Introduction
Tail docking of cows in the dairy industry[*]—the partial amputation of up to two-thirds of the tail—is a procedure typically performed without anesthetic[1] and is accomplished by the application of a tight, rubber ring that restricts blood flow to the distal portion of the tail, which atrophies and detaches[2] or is removed with a sharp instrument.[3]
Proponents of tail docking have suggested the mutilation offers a number of benefits, including improved cow cleanliness, udder health, milk quality, and worker health.[4] However, some of these justifications have been based on "personal on-farm observation rather than controlled research," according to the editor of industry journal Dairy Herd Management.[5] Indeed, a recent review and discussion of tail docking of cows determined that there are no apparent animal health, animal welfare, or human health justifications to support tail docking and concluded that the routine practice should be discouraged.[6] Other scientific reviews have reached similar conclusions.[7],[8]
In addition to the lack of efficacy of tail docking from an animal or human health perspective, animal welfare concerns, including distress and pain experienced by tail-docked cows, support discontinuation of the mutilation within the dairy industry. Dairy Herd Management editor Thomas Quaife concluded, "The cumulative body of research on tail docking speaks loudly. The early reported benefits do not exist, and tail docking is now more of a producer preference than a cow cleanliness/udder health issue. In light of this new research, and the public's heightened concerns regarding animal welfare, the dairy industry should eliminate the routine practice of docking tails."[9]
Prevalence of Tail Docking in the U.S. Dairy Industry
Annually in the United States, approximately 9 million cows are raised for milk,[10] with 1.7 million confined on 2,125 farms in California, the nation's top-ranking dairy-producing state.[11] A survey by the U.S. Department of Agriculture in 2001 found that 50.5% of U.S. dairy operations practiced tail docking. Some dairy farmers tail-docked only a small percentage of their herd, but approximately 1 in 6 dairy producers docked the tails of 100% of the herd.[12] A Colorado State University 2005-2006 survey of 113 dairy facilities reported that 82.3% of dairies surveyed practiced tail-docking.[13] Indeed, cows are increasingly tail-docked in North America.[14],[15],[16]
Cow Cleanliness and Udder Health
It has been suggested that as cows' tails become soiled through contact with the milking gutter,[17] urine,[18] feces, and debris,[19] the cleanliness and health of the animal are diminished and milk quality decreases.[20] Regarding hygiene, of particular concern is mastitis, a painful disease of the udder. Scientific research does not support claims that tail-docked cows have better hygiene or improved milk quality.[21],[22],[23],[24],[25],[26],[27] In addition, no differences in frequency of mastitis have been found between tail-docked and intact cows.[28]
In one study examining more than 400 cows housed in a free-stall system, researchers found that docking tails improved neither health nor hygiene and concluded that because of "the lack of cleanliness and udder health benefits associated with docking, we see little merit to adopting this procedure."[29] A similar determination was made by researchers who studied more than 1,200 lactating cows from eight Wisconsin farms: "[T]ail docking made no consistent difference in animal cleanliness." The scientists concluded that their "study was unable to identify a significant improvement in cow cleanliness or milk quality that could be attributed to tail docking," that "other management decisions may play a more significant role in determining milk quality," and that "no positive benefits to the cows have been identified."[30]
Worker Health
Proponents of tail docking maintain that the mutilation may benefit workers' comfort and health by reducing their contact with the soiled tails of cows, a possible route of disease transmission on dairy farms.[31] However, in the most comprehensive review of scientific literature on tail docking to date, Carolyn Stull of the University of California-Davis School of Veterinary Medicine and her colleagues found the "available data do not support claims that docking improves the dairy worker's comfort or safety or the health or cleanliness of the cow's udder."[32] Indeed, researchers in New Zealand concluded that improving hygiene and wearing protective clothing are effective in reducing the risk of disease infection from dairy cows,[33] and, rather than tail docking, "the best solution is to control the source of infection in the cattle."[34] In a later study, the scientists again confirmed that "the only way to eliminate the problem is to prevent the milker's exposure to infected cattle urine in the milking shed, and this can only be achieved by the control of leptospirosis in the livestock. It is believed that the most efficient means of achieving this is to vaccinate the cattle and prevent them from becoming infected."[35]
Animal Welfare Concerns
The practice of tail docking cows has been shown to negatively impact animal welfare. Numerous researchers have found that partially amputating the tail reduces the animals' ability to switch away biting insects,[36],[37],[38],[39] particularly flies, leading to increased fly counts on the hind quarters of docked animals,[40] and increasing fly-avoidance behaviors, including foot-stomping and head-turning.[41] A study published in the Journal of Dairy Science found that tail-docked cows exhibited behaviors indicative of discomfort, including standing more than intact cows ("cows tend to stand when uncomfortable"[42]), suffered more fly attacks, and showed increased fly-avoidance behaviors—findings that led the researchers to conclude intact tails are needed for fly avoidance in hutches during the height of fly season.[43] Scientists have reported, "The results suggested that fly avoidance behavior is compromised by switch trimming but not as severely as by tail docking, which prevents normal fly avoidance behavior and is detrimental to the cow's welfare."[44]
