Double coat & shedding

Double coat

The coat characteristics of dogs are influenced by multiple genes and determine both coat structure (single- or double-layered) and shedding behaviour. A double coat consists of coarse guard hairs forming the top coat and a softer, insulating undercoat, while single-coated dogs lack a true undercoat. Dogs with a double coat typically show more noticeable seasonal shedding due to the cyclic loss of the undercoat.

A genetic variant associated with the presence of a double coat is located upstream of the ADRB1 gene on chromosome 28. This variant is used as an associated marker, as the causal mutation responsible for undercoat development has not yet been identified. The exact mode of inheritance has not been fully established; however, available data suggest that the marker behaves in a recessive-like manner in many breeds.

Dogs with the C/C genotype are generally associated with a double coat, while dogs with the T/T genotype are typically associated with a single coat. Heterozygous dogs (T/C) most often show a single coat, although coat expression may vary depending on breed and genetic background.

Shedding

Besides the coat structure, shedding intensity is also influenced by independent genetic factors. Variants in the MC5R (melanocortin 5 receptor) gene have been associated with reduced shedding in dogs. When shedding is scored on a scale from light (0) to heavy (1), dogs carrying at least one copy of the MC5R shedding‑reducing variant consistently show a markedly lower shedding score than dogs lacking the variant. This effect is most pronounced in medium‑haired dogs without wire‑hair or furnishings, where MC5R status can significantly influence the amount of visible shedding. Dogs carrying these MC5R variants may therefore shed less overall and show less pronounced seasonal shedding, regardless of whether they have a single or double coat.

It is important to understand that shedding is a normal biological process, and the amount and timing of shedding can vary widely between individual dogs. Breed characteristics, age, hormonal status (for example neutering), seasonal changes, and overall health all influence how much hair a dog sheds and how visible the undercoat appears, even among dogs with the same genetic results. Additionally, grooming practices can affect coat appearance: for example, shaving a double-coated dog may alter the texture of the regrowing coat, as the undercoat often grows back faster than the guard hairs.

Relevant tests:

• H464: Double Coat (Coat Composition, CFA28-related)
• H299: Coat Type SD-Locus (Shedding MC5R)