Tail hair won’t grow

Our six-year-old Labrador bitch had a very fine tail, but she kept whacking it on things. Finally, after one whack too many, the tail became infected. We took her to the vet and she had to have quite a bit of tail lopped off. She was left with a bald tip of about 9in, but after six months no hair has grown there.

Our vet is baffled and we have tried adding oil and vitamin supplements to her food without success. Though it does not bother her, we do not want her to lose any more of her tail. What do you advise?

From what you describe, I assume her tail was shaved prior to surgical amputation and that the hair on that portion of the remaining stump has failed to regrow. Though I don’t recall seeing anything as obvious as you describe, there might be an explanation.

Breeds such as the Labrador retriever have a double coat consisting of a dense insulating undercoat and a more robust outer coat. Both types of hair grow in three distinct cycles, but while the undercoat may be shed more or less continually, the outer “guard” hairs are shed, and replaced, far less frequently.

The three growth cycles comprise an active growth phase, termed anagen, in which the hair reaches its genetically determined length. It then passes through a transient catagen phase and finally enters a resting phase called telogen. The anagen phase is short and lasts probably no more than a month or so. However, in dogs such as Labradors that were originally bred to resist harsh northern climates, the telogen phase may last for years. At some point the telogen hair falls out and is replaced by a newly developing anagen hair, but unfortunately the trigger for the telogen hair to fall out and new hair to grow is not known.

It is conceivable that the hair over your bitch’s tail has entered a prolonged telogen phase and you might simply have to wait for it to be replaced naturally. It might be worth having a biopsy taken — a skin section from the affected area that your vet would then send away to be examined under the microscope by a pathology laboratory. TB