Additionally, the practice of tail docking has been shown to result in behavioral and physiological signs of distress and pain. For example, tail docking of lambs with rubber rings has been found to produce significant increases in activity of pain receptors in the tail stump.[45] One study on Holstein cows found that on the sixth day after tail docking, the rubber-ringed groups spent longer with their tails pressed to their bodies.[46] Another concern is the formation of abnormal growths of nerve fibers, or neuromas, in the post-amputation stump that could lead to chronic pain. Neuromas have been found in numerous other species after similar amputations, including lambs, chickens, and, most recently, calves,[47] and these bundles exhibit abnormal nerve discharge patterns, which are thought to be painful.[48],[49]
In some cases, pain can be prolonged after tail docking due to inflammation and the onset of infection at the lesion.[50] It has been shown that abnormal behaviors indicative of pain can persist for up to 41 days after castration and tail docking of lambs,[51] and improper band placement on dairy cows can lead to excessive swelling.[52] Also reported to develop in animals after tail docking is clostridial disease, including gangrene and tetanus.[53]
Alternative to Tail Docking
In addition to improving handling and housing management, switch-trimming—the "periodic trimming of the long hairs growing at the distal end of the tail"[54]—is an effective and humane alternative. Researchers found that after comparing cattle who had been tail-docked, switch-trimmed, or left intact, "the proportion of flies on the rear quarters of trimmed cows was intermediate between that of cows with complete and docked tails" and offered that a "compromise between milking personnel's comfort might be achieved by trimming the switch in the spring (when the tail was more likely to be dirty) and allowing it to grow back over the summer (when fly numbers are highest)."[55]
Scientific and Expert Opposition to Tail Docking of Cows in the Dairy Industry
Both the Canadian Veterinary Medical Association (CVMA) and the American Veterinary Medical Association (AVMA) oppose tail docking.[56],[57] The CVMA states that "the practice of tail docking of dairy cattle has evolved with the assumption that this procedure will reduce the somatic cell count and risk of mastitis. These perceived benefits have not been substantiated in the scientific studies to date. Furthermore, it has been shown that cows are unable to effectively keep flies away once the tail is docked. The CVMA does not accept the exposure of an animal to a surgical procedure in the absence of a justifiable benefit."[58] In its "Tail Docking of Cattle" position statement, the AVMA "opposes routine tail docking of cattle. Current scientific literature indicates that routine tail docking provides no benefit to the animal, and that tail docking can lead to distress during fly seasons. When medically necessary, amputation of tails must be performed by a licensed veterinarian."[59] Indeed, researchers from Colorado State University stated that "[t]he discomfort suffered by cows at the time of docking and throughout life as a result of not being able to swish flies is not reasonable, because the only benefit is to milkers in the milking parlor" and noted that some producers "had quit tail-docking due to difficulty defending the practice."[60]
Industry representatives, experts, and scientists who have discouraged tail docking include the Milk and Dairy Beef Quality Assurance Center,[61] leading scientific expert Dr. Temple Grandin,[62] and numerous welfare assessment programs.[63] According to the California Dairy Quality Assurance Program, "there is no benefit to tail docking normal, healthy tails in dairy cattle based on peer-reviewed scientific studies and governmental sponsored research."[64] The American Association of Bovine Practitioners's stated position reads: "The AABP is not aware of sufficient scientific evidence in the literature to support tail docking in cattle. However, if tail docking is deemed as necessary for proper care and management of production animals in certain conditions, veterinarians should counsel clients on proper procedures, benefits, and risks."[65] University of Wisconsin researchers determined, "Contrary to popular opinion, there does not appear to be any influence of tail docking on cleanliness of udders or legs, nor does there appear to be a relationship between tail docking and milk quality. Other factors such [as] individual animal behavior, housing, handling and facility management have much greater influence on animal hygiene and mastitis than tail docking."[66] This finding was corroborated by University of British Columbia scientists who concluded that there was "no difference between cows with intact tails and those that had been docked in terms of any of our cleanliness measures, somatic cell counts (a measure of udder health), or cases of mastitis as diagnosed by the herd veterinarian."[67]
Tail docking of cows in the dairy industry has been banned in several countries, including the Netherlands, Norway, Sweden, Switzerland, and the United Kingdom.[68] However, despite criticism of the mutilation on the bases of scientific research and welfare concerns, the practice is still allowed in the United States.
