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Based on erosion coupon tests, a sand erosion model for 17-4PH steel was developed. The developed erosion model was validated against the results of compressor erosion tests from a generic rig and from other researchers. A high-fidelity computational fluid dynamics (CFD) model of the test rig was built, a user-defined function was developed to implement the erosion model into the ANSYS CFD software, and the turbulent, two-phase flow-field in multiple reference frames was solved. The simulation results are consistent with the test results from the compressor rig and with experimental findings from other researchers. Specifically, the sand erosion blunts the leading edge, sharpens the trailing edge and increases pressure-surface roughness. The comparisons between the experimental observations and numerical results as well as a quantitative comparison with three other sand erosion models indicate that the developed sand erosion model is adequate for erosion prediction of engine components made of 17-4PH steel.
Frequent freezing injury greatly influences winter wheat production; thus, effective prevention and a command of agricultural production are vital. The freezing injury monitoring method integrated with ‘3S’ (geographic information systems (GIS), global positioning system (GPS) and remote sensing (RS)) technology has an unparalleled advantage. Using HuanJing (HJ)-1A/1B satellite images of a winter wheat field in Shanxi Province, China plus a field survey, crop types and winter wheat planting area were identified through repeated visual interpretations of image information and spatial analyses conducted in GIS. Six vegetation indices were extracted from processed HJ-1A/1B satellite images to determine whether the winter wheat suffered from freezing injury and its degree of severity and recovery, using change vector analysis (CVA), the freeze injury representative vegetation index and the combination of the two methods, respectively. Accuracy of the freezing damage classification results was verified by determining the impact of freezing damage on yield and quantitative analysis. The CVA and the change of normalized difference vegetation index (ΔNDVI) monitoring results were different so a comprehensive analysis of the combination of CVA and ΔNDVI was performed. The area with serious freezing injury covered 0.9% of the total study area, followed by the area of no freezing injury (3.5%), moderate freezing injury (10.2%) and light freezing injury (85.4%). Of the moderate and serious freezing injury areas, 0.2% did not recover; 1.2% of the no freezing injury and light freezing injury areas showed optimal recovery, 15.6% of the light freezing injury and moderate freezing injury areas showed poor recovery, and the remaining areas exhibited general recovery.
This study aimed to review the evidence base regarding cognitive impairment and the development of dementia in patients with very late-onset schizophrenia-like psychosis (VLOSLP).
We conducted a systematic literature search of PubMed, PsycINFO and Web of Science according to Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines. Two reviewers independently screened records first by title and abstract and then by full text, resolving differences after each stage. Selected studies were assessed for quality using the GRADE system, and data on study design, participants, cognitive ability and rates of developing dementia were extracted and synthesised.
Seventeen publications were identified for review. They were generally poor in quality and heterogenous in design. VLOSLP patients were found to have impaired global cognition compared to non-psychotic controls, but no difference was found between VLOSLP patients and aged early-onset schizophrenia (EOS) patients. No single cognitive domain was consistently affected. Patients with VLOSLP demonstrated significantly higher rates of dementia diagnosis (ranging from 4.4% over 3 years to 44.4% over 15 years) than controls, but no difference was found between VLOSLP patients and aged EOS patients.
VLOSLP may not necessarily predict cognitive decline, but few studies have adequately investigated cohorts on a longitudinal basis. Heterogeneity between and within cohorts and varying selection criteria compromise the clinical generalisability of studies investigating the association between VLOSLP and neurodegenerative disease. Further studies on the clinical presentation, cognitive profile and neuropathology of VLOSLP with comparison to EOS/late-onset schizophrenia (LOS) and neurodegenerative disease are needed to better inform the diagnosis and management of VLOSLP.
To eliminate the effect of ocean currents for optimal path planning for unmanned underwater vehicles (UUVs) in the underwater environment, an intelligent algorithm is designed and proposed in this paper. The algorithm consists of two parts: an artificial potential field-based algorithm that derives the shortest path and avoids collision accidents; and an adjusting function that eliminates the effect of ocean currents. The planning results of the intelligent algorithm are presented in detail, and compared with the conventional algorithm that does not consider the effect of currents. The effectiveness of the optimised path planning method given in this paper is proved.
