Hair follicles grow in repeated cycles in a mosaic pattern so that the whole hair coat isn’t lost at one time. Peaks of hair replacement occur in the spring and autumn.
Phases in hair growth cycle:
Hair growth cycle has three phases which Growth phase, transition phase and resting phase. In different phases hair undergoes certain activities as the name depicts.
Anagen: Growth phase.
- The majority of hair follicles will be in this phase (about 85%).
- The length of the hair is decided in this phase.
- This phase lasts around 2 years to 8 years.
- Hair grows 0.5 inch per month.
- In this phase the hair is sensitive. So, the hair may affect its growth with many factors like stress, deficiencies (due to deficiency the activity of the hair root is reduced and the growth phase is limited or decreased), hormonal imbalance, photoperiod, ambient temperature.
Catagen: Transition phase.
- Root shrinks up to 1/3rd of its original size.
- This phase lasts for 2 to 4 weeks.
- The hair root is detached from the papilla and comes outside the follicle.
- As the hair is detached from the papilla, there is no nutrition supplement for the follicle which results in shrinking.
Telogen: Resting phase.
- 10% to 15% of hair is in this phase.
- This phase lasts around 5 months.
- In this phase hair doesn’t grow and just seems to be attached, but internally it’s detached from papilla, which means it has no nutrient supplement.
- This hair is prone to be removed on pulling.
- After the telogen phase the follicle re-enters anagen and re attaches with the dermal papilla. If the hair is not pulled out, then the new hair coming from that follicle pushes out the old hair.
The most important factors controlling moulting are ambient temperature and photoperiod, and this means that animals kept indoors in a near-constant environment may shed all year-round.