Conclusion
Scientific research suggests that tail docking, a practice known to cause distress, pain, and stress in cows, benefits neither animal nor human health. Financial considerations may also favor discontinuing tail docking, as increased fly attacks have been linked to disrupted grazing, slower growth, and reduced milk production and weight gain.[69] In order to improve the welfare of farmed animals and to align with positions held by several governments, North America's largest veterinary medical associations, experts, scientists, and representatives of industry, tail docking of cows in the dairy industry should be disallowed.
[*] For more information, see "An HSUS Report: The Welfare of Cows in the Dairy Industry."
References
[1] Niman NH. 2005. The unkindest cut. The New York Times, March 7. www.nytimes.com/2005/03/07/opinion/07niman.html. Accessed September 23, 2008.
[2] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2004. Tail docking in dairy cattle. University of California, Davis, School of Veterinary Medicine, April 13. www.vetmed.ucdavis.edu/vetext/INF-AN/Tail-Docking-Dairy.pdf. Accessed September 23, 2008.
[3] University of California Cooperative Extension. 1998. Dairy Care Practices, 2nd Edition. University of California, Davis. www.vetmed.ucdavis.edu/vetext/INF-DA/INF-DA_CAREPRAX4.HTML. Accessed September 23, 2008.
[4] Schreiner D and Ruegg P. 2005. Dairy briefing: understanding the impact of tail docking in dairy cattle. University of Wisconsin Agriculture & Extension Service Center.
[5] Quaife T. 2002. Tail docking makes little sense. Dairy Herd Management, October 16. www.dairyherd.com/news_editorial.asp?pgID=724&ed_id=2190. Accessed September 23, 2008.
[6] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2002. Evaluation of the scientific justification for tail docking in dairy cattle. Journal of the American Veterinary Medical Association 220(9):1298-303.
[7] American Veterinary Medical Association. 2006. Backgrounder: welfare implications of tail docking of dairy cattle. www.avma.org/issues/animal_welfare/tail_docking_cattle_bgnd.asp. Accessed September 23, 2008.
[8] Canadian Veterinary Medical Association. 2003. Tail docking of dairy cattle. http://canadianveterinarians.net/ShowText.aspx?ResourceID=25. Accessed September 23, 2008.
[9] Quaife T. 2002. Tail docking makes little sense. Dairy Herd Management, October 16. www.dairyherd.com/news_editorial.asp?pgID=724&ed_id=2190. Accessed September 23, 2008.
[10] U.S. Department of Agriculture National Agricultural Statistics Service. 2008. Milk cows: inventory by year, U.S.: 1998-2007. www.nass.usda.gov/Charts_and_Maps/Milk_Production_and_Milk_Cows/milkcows.asp. Accessed September 23, 2008.
[11] California Department of Food & Agriculture. A consumer's look at California's dairy landscape in 2003.
[12] U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services. 2003. Part III: Reference of dairy cattle health and health management practices in the United States, 2002. National Animal Health Monitoring System, Fort Collins, CO #N400.1203. http://nahms.aphis.usda.gov/dairy/dairy02/Dairy02Pt3.pdf. Accessed September 23, 2008.
[13] Fulwider WK, Grandin T, Rollin BE, Engle TE, Dalsted NL, and Lamm WD. 2008. Survey of dairy management practices on one hundred thirteen north central and northeastern United States dairies. Journal of Dairy Science 91(4):1686-92.
[14] Tucker C. 2000. Tail docking and cow cleanliness. Western Dairy Digest 1(3):14. www.dairyman.ca/Digest/Archive/issues/WDD013/01314.pdf. Accessed September 23, 2008.