Particulate deposits in aero-engine turbines change the profile of blades, increase the blade surface roughness and block internal cooling channels and film cooling holes, which generally leads to the degradation of aerodynamic and cooling performance. To reveal particle deposition effects in the turbine, unsteady simulations were performed by investigating the migration patterns and deposition characteristics of the particle contaminant in a one-stage, high-pressure turbine of an aero-engine. Two typical operating conditions of the aero-engine, i.e. high-temperature take-off and economic cruise, were discussed, and the effects of particle size on the migration and deposition of fly-ash particles were demonstrated. A critical velocity model was applied to predict particle deposition. Comparisons between the stator and rotor were made by presenting the concentration and trajectory of the particles and the resulting deposition patterns on the aerofoil surfaces. Results show that the migration and deposition of the particles in the stator passage is dominated by the flow characteristics of fluid and the property of particles. In the subsequential rotor passage, in addition to these factors, particles are also affected by the stator–rotor interaction and the interference between rotors. With higher inlet temperature and larger diameter of the particle, the quantity of deposits increases and the deposition is distributed mainly on the Pressure Side (PS) and the Leading Edge (LE) of the aerofoil.
To improve the endurance performance of long-endurance Unmanned Aerial Vehicles (UAVs), a smart morphing method to adjust the UAV and flight mode continuously during flight is proposed. Using this method as a starting point, a smart morphing long-endurance UAV design is conducted and the resulting improvement in the endurance performance studied. Firstly, the initial overall design of the smart morphing long-endurance UAV is carried out, then the morphing form is designed and various control parameters are selected. Secondly, based on multi-agent theory, an architecture for the smart morphing control system is built and the workflow of the smart morphing control system is planned. The morphing decision method is designed in detail based on the particle swarm optimisation algorithm. Finally, a simulation of the smart morphing approach in the climb and cruise stages is carried out to quantitatively verify the improvement in the endurance performance. The simulation results show that the smart morphing method can improve the cruise time by 4.1% with the same fuel consumption.
A variable annuity (VA) is an equity-linked annuity that provides investment guarantees to its policyholder and its contributions are normally invested in multiple underlying assets (e.g., mutual funds), which exposes VA liability to significant market risks. Hedging the market risks is therefore crucial in risk managing a VA portfolio as the VA guarantees are long-dated liabilities that may span decades. In order to hedge the VA liability, the issuing insurance company would need to construct a hedging portfolio consisting of the underlying assets whose positions are often determined by the liability Greeks such as partial dollar Deltas. Usually, these quantities are calculated via nested simulation approach. For insurance companies that manage large VA portfolios (e.g., 100k+ policies), calculating those quantities is extremely time-consuming or even prohibitive due to the complexity of the guarantee payoffs and the stochastic-on-stochastic nature of the nested simulation algorithm. In this paper, we extend the surrogate model-assisted nest simulation approach in Lin and Yang [(2020) Insurance: Mathematics and Economics, 91, 85–103] to efficiently calculate the total VA liability and the partial dollar Deltas for large VA portfolios with multiple underlying assets. In our proposed algorithm, the nested simulation is run using small sets of selected representative policies and representative outer loops. As a result, the computing time is substantially reduced. The computational advantage of the proposed algorithm and the importance of dynamic hedging are further illustrated through a profit and loss (P&L) analysis for a large synthetic VA portfolio. Moreover, the robustness of the performance of the proposed algorithm is tested with multiple simulation runs. Numerical results show that the proposed algorithm is able to accurately approximate different quantities of interest and the performance is robust with respect to different sets of parameter inputs. Finally, we show how our approach could be extended to potentially incorporate stochastic interest rates and estimate other Greeks such as Rho.
