Table 1 Variables, criteria, scores, content validity and reproducibility of the acute pain scale in horses

Criteria

Score

Content validity ¹

EV1 X EV2

EV1 X EV3

EV1 X EV4

EV2 X EV3

EV2 X EV4

EV3 X EV4

Posture

Positioning in the stall

The horse’s head is at the outside door

0

0.7

0.6 (0.4-0.7)

0.6 (0.4-0.8)

0.6 (0.5-0.8)

0.7 (0.5-0.8)

0.5 (0.3-0.7)

0.6 (0.4-0.7)

The horse is inside the stall, but looking at the outside door. Observing the environment

1

*

0.5 (0.3-0.7)

0.4 (0.2-0.6)

0.5 (0.3-0.7)

0.5 (0.3-0.7)

0.3 (0.1-0.6)

0.4 (0.2-0.6)

The horse is eating

0

*

0.7 (0.4-1.0)

0.7 (0.5-1.0)

0.6 (0.3-0.9)

0.8 (0.6-1.0)

0.7 (0.4-1.0)

0.7 (0.4-1.0)

The horse is not close to the outside stall door and does not look interested in the environment

2

1

0.9 (0.6-1.0)

0.6 (0.3-1.0)

0.7 (0.4-1.0)

0.7 (0.4-1.0)

0.8 (0.6-1.0)

0.8 (0.6-1.0)

Head position

Above the withers or grazing

0

1

0.4 (0.1-0.7)

0.4 (0.1-0. 7)

0.5 (0.2-0.7)

0.6 (0.3-1.0)

0.6 (0.2-0.9)

0.8 (0.6-1.0)

At the level of the withers

1

*

0.3 (0–0.7)

0.3 (0–0.6)

0.3 (0–0.6)

0.5 (0.1-1.0)

0.3 (−0.2-0.7)

0.5 (−0.1-1.0)

Below the withers but not eating

2

1

NE

NE

NE

1.0 (1.0-1.0)

0.7 (0.04-1.0)

0.7 (0.04-1.0)

Interactive behaviour

Response to opening the door

The horse moves towards the door or is already positioned at the outside door

0

0.7

0.7 (0.6-0.9)

0.7 (0.5-0.9)

0.4 (0.2-0.6)

0.7 (0.6-0.9)

0.4 (0.2-0.6)

0.5 (0.3-0.8)

The horse looks at the door, but does not move towards the door

1

0.7

0.6 (0.4-0.8)

0.5 (0.2-0.7)

0.3 (0.1-0.6)

0.6 (0.4-0.8)

0.3 (0.1-0.6)

0.5 (0.2-0.7)

The horse does not respond to opening the door

2

0.7

0.4 (0–0.8)

0 (0–0)

0.5 (0.0-0.9)

0.3 (−0.2-0.8)

0.2 (−0.2-0.7)

0 (0–0)

Response to approach and presence of the observer

Moves towards or looks to the observer

0

0.7

0.2 (0.1-0.3)

0.3 (0.1-0.4)

0 (0–0.1)

0.5 (0.3-0.7)

0 (−0.1-0.2)

0.1 (−0.1-0.3)

Moves away from the observer

1

0.7

0.1 (−0.2-0.4)

0.2 (−0.2-0.6)

0 (0–0)

0 (0–0)

0 (0–0)

0 (0–0)

Does not move

2

0.7

0.2 (0–0.3)

0.2 (0–0.4)

0.1 (0–0.1)

0.5 (0.2-0.7)

0.1 (−0.1-0.3)

0.1 (0–0.4)

Appetite

Appetite for hay

The horse eats hay

0

0.7

0.2 (−0.2-0.6)

0.7 (0–1.0)

0.7 (0–1.0)

0.3 (−0.1-0.7)

0.3 (−0.1-0.7)

1.0 (1.0-1.0)

The horse does not eat hay

1

0.7

0.3 (−0.2-0.7)

0.7 (0–1.0)

0.7 (0–1.0)

0.3 (−0.1-0.8)

0.3 (−0.1-0.8)

1.0 (1.0-1.0)

Response to concentrate food

Moves to the food and eats

0

0.7

−0.2 (−0.3- -0.1)

0.4 (0–0.7)

0.3 (0–0.6)

0.2 (0.1-0.5)

−0.1 (−0.2- -0.1)

0.4 (0–0.7)

Hesitates to move towards the food, but eats

1

0.7

−0.1 (−0.2- -0.1)

0.6 (0.2-0.9)

0.4 (0.1-0.8)

0.2 (−0.1-0.5)

−0.1 (−0.2- -0.1)

0.4 (0–0.7)

Shows no interest in food, not eating

2

0.7

NE

NE

NE

NE

NE

NE

Activity

Locomotion

The horse moves freely alone

0

0.7

0.1 (0–0.2)

0.5 (0.3-0.8)

0.3 (0.1-0.6)

0.1 (0–0.2)

0.1 (0–0.2)

0.3 (0.1-0.6)

The horse does not move, or is reluctant to move

1

1

0.1 (0–0.3)

0.5 (0.3-0.8)

0.5 (0.2-0.8)

0.1 (0–0.2)

0.1 (0–0.3)

0.5 (0.2-0.9)

The horse is agitated, restless

2

1

NE

NE

NE

NE

0.1 (−0.2-0.5)

NE

Locomotion when led by the evaluator

The horse moves freely when led

0

0.7

0 (−0.2-0.1)

0.3 (0–0.7)

0.7 (0.4-1.0)

0.1 (0–0.3)

0.1 (0–0.2)

0.6 (0.3-1.0)

The horse does not move, or is reluctant to move when led

1

1

0.1 (0–0.2)

0.5 (0.1-0.9)

