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Trichomonas gallinae (T. gallinae) is a flagellated protozoan and the causative agent of trichomoniasis, or canker, in birds. In the current study, the prevalence of T. gallinae was firstly investigated in five breeds. According to the results of the prevalence study, White King pigeons were selected as the experimental animals. A total of 135 White King squabs at one day of age were randomly divided into two groups and raised in separate isolators. The challenged group (N = 100) was challenged intranasally with 5 × 106 parasites/mL of the T. gallinae strain, and the control group (N = 35) was intranasally administered medium of equivalent volume. At 1, 2, 3 and 5 days post infection (DPIs), the crops and esophagi were collected for RNA extraction and formaldehyde fixation. The results showed that prevalence of T. gallinae in the five breeds ranged from 27.13% (White Carneau) to 43.14% (White King). After the challenge, mild microscopic lesions were observed in both tissues. Apoptosis rates were higher in the challenged group than in the control group at 2 and 5 DPIs in the crop and at 1, 2 and 7 DPIs in the esophagus. For both tissues, relative expression of IL-1β increased dramatically at the beginning and decreased at 5 DPIs, and TGF-β increased stably in the challenged group.

Objective The better understanding of laying pattern of birds is crucial for developing breed-specific proper breeding scheme and management. Methods Daily egg production until 50 wk of age of six chicken breeds including one layer (White Leghorn, WL), three dual-purpose (Rhode Island Red, RIR; Columbian Plymouth Rock, CR; and Barred Plymouth Rock, BR), one synthetic dwarf (DY), and one indigenous (Beijing-You Chicken, BYC) were used to characterize their clutch traits and egg production. The age at first egg, egg number, average and maximum clutch length, pause length, and number of clutches and pauses were calculated accordingly. Results The egg number and average clutch length in WL, RIR, CR, and BR were higher than those in DY and BYC (p

ABSTRACT: Heterosis is the major benefit of crossbreeding and has been exploited in laying hens breeding for a long time. This genetic phenomenon has been linked to various modes of nonadditive gene action. However, the molecular mechanism of heterosis for egg production in laying hens has not been fully elucidated. To fill this research gap, we sequenced mRNAs and lncRNAs of the ovary stroma containing prehierarchical follicles in White Leghorn, Rhode Island Red chickens as well as their reciprocal crossbreds that demonstrated heterosis for egg number and clutch size. We further delineated the modes of mRNAs and lncRNAs expression to identify their potential functions in the observed heterosis. Results showed that dominance was the principal mode of nonadditive expression exhibited by mRNAs and lncRNAs in the prehierarchical follicles of crossbred hens. Specifically, low-parent dominance was the main mode of mRNA expression, while high-parent dominance was the predominant mode of lncRNA expression. Important pathways enriched by genes that showed higher expression in crossbreds compared to either one or both parental lines were cell adhesion molecules, tyrosine and purine metabolism. In contrast, ECM-receptor interaction, focal adhesion, PPAR signaling, and ferroptosis were enriched in genes with lower expression in the crossbred. Protein network interaction identified nonadditively expressed genes including apolipoprotein B (APOB), transferrin, acyl-CoA synthetase medium-chain family member (APOBEC) 3, APOBEC1 complementation factor, and cathepsin S as hub genes. Among these potential hub genes, APOB was the only gene with underdominance expression common to the 2 reciprocal crossbred lines, and has been linked to oxidative stress. LncRNAs with nonadditive expression in the crossbred hens targeted natriuretic peptide receptor 1, epidermal differentiation protein beta, spermatogenesis-associated gene 22, sperm-associated antigen 16, melanocortin 2 receptor, dolichol kinase, glycine amiinotransferase, and prolactin releasing hormone receptor. In conclusion, genes with nonadditive expression in the crossbred may play crucial roles in follicle growth and atresia by improving follicle competence and increasing oxidative stress, respectively. These 2 phenomena could underpin heterosis for egg production in crossbred laying hens.