Phytase has long been used to decrease the inorganic phosphorus (Pi) input in poultry diet. The current study was conducted to investigate the effects of Pi supplementation on laying performance, egg quality and phosphate–calcium metabolism in Hy-Line Brown laying hens fed phytase. Layers (n = 504, 29 weeks old) were randomly assigned to seven treatments with six replicates of 12 birds. The corn–soybean meal-based diet contained 0.12% non-phytate phosphorus (nPP), 3.8% calcium, 2415 IU/kg vitamin D3 and 2000 FTU/kg phytase. Inorganic phosphorus (in the form of mono-dicalcium phosphate) was added into the basal diet to construct seven experimental diets; the final dietary nPP levels were 0.12%, 0.17%, 0.22%, 0.27%, 0.32%, 0.37% and 0.42%. The feeding trial lasted 12 weeks (hens from 29 to 40 weeks of age). Laying performance (housed laying rate, egg weight, egg mass, daily feed intake and feed conversion ratio) was weekly calculated. Egg quality (egg shape index, shell strength, shell thickness, albumen height, yolk colour and Haugh units), serum parameters (calcium, phosphorus, parathyroid hormone, calcitonin and 1,25-dihydroxyvitamin D), tibia quality (breaking strength, and calcium, phosphorus and ash contents), intestinal gene expression (type IIb sodium-dependent phosphate cotransporter, NaPi-IIb) and phosphorus excretion were determined at the end of the trial. No differences were observed on laying performance, egg quality, serum parameters and tibia quality. Hens fed 0.17% nPP had increased (P < 0.01) duodenum NaPi-IIb expression compared to all other treatments. Phosphorus excretion linearly increased with an increase in dietary nPP (phosphorus excretion = 1.7916 × nPP + 0.2157; R2 = 0.9609, P = 0.001). In conclusion, corn–soybean meal-based diets containing 0.12% nPP, 3.8% calcium, 2415 IU/kg vitamin D3 and 2000 FTU/kg phytase would meet the requirements for egg production in Hy-Line Brown laying hens (29 to 40 weeks of age).
This study aimed to investigate the clinical characteristics and to analyse the epidemiological features of coronavirus disease 2019 (COVID-19) patients during convalescence. In this study, we enrolled 71 confirmed cases of COVID-19 who were discharged from hospital and transferred to isolation wards from 6 February to 26 March 2020. They were all employees of Zhongnan Hospital of Wuhan University or their family members of which three cases were <18 years of age. Clinical data were collected and analysed statistically. Forty-one cases (41/71, 57.7%) comprised medical faculty, young and middle-aged patients (aged ⩽60 years) accounted for 81.7% (58/71). The average isolation time period for all adult patients was 13.8 ± 6.1 days. During convalescence, RNA detection results of 35.2% patients (25/71) turned from negative to positive. The longest RNA reversed phase time was 7 days. In all, 52.9% of adult patients (36/68) had no obvious clinical symptoms, and the remaining ones had mild and non-specific clinical symptoms (e.g. cough, sputum, sore throat, disorders of the gastrointestinal tract etc.). Chest CT signs in 89.7% of adult patients (61/68) gradually improved, and in the others, the lesions were eventually absorbed and improved after short-term repeated progression. The main chest CT manifestations of adult patients were normal, GGO or fibre streak shadow, and six patients (8.8%) had extrapulmonary manifestations, but there was no significant correlation with RNA detection results (r = −0.008, P > 0.05). The drug treatment was mainly symptomatic support therapy, and antibiotics and antiviral drugs were ineffective. It is necessary to re-evaluate the isolation time and standard to terminate isolation for discharged COVID-19 patients.
Antibiotics are designed to affect gut microbiota and subsequently gut homeostasis. However, limited information exists about short- and long-term effects of early antibiotic intervention (EAI) on gut homeostasis (especially for the small intestine) of pigs following antibiotic withdrawal. We investigated the impact of EAI on specific bacterial communities, microbial metabolites and mucosal immune parameters in the small intestine of later-growth-stage pigs fed with diets differing in CP levels. Eighteen litters of piglets were fed creep feed with or without antibiotics from day 7 to day 42. At day 42, pigs within each group were offered a normal- or low-CP diet. Five pigs per group were slaughtered at days 77 and 120. At day 77, EAI increased Enterobacteriaceae counts in the jejunum and ileum and decreased Bifidobacterium counts in the jejunum and ileum (P < 0.05). Moreover, tryptamine, putrescine, secretory immunoglobulin (Ig) A and IgG concentrations in the ileum and interleukin-10 (IL-10) mRNA and protein levels in the jejunum and ileum were decreased in pigs with EAI (P < 0.05). At day 120, EAI only suppressed Clostridium cluster XIVa counts in the jejunum and ileum (P < 0.05). These results suggest that EAI has a short-term effect on specific bacterial communities, amino acid decarboxylation and mucosal immune parameters in the small intestine (particularly in the ileum). At days 77 and 120, feeding a low-CP diet affected Bifidobacterium, Clostridium cluster IV, Clostridium cluster XIVa and Enterobacteriaceae counts in the jejunum or ileum (P < 0.05). Moreover, feeding a low-CP diet increased the concentrations of Igs in the jejunum and decreased pro-inflammatory cytokines levels in the jejunum and ileum (P < 0.05). At day 120, feeding a low-CP diet increased short-chain fatty acid concentrations, reduced ammonia and spermidine concentrations and up-regulated genes related to barrier function in the jejunum and ileum (P < 0.05). These results suggest that feeding a low-CP diet changes specific bacterial communities and intestinal metabolite concentrations and modifies mucosal immune parameters. These findings contribute to our understanding on the duration of the impact of EAI on gut homeostasis and may provide basis data for nutritional modification in young pigs after antibiotic treatment.