0.8 (0.5-1.0)

0.1 (0–0.3)

0.1 (0–0.2)

0.6 (0.3-1.0)

The horse is agitated, restless

2

1

NE

NE

NE

NE

NE

NE

Criteria

Score

Content validity ¹

EV1 X EV2

EV1 X EV3

EV1 X EV4

EV2 X EV3

EV2 X EV4

EV3 X EV4

Palpation

Response to palpation of the painful area (approximately 3 cm besides the wound)

No response or change in relation to pre-procedure palpation response of the surgical wound

0

1

0.5 (0.3-0.6)

0.7 (0.5-0.8)

0.7 (0.5-0.8)

0.7 (0.5-0.8)

0.6 (0.5-0.3)

0.7 (0.6-0.9)

Mild reaction to palpation of the surgical wound

1

1

0.3 (0.1-0.5)

0.5 (0.3-0.7)

0.6 (0.5-0.8)

0.4 (0.3-0.6)

0.3 (0.1-0.5)

0.4 (0.2-0.6)

Violent reaction to palpation of the surgical wound

2

1

0.3 (0–0.6)

0.4 (0.2-0.7)

0.6 (0.3-0.9)

0.6 (0.4-0.8)

0.4 (0.1-0.7)

0.5 (0.2-0.7)

Interactive behaviour

Response to an auditory stimulus (clap hands)

Moves and/or pays attention with ears or head movements

0

*

0.3 (0.1-0.5)

0.4 (0.1-0.6)

0.3 (0–0.5)

0.4 (0.1-0.6)

0.5 (0.2-0.7)

0.6 (0.4-0.8)

Calm, no response

1

*

0.4 (0.2-0.7)

0.5 (0.-3-0.8)

0.4 (0.1-0.6)

0.4 (0.1-0.6)

0.5 (0.2-0.7)

0.6 (0.4-0.8)

No response to auditory stimulus due to prostration

2

*

NE

NE

NE

NE

NE

NE

Miscellaneous behaviours

Looking at the flank

The horse does not look at the flank

0

0.7

0.4 (0.2-0.7)

0.3 (0.1-0.5)

0.4 (0.2-0.7)

0.5 (0.3-0.7)

0.5 (0.3-0.7)

0.6 (0.4-0.7)

The horse looks at the flank

1

0.7

0.4 (0.2-0.7)

0.3 (0.1-0.5)

0.4 (0.2-0.7)

0.5 (0.3-0.7)

0.5 (0.3-0.7)

0.6 (0.4-0.8)

Kicking at the abdomen

The horse does not kick the abdomen

0

0.7

0 (0–0)

0.1 (−0.1-0.4)

0.3 (0–0.7)

0 (−0.1-0)

0 (0–0)

0.3 (0–0.6)

The horse kicks at the abdomen

1

0.7

NE

0.2 (0–0.5)

0.5 (0–0.9)

NE

NE

0.3 (0–0.6)

Lifting hind limbs

No lifting of hind limbs

0

*

0.5 (0.3-0.7)

0.5 (0.4-0.7)

0.6 (0.4-0.8)

0.4 (0.2-0.6)

0.5 (0.3-0.7)

0.6 (0.4-0.8)

Lifting hind limbs

1

*

0.3 (0.1-0.5)

0.4 (0.2-0.5)

0.5 (0.3-0.7)

0.2 (0–0.4)

0.3 (0.1-0.5)

0.6 (0.4-0.8)

Lifting hind limbs and extending the head

2

*

0.2 (0–0.5)

0 (0–0)

0 (0–0)

0 (0–0)

0.1 (−0.1-0.3)

0 (0–0)

Head movement

Head straight ahead most of the time

0

*

0.1 (0–0.2)

0.1 (−0.2-0.4)

0.6 (0.3-0.9)

0 (−0.1-0.2)

0.2 (0–0.4)

0.4 (0–0.7)

Lateral and/or vertical occasional head movements

1

*

0 (−0.1-0.1)

0 (−0.1-0)

0.5 (0.2-0.8)

0 (−0.1-0.2)

0.1 (0–0.3)

0.3 (0–0.7)

Lateral and/or vertical continuous head movements

2

*

0 (0–0)

NE

NE

NE

NE

NE

Pawing on the floor (fore limbs)

Quietly standing, no pawing

0

0.7

0.2 (0–0.5)

0.2 (0–0.4)

0.2 (0–0.5)

0.3 (0–0.5)

0.5 (0.2-0.7)

0.7 (0.5-0.9)

Pawing

1

1

0.3 (0–0.6)

0.2 (0–0.4)

0.2 (0–0.5)

0.4 (0.1-0.7)

0.5 (0.2-0.7)

0.7 (0.5-0.9)

Others

Moving the tail sharply and repeatedly

1

*

0.1 (−0.1-0.2)

0.3 (0.1-0.4)

0.1 (−0.1-0.4)

0.2 (0–0.4)

0.2 (0–0.4)

0.4 (0.3-0.6)

Moving the tail sharply and repeatedly and lifting the hind limbs

2

*

0.4 (0.1-0.7)

0.4 (0.2-0.6)

0.4 (0.1-0.7)

0.3 (0.1-0.5)

0.5 (0.2-0.8)

0.5 (0.3-0.7)

Partial penis protrusion

1

*

0.4 (0.1-0.5)

0 (−0.2-0.2)

0.1 (−0.1-0.4)

0.2 (0–0.5)

0.1 (−0.1-0.3)

0.3 (0–0.5)

Penis protrusion

0

*

0.4 (0.2-0.6)

0.2 (0–0.4)

0.5 (0.2-0.7)

0.4 (0.1-0.7)

0.5 (0.3-0.8)

0.7 (0.5-0.9)