Dr Morgan Morrow Swine Veterinary Specialist

Industry-specific guidelines for euthanasia, such as the National Pork Producers Council guide, On-Farm Eutha-nasia of Swine[1], and university-produced Extension training materials, such as On-Farm Euthanasia: Better Ways[2], generally agree closely with methods and processes accepted by the American Veterinary Medical Association (AVMA). Unfortunately, these guidelines do not help producers decide if and when an individual animal should be euthanized to end its suffering.

Suffering can be conceptualized as the product of pain and its duration. By daily monitoring, farm managers usually can estimate duration, but the difficulty of estimating the intensity of pain remains. Further, overt pain behaviors in pigs can be difficult to evaluate. Pain may reduce normal pig social behaviors and vocalization, while vocalization in response to handling may be more pronounced. Changes in gait and a reluctance to move also may be observed (Dombromylskyj, et al.)[3]. Managers usually can identify those animals suffering the most because they exhibit aberrant behavior or the presence of visible lesions (e.g., burns, lacerations, compound fractures) makes it obvious. However, the issue often is clouded because a condition may be visually striking but less painful (e.g., prolapses) or inconspicuous but more painful (e.g., arthritis).

Various methods of generating a pain score and assessing animal pain have been reviewed by Dombromylskyj and coworkers[3]. Objective measures, such as heart rate, respiratory rate, and temperature are unreli-able guides to the presence of pain, as are humoral factors such as epinephrine, norepinephrine, and cortisol. These measures may be useful when integrated into a pain-scoring system, but they are of limited use when used alone, as they are influenced by many factors other than pain.

Nonverbal human-infant pain scales adopted for use in animals include the simple descriptive scale (SDS), the numerical rating scale (NRS), and the visual analog scale (VAS). Although the SDS is less sensitive than the NRS or the VAS, comparisons of inter-observer variability have shown reasonable agreement between observers using the SDS to assess postoperative pain in dogs (Holton)[4].

Individual managers usually resort to a very subjective assessment often heavily weighted by the perceived ability of the animal to return a profit. Focus groups consisting of North Carolina farm managers have told us that having clear criteria for when to euthanize an animal would help reduce some of the job stress they feel.

Unlike the companion animal arena, where there is much discussion and many suggested guidelines on the appropriateness and timing for euthanasia, there are relatively few guidelines for when a farm animal should be euthanized. Most of the companion animal guidelines are very subjective (e.g., ability to enjoy food, ability to breathe freely and without difficulty, ability to eat and drink without pain, ability to respond to owner and family), but when taken together they are helpful in creating a euthanasia profile. Other guidelines are more objective. Duncan[5] recommends euthanizing companion animals if they have:

• Weight loss: 20 to 25 percent of total body weight, characterized by muscle wasting.
• Extreme weakness/Inability: No desire to eat or drink, persisting for 24 hours or more.
• Moribund state: Depression and body temperature below 99^o F.
• Infection: Involving one or more organ systems, and the condition fails to respond to treatment within an appropriate amount of time.
• Respiratory/cardiovascular problems: Failure of these systems, including blood loss or anemia resulting in a hematocrit below 20%.
• Nervous/musculoskeletal problems: Injuries that cannot be healed, resulting in uncontrolled seizures or the loss of a limb.

Similar guidelines could be adapted for farm animals. For example, the following general guidelines could apply to pigs of any weight or age:

• Weight loss of 20 to 25 percent of total body weight, characterized by muscle wasting.
• Extreme weakness or inability, with a lack of desire to eat or drink persisting for 24 hours or more.
• Suffering from any infection/disease that fails to respond to treatment.

Some farming systems have adopted specific protocols to help managers cope with the difficult decision of what to euthanize and what to keep. For example, the "two-strike" system has two criteria that must be fulfilled before a weaner pig is euthanized: Underweight (e.g., less than 6 pounds on a farm with an 18-day weaning) and has a disability such as a rupture, or navel ill, or lameness, or poor body condition. This introduces a special category of concern for pork producers - the lightweight pig. It has been long accepted that lightweight piglets at birth are lightweight at weaning (England)[6]. Others have established that lightweight pigs at weaning remain small, are a significant contributor to variation in slaughter weight, and, as such, are a major problem in assembling slaughter loads. In 3-site production, where the system rewards farrowing house and nursery managers for dispatching more pigs, there tend to be more pigs shipped than there should be. Consequently, nursery and finishing managers then struggle with the issue of how to handle the underweight/disadvantaged pigs they receive.

To help us better understand the issues involved and the compromises producers will have to make, we at North Carolina State University are working on a project designed to develop the protocol for handling compromised pigs. For our project, we are collecting economic and pig welfare information that producers can use to make informed decisions on which pigs should be euthanized and when.

References

Reproduced Courtsey