Distributed real-time avionics networks have been subjected to a great evolution in terms of functionality and complexity. A direct consequence of this evolution is a continual growth of data exchange. AFDX standardised as ARINC 664 is chosen as the backbone network for those distributed real-time avionics networks as it offers high throughput and does not require global clock synchronisation. For certification reasons and engineering research, a deterministic upper bound of the end-to-end transmission delay for packets of each flow should be guaranteed. The Forward Approach (FA) is proposed for the computation of the worst-case end-to-end transmission delay. This approach iteratively estimates the maximum backlog (amount of the pending packets) in each visited switch along the transmission path, and the worst-case end-to-end transmission delay can be computed. Although it is pessimistic (overestimated), the Forward Approach can provide a tighter upper bound of the end-to-end transmission delay while considering the serialisation effect. Recently, our research finds the computation of the serialisation effect might induce an optimistic (underestimated) upper bound. In this paper, we analyse the pessimism in the Forward Approach and the optimism induced by the computation of the serialisation effect, and then we provide a new computation of the serialisation effect. We compare this new computation with the original one, the experiments show that the new computation reduces the optimism and the upper bound of the end-to-end transmission delay can be computed more accurately.
Studies revealed that prenatal stress (PS) may increase the vulnerability to depression in their offspring, and ERK-CREB signal system might play a role in its mechanism.
Objectives and aims
The present study investigated the effect of MK-801 on depressive-like behavior and its impacts on ERK2, CREB, Bcl-2 mRNA expression in PS female rat offspring.
The pregnant rats were randomly divided into three groups, the control group (Con) was left undisturbed, the PS-saline group (PS-saline) and the PS-MK-801 group (PS-MK-801) were subjected to restraint stress on days 14–20 of pregnancy three times daily for 45 min, and received an i.p. administration of saline or MK-801(sigma, 0.2 mg/kg) 30 min before the first stress respectively. Forced swimming test was undertaken to assess depressive-like behavior in one month female offspring. ERK2, CREB, Bcl-2 mRNA in the hippocampus, frontal cortex, and striatum were detected by RT-PCR.
PS-saline spent significantly more immobile time compared to Con and PS-MK-801 (P < 0.05). ERK2 and CREB mRNA expression in hippocampus and frontal cortex was significantly decreased in PS-saline compared to Con and PS-MK-801 (P < 0.05), while in striatum CREB mRNA expression in PS-saline was lower than Con (P < 0.05). Bcl-2 mRNA expression in hippocampus and striatum was significantly decreased in PS-saline (P < 0.05), and in frontal cortex, its expression was significantly lower in PS-saline and PS-MK-801 (P < 0.05).
PS may suppress ERK-CREB signal pathway in female offspring rats, which could be partly prevented by MK- 801. (Supported by National Natural Science Foundation of China, No: 30970952).
Current available antidepressants exhibit low remission rate with a long response lag time. Growing evidence has demonstrated acute sub-anesthetic dose of ketamine exerts rapid, robust, and lasting antidepressant effects. However, a long term use of ketamine tends to elicit its adverse reactions. The present study aimed to investigate the antidepressant-like effects of intermittent and consecutive administrations of ketamine on chronic unpredictable mild stress (CUMS) rats, and to determine whether ketamine can redeem the time lag for treatment response of classic antidepressants. The behavioral responses were assessed by the sucrose preference test, forced swimming test, and open field test. In the first stage of experiments, all the four treatment regimens of ketamine (10 mg/kg ip, once daily for 3 or 7 consecutive days, or once every 7 or 3 days, in a total 21 days) showed robust antidepressant-like effects, with no significant influence on locomotor activity and stereotype behavior in the CUMS rats. The intermittent administration regimens produced longer antidepressant-like effects than the consecutive administration regimens and the administration every 7 days presented similar antidepressant-like effects with less administration times compared with the administration every 3 days. In the second stage of experiments, the combination of ketamine (10 mg/kg ip, once every 7 days) and citalopram (20 mg/kg po, once daily) for 21 days caused more rapid and sustained antidepressant-like effects than citalopram administered alone. In summary, repeated sub-anesthestic doses of ketamine can redeem the time lag for the antidepressant-like effects of citalopram, suggesting the combination of ketamine and classic antidepressants is a promising regimen for depression with quick onset time and stable and lasting effects.
