Analgesia and/or anaesthesia during piglet castration – part I: efficacy of farm protocols in pain management

Figures & data

Table 1. Summary description of the experimental treatments, timing and type of application, type and amount of products used (HAND = Handling; CRTL = Negative control; MEL = Meloxicam; AZA = Azaperone; AZA-MEL = Azaperone + Meloxicam; PROC = Procaine; PROC-MEL = Procaine + Meloxicam).

Item	HAND	CRTL	MEL	AZA	AZA-MEL	PROC	PROC-MEL
No. of piglets	50	50	50	50	50	50	50
Route of administration		One intramuscular injection	One intramuscular injection	One intramuscular injection	Two intramuscular injections	Two subcutaneous injections overlaying each testicle	Two subcutaneous injections overlaying each testicle + one intramuscular injection
Volume/piglet and dosage		0.1 mL physiological saline	0.2 mL (0.4 mg/kg b.w.) meloxicam	0.1 (2 mg/kg b.w.) azaperone	0.2 mL (0.4 mg/kg b.w.) meloxicam + 0.1 (2 mg/kg b.w.) azaperone	0.3 mL (6 mg/kg b.w.) procaine hydrochloride	0.3 mL procaine hydrochloride (6 mg/kg b.w.) + 0.2 mL (0.4 mg/kg b.w.) meloxicam
Time of drug administration		10 min before castration	10 min before castration	10 min before castration	10 min before castration	10 min before castration	10 min before castration
Handling at the time of castration	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Castration	No	Yes	Yes	Yes	Yes	Yes	Yes

Table 2. Summary of the timing of different experimental measures made to evaluate pain in piglets.

Type of evaluation	Blood sampling	Skin pressure sensitivity	Behaviour	Total
No. of litters	18	14	18	50
No. of piglets per treatment group	18	14	18	50
Total no. of piglets	126	98	126	350
Timing of the measurement in relation to castration (min):
Before treatments (T-20)	✓	✓
0 (immediately after, T0)			✓ Scans every 3 min
20 (T20)		✓
60 (T60)	✓	✓
180 (T180)	✓	✓

Table 3. Ethogram of behaviours used in the study (modified from Gottardo et al. 2016).

Behaviour	Description
Lying	Piglet is in lateral (body weight supported by side, shoulder and ribs in contact with floor) or sternal (body weight supported by belly, sternum in contact with floor) recumbence
Standing	Piglet is standing still; body weight supported by all four legs
Sitting	Body weight supported by hind-quarters flexed with ischium on the floor and front legs extended
Walking	Piglet is in locomotion, moving forward one leg at a time
Suckling	Piglet is suckling at the sow’s udder
Isolated	Apart from other piglets, alone or with one piglet at the most. A distance of at a lest 40 cm (about the width of two piglets) separate the animal from the closest littermate
Nest	Piglet is in the nest area (with at least half of the body under the cone of light of the lamp)
Resting close to the sow	Piglet is lying or sleeping in close contact with the sow
Teat-seeking	Attempts to find a teat by walking and pushing other piglets while most of the others are suckling
Pain-related	Piglet shows signs of pain including: tremors, rubbing the scrotum area on the floor, hunching the back, wagging the tail
Latency before movement	Time spent by the piglet to start walking once it has been placed in the farrowing crate after treatment
Latency before suckling	Time spent by the piglet to start suckling the udder once it has been placed in the farrowing crate following castration

Figure 1. The effect of treatment on serum cortisol concentration in piglets at different times (T60 and T180) after castration. Different letters (a, b, c, d) mean significant differences between values. [HAND = Handling; CRTL = Negative control; MEL = Meloxicam; AZA = Azaperone; AZA-MEL = Azaperone + Meloxicam; PROC = Procaine; PROC-MEL = Procaine + Meloxicam].

Figure 2. The effect of time on the average maximal pressure applied by algometer to the scrotum and eliciting a response in piglets after castration (mean of the castrated groups: CTRL; MEL; AZA; AZA-MEL; PROC; PROC-MEL treatments) or handling. Different letters mean significant differences between values. (HAND = Handling; CRTL = Negative control; MEL = Meloxicam; AZA = Azaperone; AZA-MEL = Azaperone + Meloxicam; PROC = Procaine; PROC-MEL = Procaine + Meloxicam).

