Piglet Processing and Swine Welfare

Livestock Update, May 2009

Dr. Allen Harper
Extension Animal Scientist – Swine
Virginia Tech Tidewater AREC

A well respected trade publication with heavy emphasis on animal agriculture recently ran opposing articles debating certain aspects of the animal rights movement and animal welfare issues (Feedstuffs, April 20, 2009 issue). At the risk of oversimplifying, one article takes the position that those in commercial animal agriculture misunderstand the basis of public concern about animal welfare and over emphasize the value of science in arriving at animal welfare practices and policy (Rollin, 2009). The article on the other side of the debate touts science and technology as important components of food animal welfare and production, and points out that extremist groups use isolated instances of animal mistreatment to promote their agenda of a meatless society to the general public (Kopperud, 2009).

Science is performed by people and therefore is not, nor can it be perfect. This includes the food animal sciences. But good science that uses objective, well-designed methodology can and must be considered in the attempt to arrive, as close as possible, to reliable truths about animal welfare. In the case of commercial swine production use of total confinement gestation stalls represents the most contentious animal welfare issue. But other areas of concern exist. For example processing of nursing piglets involves practices that involve brief but recognizable pain to the piglet such as needle teeth clipping, tail docking, castration, iron supplementation and ear notching or tagging. Ironically two of these practices, needle teeth clipping and tail docking, are performed to reduce potential pain or welfare problems during subsequent development. It is reasonable to assume that the methods used to perform piglet processing tasks can influence the level of stress or pain imposed. A recently reported study from USDA and Purdue University animal scientists bears this out, and provides some useful information for managers and stockpersons operating sow farms (Marchant-Forde and coworkers, 2009).

Using behavioral, physiological and performance measures, the researchers compared two commonly available methods for each of five piglet processing procedures. For needle teeth clipping they compared use of side cutting pliers to a special rotary grinder from a veterinary supply firm. For tail docking they compared cold-clipping with side cutting pliers to the use of a hot-blade, cauterizing clipper from a veterinary supply firm. For castration they compared scrotal incision and pulling each testicle free from the cord verses cutting each testicle free of the cord. For iron administration they compared use of intramuscular injection with iron dextran solution to oral administration of iron enriched paste. And finally, for individual piglet identification they compared ear notching to use of piercing with a numbered ear tag. All pigs were 2 to 3 days of age when processing took place, which is similar to processing age on many commercials farms. To minimize bias during the study, a single technician who had no prior experience with piglet processing was thoroughly trained in each method and subsequently performed all practices throughout the course of the study. Multiple observations, recordings and samples were taken for each head-to-head comparison and the results were statistically analyzed and reported.

Needle Teeth Clipping. The study found that of the two methods, use of the grinding instrument to trim needle teeth required significantly more time per pig than clipping with small side-cutters (56 seconds verses 39 seconds per pig). Grinding of needle teeth increased piglet blood levels of two classical stress hormones cortisol and beta endorphin to a greater degree than did clipping. In addition, body weight gain to 14 days of age numerically favored pigs with teeth clipping over those treated by grinding.

Needle teeth clipping is performed on commercial farms to reduce scaring to the sow’s udder and to prevent facial wounds when littermate piglets fight. Interestingly a case study conducted at the Virginia Tech Tidewater AREC swine unit and at a nearby commercial farm illustrated variation in the need to clip needle teeth in piglets (Estienne and coworkers, 2003). In that study not clipping needle teeth resulted in significant occurrence of wounds to sow udders and littermate piglets at the experiment station farm but not on the commercial farm, even though the farrowing facilities and management practices were similar at both. Some difference existed between the two, perhaps genetics of the herds, that resulted in needle teeth damage at one farm but not at the other. The bottom line: clipping needle teeth with small side-cutters took less time per pig and produced less stress (perhaps in part because it took less time) than the special grinding instrument. The decision to clip needle teeth at all on a given farm should be assessed on a farm by farm basis; if the incidence of sow udder and pig facial wounds is low, needle teeth trimming may not be needed at all.

Tail Docking. The USDA/Purdue study found that using the hot-blade cauterizing instrument for tail docking took longer than cold clipping with side cutters (20 verses 17 seconds per pig). The hot bladed cauterizing procedure also resulted in longer, higher pitched vocalizations (squealing) and resulted in slower piglet growth to 14 days than cold clipping.

Tail docking is performed on small piglets to prevent the potential for tail biting problems among pen mates as pigs grow and develop. The bottom line of the study: the hot-bladed cauterizing process is a reasonable concept to reduce bleeding. However, the data indicates that with proper technique, simple cold clipping with sanitized side cutters is quicker, more efficient and, based on pig vocalizations, less painful to the piglet than the hot-blade cauterized docking procedure.

Castration. Castration is performed on young boar pigs for two principle reasons. The first is behavioral. As the age and body size of sexual maturity is reached, boars tend to be more aggressive with pen mates and more difficult to handle than barrows of similar age and weight. The second and perhaps most important reason is that meat from boars that are nearing sexual maturity has high potential for an odor and flavor problem commonly called “boar taint.”

