大豆异黄酮对育成期蛋用种公鸡生殖激素分泌的影响

本试验旨在研究大豆异黄酮(SI)对育成期蛋用种公鸡睾丸发育、血浆生殖激素水平以及与睾酮(T)合成相关的酶和蛋白表达的影响。选用108只10周龄的‘京红1号’蛋用公鸡随机分成6组，每组3个重复，每个重复6只鸡。以玉米-鱼粉型饲料为基础日粮，分别添加不同剂量SI：0、5、10、15、20、25 mg/kg。试验预饲期为1周，正式试验8周。试验结束后采集血液，检测血浆生殖激素(T、LH、FSH和GnRH)浓度。采血后处死，取睾丸组织，称重后检测睾丸组织中与T合成相关的酶(P450scc、3β-HSD)和蛋白(StAR)mRNA的表达量的变化。结果表明：（1）添加量在5~15 mg/kg范围时，SI对育成期蛋用种公鸡进睾丸的生长发育有促进作用，其中添加量为5 mg/kg，睾丸重量和睾丸指数均极显著增加(P＜0.01)。添加量在25 mg/kg时，睾丸指数较对照组极显著降低(P＜0.01)。（2）SI添加量为5 mg/kg时，对生殖激素分泌的促进作用最为明显，添加量达到25 mg/kg时，各激素分泌水平下降。（3）SI添加量在5~15 mg/kg范围时，StAR mRNA表达量显著提高(P＜0.05)，而P450scc和3β-HSD mRNA表达无显著差异(P＞0.05)。在本试验条件下，SI添加量为5 mg/kg时，能够促进育成期蛋用种公鸡睾丸发育、提高StAR mRNA表达量和生殖激素分泌水平。饲料中SI的安全添加范围为5~20 mg/kg。

Effect of Soybean Isoflavones on Reproductive Hormone Secretion of Young Breeder Roosters

The present experiment was conducted to study the effect of soybean isoflavones (SI) on testis development, levels of plasma reproductive hormones, testosterone synthesis related enzyme and protein mRNA expression of young breeder rooster. One hundred and eight 10- week- old breeder roosters were randomly divided into 6 groups, each group had three repeats, and 6 roosters in each repeat. Corn-fishmeat diets was used as basal meal, and different doses of SI was added: 0 mg/kg, 5 mg/kg, 10 mg/kg, 15 mg/kg, 20 mg/kg, 25 mg/kg, respectively. The experiment lasted for 9 weeks, including one week pre- trial feeding. Plasma hormone (GnRH, T, LH, and FSH) were detected by collecting plasma at the end of the experiment. The testis samples were collected and weighed, the expression level of mRNA of testosterone synthesis related to both enzyme (P450scc, 3β-HSD) and protein (StAR,) was investigated. The results showed that: (1) among the dose range of 5-15 mg/kg, SI promoted the testicular development of young breed roosters, especially with the additive amount of 5 mg/kg, the testis weight and testis index were significantly increased (P＜0.01); with the dose of 25 mg/kg, testis index was significantly decreased (P＜0.01); (2) when the additive amount of SI was 5 mg/kg, the effect of promoting reproductive hormone secretion was most obvious; when the additive amount of SI was 25 mg/kg, the level of reproductive hormone secretion was decreased; (3) among the additive range of 5- 15 mg/kg, the level of StAR mRNA was significantly increased (P＜0.05), but there was no significant difference in the expression of P450scc and 3β-HSD (P＞0.05). In the present experiment, when the additive amount was 5 mg/kg, SI promoted the testicular development of young breed roosters and enhanced the expression amount of StAR mRNA and the level of reproductive hormone secretion. The safe additive range of SI was 5-20 mg/kg.