Ketamine exerts fast acting, robust, and lasting antidepressant effects in a sub-anesthetic dose, however, the underlying mechanisms are still not fully elucidated. Recent studies have suggested that ketamine's antidepressant effects are probably attributed to the activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. The present study aimed to observe the effects of AMPA receptor modulators on mammalian target of rapamycin (mTOR) and brain-derived neurotrophic factor (BDNF) expression during the procedure of ketamine exerting antidepressant effects. Therefore, we pretreated rats with NBQX, an AMPA receptor antagonist, or CX546, an AMPA receptor agonist, and subsequently observed the immobility time during the forced swimming test (FST) and the hippocampal and prefrontal cortical levels of mTOR and BDNF. The results showed ketamine decreased the immobility time of rats during the FST and increased the hippocampal and prefrontal cortical mTOR and BDNF. NBQX pretreatment significantly increased the immobility time and decreased the levels of mTOR and BDNF when compared with vehicle 1 (DMSO) pretreatment. CX546 pretreatment significantly decreased the immobility time and increased the levels of mTOR and BDNF when compared with vehicle 2 (DMSO + ethanol) pretreatment. Our results suggest ketamine-induced antidepressant effects are associated with AMPA receptors-mediated upregulation of mTOR and BDNF in rat hippocampus and prefrontal cortex.
Recently, a triple-network model suggested the abnormal interactions between the executive-control network (ECN), default-mode network (DMN) and salience network (SN) are important characteristics of addiction, in which the SN plays a critical role in allocating attentional resources toward the ECN and DMN. Although increasing studies have reported dysfunctions in these brain networks in Internet gaming disorder (IGD), interactions between these networks, particularly in the context of the triple-network model, have not been investigated in IGD. Thus, we aimed to assess alterations in the inter-network interactions of these large-scale networks in IGD, and to associate the alterations with IGD-related behaviors.
DMN, ECN and SN were identified using group-level independent component analysis (gICA) in 39 individuals with IGD and 34 age and gender matched healthy controls (HCs). Then alterations in the SN-ECN and SN-DMN connectivity, as well as in the modulation of ECN versus DMN by SN, using a resource allocation index (RAI) developed and validated previously in nicotine addiction, were assessed. Further, associations between these altered network coupling and clinical assessments were also examined.
Compared with HCs, IGD had significantly increased SN-DMN connectivity and decreased RAI in right hemisphere (rRAI), and the rRAI in IGD was negatively associated with their scores of craving.
These findings suggest that the deficient modulation of ECN versus DMN by SN might provide a mechanistic framework to better understand the neural basis of IGD and might provide novel evidence for the triple-network model in IGD.
Childhoods in urban or rural environments may differentially affect risk for neuropsychiatric disorders. Here, we leveraged on dramatic urbanization and rural-urban migration since the 1980s in China to explore the hypothesis that rural or urban childhoods may differentially influence memory processing and neural responses to neutral and aversive stimuli.
Explore the underlying mechanisms of childhood environment effect on brain function and neuropsychiatric risk.
We examined 420 adult subjects with similar current socioeconomic status and living in Beijing, China, but with differing rural (n = 227) or urban (n = 193) childhoods. In an episodic memory paradigm scanned in a 3 T GE MRI, subjects viewed blocks of neutral or aversive pictures in the encoding and retrieval sessions.
Episodic memory accuracy for neutral stimuli was less than for aversive stimuli (P < 0.001). However, subjects with rural childhoods apparently performed less accurately for memory of aversive but not neutral stimuli (P < 0.01). In subjects with rural childhoods, there was relatively increased engagement of bilateral striatum at encoding, increased engagement of bilateral hippocampus at retrieval of neutral and aversive stimuli, and increased engagement of amygdala at aversive retrieval (P < 0.05 FDR corrected, cluster size > 50).
