Behavior and welfare of Intramuscular or Subcutaneous injection in finishing pigs
and piglets. #TH175
Kimberly Guay, and John J McGlone. Pork Industry Institute, Texas Tech University, Lubbock, TX.
Abstract:
Introduction:
Physical castration Physical castration (PC), typically performed at approximately 5 d of age, can be
stressful for pigs. One alternative to PC is to immunological castration (IC), but the stress of the
handling associated with immunological castration (or other immunizations) has not been assessed.
Our objectives were to determine if subcutaneous (SC) or intramuscular (IM) injections were more
painful or stressful than PC for piglets as well as measure the pain and stress associated with
receiving a SC or IM injection in finishing pigs. To do this, we ran two experiments in which litter
served as blocks in this randomized complete block design. After farrowing, 3 to 5 d old male piglets
were randomly assigned to nothing (NO), SHAM handling (SHAM), IM, SC or PC with no pain relief.
Piglets were videotaped and behavior was sampled for 1 h prior and 1 h post treatment. Behavior
monitored included standing, walking, lying, nursing, lying with sow contact and signs of pain (standing
hunched over, shaking). Finishing pigs received SC, IM, SHAM or NO injection. Finishing pigs were
also monitored for 1 h pre and post treatment, and monitored for eating, drinking, lying, standing,
walking, vocalization, open mouth breathing, blotchy skin and signs of irritation (rubbing the injection
site). Blood was collected from all pigs for cortisol analysis 60 min post treatments so that the handling
of blood collection did not impact the pig behavior. Analysis was in SAS using General Linerar Models
procedure. PC piglets showed less (P < 0.05) lying in contact with sows and more (P < 0.05) pain-like
behaviors than IM, NO, or SHAM treatments, but SC did not differ from PC. SHAM finishing pigs spent
more time lying than the pigs in other treatment groups (P < 0.05). Cortisol did not differ among
treatments for neither piglets nor finishing pigs. In conclusion, IM injections do not change piglet
behaviors relative to no handling or sham handling. SC injections caused a small change in piglet and
finishing pig behaviors. PC caused measureable pain-like behaviors and general behavioral
dysregulation.
KEYWORDS: Castration, Injection, Pigs
Physical castration is stressful for piglets and many types of anesthesia and analgesia are limited in relieving pain Physical castration (PC) is a common management practice on
commercial swine farms in the U.S. Castration is performed primarily reduce the accumulation of boar taint compounds, aggressive behavior in post-pubertal male pigs, and undesirable
pregnancy at slaughter; however, consumer attitude toward PC becomes more negative as time goes by. Attempts to reduce the pain and distress by use of local or general anesthetics
were insufficient to date. One alternative to PC is to immunologically castrate (IC) mail pigs. Immunological castration yields a carcass without boar taint and may improve pig welfare by
reducing the stress of physical, but the stress of the IC process has not been assessed. Aside from IC, many pigs receive some sort of injection during their lifetime for health reasons.
Results:
Objectives:
• Our overall goal was to define a welfare matrix for pig castration procedures.
• Our specific goal was to define the relative stress of receiving an injection in piglets and finishing pigs. Piglets were used to define the relative experience of PC compared with the
stress of injection in littermates.
This experiment was conducted at the Texas Tech Pig Farm, New Deal, TX. Commercial lines, high-performance of modern genetics (PIC, Inc., Hendersonville, TN)
were used in this study. Piglets were born within 1 month of each other from a common set of sows. Piglets and sows were housed in farrowing crates in adjacent
rooms. Finishing pigs (barrows and gilts) were also from a common set of sows and weaned together at approximately 3 wk of age. At that time, they were transferred
to a nursery for approximately 7 wk, then moved to the test finishing barn located at the same facility. Finishing pigs were kept in groups of 5 and fed a corn-soy diet
formulated to exceed NRC nutrient requirements. Finishing pigs had ad libitum access to feed and water. Bunk feeders allowed for 4 pigs to eat simultaneously, and 1
water nipple was present in each pen. This work was reviewed and approved by the Texas Tech University Animal Care and Use Committee before the project began.
All work was performed by IACUC trained TTU personnel.
