Strength of correlation between metric and ethical value

Captures a broad range of what is important

Short causal chain between the metric and what we care about

Able to be used across a wide range of interventions

Cross applicability to different animals

Robustness across different ethical systems

Useful for people reading our research

Precedence in other communities of use

Ability and ease of numerically quantifying, even if abstract numbers.

Ease/speed of use (for example how hard it is to put the number into a CEA)

Can be measured objectively

Generates few false positives or false negatives

Doesn't require additional effort to re-understand every time it is used.

Doesn't require specific skills, tools, or measuring instruments

Understandable for our audience, easy to justify

Scores 20 to 15: Negligible abnormal deaths, abnormal deaths quick and/or relatively painless. Painkillers accessible for painful deaths.
Scores 15 to 5: 1%-10% death rate, quick or mostly low pain.
Scores 5 to -5: 10-20%, death rate, longer or medium pain.
Scores -5 to -15: 20-50% death rate, both long and medium pain.
Scores -15 to -20: 50%+ death rate, duration of death very long and amount of pain and suffering is very high.

The ratio of deaths to the population.
The reason for death.
The duration of time death takes place over.
Slaughter process (speed and painfulness).

Scores 20 to 15: Very confident I would enjoy this life greatly 7-10/10.
Scores 15 to 5: Somewhat confident I would enjoy this life.
Scores 5 to -5: Unsure if I would think this life is net positive.
Scores -5 to -15: Somewhat confident I would not enjoy this life.
Scores -15 to -20: Very confident I would not enjoy this life.

Scores 17 to 14: No or very low disease, injury, or functional impairment.
Scores 14 to 5: Disease, injury, or functional impairment is within the animal’s homeostatic capacity with no or minor debility or incapacity.
Scores 5 to -5: Moderate debility or incapacity from which complete recovery occurs spontaneously or can be easily effected therapeutically.
Scores -5 to -14: Marked debility or incapacity where euthanasia is appropriate. Death caused in a small proportion of animals.
Scores -14 to -17: Extreme debility or incapacity. Unpleasant death.

Scores 15 to 10: Fluids available in quantities that satisfy thirst. Food meets body maintenance requirements and the demands of pregnancy, lactation, exercise, growth, thermal challenge, recovery from illness/injury, etc.
Scores 10 to 5: Water or food excesses or restrictions cause minor, readily reversed effects on physiological state, performance, or body condition.
Scores 5 to -5: Water or food excesses or restrictions cause serious short-term or moderate long-term effects which are easily reversed once the animal resumes having a good-quality diet.
Scores -5 to -10: Water or food excesses or restrictions cause levels of debility where euthanasia is appropriate.
Scores -10 to -15: Water or food excesses or restrictions cause death or unbearable suffering.

Inadequate dietary intake.
Inadequate access to food.
Micronutrient deficiencies (vs lack of food energy or macronutrients).
Standards for minimum age for weaning not met.
Water excesses or restrictions.

Scores 15 to 10: Very low anxiety, fear, pain, or distress on average over life.
Scores 10 to 5: Minor discomfort or low-level apprehension or anxiety for short periods semi frequently.
Scores 5 to -5: Moderate anxiety, fear, pain, or distress for short periods, or minor discomfort or distress for long periods.
Scores -5 to -10: Moderate anxiety, fear, pain, or distress for long periods, or marked anxiety, fear, pain or distress where the suffering ends before it becomes excessive and either the animal completely recovers or dies.
Scores -10 to -15: Severe, inescapable, and unrelieved anxiety, fear, pain, or distress at or beyond the limits of reasonable endurance.

Self-narcotization.  
Activity (energy, play, sleep patterns, arousal).
Pain relief for castration, dehorning or disbudding / Beak trimming, Tail docking.
Isolation.
Length of transport.
Lack of enrichment.

Scores 5 to 3: Environmental conditions do not require adaptive physical changes.
Scores 3 to 1: Environmental conditions require adaptive physical changes but are within the animal’s homeostatic capacity.
Scores 1 to -1: Environmental conditions elicit body responses beyond the animal’s physiological adaptive capacity, but untoward effects are reversed by restoration of benign conditions and, if necessary, therapeutic intervention.
Scores -1 to -3: Environmental conditions cause levels of debility where euthanasia is appropriate.
Scores -3 to -5: Environmental conditions cause death.

Scores 4 to 3: Biological markers look positive and we have some confidence in them.
Scores 3 to 1: Biological markers look possible positive but we have low evidence or confidence.
Scores 1 to -1: Biological markers unclear or there is no evidence.
Scores -1 to -3: Biological markers look possibly negative but we have low evidence or confidence.
Scores -3 to -4: Biological markers look negative and we have some confidence in them.

Cortisol
Dopamine
Endocrine changes
Circulating catecholamines and corticosteroids
Adrenal activity

Scores 4 to 3: Behavioral needs fully met.
Scores 3 to 1: Behavioral needs not met in minor ways, such as a barren environment or mild and short-term restraint.
Scores 1 to -1: Behavioral needs not met in marked short-term or moderate long-term ways, such as medium-term restrictions of instinctive behavior, unnaturally changing social groups, or treatment that results in reversible stereotypies.
Scores -1 to -3: Behavioral needs not met in marked ways, such as marked and repeated noxious stimuli from which escape is impossible, marked alterations to perceptual or motor functions, or treatment that results in self-mutilation or unusual aggression.
Scores -3 to -4: Behavioral needs severely not met, leading to psychotic-like behavior or agonistic interactions which result in severe injury or death, such as maternal deprivation, severe social isolation, or overcrowding.

Bedding
Confinement (sows in crates/hens in cages)   
Beak trimming (long term)
Restrictions of instinctive behavior, unnaturally changing social groups, or treatment that results in reversible stereotypies
Behavioral needs not met in marked ways (such as marked and repeated noxious stimuli from which escape is impossible, marked alterations to perceptual or motor functions, or treatment that results in self-mutilation or unusual aggression)
Behavioral needs severely not met, leading to psychotic-like behavior or agonistic interactions which result in severe injury or death, such as maternal deprivation, severe social isolation, or overcrowding.