Rural or urban childhoods appear associated with physiological and behavioural differences, particularly in the neural processing of aversive episodic memory at medial temporal and striatal brain regions. It remains to be explored the extent to which these effects relate to individual risk for neuropsychiatric or stress-related disorders.
Disclosure of interest
The authors have not supplied their declaration of competing interest.
Large prospective observational studies have cast doubt on the common assumption that endovascular thrombectomy (EVT) is superior to intravenous thrombolysis for patients with acute basilar artery occlusion (BAO). The purpose of this study was to retrospectively review our experience for patients with BAO undergoing EVT with modern endovascular devices.
All consecutive patients undergoing EVT with either a second-generation stent retriever or direct aspiration thrombectomy for BAO at our regional stroke center from January 1, 2013 to March 1, 2019 were included. The primary outcome measure was functional outcome at 1 month using the modified Rankin Scale (mRS) score. Multivariable logistic regression was used to assess the association between patient characteristics and dichotomized mRS.
A total of 43 consecutive patients underwent EVT for BAO. The average age was 67 years with 61% male patients. Overall, 37% (16/43) of patients achieved good functional outcome. Successful reperfusion was achieved in 72% (31/43) of cases. The median (interquartile range) stroke onset to treatment time was 420 (270–639) minutes (7 hours) for all patients. The procedure-related complication rate was 9% (4/43). On multivariate analysis, posterior circulation Alberta stroke program early computed tomography score and Basilar Artery on Computed Tomography Angiography score were associated with improved functional outcome.
EVT appears to be safe and feasible in patients with BAO. Our finding that time to treatment and successful reperfusion were not associated with improved outcome is likely due to including patients with established infarcts. Given the variability of collaterals in the posterior circulation, the paradigm of utilizing a tissue window may assist in patient selection for EVT. Magnetic resonance imaging may be a reasonable option to determine the extent of ischemia in certain situations.
The development of digestive organs and the establishment of gut microbiota in pullets play an important role throughout life. This study was conducted to investigate the effects of Bacillus subtilis (BS) on growth performance, intestinal function and gut microbiota in pullets from 0 to 6 weeks of age. Hy-line Brown laying hens (1-day-old, n = 504) were randomly allotted into four diets with a 2 × 2 factorial design: (1) basal diet group (control); (2) antibiotics group (AGP), the basal diet supplemented with 20 mg/kg Bacitracin Zinc and 4 mg/kg Colistin Sulphate; (3) BS group, the basal diet supplemented with 500 mg/kg BS and (4) mixed group, the basal diet supplemented with both AGP and BS. As a result, when BS was considered the main effect, BS addition (1) reduced the feed conversion ratio at 4 to 6 weeks (P < 0.05); (2) decreased duodenal and jejunal crypt depth at 3 weeks; (3) increased the villus height : crypt depth (V : C) ratio in the duodenum at 3 weeks and jejunal villus height at 6 weeks and (4) increased sucrase mRNA expression in the duodenum at 3 weeks as well as the jejunum at 6 weeks, and jejunal maltase and aminopeptidase expression at 3 weeks. When AGP was considered the main effect, AGP supplementation (1) increased the V : C ratio in the ileum at 3 weeks of age; (2) increased sucrase mRNA expression in the duodenum at 3 weeks as well as the ileum at 6 weeks, and increased maltase expression in the ileum. The BS × AGP interaction was observed to affect average daily feed intake at 4 to 6 weeks, and duodenal sucrase and jejunal maltase expression at 3 weeks. Furthermore, dietary BS or AGP addition improved caecal microbial diversity at 3 weeks, and a BS × AGP interaction was observed (P < 0.05) for the Shannon and Simpson indexes. At the genus level, the relative abundance of Lactobacillus was found to be higher in the mixed group at 3 weeks and in the BS group at 6 weeks. Moreover, Anaerostipes, Dehalobacterium and Oscillospira were also found to be dominant genera in pullets with dietary BS addition. In conclusion, BS could improve intestinal morphology and change digestive enzyme relative expression and caecum microbiota, thereby increasing the efficiency of nutrient utilization. Our findings suggested that BS might have more beneficial effects than AGP in the study, which would provide theoretical evidence and new insight into BS application in layer pullets.