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Breeding animals with genetic disorders that are expected to experience severe and persistent impairment of general condition.

Animals can be considered sub-threshold if: they are born and no harmful phenotype actually manifested; or the phenotype was subtle and of no welfare significance; or because of the management conditions the phenotype caused no welfare concern to the animal.

Unknown phenotype, but not expected to be harmful. Known phenotype that can be kept so that actual severity is sub-threshold or mild provided certain conditions are met. These conditions will be mandated through the project authorisation.
A mild severity classification is appropriate when animals show a distinct phenotype but this does not: reduce lifespan compared with the background strain; prevent normal feeding and movement; result in systemic disease, but does lead to an observable difference in a parameter such as growth rate, size, anatomy or behaviour.

The most common examples will be breeding of heterozygous animals that will result in severe phenotypes in homozygous offspring, including:
paralysis; seizures; fractures; or birth of living offspring with severe developmental abnormalities or expected pre-weaning death.
Breeding stock, or offspring, that are retained to a point where they show a disease phenotype in the severe category (see separate Home Office document Advisory notes on retrospective recording and reporting of actual severity of regulated procedures) will be classed as severe.
Any animals found dead on a breeding protocol, unless an informed decision (see separate Home Office document Advisory notes on recording and reporting the actual severity of regulated procedures) can be made that it is unlikely the death was preceded by severe suffering.

Offspring of rats and mice found dead or cannibalised after postnatal day five, or death of neonates in other species caused by aggressive maternal behaviour where offspring are well developed at birth (for example, pigs), where this is phenotype- and not husbandry-related. A husbandry-related cause of cannibalism would be facilities failure leading to stress in the parents, and therefore unrelated to that specific breeding programme.

Genetically modified line (spontaneous mutation or genetically altered) used for animal experiments without an impaired phenotype and Genetically modified lines whose well-being is likely to be impaired not by the genetic modification but by the animal experiment.

Examples: Reporter lines such as EGFP-expressing lines. Conditional and non-induced inducible genetically modified lines.

Genetically modified line (spontaneous mutation or genetically altered) with a mildly impaired phenotype Examples: Deafness. Blindness. Dental abnormalities not affecting feed intake. Isolated gait abnormalities. Mild coordination disorders. Immunodecient animals in SPF housing.

Genetically modified lines (spontaneous mutation or genetically altered) with a moderately impaired phenotype.

Genetically modified lines (spontaneous mutation or genetically altered) with a severely impaired phenotype. Examples: Mammary carcinoma. Colitis. Osteoporosis. Kidney disease. Atherosclerosis. Ageing. Arthritis. Sceletal abnormalities. Motor restrictions. Acetylcholinesterase. Amyotrophic lateral sclerosis. Experimental allergic encephalomyelitis. Huntington’s chorea.

Phenotype does not differ from wild type.

Phenotype with mild disorders and mild clinical pictures, e.g. change in blood lipids.

Phenotype with moderate disorders and moderate clinical pictures, e.g. increase in aggression, anxiety.

Phenotype with severe disorders and severe clinical pictures, e.g. haemophilia.

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Mutants (spontaneous mutation or genetically altered) with mild clinically manifest diseases, disorders or abnormalities.

Mutants (spontaneous mutation or genetically altered) with clinically manifest diseases and/or disorders which are compensated by means of appropriate therapeutic measures.

Mutants (spontaneous mutation or genetically altered) with severe clinically manifest diseases or disorders without therapy to reduce constraint.

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Experimental marking and genotyping using non-invasive methods.

Experimental marking using invasive methods and tissue collection under anaesthesia for the genotyping of adult animals.

Experimental interventions to regulate reproduction or for genotyping of adult animals.