• Pigs were videotaped and behavior was sampled for 1 hr prior and 1 hr post treatment (all four treatments were administered concurrently. Behavior was monitored
for signs of stress or irritation: standing, walking, lying with contact, lying with no contact, nursing, and signs of pain (standing hunched over, shivering). Data were
collected as a scan sample every 1 min for each pig expressing a mutually-exclusive behavior. Blood was collected from the jugular vein (7-10 mL) from pigs 60 min
post treatment to prevent handling of blood collection from impacting the piglets’ behavior.
• Finishing pigs. Fifty pigs of approximately 5 mo of age were assigned treatment groups: control-no handling (NO); control-sham handling to mimic injection (SHAM),
IM saline injection (2 mL), SC saline injection (2 mL).
• Pigs were videotaped and behavior was sampled for 1 hr prior and 1 hr post treatment (all four treatments were administered concurrently. Behavior was monitored
for signs of stress or irritation: standing, walking, laying, eating, shivering (all pigs); rubbing injection site, drinking, vocalization, open mouth breathing, red skin
(finishing pigs); and lying with contact (piglets). Blood was collected from the jugular vein (10 mL) from all pigs 60 min post treatments so that the handling of blood
collection did not impact the pig behavior.
Hormonal Assay. Plasma cortisol concentrations were measured using commercially available Enzyme Linked Immunosorbent Assay kits (Enzo Life Sciences, Inc.,
Farmingdal, NY, USA). All samples were analyzed in duplicate. The sensitivity level of the assay system was 56.72 pg/mL (range 156 – 10000 pg/mL). The inter-assay
coefficients of variation was 10.76%. The intra-assay coefficient of variation ranged from 8.47% to 9.26%.
Statistical Analyses. Data were analyzed using the GLM procedure of SAS (SAS Inst., Inc., Cary, NC). The experimental design was a completely random design, with a
split-plot over time (time being each min of the observation period) and pig was the experimental unit. Data for piglets and finishing pigs were analyzed separately. Least
squares means were separated using the PDIFF option of SAS.
Table 1. Post-treatment behaviors of piglets given an IM injection, SC injection, nothing,
SHAM castration, or physically castrated.
Table 2. Pre- and Post-treatment behaviors of finishing pigs given a SHAM injection
(touch to neck), IM injection, SC injection, or nothing.
Behavior
Nothing
Sham
IM
SC
Castrated
SE
P- value
TRT
Behavior
Nothing
Sham
IM
SC
SE
P- value
TRT
P-value
TRT*PER
Lying alone
3.10
4.05
1.19
1.67
8.81
2.05
0.10
Lying
77.71
87.59
80.04
80.66
2.25
0.02
0.30
Lying with
contact
64.52
67.86
66.66
62.61
58.82
3.48
0.40
Feeding
6.87
3.26
3.72
4.06
1.69
0.44
0.02
Sitting
1.67
Sitting
0.55
0.13
0.96
1.42
0.50
0.32
0.56
1.67
3.57
2.62
0.9
0.55
6.67
4.76
9.28
6.42
9.52
1.66
0.24
Walking
6.19
4.05
6.43
2.86
5.00
1.55
0.46
Standing
5.99
3.52
4.50
5.82
1.13
0.38
0.63
Nursing
17.86
16.68
14.76
22.86
14.05
3.08
0.31
Walking
6.62
3.99
7.02
6.07
1.31
0.38
0.71
Exhibiting pain
0.00
0.00
0.00
0.00
1.19
0.35
0.09
Drinking
1.90
0.69
3.19
1.47
0.83
0.05
0.51
Behavior
Mean before Trt
Std Dev
Mean after Trt
Std Dev
Lying
77.69
25.96
85.31
13.44
Feeding
4.73
7.57
4.22
8.66
Sitting
0.94
2.80
0.59
1.86
Standing
6.82
11.87
3.09
2.92
Walking
6.41
7.09
5.45
6.17
Drinking
2.92
5.81
0.70
1.32
Figure 1. Percent time piglets spent lying without contact of littermate or sow for 1 hr post treatment,
(IM injection, SC injection, nothing, SHAM castration or physically castrated) P = 0.098.
