshop, October 26 & 27, 2004. pp 103-104.
15. Fraser D, Thompson BK. Armed sibling rivalry among suckling piglets. Behav Ecol Sociobiol 1991;29:9-15.
16. Reese D, Straw BE. Teeth clipping—have you tried to quit? Nebraska Swine Reports 2005.
17. Kritas SK, Morrison RB. Relationships between tail biting in pigs and disease lesions and condemnations at slaughter. Vet Record 2007;160:149-152.
18. Wallgren P, Lindahl E. The influence of tail biting on performance of fattening pigs. Acta Vet Scand. 1996;37:453-60.
19. England D C, Spurr DT. Litter Size of Swine Confined during Gestation. J. Anim Sci. 1969;28:220-223.
20. Nannoni E. Tail docking in pigs: a review on its short- and long-term consequences and effectiveness in preventing tail biting. Italian Journal of Animal Science 2014;13:3095.
21. Hickman M. The pain of tail-docking: a fact of life for millions of pigs. The Independent 2007;December 1:26.
22. McGlone JJ, Sells J, Harris S et al. Cannibalism in growing pigs: effects of tail docking and housing system in behavior, performance and immune function. Texas Tech Univ Agric Sci Tech Rep1990;No T-5-283:69-71.
23. Sutherland MA, Bryer PJ, Krebs N et al. The effect of method of tail docking on tail-biting behaviour and welfare of pigs. Anim Welf 2009;18:561-570.
24. Sutherland MA, Bryer PJ, Krebs N et al. Tail docking in pigs: acute physiological and behavioural responses. Anim 2008; 2:292-297.
25. Prunier A, Mounier AM, Hay M. Effects of castration, tooth resection, or tail docking on plasma metabolites and stress hormones in young pigs. J Anim Sci 2005;83:216-222.
26. Simonsen HB, Klinken L, Bindsell E. Histopathology of intact and docked piglets. Br Vet J 1991;147:407-412.
27. Breuer K, Sutcliffe M, Mercer J et al. Heritability of clinical tail-biting and its relation to performance traits. Livestock Production Sci 2005;93:87-94.
28. Hunter EJ, Jones TA, Guise HJ, et al. The relationship between tail biting in pigs, docking procedure and other management practices. Vet J 2001;161:72-79.
29. Zonderland JJ, van Riel JW, Bracke MBM et al. Tail posture predicts tail damage among weaned pigs. Appl Anim Behav Sci 2009;121:165-170.
30. Kritas SK, Morrison RB. Observations on tail-biting in affected barns. American Association of Swine Veterinarians. https://www.aasv.org/shap/issues/v12n1/v12n1p17.pdf Accessed November 19, 2015.
31. Walker PK, Bilkei G. Tail-biting in outdoor pig production. Vet J 2006;171:367-369.
32. Zonderland JJ, Wolthuis-Fillerup, van Reenen CG et al. Prevention and treatment of tail biting in weaned pigs. Appl Anim Behav Sci 2008;110:269-281.
33. Scollo A, Di Martino G, Bonfanti L et al. Tail docking and the rearing of heavy pigs: The role played by gender and the presence of straw in the control of tail biting, blood parameters, behaviour and skin lesions. Research in Veterinary Science 2013;95:825-830.
34. Schmolke SA, Li YZ, Gonyou HW. Effect of group size on performance of growing-finishing pigs. J Anim Sci 2003;81:874-878.
35. Moinard C, Mendl M, Nicol CJ et al. A case control study of on-farm risk factors far tail biting in pigs. Appl Anim Behav Welf 2003;81:333-355.
36. Jankevicius M, Widowski T. The effect of ACTH on pigs’ attraction to salt of blood-flavored tail-models. Appl Anim Behav Sci 2004;87:55-68.
37. Jankevicius M. Does balancing for color affect pigs’ preference of different flavored tail-models? Appl Anim Behav Sci 2003;84:159-165.
38. Tenbergen R, Friendship R, Cassar G et al. Investigation of the use of meloxicam for reducing pain associated with castration and tail docking and improving performance in piglets. Journal of Swine Health and Production 2014;22:64-70.
39. Edwards SA. Tail biting in pigs: understanding the intractable problem. Vet J 2006;171:198-199.
40. Bracke MBM, De Lauwere CC, Wind SMM et al. Attitudes of Dutch pig farmers towards tail biting and tail docking. Journal of Agricultural and Environmental Ethics 2013;26:847-868.
41. Stark KDC, Morris RS, Pfeiffer DU. Comparison of electronic and visual identification systems in pogs. Livestock Prod Sci 1998;53:143-152.
42. Madec F, Geers R, Vesseur P et al. Traceability in the pig production chain. Rec Sci Tech Off Int Epiz 2001;20:523-537.
43. Rollin BE. Farm Animal Welfare: Social, Bioethical, and Research Issues. Blackwell Publishing, 2003, pg. 96.
44. Bovey KE, Widowski TM, Dewey CE et al. The effect of birth weight and age at tail docking and ear notching on the behavioral and physiological responses of piglets. Journal of Animal Science 2014;92:1718-1727.
45. Santamarina C, Hernandez-Jover M, Babot D et a;. Comparison of visual and electronic devices in pigs: slaughterhouse performance. J Anim Sci 2007;85:497-502.
46. Forsberg F. Individual identification in pigs using microchips. Master’s thesis. Swedish University of Agricultural Sciences: 2014. Available at: http://stud.epsilon.slu.se/6356/7/forsberg_f_140115.pdf. Accessed 25 June 2014.
47. Caja G, Hernandez-Jover M, Conill C et al. Use of ear tags and injectable transponders for the identification and traceability of pigs from birth to the end of the slaughter line. J Anim Sci 2005;83:2215-2224.
48. Hofmo PO. Sperm sorting and low dose insemination in the pig—an update. Acta Vet Scand 2006;48:s11.
49. Day JEL, Spoolder HAM, Burfoota A et al. The separate and interactive effects of handling and environmental enrichment on the behaviour and welfare of growing pigs. Appl Anim Behav Sci 2002;75:177-192.
50. Brach EJ, Scobie BS, Raymond DP. Hog tattooing techniques. J Agri Eng Res 1988;41:339-344.
51. Webb J. Tracking pork from pen to plate. Advances Pork Prod 2004;15:33-41.
52. Gonzales BU, Butler F, McDonnell K et al. The end of the identity crisis? Advances in biometric markers for animal identification. Irish Vet J 62;204-208.
53. Anil L, Anil S, Deen J. Pain detection and amelioration in animals on the farm: issues and options. J Appl Anim Welf Sci 2005:8;261-278.