Effects Of Dietary Zinc Level On Performance Of Cashmere Production And Cashmer Production-related Hormones Of Shanbei White Cashmere Goats During Cashmere Growing Period

This experiment was conducted to study the effects of dietary zinc level on growth performance,cashmere performance,the contents of cashmere growth-related hormone and growth-related factor as well as the activity and morphology of hair follicles in Shanbei white cashmere goats during cashmere growing period,in order to determine the optimal dietary zinc leave of Shanbei white cashmere goats during cashmere growing period.The experiment was designed in a single factor random block.Thirty-two Shanbei white cashmere goats at 8 months of age with physical fitness and similar weight were selected and divided into 4 groups with 4 replicates per group and 2 goats per replicate.The goats in control group(group I)were fed a basal diet containing 28.57 mg/kg DM zinc,and the goats in experimental groups(group ?,? and ?)were fed the basal diet supplemented with zinc sulfate(feed grade),and the dietary zinc level of the experiment diets was 50?70?100 mg/kg DM respectively.The pre-test period was 15 days and the formal test period was 6 months.The results showed as: Result 1.1)Dietary zinc level had no significant influences on dry matter intake(DMI)and feed/gain(F/G)of Shanbei white cashmere goats(P > 0.05).Goats in group ? had the greatest average daily gain(ADG),and the ADG in group ? had significant difference compared with group I(P < 0.05),while had no significant difference compared with groups ? and ?(P > 0.05).2)Dietary zinc level had no significant influences on cashmere diameter at initial experiment and last experiment and cashmere production(P > 0.05).Cashmere length in group was significantly higher tha? n that in group(? P < 0.05).Cashmere length at last experiment in group was significantly higher than that in group? s I and(? P < 0.01 and P < 0.05,respectively).Cashmere growth and cashmere growth rate in group III were significantly higher than those in group I and(? P < 0.05),and no significant difference was observed between groups III and(? P > 0.05).Result 2.With the succession of cashmere growing period,melatonin(MLT),insulin like growth factor-1(IGF-1)and growth hormone(GH)contents in serum of goats showed increasing trend and serum prolactin(PRL)content was showed decreasing trend.Dietary zinc level had no significant influences on serum MLT and PRL contents in the whole experiment period and GH content in the mid-term experiment(P > 0.05).Serum IGF-1 content in the mid-term experiment in group III was significantly higher than that in group ?(P < 0.05).Serum IGF-1 content in the last experiment in group III was significantly higher than that in groups I and ?(P < 0.05).Serum GH content in the last experiment in group III was significantly higher than that in group I(P < 0.05).Result 3.Dietary zinc level had no significant influence to the activity and morphology of hair follicles during cashmere growing period(P > 0.05).In summary,dietary zinc could improve the cashmere growth by increasing the contents of IGF-1 and GH,the optimal dietary zinc level of Shanbei white cashmere goats during cashmere growing period is 70 mg/kg DM.