Cui Yao-Ming, Wang Jing, Zhang Hai-Jun, Qi Guang-Hai, Qiao Han-Zhen, Gan Li-Ping, Wu Shu-Geng
Laboratory of Quality and Safety Risk Assessment for Animal Products on Feed Hazards (Beijing) of the Ministry of Agriculture and Rural Affairs, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.
College of Biological Engineering, Henan University of Technology, Zhengzhou, China.
Front Microbiol. 2022 Mar 10;13:819427. doi: 10.3389/fmicb.2022.819427. eCollection 2022.
We investigated the effect of photoperiod on ileal morphology, barrier function, short-chain fatty acid (SCFA) contents, microbial flora, melatonin expression, and synthesis in laying ducks. After adaption, a total of 180 Jinding laying ducks (252 days old) were randomly divided into three treatments, receiving 12L (hours of light):12D (hours of darkness), 16L:8D, or 20L:4D. Each treatment had six replicates with 10 birds each. The formal experiment lasted 58 days. Compared with 12L:12D, the significantly higher values of villus height and goblet cell percentage (GCP) were observed in 16L:8D treatment, accompanied with the higher mRNA relative expression of zonula occludens-1, zonula occludens-2, zonula occludens-3, claudin-1, occludin, and mucin 2 ( < 0.05). Besides, significantly higher values of acetate and propionate, butyrate and total SCFA concentrations were simultaneously observed in ileal chyme of 16L:8D treatment ( < 0.05). For the ileal microbial community, the results of principal coordinate analysis (PCoA) visually presented that three photoperiod groups were mainly scattered into three clusters, indicating that the microbiota composition in different photoperiod treatments were quite dissimilar. Lower values of Shannon indicators were observed in the 20L:4D treatment ( < 0.05), meaning that the microbiota α-diversity decreased in the 20-h photoperiod. The relative abundance of Actinobacteria, Fusobacteria, and Proteobacteria at phylum level and , , and at genus level kept an appropriate balance in the 16L:8D photoperiod. Melatonin level in serum decreased with the increasing photoperiods at 6:00 and 12:00, which was consistent with melatonin receptor expressions in the hypothalamus and ileal tissue. Meanwhile, the adenosine 3',5'-cyclic phosphate (cAMP) contents were significantly downregulated in the pineal gland ( < 0.05), in response to the increase in photoperiod. In conclusion, an appropriate photoperiod could improve ileal morphology, barrier function, SCFA profile, and microbial flora, which may be attributed to the appropriate regulation of the circadian rhythm through melatonin as well as its receptor expression, and 16 h could be an adequate photoperiod for laying ducks.
我们研究了光照周期对蛋鸭回肠形态、屏障功能、短链脂肪酸（SCFA）含量、微生物菌群、褪黑素表达及合成的影响。适应期过后，将180只金定蛋鸭（252日龄）随机分为三组，分别接受12小时光照（L）：12小时黑暗（D）、16L：8D或20L：4D的光照处理。每组有6个重复，每个重复10只鸭。正式试验持续58天。与12L：12D组相比，16L：8D处理组的绒毛高度和杯状细胞百分比（GCP）显著更高，同时紧密连接蛋白1、紧密连接蛋白2、紧密连接蛋白3、闭合蛋白1、闭合蛋白和黏蛋白2的mRNA相对表达量也更高（P<0.05）。此外，16L：8D处理组回肠食糜中的乙酸盐和丙酸盐、丁酸盐以及总SCFA浓度也显著更高（P<0.05）。对于回肠微生物群落，主坐标分析（PCoA）结果直观显示，三个光照周期组主要分散为三个簇，表明不同光照周期处理下的微生物群组成差异很大。20L：4D处理组的香农指数值较低（P<0.05），这意味着在20小时光照周期下微生物群的α多样性降低。在16L：8D光照周期下，门水平上放线菌门、梭杆菌门和变形菌门以及属水平上[具体属名未给出]、[具体属名未给出]和[具体属名未给出]的相对丰度保持适当平衡。血清中褪黑素水平在6:00和12:00时随光照周期增加而降低，这与下丘脑和回肠组织中褪黑素受体的表达一致。同时，松果体中3',5'-环磷酸腺苷（cAMP）含量因光照周期增加而显著下调（P<0.05）。总之，适宜的光照周期可改善蛋鸭回肠形态、屏障功能、SCFA谱和微生物菌群，这可能归因于褪黑素及其受体表达对昼夜节律的适当调节，16小时可能是蛋鸭适宜的光照周期。