ABSTRACT: The study investigated the effects of supplementation of bile acids in drinking water on antitrichomonal activity, growth performance, immunity and microbial composition of pigeon. A total of 180 pairs of White King parent pigeons were randomly assigned to 5 treatments of 6 replications with 6 pairs of parent pigeons and 12 squabs in each replicate. The control (CON) group drank water without any additions. The metronidazole (MTZ) group drank water with 500 μg/mL metronidazole for 7 d and without any additions in other days. The else groups drank water with 500, 750, and 1,250 μg/mL bile acid (BAL, BAM, BAH) for 28 d. The results showed that Trichomonas gallinae (T. gallinae) in MTZ, BAL, BAM, and BAH groups were lower than that in CON group at 14, 21, and 28 d of parent pigeons (P < 0.05) and at 21 and 28 d of squabs (P < 0.05). Albumin and alanine transaminase in CON group were higher than those in MTZ, BAL, and BAH groups (P < 0.05). The levels of soluble CD8 were higher in MTZ and BAH groups compared with CON group (P < 0.05). The lesions in oral mucosa, thymus, liver, and spleen tissues of CON group could be observed. Abundance-based coverage estimator (ACE) index in BAH group was higher than that in CON and MTZ groups. Simpson index in CON and BAH groups was higher than MTZ group (P < 0.05). Lactobacillus was the highest colonized colonic bacteria in genera that were 77.21, 91.20, and 73.19% in CON, MTZ, and BAH, respectively. In conclusion, drinking water supplemented with 500, 750, and 1,250 μg/mL bile acid could inhibit growth of T. gallinae in both parent pigeons and squabs. Squabs infected with T. gallinae in control group had higher mortality rate and more serious tissue lesions. Squabs in bile acids treated group had more sCD8 in serum and abundant intestinal morphology. Bile acids could be an efficient drinking supplements to inhibit T. gallinae and improve pigeon adaptive immunity and intestinal health.

ABSTRACT: Pigeon has the specific biological ability to produce pigeon milk (also known as crop milk) by its crop. Circular RNAs (circRNAs) are important noncoding RNAs acting as the sponges of miRNAs, but the molecular mechanism of circRNAs regulating crop milk production has not been reported in pigeon. We compared expression profiles of crops during lactating and nonlactating crops, and networks of competing endogenous RNAs (ceRNAs) were constructed. The results showed a total of 8,723 circRNAs were identified, and there were 770 differentially expressed circRNAs (DECs) between these two different periods of crops. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the host genes of DECs were enriched in GnRH, MAPK, Insulin, Wnt, and AMPK signaling pathways. Furthermore, gga_circ_0000300 interacted with miR-92-2-5p, which targeted genes participating in lactation and milk composition synthesis. Gga_circ_0003018, gga_circ_0003019 and gga_circ_0003020 could bind with let-7c-5p regulating SOCS3 in crop milk production. These findings provide the circRNAs expression profiles and facilitate the analysis of molecular mechanism of crop milk production in pigeon.

ABSTRACT: The crop of pigeon has specific characteristics as producing crop milk in the lactating period. However, the exact mechanisms underlying the regulation of crop lactation remain unclear. miRNAs, the essential regulators of gene expression, are implicated in various physiological and biological activities. In this study, we discovered a new miRNA that regulated phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta (PIK3CD) and crop fibrocyte proliferation. Results of the luciferase reporter assay suggested that miR-193-5p suppressed PIK3CD expression by targeting a conserved binding site in the 3′-untranslated region (UTR) of PIK3CD mRNA. MiR-193-5p promoted crop fibrocyte proliferation and migration, whereas PIK3CD inhibited these effects. These findings suggested an important regulatory role of miR-193-5p in crop fibrocyte proliferation, suggesting that miR-193-5p and PIK3CD might be important regulators of crop milk production.

Abstract Background Effect of monochromatic green light illumination on embryo development has been reported in chickens. The avian pineal gland is an important photo-endocrine organ formed by a mediodorsal protrusion during embryonic development. However, the involvement of pineal gland in the light transduction process remains to be elucidated. In the present study, we investigated the influence of monochromatic green light on hatching time and explored the possible mechanism via pineal function. Results A total of 600 eggs of White Leghorn (Shaver strain) were incubated under photoperiods of either 12 h of light and 12 h of darkness using monochromatic green light (12L:12D group) or 24 h of darkness (0L:24D group) for 18 d. Compared to 0L:24D group, the green light stimulation shortened the hatching time without extending the hatch window or impairing hatchability. The liver of embryos incubated in the 12L:12D light condition was heavier than those of the 0L:24D group on d 21 post incubation which may be linked to the observed increase in the serum concentration of insulin-like growth factor 1 (IGF-1); primary secretion of the liver. Histological structure analysis of pineal gland demonstrated that the light stimulation increased follicle area, wall thickness and lumen area on d 10 and d 12 post incubation. Rhythmic function analysis demonstrated that three clock related genes (brain and muscle ARNT-like-1, BMAL1; circadian locomotor output cycles kaput, CLOCK; and cryptochrome-1, CRY1) and a melatonin rate-limiting enzyme related gene (arylalkylamine N-acetyltransferase, AANAT) were rhythmically expressed in the pineal gland of the 12L:12D group, but not in the 0L:24D group. Simultaneously, the light stimulation also increased the concentration of melatonin (MT), which was linked to hepatocyte proliferation and IGF-1 secretion in previous studies. Conclusions The 12L:12D monochromatic green light stimulation during incubation shortened hatching time without impairing hatching performance. Pineal gland’s early histological development and maturation of its rhythmic function were accelerated by the light stimulation. It may be the key organ in the photo-endocrine axis that regulates embryo development, and the potential mechanism could be through enhanced secretion of MT in the 12L:12D group which promotes the secretion of IGF-1.

