High-temperature exposure alters the community structure and functional features of the intestinal microbiota in Shaoxing ducks (Anas platyrhynchos).

The gut microbiome is a complex ecosystem that contributes to host nutrition and health. However, our current knowledge of the relationship between ambient temperature and gut microbiota of poultry is still limited. The objective of the present study was to characterize the intestinal microbiota of ducks exposed to high ambient temperature. Sixty 60-day-old Shaoxing ducks were allocated to control and heat-treated groups. The ducks in the control group were kept at 25°C, and the ducks in the heat treatment group were raised at 30-40°C, which simulated the temperature change of day and night in summer. After 15 D, the intestinal contents of the duodenum, jejunum, and ileum were obtained from 6 ducks of each group. Genomic DNA was extracted and amplified based on the V4-V5 hypervariable region of 16S rRNA. The results showed that Firmicutes was the dominant bacterial phylum with the highest abundance in the contents of the small intestine of ducks, and the relative abundance of the phylum Firmicutes in all 3 intestinal segments was increased by high temperature. At the genus level, Lactobacillus was found to be the most dominant bacterial genus across 3 gut segments, and its abundance was increased in ducks under heat treatment. Compared with the corresponding intestine segment of control ducks, a total of 36 genera in the duodenum, 19 genera in the jejunum, and 6 genera in the ileum of heat-treated ducks were found to be significantly different in the abundance (linear discriminant analysis score >3.0, P < 0.05). Functional prediction of gut microbiota revealed that high temperature caused changes in the abundance of metabolism and transcription-related pathways. It is noteworthy that most of the altered pathways are related to metabolism. In conclusion, high temperature induced remarkable taxonomic changes in the gut microbiome of ducks, which might be related to the negative effects of high temperature in ducks. Our present study provided an important theoretical ground for high-temperature intervention.

Changes in morphology and miRNAs expression in small intestines of Shaoxing ducks in response to high temperature.

During summer days the extreme heat may cause damage to the integrity of animal intestinal barrier. Little information is available concerning morphological changes in the duck intestines in response to high temperature. And the molecular mechanisms underlying the pathogenesis of high temperature-induced intestinal injury remain undefined. MicroRNAs (miRNAs) are known to play key roles in post-transcriptional regulation of gene expression that influences various biological processes. The purpose of this study was to explore the changes in morphology and miRNA expression profiles of the three intestinal segments (duodenum, jejunum and ileum) of ducks in response to high temperature. Sixty female Shaoxing ducks (Anas platyrhynchos), 60 days old, were allocated in two groups, including control ducks kept at 25 °C, and ducks subjected to high ambient temperatures of 30-40 °C for 15 successive days, which mimicked the diurnal temperature variations experienced in hot seasons. Three ducks from each group were executed at the end of feeding experiment, and the samples of three intestinal segments were collected for morphological examination and Illumina deep sequencing analyses. Histopathological examination of the intestinal mucous membrane was performed with HE staining method. The results demonstrated that varying degrees of damage to each intestinal segment were found in heat-treated ducks, and there were more severe injuries in duodenum and jejunum than those in ileum. Illumina high-throughput sequencing and bioinformatic methods were employed in this study to identify the miRNA expression profile of three different intestinal tissues in control and heat-treated ducks. A total of 75,981,636, 88,345,563 and 100,179,422 raw reads were obtained from duodenum, jejunum and ileum, respectively, from which 74,797,633 clean reads in duodenal libraries, 86,406,445 clean reads in jejunal libraries, and 98,518,858 lean reads in ileal libraries were derived after quality control, respectively. And a total of 276 known and 182 novel miRNAs were identified in the three intestinal segments of ducks under control and heat-treated conditions. By comparing the same tissues in different conditions, 16, 18 and 15 miRNAs were found to be significantly differentially expressed between control and heat-treated ducks in duodenum, jejunum and ileum, respectively, of which 1 miRNA was expressed in both the duodenum and jejunum, 2 miRNAs were expressed in both the duodenum and ileum, and 3 miRNAs were found to be expressed in both the jejunum and ileum. In addition, two differentially expressed miRNAs in each comparison were randomly selected and validated by quantitative qRT-PCR. Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that the differentially expressed miRNAs may be involved in the high temperature-induced intestinal injury in ducks. Our work provides the comprehensive miRNA expression profiles of small intestines in the normal and heat-treated ducks. These findings suggest the involvement of specific molecular mechanisms of post-transcriptional regulation to explain the high temperature-induced changes in the duck small intestine.

Effects of metabolizable energy and crude protein levels on laying performance, egg quality and serum biochemical indices of Fengda-1 layers.

This study was conducted to investigate the effects of dietary ME and CP levels on laying performance, egg quality and serum biochemical indices of Fengda-1 layers. In a 2 × 3 factorial arrangement, 2,400 Fengda-1 layers (32 wk of age) were randomly assigned to 6 experimental diets with 2,650 and 2,750 kcal of ME/kg of diet, each containing 14.50%, 15.00% and 15.50% CP, respectively. Each dietary treatment was replicated 5 times, and feed and water were provided ad libitum. The trial lasted for 10 wk, including a 2-week acclimation period and an 8-week experimental period. Our results showed that ADFI decreased as the ME level of diet increased from 2,650 to 2,750 kcal/kg (P < 0.05). Layers fed diets with 2,750 kcal/kg ME exhibited higher mortality than those fed with 2,650 kcal/kg ME (P < 0.05). Birds fed with 14.50% and 15.00% CP had higher egg production (EP) and egg mass (EM) than those fed with 15.50% CP (P < 0.05). Yolk color increased as the ME level of the diet increased from 2,650 to 2,750 kcal/kg, however, the eggshell thickness decreased (P < 0.05). Serum concentrations of uric acid and triglyceride in layers fed diets with 2,750 kcal/kg ME were higher than those fed diets with 2,650 kcal/kg ME (P < 0.05). There was no significant interaction between ME and CP on laying performance, egg quality, or serum biochemical indices (P > 0.05). Based on the data under the experimental conditions, the optimal dietary ME and CP levels of Fengda-1 layers are 2,650 kcal/kg and 15.00% (33 to 41 wk of age).