Liu Lijuan, Zhang Siyu, Bao Jiayang, He Xiaowen, Tong Danni, Chen Cong, Ying Qingxiang, Zhang Qing, Zhang Caiqiao, Li Jian
Department of Veterinary Medicine, College of Animal Sciences, Zhejiang University, Hangzhou, China.
Yanping Bureau of Animal Husbandry, Veterinary & Aquatic Products, Nanping, China.
Front Endocrinol (Lausanne). 2018 Jul 30;9:426. doi: 10.3389/fendo.2018.00426. eCollection 2018.
The high concentration of melatonin (MEL) in the intestinal mucosa suggests that it has a special physiological function in intestine. In hens, previous studies have shown that MEL treatment promoted egg-laying performance. Considering the importance of amino acids (AA) for egg formation, we hypothesized that MEL may enhance the intestinal absorption of AA from the feed, thus promoting egg laying performance. In this study, we supplemented the hens with MEL for two consecutive weeks. The results showed that, compared with control group, feeding with 0.625 mg MEL/kg diets gave rise to higher egg laying rate (by 4.3%, = 0.016), increased eggshell thickness (by 16.9%, < 0.01) and albumen height (by 4.5%, = 0.042). Meanwhile, feeding with 0.625 and 2.5 mg MEL/kg diets could significantly increase serum levels of aspartic acid, threonine, serine, glutamic acid, glycine, alanine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine, arginine, and proline. Furthermore, a 0.625 mg MEL/kg diets could significantly increase the expression of (by 3949.9%), (by 6045.9%) (by 603.5%), and (by 412.7%) in the jejunum. Additionally, in the cultured intestinal crypt "organoids," treatment with 0.5 μM MEL could significantly enhance the expression of and mRNAs by 35.4%, 110.0%, and 160.1%, respectively. Detection of MEL concentration in serum and intestinal fluid suggested that lower dosage of MEL feeding was mainly acted on intestine locally, and further increased intestinal antioxidases ( or ) mRNA expression. Taken together, we demonstrated that MEL feeding in laying hens could locally promote the expression and function of AA transporter in small intestine by up-regulating antioxidases expression, and finally elevate laying performance.
肠黏膜中高浓度的褪黑素（MEL）表明其在肠道具有特殊的生理功能。在母鸡中，先前的研究表明，MEL处理可提高产蛋性能。考虑到氨基酸（AA）对蛋形成的重要性，我们推测MEL可能会增强肠道对饲料中AA的吸收，从而提高产蛋性能。在本研究中，我们连续两周给母鸡补充MEL。结果表明，与对照组相比，饲喂0.625 mg MEL/kg日粮可提高产蛋率（提高4.3%，P = 0.016），增加蛋壳厚度（增加16.9%，P < 0.01）和蛋白高度（增加4.5%，P = 0.042）。同时，饲喂0.625和2.5 mg MEL/kg日粮可显著提高血清中天冬氨酸、苏氨酸、丝氨酸、谷氨酸、甘氨酸、丙氨酸, 异亮氨酸、亮氨酸、酪氨酸、苯丙氨酸、赖氨酸、组氨酸、精氨酸和脯氨酸的水平。此外，0.625 mg MEL/kg日粮可显著提高空肠中（提高3949.9%）、（提高6045.9%）、（提高603.5%）和（提高412.7%）的表达。此外，在培养的肠隐窝“类器官”中，用0.5 μM MEL处理可分别显著提高和mRNA的表达35.4%、110.0%和160.1%。血清和肠液中MEL浓度的检测表明，较低剂量的MEL饲喂主要作用于肠道局部，并进一步增加肠道抗氧化酶（或）mRNA的表达。综上所述，我们证明了给蛋鸡饲喂MEL可通过上调抗氧化酶的表达来局部促进小肠中AA转运体的表达和功能，最终提高产蛋性能。