Providing green light during incubation has been shown to accelerate the embryo development and shorten the hatching time in broilers. Few studies have concentrated on the exact effects on layer breeders in the aspects of hatching and posthatch performance. In this study, 4 strains of layer breeder eggs, namely White Leghorn, Rhode Island Red, Columbia Rock, and Barred Rock were used to assess the effects of monochromatic green light during embryogenesis on hatching performance, chick quality, and pubertal growth. Each strain of 600 eggs was incubated under photoperiods of either 12 h of light and 12 h of darkness (12L:12D, light group) or 0 h of light and 24 h of darkness (0L:24D, dark group) for 18 D, with 2 replicates for each treatment. The results showed hatch time, time reaching 90% hatch, and average hatch time were significantly shorter among the 4 strains in the light group (P 0.05). There was no significant difference in hatchability of fertile eggs, chick weight/egg weight, or chick quality among the 4-strain eggs between the light group and dark group (P > 0.05). There was no difference (P > 0.05) in posthatch BW between different light treatments of the 3 strains (White Leghorn, Columbia Rock, and Barred Rock), whereas the BW of Rhode Island Red was higher in light group than that of the dark group at 8 to 12 wk of age (P

The prevalence of crossed beaks ranging from 0.2 to 7.4% was documented in at least 12 chicken strains. Previous studies focused largely on candidate molecules, whereas the morphological observation was missing. This study reported a detailed phenotype and prevalence of crossed beaks based on morphological observation in nine thousand nine hundred 1-day-old female Beijing-You chicks. Affected chicks were classified into 2 categories based on the direction of the mandibular deformation: left and right. Each category was selected to sacrifice for the measurement of length, width, and thickness of the bilateral mandibular ramus (MR). The normal chicks were used as controls. Paraffin section was made for the bilateral MR of a crossed beak and a normal control for histology analysis. A total of 97 out of 9,900 chickens showed beak deformity including 71 crossed beaks (0.72%) and 26 side beaks (0.26%) for which the upper and lower beak were both bent in the same direction. There was no difference in the direction of the bend of the lower beak in crossed beaks (P > 0.05). The incidence of crossed beaks increased quickly from 0 to 56 d and no new incidence after 56 d. The angle of the crossed beaks was below 5° in the first week and had grown more severe with age until 56 d. The mandible structure showed that condyle served as a growth center for the MR extension. The short-side MR of crossed beaks was thicker than normal ones (P

Crossbreeding is normally applied to improve the economical traits of chickens. However, feed efficiency and its relationship with egg quality have rarely been explored in crossbreds. Herein, White Leghorn and Beijing You chickens were selected to generate purebreds (WW, YY) and reciprocal crossbreds (YW, WY), which were evaluated in terms of daily feed intake (DFI), feed conversion ratio (FCR), and residual feed intake (RFI) at 43 to 46 and 69 to 72 weeks of age, respectively. We found that WY was more efficient than YW in both laying periods. The correlation analysis showed that RFI was highly correlated with DFI (0.49 to 0.84) but unrelated to egg mass, and FCR was negatively correlated with egg mass (−0.77 to −0.43) in both purebreds and crossbreds. Moreover, RFI was not correlated with egg quality traits within each genetic group, except for the egg yolk ratio (0.27) in WW. FCR was negatively correlated with eggshell weight and thickness (−0.33 to −0.19) in WW and WY. Compared to FCR, selection for RFI could improve feed efficiency without significant changes in egg mass and quality in chickens. These findings provide new insights into the improvement of feed efficiency using rational parental lines in chicken crossbreeding.

