|
North Carolina
State University Return
to main menu
The Humane
Euthanasia—On-Farm Applications W. E. M. Morrow, S. Miller, R. E. Meyer1, J. Roberts2 and D. Lascelles3 1Department
of Clinical Sciences, College of Veterinary Medicine, Mississippi State
University 2Department of Population Health and
Pathobiology, College of Veterinary Medicine, North Carolina State University 3Department
of Clinical Sciences, College of Veterinary Medicine, North Carolina State
University Introduction
In
general, an animal should be culled when it is no longer profitable or
euthanatized when it is inhumane to allow it to continue living. The difficulty all farm managers encounter
is defining when animals become uneconomic and whether to treat or
euthanatize the compromised animal.
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 of North Carolina farm managers have told us that having
clear criteria for when to euthanatize 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 euthanatized. Many 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 are helpful in creating a
euthanasia profile. Other guidelines are more objective; Duncan (1988)
recommends that companion animals should be euthanatized if they have: ·
Weight loss: 20-25% 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 99oF ·
Infection: involving one or more organ
systems, which fails to respond to treatment within an appropriate amount of
time ·
Respiratory/cardiovascular: failure of
these systems, including blood loss or anemia resulting in a hematocrit below
20% ·
Nervous/musculoskeletal: 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 20-25% 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 which fails to respond to treatment. In addition, some farming
systems have adopted specific protocols to help managers decide what to
euthanatize and what to keep. For example, the “two-strike” system has two
criteria that must be fulfilled before a weaner pig is euthanatized:
underweight (e.g., less that 8 lb on a farm with 18 day weaning) and have 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 1974). Others have established that lightweight pigs at weaning
remain small and are a significant contributor to the variation in slaughter
weight and, as such, a major problem in assembling slaughter loads. In 3-site production, where the
system rewards nursery managers for dispatching more pigs, there tends to be
more pigs shipped than there should be. Conversely, finishing managers
struggle with the issue of how to handle the underweight/disadvantaged pigs
they are shipped. Industry-specific
guidelines for euthanasia, such as the National Pork Producers Council guide
“On Farm Euthanasia of Swine” (NPPC 04259-4/97) and university-produced
extension training materials such as “On-Farm Euthanasia: Better Ways”
(Morrow and Meyer, 2001), generally agree closely with AVMA-accepted methods
and processes. Unfortunately, these guidelines do not help producers decide
if and when any individual animal should be euthanatized to end its
suffering. Suffering can be conceptualized as the product of pain and its
duration. By daily monitoring, farm managers can usually estimate duration
but the difficulty of estimating pain remains. 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 reluctance to move may also be observed
(Dombromylskyj et al in Flecknell and Waterman-Pearson 2000). Managers can
usually identify those animals suffering the most because they exhibit
aberrant behavior or the presence of visible lesions (e.g., burns,
lacerations, compound fractures) make it obvious. However, the issue 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
(in Flecknell and Waterman-Pearson, 2000). Objective measures, such as
heart rate, respiratory rate, and temperature are unreliable 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 are of limited use when used alone as they are influenced
by so many factors other than pain. Our
study developed a protocol for handling compromised pigs. We collected economic and welfare
information that producers can use to make informed decisions on when pigs
should be euthanatized. Materials and Methods The StudyThe study was conducted in 2002-2003 in 5
commercial nursery sites (Farms 1-5) owned by 4 separate entities (A, B, C,
and D. Two farms were owned by the
same entity) in North Carolina. Each
farm was part of a 3-site production system and regularly received
nursery-aged pigs from their supplying owner and after growing for about 6
weeks the pigs were shipped to their respective finishing sites. Batches of pigs were assigned to treatment
(heavy, medium or light euthanasia) before the pigs arrived on site but at
the convenience of the owners (Table 1). Each owner was
requested to complete at least 12 batches (4 heavy, 4 medium and 4 light) but
not all were able to achieve this.