[15] Tucker CB and Weary DM. 2002. Tail docking in dairy cattle. Animal Welfare Information Center Bulletin 11(3-4). www.nal.usda.gov/awic/newsletters/v11n3/11n3tuck.htm. Accessed September 23, 2008.
[16] Tucker CB, Fraser D, and Weary DM. 2001. Tail docking dairy cattle: effects on cow cleanliness and udder health. Journal of Dairy Science 84(1):84-7. http://jds.fass.org/cgi/reprint/84/1/84.pdf. Accessed September 23, 2008.
[17] Eicher SD, Morrow-Tesch JL, Albright JL, and Williams RE. 2001. Tail-docking alters fly numbers, fly-avoidance behaviors, and cleanliness, but not physiological measures. Journal of Dairy Science 84:1822-8. http://jds.fass.org/cgi/reprint/84/8/1822.pdf. Accessed September 23, 2008.
[18] American Veterinary Medical Association. 2006. Backgrounder: welfare implications of tail docking of dairy cattle. www.avma.org/issues/animal_welfare/tail_docking_cattle_bgnd.asp. Accessed September 23, 2008.
[19] Tucker CB, Fraser D, and Weary DM. 2001. Tail docking dairy cattle: effects on cow cleanliness and udder health. Journal of Dairy Science 84(1):84-7. http://jds.fass.org/cgi/reprint/84/1/84.pdf. Accessed September 23, 2008.
[20] Schreiner D and Ruegg P. 2005. Dairy briefing: understanding the impact of tail docking in dairy cattle. University of Wisconsin Agriculture & Extension Service Center.
[21] Tucker CB and Weary DM. 2002. Tail docking in dairy cattle. Animal Welfare Information Center Bulletin 11(3-4). www.nal.usda.gov/awic/newsletters/v11n3/11n3tuck.htm. Accessed September 23, 2008.
[22] Tucker CB, Fraser D, and Weary DM. 2001. Tail docking dairy cattle: effects on cow cleanliness and udder health. Journal of Dairy Science 84(1):84-7. http://jds.fass.org/cgi/reprint/84/1/84.pdf. Accessed September 23, 2008.
[23] Schreiner DA and Ruegg PL. 2002. Effects of tail docking on milk quality and cow cleanliness. Journal of Dairy Science 85(10):2503-11.
[24] University of California Cooperative Extension. 1998. Dairy Care Practices, 2nd Edition. University of California, Davis. www.vetmed.ucdavis.edu/vetext/INF-DA/INF-DA_CAREPRAX4.HTML. Accessed September 23, 2008.
[25] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2002. Evaluation of the scientific justification for tail docking in dairy cattle. Journal of the American Veterinary Medical Association 220(9):1298-303.
[26].Stull CL, Berry SL, Reed BA, and Payne MA. 2004. California Dairy Quality Assurance Program. Dairy Welfare Evaluation Guide (University of California, Davis). www.cdqa.org/ahw/dweg/. Accessed September 23, 2008.
[27] De Grassi A. 2001. A look at bovine welfare—what's good, what's bad, and the lessons within. Journal of the American Veterinary Medical Association 219(10):1369-73.
[28] Albright JL. 2000. Dairy cattle behaviour, facilities, handling and husbandry. In: Grandin T (ed.), Livestock Handling and Transport, 2nd Edition (Wallingford, U.K.: CABI Publishing).
[29] Tucker CB, Fraser D, and Weary DM. 2001. Tail docking dairy cattle: effects on cow cleanliness and udder health. Journal of Dairy Science 84(1):84-7. http://jds.fass.org/cgi/reprint/84/1/84.pdf. Accessed September 23, 2008.
[30] Schreiner D and Ruegg P. 2005. Dairy briefing: understanding the impact of tail docking in dairy cattle. University of Wisconsin Agriculture & Extension Service Center.
[31] Stookey JM. 1994. Is intensive dairy production compatible with animal welfare? In: Proceedings of the 1994 Western Dairy Canadian Dairy Seminar. Advances in Dairy Technology 6:209-19. www.usask.ca/wcvm/herdmed/applied-ethology/articles/dairysem.html. Accessed September 23, 2008.
[32] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2002. Evaluation of the scientific justification for tail docking in dairy cattle. Journal of the American Veterinary Medical Association 220(9):1298-303.
