Effects of a topically applied anaesthetic on the behaviour, pain sensitivity and weight gain of dairy calves following thermocautery disbudding with a local anaesthetic

Figures & data

Figure 1. Diagrammatic representation showing the allocation within farms of calves to be disbudded in a crate or sedated, and to receive no further treatment (C), or receive a topical anaesthetic (TA) or meloxicam (M). The first cohort was observed after disbudding for behavioural measurements, and 3–21 days later the second cohort had pain sensitivity measurements recorded after disbudding.

Table 1. Description of the six different treatment groups used to investigate the effect of a topical anaesthetic (TA)^a on the behaviour, pain sensitivity and weight gain of dairy calves following cautery disbudding.

Group	Treatment
1	Crate disbudding, local anaesthetic and TA placebo	5 mL lignocaine^b applied to each horn bud, 4 mL TA placebo after disbudding
2	Crate disbudding, local anaesthetic and meloxicam and TA placebo	5 mL lignocaine^b applied to each horn bud, 1.4 mL S/C meloxicam^c, 4 mL TA placebo after disbudding
3	Crate disbudding, local anaesthetic and TA	5 mL lignocaine^b applied to each horn bud, 4 mL TA after disbudding
4	Sedation disbudding, local anaesthetic and TA placebo	0.8 mL I/M xylazine^d, 5 mL lignocaine^b applied to each horn bud, 4 mL TA placebo after disbudding
5	Sedation disbudding, local anaesthetic and meloxicam and TA placebo	0.8 mL I/M xylazine^d, 5 mL lignocaine^b applied to each horn bud, 1.4 mL S/C meloxicam^c, 4 mL TA placebo after disbudding
6	Sedation disbudding, local anaesthetic and TA	0.8 mL I/M xylazine^d, 5 mL lignocaine^b applied to each horn bud, 4 mL TA after disbudding

^aTri-Solfen (Bayer New Zealand Ltd, Auckland, NZ).

^b20 mg/mL lignocaine (Bomacaine, Bayer New Zealand).

^c20 mg/mL meloxicam (Metacam20; Boehringer Ingelheim NZ Ltd, Auckland, NZ).

^d20 mg/mL xylazine (Xylazine 2% Injection; Phoenix Pharm Distributors, Auckland, NZ).

Table 2. Definitions of behaviours that were observed in dairy calves following cautery disbudding.

Behaviour	Description
Ear flicking	Calf rapidly moves one or both ears to the front and back independent of a head shake. Each time movement constitutes as an ear flick.
Head shaking	Calf rapidly shakes head from one side to the other. Recorded as one behaviour when the head moved slowly or was in a resting position.
Head scratching	Calf lifts hind leg to scratch top of head with foot or rubs head against sides of the pen.

Figure 2. Diagram showing the position of pressure algometer placement for measurement of pain sensitivity in calves following disbudding. The black ovals indicate the position of the horn bud wound and the numbers indicate the location for placement of the pressure algometer.

Table 3. Number of calves enrolled on three farms in six different treatment groups used to investigate the effect of a topical anaesthetic (TA) on dairy calves following cautery disbudding.

Treatment	Farm
	1	2	3	Total
Crate-control	10	6	47	63
Crate-meloxicam	10	6	46	62
Crate-TA	10	6	46	62
Sedation-control	10	6	44	60
Sedation-meloxicam	9	6	43	58
Sedation-TA	10	6	43	59
Total	59	36	269	364

Figure 3. Median number of (a) ear flicks, (b) head scratches and (c) head shakes per minute recorded in calves after disbudding in crates with no further treatment (red solid line), or were treated with meloxicam (brown dotted line), or a topical anaesthetic (green dashed line), or were sedated with no further treatment (turquoise dashed line), or were also treated with meloxicam (blue dotted line), or a topical anaesthetic (pink dashed line).

Table 4. Results of the mixed effects negative binomial regression model for variables associated with the number of ear flicks per minute recorded in dairy calves (n = 94) on three farms between 0–22 hours following cautery disbudding, that were allocated to six treatment groups (see Table 1).

Variable	IRR	95% CI	P-value^a
Intercept	0.04	0.03–0.06	<0.001
Farm
Farm 1			Ref
Farm 2	0.63	0.46–0.87	0.005
Farm 3	0.66	0.49–0.89	0.007
Time (hours)
0–3			Ref
5	1.96	1.54–2.46	<0.001
7	2.29	1.85–2.84	<0.001
9^b	3.65	2.56–5.20	<0.001
12	0.18	0.12–0.28	<0.001
22	2.16	1.75–2.66	<0.001
Treatment
Crate-control			Ref
Crate-meloxicam	0.55	0.37–080	0.002
Crate-TA^c	0.54	0.37–0.78	0.001
Sedation-control	0.58	0.40–0.86	0.006
Sedation-meloxicam	0.59	0.41–0.85	0.004
Sedation-TA	0.22	0.14–0.33	<0.001

^aSignificance of incidence rate ratio (IRR).

