The Research On Patterns And Mechanisms Of Cashmere Growth Induced By Melatonin

The study is consisted of two parts, which was conducted to determine the model and mechanism of melatonin regulate cashmere growth. Part one, regulation model:The effects of melatonin implantation in the spring (melatonin was implanted in March and May, in March, May and July), winter (melatonin was implanted in October and December, in October, December and February) or in whole year (from March,2012 to March,2013) on cashmere production in Liaoning cashmere goats, and melatonin implantation during the cashmere non-growing period (melatonin was implanted in April and June, in June) or during the latter-growing period (melatonin was implanted in December and February) on the productivity of Inner Mongolian cashmere goats. Results of the induction model showed that:(1) Currently most of the Liaoning cashmere goats have the characteristic of cashmere stay growing thoughout the year. The results indicated that use of melatonin implants was effective in increasing cashmere growth in cashmere-perennial-type Liaoning cashmere goats, but the cashmere yield was increased only in the group of melatonin implantation in whole year (P<0.05). There was early shedding in varying degrees in all of melatonin-treated goats except for the goats with melatonin implanted in October and December, of which the goats with melatonin treated in whole year were the most severe. (2) Melatonin implanted during cashmere non-growing period stimulated the cashmere growth ahead of time in Inner Mongolian cashmere goats, and it prevent the earlier cashmere shedding by combining the induced growth of cashmere fleece with the typical growth. Melatonin implantation in April and June increased cashmere yield and maximum cashmere length by 16.2% and 17.3%(P<0.05), respectively. The cashmere growth rate of goats treated with melatonin during the cashmere latter-growing period was increased only in March. It failed to prolong cashmere growth, and there were no effects on cashmere yield and length. In addition, melatonin implants did not affect the fibre diameter, dam growth rate or reproductive performance. Part two, regulation mechanism: The effects of melatonin implantation in the spring (melatonin was implanted in March and May, in March, May and July) on plasma hormones and follicle density in Liaoning cashmere goats, and melatonin implantation during the cashmere non-growing period (in April and June) on the cashmere production, plasma hormones and RORa gene expression in Inner Mongolian cashmere goats. Results of the regulation mechanism showed that:(3) Melatonin implantation in spring increased plasma melatonin concentrations and decreased plasma prolactin concentrations in cashmere-perennial-type Liaoning cashmere goats (P<0.05), but did not affect the plasma IGF-I, T3 or T4. Melatonin implantation increased secondary follicle density (P<0.05) and achieved a certain number in primary hair follicle in advance. (4) In Inner Mongolian cashmere goats treated with melatonin in April and June, the average initiation date was earlier than in control goats (P<0.05), causing the duration of cashmere growth extend 37 days in melatonin-treated goats (P<0.05). In addition, melatonin implantation increased cashmere yield by 34.5%(P<0.05), cashmere length by 21.3%(P<0.05), and decreased fibre diameter by 4.4%(P<0.05). Melatonin implantation increased plasma melatonin concentrations and decreased plasma prolactin concentrations in daylight and at night, and it increased the expression of RORa gene (P>0.05). The above findings suggest that:Liaoning cashmere goats have the characteristic of cashmere stay growing thoughout the year. Melatonin implants was effective in increasing cashmere growth in cashmere-perennial-type Liaoning cashmere goats, but did little to boost cashmere production. The early shedding could be prevented by planned administration of melatonin. Melatonin implants in April and June is an effective regulation model in Inner Mongolian cashmere goats. Melatonin implantation during the cashmere latter-growing period cannot be used to prolong cashmere growth in seasonal-type cashmere goats, which suggests that the cashmere growth all year round is infeasible. Exogenous melatonin may prolong cashmere growth in order to promote cashmere production by increasing plasma melatonin concentrations, decreasing prolactin concentrations, increasing secondary follicle density and RORa gene expression.