[33] Mackintosh CG, Schollum LM, Harris RE, et al. 1980. Epidemiology of leptospirosis in dairy farm workers in the Manawatu. Part I: A cross-sectional serological survey and associated occupational factors. New Zealand Veterinary Journal 28:245-50.
[34] Mackintosh CG, Schollum LM, Harris RE, et al. 1980. Epidemiology of leptospirosis in dairy farm workers in the Manawatu. Part I: A cross-sectional serological survey and associated occupational factors. New Zealand Veterinary Journal 28:245-50.
[35] Mackintosh CG, Schollum LM, Blackmore DK, and Marshall RB. 1982. Epidemiology of leptospirosis in dairy farm workers in the Manawatu. Part II. A case-control study of high and low risk farms. New Zealand Veterinary Journal 30:73-6.
[36] University of California Cooperative Extension. 1998. Dairy Care Practices, 2nd Edition. University of California, Davis. www.vetmed.ucdavis.edu/vetext/INF-DA/INF-DA_CAREPRAX4.HTML. Accessed September 23, 2008.
[37] Stull CL, Berry SL, Reed BA, and Payne MA. 2004. California Dairy Quality Assurance Program. Dairy Welfare Evaluation Guide (University of California, Davis). www.cdqa.org/ahw/dweg/. Accessed September 23, 2008.
[38] Morrow-Tesch JL. 2001. Evaluating management practices for their impact on welfare. Journal of the American Veterinary Medical Association 219(10):1374-6.
[39] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2002. Evaluation of the scientific justification for tail docking in dairy cattle. Journal of the American Veterinary Medical Association 220(9):1298-303.
[40] Eicher SD, Morrow-Tesch JL, Albright JL, and Williams RE. 2001. Tail-docking alters fly numbers, fly-avoidance behaviors, and cleanliness, but not physiological measures. Journal of Dairy Science 84:1822-8. http://jds.fass.org/cgi/reprint/84/8/1822.pdf. Accessed September 23, 2008.
[41] Eicher SD, Morrow-Tesch JL, Albright JL, and Williams RE. 2001. Tail-docking alters fly numbers, fly-avoidance behaviors, and cleanliness, but not physiological measures. Journal of Dairy Science 84:1822-8. http://jds.fass.org/cgi/reprint/84/8/1822.pdf. Accessed September 23, 2008.
[42] Eicher SD, Morrow-Tesch JL, Albright JL, and Williams RE. 2001. Tail-docking alters fly numbers, fly-avoidance behaviors, and cleanliness, but not physiological measures. Journal of Dairy Science 84:1822-8. http://jds.fass.org/cgi/reprint/84/8/1822.pdf. Accessed September 23, 2008.
[43] Eicher SD and Dailey JW. 2002. Indicators of acute pain and fly avoidance behaviors in Holstein calves following tail-docking. Journal of Dairy Science 85:2850-8.
[44] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2002. Evaluation of the scientific justification for tail docking in dairy cattle. Journal of the American Veterinary Medical Association 220(9):1298-303.
[45] Molony V and Kent JE. 1997. Assessment of acute pain in farm animals using behavioral and physiological measurements. Journal of Animal Science 75:266-72.
[46] Tom EM, Duncan IJH, Widowski TM, Bateman KG, and Leslie KE. 2002. Effects of tail docking using a rubber ring with or without anesthetic on behavior and production of lactating cows. Journal of Dairy Science 85:2257-65.
[47] Eicher SD, Morrow-Tesch JL, Albright JL, Dailey JW, Young CR, and Stanker LH. 2000. Tail-docking influences on behavioral, immunological, and endocrine responses in dairy heifers. Journal of Dairy Science 83:1456-62.
[48] Gentle MJ. 1986. Neuroma formation following partial beak amputation (beak trimming) in the chicken. Research in Veterinary Science 41(3):383-5.
[49] Breward J and Gentle MJ. 1985. Neuroma formation and abnormal afferent nerve discharges after partial beak amputation (beak trimming) in poultry. Experientia 41(9):1132-4.
[50] Sneddon LU and Gentle MJ. 2001. Pain in farm animals. Workshop of the Research Consortium Sustainable Animal Production. www.agriculture.de/acms1/conf6/ws5apain.htm. Accessed September 23, 2008.