^bThe number of ear flicks per minute was 3.65 (95% CI = 2.56–5.20) times greater at 9 hours than at 0–3 hours.

^cThe number of ear flicks per minute was 0.54 (95% CI = 0.37–0.78) times lower in calves treated with topical anaesthetic following disbudding in a crate than calves not treated with topical anaesthetic.

IRR = Incident rate ratio; Ref = reference category; TA = topical anaesthetic.

Table 5. Results of the mixed effects negative binomial regression model for variables associated with the number of head scratches per minute recorded in dairy calves (n = 94) on three farms between 0–22 hours following cautery disbudding, that were allocated to six treatment groups (see Table 1).

Variable	IRR	95% CI	P-value^a
Intercept	0.002	0.001–0.003	<0.001
Farm
Farm 1			Ref
Farm 2	0.44	0.27–0.71	0.001
Farm 3	0.51	0.33–0.78	0.002
Time (hours)
0–3			Ref
5	1.98	1.25–3.14	0.004
7	1.60	1.06–2.42	0.026
9^b	2.85	1.58–5.14	<0.001
12	0.38	0.17–0.85	0.019
22	1.55	1.02–2.34	0.038
Treatment
Crate-control			Ref
Crate-meloxicam	1.04	0.58–1.84	0.906
Crate-TA	1.15	0.66–2.01	0.63
Sedation-control	0.62	0.35–1.11	0.105
Sedation-meloxicam	0.47	0.26–0.85	0.013
Sedation-TA^c	0.44	0.23–0.83	0.011

^aSignificance of incidence rate ratio (IRR).

^bThe number of head scratches per minute was 2.85 (95% CI = 1.58–5.14) times greater at 9 hours than at 0–3 hours.

^cThe number of head scratches per minute was 0.44 (95% CI = 0.23–0.83) times lower in sedated calves treated with topical anaesthetic following disbudding than calves not treated with topical anaesthetic following disbudding in a crate.

IRR = Incident rate ratio; Ref = reference category; TA = topical anaesthetic.

Table 6. Mean (min, max) algometer readings (N) for all pain sensitivity measurements in dairy calves (n = 124) on three farms between 0–24 hours following cautery disbudding, that were allocated to six treatment groups (see Table 1).

Treatment	0–1 hour	2–5 hours	6–11 hours	12–24 hours
Crate-control	25.7 (0.2, 73.2)	17.5 (0.6, 79.8)	16.1 (0.2, 66.0)	24.6 (2.4, 83.2)
Crate-meloxicam	21.9 (0, 70.2)	21.3 (1.0, 87.6)	18.6 (0.6, 86.8)	25.8 (1.6, 66.8)
Crate-TA	27.4 (0, 64.8)	22.0 (0.2, 76.4)	17.7 (0.4, 61.0)	25.2 (1.6, 66.8)
Sedation-control	38.6 (11.7, 86.0)	26.7 (3.6, 77.6)	22.2 (0.2, 82.4)	29.9 (3.4, 79)
Sedation-meloxicam	40.8 (3.6, 89.2)	31.8 (2.0, 93.8)	25.2 (0.2, 99.8)	29.9 (3.4, 89.0)
Sedation-TA	42.5 (4.2, 94.6)	36.4 (3.4, 100.4)	23.5 (1.4, 84.2)	30.0 (2.8, 84.0)

TA = Topical anaesthetic.

Table 7. Results of the linear regression model for variables associated with algometer readings (N) for pain sensitivity recorded in dairy calves (n = 1,828 measurements from 124 calves) on three farms between 2–24 hours following cautery disbudding, that were allocated to six treatment groups (see Table 1).

Variable	Estimate	95% CI	P-value^a
Intercept	15.52
Treatment
Crate-control			Ref
Crate-meloxicam	1.09	−3.63–5.80	0.65
Crate-TA	1.89	−2.98–6.75	0.45
Sedation-control	6.5	1.64–11.35	0.01
Sedation-meloxicam	8.48	3.61–13.35	<0.001
Sedation-TA^b	9.10	4.30–13.90	<0.001
Farm
Farm 1			Ref
Farm 2	−3.5	−7.23–0.23	0.07
Farm 3	15.42	11.92–18.92	<0.001
Time (hours)
12–24			Ref
2–5	2.82	1.41–4.24	<0.001
6–11^c	−5.31	−6.37 to −4.25	<0.001
Location
Left top			Ref
Left side	−5.53	−6.80 to −4.25	<0.001
Right top	4.85	3.56–6.13	<0.001
Right side	−1.03	−2.31–0.25	0.11

^aSignificance of estimate.

^bThe force required to elicit a pain response was 9.10 (95% CI = 4.30–13.90) N greater for sedated calves treated with topical anaesthetic following disbudding than for calves not treated with topical anaesthetic following disbudding in a crate.

^cThe force required to elicit a pain response was 5.31 (95% CI = 4.25–6.37) N less for calves tested between 6–11 hours after disbudding than for calves tested at 22–24 hours.

Ref = reference category; TA = topical anaesthetic.