Pigs within batches were screened upon entering the nursery and either
euthanised, tagged or penned normally depending on their condition and the
assigned treatment. The heavy
protocol triggered euthanasia for conditions that were less severe
(compromising) than the medium protocol, and the light protocol triggered
euthanasia only for the most compromised pigs (Table 2). Pigs with conditions not sever enough to
trigger euthanasia were ear-tagged and monitored daily by farm staff for
changes in their condition. Farms
Farms
varied in where they housed tagged pigs and the status of porcine
reproductive and respiratory disease (PRRS) in the herds supplying the
nursery pigs: Farm
A/1: Tagged pigs were left in the pens they were found in. The pig flow was a
known PRRS positive flow with clinical problems. Two batches were processed
and mean batch size was 3585 pigs. 200 pigs were euthanized and 80 tagged. Farm
B/2: Tagged pigs were grouped into set pens if small or lightweight, but were
left in the pens they were found if large or normal weight. The pig flow was
known to be PRRS positive but not a clinical problem at this time. 12 batches
were processed and mean batch size was 587 pigs. Farm
B/3: Tagged pigs were grouped into set pens if small or lightweight, but were
left in their original pens if of normal weight or heavier. This practice was
used to prevent heavier lame pigs from beating up on small weak tagged pigs.
The pig flow was known to be PRRS positive but not a clinical problem at this
time. Twelve batches were processed
and mean batch size was 801 pigs. Farm
C/4: Tagged pigs were grouped into set pens. The pig flow was a healthy
PRRS-free flow. Six batches were processed and mean batch size was 2207 pigs. Farm
D/5: Tagged pigs were grouped into set pens. The site was recently
depopulated and the pig flow was a healthy PRRS-free flow. 15 batches were
processed and mean batch size was 930 pigs. Any pig requiring treatment was treated
according to standard operating procedures on the study farms. The time taken
to administer treatment was recorded as was the amount, type, and cost of
drugs administered. If more than one
pig was treated at the same time (e.g., injecting 5 pigs with an antibiotic)
the time taken to treat the group was averaged and the mean cost in time
assigned to individual pigs. Tagged pigs were euthanized if their condition
progressed to a level that triggered euthanasia for their treatment group. The conditions monitored and the levels
triggering euthanasia were decided in advance by consensus with the investigators
and veterinarians responsible for the health of the pigs studied (Table 2). If pigs
died they were weighed and date noted. Value of pigsThe value of each
welfare compromised (tagged) pig in each batch was established at shipping by
partial budget. Additional income
was calculated as the product of the animal’s weight at shipping by the
standard value of $0.80 per lb. The cost of drugs administered was set at a
standard value per ml of $0.563 ceftiofur sodium, $0.04 tylosin, $0.03
penicillin G, $0.05 long acting oxytetracycline. Cost of time was set at $10/hour. The value of the batch was
the sum of the value of all compromised pigs in the batch. Assigning a welfare score
At the time they were
received at the nursery and each day thereafter, farm staff observed the pigs
under their care and determined if they needed treatment, if euthanasia was
warranted and their condition; specifically if they changed levels in the
physical condition they were experiencing.
Conditions and levels were recorded for each pig. To determine the status of welfare
associated with each condition (e.g., lame, tail bitten, ruptures) and its
level of severity (i.e, A, B, C, or D) an expert panel was asked to create a
welfare score by ranking each level of each specific condition from 0 to 10
(0 no effect on welfare, 1 little effect on welfare, to 10 worst possible
effect on welfare) (Table 3). When a pig had 2 or more
physical conditions then the welfare scores for each condition were summed to
make a final welfare score. For example, if a pig had damaged digits at level
B (score 3) and a rupture at level A (score 1) then that pigs total welfare
score was 4 and the level of severity was reassigned to level A to reflect
its compromised welfare state. The
welfare score assigned to pigs was the product of the assigned initial score
for their condition and level and the number of days they experienced that
condition, that is, until they recovered, died, were euthanized or left the
nursery to go to the finishing stage (e.g., a weak pig, level A, for 30 days
would score 90 (3 x 30). Thus a low welfare score indicated fewer pigs were
compromised for less time and a high score indicated more pigs were
compromised for longer. Data analysis
The model was of
hierarchical design. For each dependent variable (value and welfare) we
performed an analysis of co-variance (ANCOVA) in the GLM procedure of SAS (Version
8.01 for Windows, 98; Statistical Analysis Systems Institute Inc, Cary North
Carolina). The batch (one turn of a nursery room) was the experimental
unit. The model included farm, protocol,
barn, reason and the level of reason as nominal (class) data. Barn was nested in farm and level nested
in reason. The dependent variables were the value ($) and welfare. For sensitivity analysis
on the economic value, welfare, cost of treatment etc., a decision tree was
constructed using the results from the mixed model ANOVA in Data 4.0,
published by TreeAge Software http://www.treeage.com The decision tree diagram
represented in chronological order the alternative states for the pigs for
their duration of stay in the nursery.