The USDA/Purdue study found that both tearing the testicle from its attached cord and cutting the testicle free produced substantial high pitched vocalizations indicating there was pain associated with both procedures. However, aside from the time required to perform each method there were few notable differences between methods. The researchers indicated that greater attention to detail was needed with the tear method to assure gripping and careful pulling to separate the testicle from its cord. As a result the cord tear method required 96 seconds per pig compared to 70 seconds per pig for the cord cut method. Tearing is believed to minimize bleeding in the process. The bottom line: as long as boar taint problems exist in North American pork production, castration of boar piglets is necessary. Whether cord tear or cut methods are used, perhaps the most important aspect for minimizing pain and stress is that the procedure be performed by a well trained, conscientious technician. A well accepted published procedure can be found in the Pork Industry Handbook (Reese and coworkers, 2007) and is outlined as follows.

Castration Method for One Person Using a Surgical Knife (adapted from PIH 01-01-07)
         1. Hold the piglet by both hind legs with its head down.
         2. Using the thumb, push up on both testicles.
         3. Make an incision through the skin of the scrotum over each testicle in the direction of the tail.
         4. Be sure the incisions are made low on the scrotal sac to allow for fluid drainage.
         5. It does not matter if you cut through the white membrane of each testicle or not.
         6. Pop the testicles through each incision and pull on them slightly.
         7. Pull each testicle out while pressing your thumb against the piglet’s pelvis.
         8. Thumb pressure on the pelvis is important to ensure that the testicular cords break off at the point of your thumb rather than deep inside the body, which may promote development of a hernia.
         9. If necessary the testicle may be cut free of the cord using a scraping motion.
         10. Cut away any cord or connective tissue protruding from the incision and spray the wound with antiseptic.

Iron Supplementation. In the study there was very little evidence of any differences in piglet welfare or stress between the intramuscular injection of iron solution verses the oral dosing procedure. If performed properly either method is considered effective in preventing anemia in indoor reared nursing piglets. The study did indicate a numerical time savings with intramuscular injection and this observation agrees with previous work. The researchers also commented that oral dosing was more difficult to carry out. The bottom line: because sow milk is inherently low in iron, piglets farrowed and reared in confinement facilities require supplemental iron to prevent piglet anemia. Data from the USDA/Purdue and other studies indicates that intramuscular injection with iron dextran solution is the most efficient and welfare-friendly means of supplementation.

Piglet Identification with Ear Notching or Tagging. The need to individually identify piglets will vary depending on the type of farm and pigs being produced. Farms producing pigs strictly as market animals may only require simple age or birth month identification while pigs destined to become breeding stock require very specific individual identification. Ear notching systems that utilize special ear notch cutting pliers have been around for many years. Indeed ear notching provides a very permanent means of lifetime identification for individual pigs. Ear tags are also readily available but do have the potential for loss or wear over time.

The study found that ear notching took longer than tagging (32 verses 20 seconds per pig) and resulted in greater high pitched vocalizations, higher wound scores and greater plasma cortisol concentration. The bottom line: tagging was less stressful than ear notching to piglets. In cases where precise lifetime identification of pigs is not essential, a less stressful identification method such as tagging or other lower stress method is preferred. On farms producing terminal market pigs, simple month of birth or group identification may suffice.

In summary piglet processing is a necessary husbandry component on farrowing farms. While the procedures may cause temporary pain, some of them are performed to assure health and welfare as the pigs grow and develop. Based on the study highlighted in this article (Marchant-Forde and coworkers, 2009), among commonly used methods, needle teeth clipping with side cutters is preferred to grinding (if needle teeth resection is deemed necessary on the farm). Cold clipping with sanitized side cutters is preferable to hot-blade cauterized clipping for tail docking. Intramuscular iron solution injection is preferred to oral dosing with iron paste for iron supplementation. And, when individual pig identification is essential, ear tagging is considered less stressful to pigs than ear notching, but there is risk of tag loss or wear over time. A well-trained, conscientious technician is essential to minimize stress and optimize piglet welfare when any processing procedures are performed.

References:

--Estienne, M.J., B.R. Horsley, A.F. Harper. 2003. Case study: Effects of resection of pig needle teeth on pig and sow injuries and pre- weaning pig performance. Professional Animal Scientist 19:68-71.
--Kopperud, S. 2009. To underestimate farmers, ranchers is a serious mistake (commentary). Feedstuffs, vol. 81, issue 16 (April 20, 2009).
--Marcharte-Forde, J.N., D.C. Lay, Jr., K.A. McMunn, H.W. Cheng, E.A. Pajor, and R.M. Marchant-Forde. 2009. Postnatal piglet husbandry practices and well-being: The effects of alternative techniques delivered separately. Journal of Animal Science 87:1479-1492.
--Reese, D.E., T.G. Hartsock, and W.E.M. Morrow. 2007. Baby pig management – birth to weaning. Pork Industry Fact Sheet 01-01-07. --The New Pork Industry Handbook, Purdue University Agricultural Distribution Center, West Lafayette, IN.
--Rollin, B.E. 2009. What ag must understand (commentary). Feedstuffs, vol. 81, issue 16 (April 20, 2009).