Trichomoniasis gallinae (T. gallinae) is one of the most pathogenic parasites in pigeon, particularly in squabs. Oral cavity is the main site for the host-parasite interaction. Herein, we used RNA-sequencing technology to characterize lncRNA and mRNA profiles and compared transcriptomic dynamics of squabs, including four susceptible birds (S) from infected group, four tolerant birds (T) without parasites after T. gallinae infection, and three birds from uninfected group (N), to understand molecular mechanisms underlying host resistance to this parasite. We identified 29,809 putative lncRNAs and characterized their genomic features subsequently. Differentially expressed (DE) genes, DE-lncRNAs and cis/trans target genes of DE-lncRNAs were further compared among the three groups. The KEGG analysis indicated that specific intergroup DEGs were involved in carbon metabolism (S vs. T), metabolic pathways (N vs. T) and focal adhesion pathway (N vs. S), respectively. Whereas, the cis/trans genes of DE-lncRNAs were enriched in cytokine-cytokine receptor interaction, toll-like receptor signaling pathway, p53 signaling pathway and insulin signaling pathway, which play crucial roles in immune system of the host animal. This suggests T. gallinae invasion in pigeon mouth may modulate lncRNAs expression and their target genes. Moreover, co-expression analysis identified crucial lncRNA-mRNA interaction networks. Several DE-lncRNAs including MSTRG.82272.3, MSTRG.114849.42, MSTRG.39405.36, MSTRG.3338.5, and MSTRG.105872.2 targeted methylation and immune-related genes, such as JCHAIN, IL18BP, ANGPT1, TMRT10C, SAMD9L, and SOCS3. This implied that DE-lncRNAs exert critical influence on T. gallinae infections. The quantitative exploration of host transcriptome changes induced by T. gallinae infection broaden both transcriptomic and epigenetic insights into T. gallinae resistance and its pathological mechanism.

Crossed beaks have been observed in at least 12 chicken strains around the world, which severely impairs their growth and welfare. To explore the intrinsic factor causing crossed beaks, this study measured the length of bilateral mandibular ramus of affected birds, and investigated the genome-wide DNA methylation profiles of normal and affected sides of mandibular condyle. Results showed that the trait was caused by impaired development of unilateral mandibular ramus, which is extended through calcification of mandibular condyle. The methylation levels in the CG contexts were higher than that of CHG and CHH, with the highest methylation level of gene body region, followed by transcription termination sites and downstream. Subsequently, we identified 1,568 differentially methylated regions and 1,317 differentially methylated genes in CG contexts. Functional annotation analysis of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes showed that these genes were involved in bone mineralization and bone morphogenesis. Furthermore, by combining the WGBS and previous RNA-Seq data, 11 overlapped genes were regulated by both long non-coding RNA and DNA methylation. Among them, FIGNL1 is an important gene in calcification of mandibular condyle. Generally, because the affected genes play key roles in maintaining mandibular calcification, these changes may be pivotal factors of crossed beaks.

The 2 × 4 factorial experiment was designed to determine the effect of strain and photostimulation age on sexual maturity and reproductive performance of rooster breeders. A total of 96 White Leghorn (WL) and 120 Beijing You Chicken (BYC) roosters were randomly allocated to 4 treatments at 14 wk of age. The treatments represent photostimulation at 16, 18, 20, and 22 wk of age, respectively (PS16, PS18, PS20, and PS22), in both strains. Photostimulation was achieved by increasing the day length from 8L:16D to 14L:10D and by increasing lighting intensity from 10 lx to 80 lx. Three birds from each interaction were sacrificed to characterize the comb and testis weights at 4 time points: 1 d before photostimulation and 2, 4, and 6 wk after photostimulation. Semen quality and hatching performance with the semen of the experimental roosters were measured at 30 and 45 wk of age, respectively. Results showed that the testis weight of PS20 and PS22 in WL and BYC was 6.4- and 2.9-fold higher than that of PS18 before photostimulation, while testis weight of PS18 in both strains increased sharply after photostimulation. The diameter of seminiferous tubules increased in the photostimulated roosters as compared with the nonphotostimulated ones, and mature spermatozoa were produced 4 wk after photostimulation and at 20 wk of age for PS16. The WL had lower semen volume and total sperm count than BYC (P 0.05). In addition, semen quality traits were not affected by age at photostimulation (P > 0.05) in both strains. The fertility and hatching performance were not affected by strain or photostimulation age (P > 0.05). In summary, the sexual maturation of rooster breeders can be advanced by photostimulation at an early age, which does not lead to a difference in semen quality or hatching performance at adult stage.