When pigs first entered the nursery they would be allocated to the
treatment protocol (light, medium or heavy).
Then pigs would be examined and determined whether they were in a well
or compromised state. If compromised,
the reason (state) was determined by clinical examination and its level
(state) of severity. Depending on the
protocol, reason, and level then the manager would determine if the pig was
either euthanized immediately or tagged and observed daily. To construct the tree,
the value (utility) of each of the potential outcomes (e.g., no value if
euthanized) and the probability of that outcome occurring was calculated from
the farm data. From the constructed
tree the expected utility of each decision was calculated by weighting the
value of each outcome with the probability that the outcome will occur. Then the weighted values for all outcomes
for any branch of the tree was summed (folding or rolling back) giving an
estimate for the value of that decision. The branch with the highest expected
value ($) or lowest expected value (welfare) is expected to be the most
favorable outcome for the population studied. The sensitivity of the results
to changing inputs was calculated by varying the cost of treatment,
probability of euthanasia, probability of tagged pigs dying/surviving and
final value of the pig. The distribution for the
initial reason was set as the same for all protocol (disregarding the chance
that some reasons were disproportionally allocated among the protocol). The data from 1904 pigs were used in the
decision tree analysis; 1931 were available but the 1 beaten (multiple fight
wounds) pig and the 24 with reason “unknown” were deleted from the data
set. Results and Discussion: A
total of 51,041 nursery age pigs in 47 batches were screened upon entering
the 5 farms and of those, 819 (1.6%) were immediately euthanized and 1118
(2.19%) were tagged and followed. Of the tagged pigs, 186 (16.64%) died, 924
(82.65%) were shipped to finishing and 8 were lost to follow up (Table 1). For
the 7 categories (damaged digits, lame, light weight, repaired rupture,
rupture, weak, or two or more) where more than 10 pigs were tagged the
percentage mortality ranged from 5.16% (repaired rupture) to 64.3% (weak). For
the conditions where more than 10 pigs died the percentage of deaths
numerically increased as the level increased; lame/A 27.27% and lame/B
53.57%, light weight/B 9.54% and light weight/C 17.73% (Table
4). There was considerable variation in the reasons for which pigs were
compromised, (e.g., 1100 lightweight compared with 41 damaged digits) (Table 4). References Duncan, J. C.
(1988). Careers in Veterinary Medicine, Rosen Pub. Group (New York, NY). England D.C., (1974) Husbandry components in prenatal and
perinatal development in swine. J. An Sci 38:1045. On Farm Euthanasia of Swine - Options for the Producer.
Booklet #04259-4/97. American Association of Swine Practitioners and the
National Pork Producers Council, Des Moines, IA, 1997. On-Farm Euthanasia: Better Ways. Produced by W.E. Morgan
Morrow and Robert E. Meyer, North Carolina State University College of
Veterinary Medicine Biomedical Communications, 2001. Dobromylskyj P, Flecknell PA, Lascelles BD, Livingston A,
Taylor P, Waterman-Pearson A. Pain Assessment. In: Pain Management in
Animals, Flecknell PA and Waterman-Pearson A, eds. W.B. Saunders, London,
2000. Holton LL, Scott EM. Nolan, AM, Reid J, Welsh E, Flaherty
D. Comparison of three methods used for assessment of pain in dogs. J Am Vet
Med Assoc 1998; 212:61-66. Christley RM, Reid S WJ, No significant difference: use of
statistical methods for testing equivalence in clinical veterinary literature
J Am Vet Med Assoc 2003: 222:433-437. Table 1. Summary information for the Euthanasia
trial
Table
2. Criteria for euthanasia by
treatment protocol.
Table 3. Welfare score by
condition and level.
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
Euthanized on entry |
Tagged Pigs |
||
|
Level |
Number euthanized |
Number Tagged |
Number died (as % of tagged) |
Number shipped |
|
A |
5 |
14 |
|
14 |
|
B |
131 |
325 |
31 (9.54) |
294 |
|
C |
317 |
141 |
25 (17.73) |
116 |
|
D |
167 |
0 |
|
|