Castration of Pigs

Livestock Update, January 2008

Dr. Allen Harper, Extension Animal Scientist – Swine, Tidewater AREC

Background
Castration of male livestock intended for meat production is a long standing management practice.  In North American swine production, castration is essentially universal and only a select few male pigs are left intact as potential breeder boars.  There are two primary reasons for feeding out barrows rather than boars in pork production.  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 (about 200 lbs. body weight) has high potential for an odor and flavor problem commonly called “boar taint.”  Boar taint refers to objectionable odor and flavor characteristics that many consumers detect in cooked pork from intact males.

Boar taint in pork is associated with two compounds produced in the live animal: androstenone and skatole.  Androstenone is a steroid produced by the testes and concentrated in the salivary glands where it is converted to a pheromone involved in eliciting sexual behavior in gilts and sows during the mating process.  Androstenone is also deposited in the fat tissue and can be released in response to heat during cooking thus contributing to boar taint.  Skatole is a compound produced by bacteria in the hindgut of the boar.  It is absorbed across the intestinal wall into the blood stream, is metabolized by the liver and may be excreted or absorbed into fat tissue where it may cause boar taint (Squires, 1999).

Castration: Another Swine Welfare Controversy?
Some interesting developments are taking place in several European countries with regard to castration of pigs (Arnot and Gauldin, 2007).  For example, legislation has passed in Norway and Switzerland that will ban castration of pigs starting in 2009.  Certain major supermarkets in the Netherlands have announced that they will no longer sell meat from castrated pigs unless the animals received anesthesia prior to the procedure.  The fast food chain McDonald’s of the Netherlands has announced that it will no longer sell products containing pork from castrated pigs.  A similar announcement has been made by Burger King in the Netherlands.

Here in the U.S. the predominant swine welfare issue has been the use of individual gestation stalls for housing sows during the breeding period and throughout pregnancy.  Indeed in Florida, Arizona and Oregon, legislation has recently been passed banning the use of gestation stalls and requiring group housing of breeder sows; and some swine production integrators have announced conversion of production systems to include group housing of sows during extended periods of the production cycle.  But castration as a swine welfare issue has not received a lot of attention in the United States.  The reports of legislative and food service company mandates on castration in Europe have North American pork producers concerned.  Will efforts to eliminate this important management practice that helps control aggressive pig behavior and assures a desirable pork product be imposed here?

Alternatives to castration have been proposed.  However, such alternatives are much easier to talk or write about than to actually put into practice.  For example in the United Kingdom and Ireland castration of pigs is not standard practice, but pig slaughter weight and age is lighter and younger in those countries.  Typical slaughter weight in the U.K. may be 230 lbs. or less while the average slaughter weight in the United States is 269 lbs.  Packing plants in the U.S. are designed to be most efficient by processing heavier hogs and to reduce typical slaughter weights by 50 lbs. would have major logistical and economic impacts.  It has also been said that European pork consumers are willing to accept a certain amount of boar taint, but U.S. pork processors are understandably reluctant to expect this from their consumers.  Other proposed alternatives include modification of castration procedures such as the use of anesthesia when castrating or the use of chemical or immuno-castration in place of surgical castration.  Again these are easy to talk or write about, but in general practice have significant technical and economic limitations.

The Most Important Factor: Proper Castration Procedures
The American Veterinary Medical Association’s (AVMA) current policy on pig castration can be viewed as striking a balance between animal welfare and the need to efficiently produce quality pork.  This group acknowledges that castration helps control aggressive behavior in pigs and recommends that the procedure be performed at least 5 days prior to weaning to allow for sufficient healing before pigs are removed from the sow.  The group’s policy also indicates that if castration is delayed beyond 28 days of age, anesthesia or analgesia should be used and the procedure should be performed by a veterinarian on such older, larger pigs.

The AVMA policy on restricting producer performed castration to young pigs that are still suckling the sow has some scientific basis.  For example one study indicated that pigs castrated at 2 weeks of age displayed fewer indicators of pain than pigs castrated at 7 weeks of age (McGlone and Hellman, 1988).  Another study conducted during the suckling period indicated that pigs castrated at 1 day of age grew at a slower rate up to weaning than when castration was performed at 14 days of age (McGlone and co-workers, 1993).  This suggests some disruption in piglet suckling when castration is performed very early during lactation.  In a similar study Douet and co-workers (1994) found no growth differences when pigs were castrated at 1 or 10 days of age.  These limited trials coupled with the vast experience of swine farm managers and technicians indicate that castration of male pigs within a suckling litter is best performed during mid lactation or at a pig age of 4 to 14 days.  Castrating after day 3 allows piglets to receive colostrum rich first milk and establish teat order with minimal disruption during the first days of life.  It also allows ample time for testicles to descend into the scrotum and for pigs that may be at risk for scrotal hernia to be identified for special treatment.  The advantages of castrating pigs at less than 14 days of age are just as profound.  Such pigs are still relatively small and are less difficult to restrain.  The testicles are more easily separated from testicular cords and bleeding tends to be reduced.  Indeed if properly trained, one person can perform castration without assistance if pigs are within the 4 to 14 day age range.  Pigs castrated at this age have the advantage of continuing to receive antibodies through the sow’s milk which helps prevent infection and promotes fast healing prior to weaning.

Perhaps the most important aspect of pig castration is proper training and skill development of the individuals that perform the procedure.  Veterinarians, animal science educators and skilled swine managers can and should provide this training to anyone who is taking on the responsibility of piglet processing on a swine farm.  A current reference on the procedure can be found in the new Pork Industry Handbook Fact Sheet PIH 01-01-07, Baby Pig Management – Birth to Weaning (Reese and co-workers, 2007).  Several method variations are described in this publication but the most common method employed on commercial swine farms is for one person using a surgical knife.  Typically the knife is a disinfected number 12 hooked or straight blade scalpel available from veterinary supply sources.  This procedure as described in the Pork Industry Handbook is reprinted in outline form as follows.

Castration Method for One Person Using a Surgical Knife (adapted from PIH 01-01-07)

References
Arnot, C., and C. Gauldin. 2007. Castration issue divides experts. Feedstuffs (Nov. 12, 2007 issue) 79 (no.47): 8-9.

Douet, W.A., M.J. Estienne, and T.J. Hartsock. 1995. Effects of castration within 24 hours after birth or at 10 days of age on pre- and post-weaning performance in boars.  The Professional Animal Scientist 11:230-232.

McGlone, J.J., and J.M. Hellman. 1988. Local and general anesthetic effects on behavior and performance of two- and seven-week old castrated and uncastrated piglets. Journal of Animal Science 66:3049-3058.

McGlone, J.J., R.I. Nicholson, J.M. Hellman, and D.N. Herzog. 1993. The development of pain in young pigs associated with castration and attempts to prevent castration-induced behavioral changes. Journal of Animal Science 71:1441-1446.

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.

Squires, E.J. 1999. Genetics of boar taint: Implications for future use of intact males. National Swine Improvement Federation Conference and Annual Meeting proceedings; available on-line at WWW.NSIF.COM

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