Effects of melatonin administration to cashmere goats on cashmere production and hair follicle characteristics in two consecutive cashmere growth cycles

C.H Yang,C.H Duan,Z.Y Wu,Y Li,Y.Y Luan,X.J Fu,C.X Zhang,W Zhang

doi:10.1016/j.domaniend.2020.106534

C.H Yang, C.H Duan + Show 6 more

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https://doi.org/10.1016/j.domaniend.2020.106534

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Abstract

The objective of the study was to determine the long-term effects of melatonin treatment on cashmere production and hair follicle populations in cashmere goats and their activity in two consecutive cashmere growth cycles. Twenty-four female Inner Mongolian Cashmere goats were randomly allocated to two groups (n = 12), one of which received melatonin implants, the other being an untreated control group. Melatonin implants were subcutaneously inserted behind the ear at a dose of 2 mg/kg live weight on two occasions –April 30 and June 30, 2016. Hair samples were collected by combing in April of 2017 and 2018, and the weight, staple length, and diameter of the cashmere fibers were measured. Blood and skin samples were collected monthly between April and September 2016, and in April and September in 2017 for the analysis of melatonin concentration and the characteristics of secondary hair follicle populations, respectively. The results indicated that serum melatonin concentration in the treated goats was elevated (P < 0.05) relative to that of the control group, but only during the first growth cycle. Melatonin treatment of cashmere goats in one cashmere growth cycle increased the weight, staple length, and density (all P < 0.05) of the cashmere fibers and decreased fiber diameter (P < 0.01), but did not affect the characteristics of cashmere production in the subsequent annual cycle. Melatonin treatment had no effect on the population of skin secondary hair follicles for two consecutive cycles. However, in the first growth cycle after treatment, it advanced the onset of activity of skin secondary hair follicles by 2 mo (P < 0.05), and it increased the number of follicles that were active (P < 0.05). In summary, the melatonin treatment of cashmere goats in one cashmere growth cycle improved cashmere production for that cycle only, with no residual effects on the subsequent cycle, a technique acceptable to the cashmere goat industry. The enhancement of cashmere production after the treatment of goats with melatonin appears to involve the acceleration of the annual regeneration of skin secondary hair follicles and increased population of active secondary hair follicles in the skin of cashmere goats.

Highlights

Short-term melatonin treatment of cashmere goats has been shown to increase the quantity and quality of cashmere fibre
It has been shown that treatment of adult cashmere goats with exogenous melatonin prior to or during a cashmere growth cycle can advance the onset of cashmere fibre growth and lead to increased staple length and fibre weight [3,4,5]
This would mean that there could be no net gain from a single use of melatonin and this creates an uncertainty for farmers that needs to be resolved before the practical application of melatonin treatment can be recommended to the cashmere goat industry

Summary

Introduction

Short-term melatonin treatment of cashmere goats has been shown to increase the quantity and quality of cashmere fibre. There have been some reports of inconsistent results of melatonin treatment on cashmere fibre weight and staple length, presumably resulting from its effects on secondary hair follicles [3, 5, 7]. Cashmere production and secondary hair follicle characteristics were evaluated for two consecutive cashmere growth cycles following a melatonin treatment applied in the first cycle. This would enable firm recommendations to be provided to the cashmere goat industry and the detailed histological observations would give further insight into the cellular mechanisms involved in cashmere fibre growth

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Conclusion