日粮不同碘、硒水平对绒山羊绒生长相关激素及酶的影响

为探讨日粮添加不同水平的碘和硒对辽宁绒山羊非产绒期和产绒期血液中褪黑激素（MT）、催乳素（PRL）、类胰岛素生长因子（IGF—I）、生长激素（GH）、甲状腺过氧化物酶（TPO）以及脱碘酶（DIO）的影响，选择36只体况良好、体重相近（（38．0±2．94）kg）的2周岁辽宁绒山羊作为试验动物，采用2×3完全随机试验设计，随机分为6组。分别在基础日粮中添加3个水平的碘（0、2和4mg／kg，DM）和2个水平的硒（0和1mg／kg，DM）进行饲喂。试验结果表明：1）非产绒期，日粮添加碘显著提高了血液中GH和IGF1的浓度，降低了血浆MT的浓度（P〈0．05），对PRL、TPO和D10浓度没有显著影响（P〉0．05）。添加硒对血液MT、PRL、GH、IGF—I和TPO没有影响，但是显著提高了DIO的浓度（P〈0．05）。2）产绒期，日粮添加碘极显著提高了血液中IGF-I的浓度（P〈0．01），对MT、PRL、GH、TPO和DIO浓度没有影响。添加硒则显著提高了DIO的浓度（P〈0．05），对血浆MT、PRL、GH、IGF—1和TP0没有影响。通过2个阶段的比较，综合碘促绒生长作用，推断碘或甲状腺激素促进山羊绒生长的机制可能是通过调控IGF—1分泌途径实现的；硒仅提高了血液中脱碘酶的浓度。

Effects of dietary iodine and selenium on serum hormones andenzymes related with cashmere growth ofLiaoning cashmere goats

Thirty-six two-year-old Liaoning cashmere goats (body weight=(38.0(2.94)kg) were used to investigate the effects of dietary iodine (I) and selenium (Se) supplementation on the concentration of Melatonin (MT),Prolactin (PRL),Insulin-like growth factor-I (IGF-I),Growth hormone (GH),Thyroid peroxidase (TPO) and Deiodinase(DIO).The goats were evenly divided into six groups,and 2×3 factorial experimental design was applied with supplemental I/kg dry matter (DM) at 0,2 and 4 mg level and supplemental Se/kg DM at 0 and 1 mg level.Results showed that:1) In cashmere non-growth period,iodine supplementation significantly increased the concentrations of GH and IGF-1,decreased the concentration of MT (P<0.05),but there was no effect on the concentrations of PRL,TPO,DIO (P>0.05).Selenium supplementation did not affect serum MT,PRL,GH,IGF-I,TPO concentrations,but the concentration of DIO was significantly increased (P<0.05) with Selenium supplementation.2) In cashmere growth period,iodine supplementation highly increased the concentration of IGF-1 (P<0.01),but no effect was found on the concentrations of MT,PRL,GH,TPO,DIO (P>0.05).Selenium supplementation did not affect serum MT,PRL,GH,IGF-1,TPO concentrations,but the concentration of DIO was significantly increased after supplemental 1 mg Se/kg DM (P<0.05).Comparing the above two periods,we may conclude that the mechanism of iodine or thyroid hormones stimulating the cashmere fiber growth may be through the regulating the IGF-1 secretion,while Selenium supplementation can improve the concentration of serum DIO only.