Conclusion:
• Handling and injection did alter some of the behaviors of pigs after treatments were
administered. This agrees with previous studies (Hemsworth et al., 1981 and Robert et al.,
1989). However, these studies only reported these effects as acute stress, and that cortisol
levels returned to normal within 24 hr of an initial injection or handling bout. The hormone
data in this study showed no differences in the levels of serum cortisol between injections and
physical castration. This finding is contradictory from other studies that reported acute
response to a subcutaneous injection in sows (Robert et al., 1989). The difference may be in
the hormone difference between sows, gilts and barrows, however it is unclear. Hemsworth et
al. (1981) reported a decrease in reproductive function associated to an increased fear
response to the presence of humans. Regardless, the emotional stigma of physical castration
in young piglets continues to rise. McGlone and Hellman (1988) first reported that PC of
piglets caused pain-induced behavioral changes. Since then, the painful effects of physical
castration have been replicated by our laboratory and another (McGlone et al., 1993; White et
al., 1995).
• Pharmacological methods to reduce pain are not always effective (McGlone et al. 1988) are
further complicated by the approval process required by the FDA, or other governmental
entities, before these analgesics can be used in food animals.
• Several countries have outlawed physical castration without some sort of pain relief. Many
producers in these situations are marketing pigs at lighter weights to avoid boar taint
influences on meat and aggression.
• It is possible to modify a genetic program to select for lower levels of boar taint. However,
genetic lines with low levels of boar taint are not presently available on commercial farms.
Furthermore, the reproductive side effects of selecting against boar taint are not understood.
.
Literature Cited:
Standing
Table 3. Pre- and Post-treatment behavior means of finishing pigs by period.
Finishing pigs. Treatments had some slight differences in post application behavior (Table 2).
SHAM finishing pigs spent more time lying than pigs in other treatment groups (P < 0.05). There
was a treatment by time effect for feeding (P = 0.02). Cortisol did not differ among treatments for
finishing pigs. SHAM finishing pigs spent more time lying than the pigs in other treatment groups
(P < 0.05).
Materials and Methods:
• Piglets. After farrowing, 3-5 day old male piglets were randomly assigned to treatment groups. Five males within a litter served as the experimental unit. Ten litters
with at least five males each were used. Five treatment groups were examined: nothing (NO), IM saline injection (1 mL), SC saline injection (1 mL), SHAM (to mimic
physical handling during castration), and PC (no pain relief, as is the standard operating procedures at commercial farms).
2.62
Piglets. Behaviors of piglets is listed in Table 1. PC piglets showed less (P < 0.05) lying in
contact with sows and more (P < 0.05) pain-like behaviors than IM, NO, or SHAM treatments, but
SC did not differ from PC (Fig. 1). Cortisol did not differ among treatments for neither piglets nor
finishing pigs. IM injections did not change piglet behaviors relative to no handling or sham
handling. SC injections caused a small change in piglet and finishing pig behaviors. PC caused
measureable pain-like behaviors and general behavioral dysregulation (Fig. 2).
1. Hemsworth, P.H., Barnett, J.L. and Hansen, C. 1981. The influence of handling by humans on
the behavior, growth and corticosteroids in the juvenile female pig. Hormones and Behavior 15:
396-403
2. 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. J. Anim. Sci.
66:3049-3058.
3. McGlone, J. J., R. I. Nicolson, and 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. J. Anim. Sci. 71:1441-1446.Mayer, M., and Rosen, F. (1977). Interaction of
glucocorticoid and androgens with skeletal muscle. Metabolism 26, 937-962
4. Robert, S, Passillé A-MD, St-Pierre, N Pelletier, G, Petitclerc, D, Debreuil, P and Brazeau, P
1989. Effect of the stress of injections on the serum concentration of cortisol, prolactin, and
growth hormone in gilts and lactating sows. Canadian Journal of Animal Science 69, 663-672.
5. White, R. G., J. A. DeShazer, C. J. Tressler, G. M. Borcher, S. Davey, A. Waninge, A. M.
Parkhurst, M. J. Milanuk, and E. T. Clemens. 1995. Vocalization and physiological response of
pigs during castration with or without a local anesthetic. J Anim. Sci. 73:381-386.
Figure 2. Percent time piglets spent showing signs of pain (shivering, or standing with a hunched back) for
1 hr post treatment (IM injection, SC injection, nothing, SHAM castration or physically castrated) P = 0.091.