[51] Sneddon LU and Gentle MJ. 2001. Pain in farm animals. Workshop of the Research Consortium Sustainable Animal Production, citing: Kent JE, Jackson RE, Molony V, and Hosie BD. 2000. Effects of acute pain reduction methods on the chronic inflammatory lesions and behaviour of lambs castrated and tail docked with rubber rings at less than two days of age. Veterinary Journal 160(1):33-41. www.agriculture.de/acms1/conf6/ws5apain.htm. Accessed September 23, 2008.
[52] Eicher SD, Morrow-Tesch JL, Albright JL, Dailey JW, Young CR, and Stanker LH. 2000. Tail-docking influences on behavioral, immunological, and endocrine responses in dairy heifers. Journal of Dairy Science 83:1456-62.
[53] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2002. Evaluation of the scientific justification for tail docking in dairy cattle. Journal of the American Veterinary Medical Association 220(9):1298-303.
[54] University of California Cooperative Extension. 1998. Dairy Care Practices, 2nd Edition. University of California, Davis. www.vetmed.ucdavis.edu/vetext/INF-DA/INF-DA_CAREPRAX4.HTML. Accessed September 23, 2008.
[55] Stull CL, Payne MA, Berry SL, and Hullinger PJ. 2002. Evaluation of the scientific justification for tail docking in dairy cattle. Journal of the American Veterinary Medical Association 220(9):1298-303.
[56] Canadian Veterinary Medical Association. 2003. Tail docking of dairy cattle. http://canadianveterinarians.net/ShowText.aspx?ResourceID=25. Accessed September 23, 2008.
[57] American Veterinary Medical Association. 2008. AVMA policy: tail docking of cattle (current as of June 2005). www.avma.org/issues/policy/animal_welfare/tail_docking_cattle.asp. Accessed September 23, 2008.
[58] Canadian Veterinary Medical Association. 2003. Tail docking of dairy cattle. http://canadianveterinarians.net/ShowText.aspx?ResourceID=25. Accessed September 23, 2008.
[59] American Veterinary Medical Association. 2008. AVMA policy: tail docking of cattle (current as of June 2005). www.avma.org/issues/policy/animal_welfare/tail_docking_cattle.asp. Accessed September 23, 2008.
[60] Fulwider WK, Grandin T, Rollin BE, Engle TE, Dalsted NL, and Lamm WD. 2008. Survey of dairy management practices on one hundred thirteen north central and northeastern United States dairies. Journal of Dairy Science 91(4):1686-92.
[61] American Veterinary Medical Association. 2004. AVMA welfare positions evolve. Journal of the American Veterinary Medical Association 224:1729.
[62] Grandin T. 2007. Outline of cow welfare critical control points for dairies (revised March 2007). www.grandin.com/cow.welfare.ccp.html. Accessed September 23, 2008.
[63] Stull CL, Reed BA, and Berry SL. 2005. A comparison of three animal welfare assessment programs on California dairies. Journal of Dairy Science 88:1595-600.
[64] Stull CL, Berry SL, Reed BA, and Payne MA. 2004. California Dairy Quality Assurance Program. Dairy Welfare Evaluation Guide (University of California, Davis). www.cdqa.org/ahw/dweg/. Accessed September 23, 2008.
[65] Hoard's Dairyman. 2006. Hoard's has heard…. Hoard's Dairyman 151(4):111.
[66] Schreiner D and Ruegg P. 2005. Dairy briefing: understanding the impact of tail docking in dairy cattle. University of Wisconsin Agriculture & Extension Service Center.
[67] Tucker CB and Weary DM. 2002. Tail docking in dairy cattle. Animal Welfare Information Center Bulletin 11(3-4). www.nal.usda.gov/awic/newsletters/v11n3/11n3tuck.htm. Accessed September 23, 2008.
[68] Bagley CV. 2002. Tail docking of dairy cattle. Utah State University Extension. http://extension.usu.edu/files/publications/newsletter/pub__153068.htm. Accessed September 23, 2008.
[69] Eicher SD, Morrow-Tesch JL, Albright JL, and Williams RE. 2001. Tail-docking alters fly numbers, fly-avoidance behaviors, and cleanliness, but not physiological measures. Journal of Dairy Science 84:1822-8, citing: Campbell JB and Berry IL. 1989. Economic threshold for stable flies on confined livestock. Miscellaneous Publications of the Entomological Society of America 74:18-22. http://jds.fass.org/cgi/reprint/84/8/1822.pdf. Accessed September 23, 2008.