Figure 3. The effect of treatment on the average maximal pressure applied by algometer to the scrotum and eliciting a response in piglets after castration or handling. Different letters mean significant differences between values. (HAND = Handling; CRTL = Negative control; MEL = Meloxicam; AZA = Azaperone; AZA-MEL = Azaperone + Meloxicam; PROC = Procaine; PROC-MEL = Procaine + Meloxicam).

Table 4. Mean percentage of time spent by piglets performing each behaviour and relative p-value among experimental groups (HAND = Handling; CRTL = Negative control; MEL = Meloxicam; AZA = Azaperone; AZA-MEL = Azaperone + Meloxicam; PROC = Procaine; PROC-MEL = Procaine + Meloxicam).

Behaviour	HAND	CRTL	MEL	AZA	PROC	AZA-MEL	PROC-MEL	p-Value
Lying^2	37.83 ± 2.24^cd	43.33 ± 2.24^bc	34.24 ± 2.03^d	50.33 ± 2.24^ab	39.50 ± 2.24^cd	54.50 ± 2.24^a	42.05 ± 2.29^bcd	<.001
Standing^2	21.33 ± 1.90^a	15.17 ± 1.90^ab	17.20 ± 1.73^a	8.50 ± 1.90^bc	18.67 ± 1.90^a	5.17 ± 1.90^c	16.09 ± 1.95^a	<.001
Sitting^1	0.83 ± 1.72	0.83 ± 1.72	0.87 ± 1.39	0.67 ± 1.64	1.50 ± 1.85	0.17 ± 0.71	1.76 ± 2.61	ns
Walking^1	9.72 ± 6.75^a	5.56 ± 4.16^ab	9.58 ± 7.65^a	6.39 ± 7.44^ab	10.56 ± 8.20^a	1.94 ± 3.04^b	9.12 ± 7.55^a	.002
Suckling^1	12.50 ± 8.69^b	10.33 ± 6.53^b	10.62 ± 7.81^b	2.33 ± 4.55^a	8.50 ± 4.85^b	1.83 ± 3.28^a	10.23 ± 5.91^b	<.001
Isolated^1	1.67 ± 4.01^a	2.00 ± 3.56^a	2.50 ± 6.66^a	7.33 ± 9.50^b	4.17 ± 6.10^a	9.83 ± 16.13^b	1.94 ± 3.66^a	.038
Nest	34.67 ± 3.89	37.33 ± 3.89	27.38 ± 3.63	35.67 ± 3.89	33.17 ± 3.89	39.00 ± 3.89	33.11 ± 3.96	ns
Resting close to the sow^1	4.83 ± 7.43	7.17 ± 8.98	6.25 ± 8.53	9.33 ± 11.86	6.00 ± 7.20	8.00 ± 13.73	7.76 ± 9.31	ns
Teat-seeking^1	0.00 ± 0.00	0.00 ± 0.00	0.42 ± 2.04	1.11 ± 2.14	0.00 ± 0.00	0.83 ± 1.92	0.00 ± 0.00	ns
Pain-related^1	0.00 ± 0.00^b	0.00 ± 0.00^b	1.04 ± 2.94^ab	0.56 ± 1.62^ab	5.23 ± 8.66^a	0.28 ± 1.18^ab	3.23 ± 4.31^ab	<.001
Latency before movement^1	0.00 ± 0.00^b	0.00 ± 0.00^b	0.00 ± 0.00^b	6.61 ± 15.87^a	0.00 ± 0.00^b	11.72 ± 23.46^a	3.53 ± 14.55^ab	<.001
Latency before suckling^2	20.06 ± 3.49^b	24.33 ± 3.49^b	18.61 ± 3.39^b	47.78 ± 3.49^a	23.89 ± 3.49^b	50.33 ± 3.49^a	24.32 ± 3.56^b	<.001

Different letters mean statistical difference.

¹ Kruskal–Wallis test: mean ± standard deviation;

² Anova test: mean ± standard error.

Gottardo F, Scollo A, Contiero B, Ravagnani A, Tavella G, Bernardini D, De Benedictis GM, Edwards SA. 2016. Pain alleviation during castration of piglets: a comparative study of different farm options. J Anim Sci. 94(12):5077–5088.

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