Abstract:【Objective】To develop marker-assisted selection(MAS) technology of RYR1 gene in breeding of Pietrain pig populations, and improve pork quality in pig populations.【Method】PCR-RFLP assay was used to detect the allele frequency of RYR1 gene in 509 Pietrain pigs. The correlation between genotype and phenotype was analyzed using regression model. The correlation between allele frequency and phenotype was analyzed using the Bootstrap method.【Result】The predominant allele (N) frequency of RYR1 gene was 81.73% in the Pietrain pig population. The pigs with NN genotype had better performance in daily gain, the pigs with Nn genotype were better in backfat EBV, maternal and paternal indexes, and the pigs with nn genotype were better in limb trait. Breeding performance was in balance when n allele frequency was 19%. When n allele frequency was above 19%, the pigs had higher lean meat content, thinner backfat, and better body shape. When n allele frequency was below 19%, the pigs had higher growth rate.【Conclusion】When body shape, lean meat content, back fat thickness were more important goals for Pietrain pig breeding, it is suggested to increase n allele frequency in the population. When growth rate, anti-stress, and meat quality after slaughter are more important goals for breeding, it is suggested to purify the predominant allele (N) of RYR1 gene in the population.

Abstract:【Objective】To investigate the effects of dietary protein and energy levels on digestive enzyme activities in the jejunal fluid of Muscovy duck.【Method】A 3×3 factorial and completely randomized design was conducted. Totally 27 male Muscovy ducks were randomly divided into 9 groups with 3 ducks per group, and fed diets with 9 different compositions of energy and protein. Jejunal digesta was collected by fistula surgery and the activities of amylase, trypsin, chymotrypsin and lipase in jejunal fluid were determined.【Result】With the increase of energy level, trypsin activities in high and medium energy groups were significantly higher compared with low energy group(P<0.05), while chymotrypsin, amylase and lipase activities did not differ significantly. With the increase of crude protein level, trypsin activities in high and medium protein groups were significantly higher compared with low protein group(P<0.05), chymotrypsin activity in high protein group was significantly higher compared with low protein group(P<0.05), while amylase and lipase activities did not differ significantly. Protein and energy levels had no obvious interaction effect on digestive enzyme activities in the jejunal fluid of Muscovy duck.【Conclusion】Under this experimental condition, energy level has a significant effect on trypsin activity, and protein level has a significant effect on trypsin and chymotrypsin activities. Neither energy nor protein level has significant effect on amylase and lipase activities.

Abstract:【Objective】To explore the role of G protein in rabies virus (RABV) replication, reveal the reason for the difference of virus titer in neuroblastoma (NA) cells between the recombinant RABV Hep-dG with dual copy of G gene and the parental strain rHep-Flury, and lay a foundation for the study of RABV pathogenesis.【Method】The effects of G protein over-expression on transcriptions of IFN-β and related factors were examined by the virus binding assay, virus entry assay, fluorescence quantitative PCR, Western-blot and neutralizing antibody blocking assay.【Result】Hep-dG infection significantly increased the expression of IFN-β mRNA and activated the expression of the downstream factor STAT1 in NA cells. Under the low multiplicity of infection (MOI=0.01), the expression of IFN-β gene significantly increased at 24 h after Hep-dG infection and reached the highest level at 36 h. After the virus entered the cells, there were more viral Leader RNA and RIG-I mRNA, which were highly consistent with the expression of IFN-β mRNA. The block of IFN-β expression by neutralizing antibody in NA cells significantly increased the virus titer of Hep-dG in cell culture supernatant(P<0.01), which was 7.9 times before blocking. Meanwhile the virus titer of Hep-dG had no significant difference with the parental strain rHep-Flury. Compared with the negative control, transfection of 5 μg pH-G plasmid could stimulate the transcription of IFN-β(P<0.05), which showed that eukaryotic expression of RABV G protein could stimulate IFN-β transcription to a certain extent.【Conclusion】This study preliminarily reveals the cause and role of G protein in activating innate immune response. Over-expression of RABV G protein activates the RIG-I-mediated IFN-β pathway by promoting transcription of the viral Leader RNA, which in turn inhibits Hep-dG replication in NA cells and finally results in the lower virus titer in NA cells.

Abstract:【Objective】To investigate the antibacterial mechanism of thymol to methicillin-resistant Staphylococcus aureus (MRSA), and provide a reliable theoretical basis for the exploitation of high efficient and low toxic anti-MRSA medicine.【Method】The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of thymol to MRSA standard strain USA300 were determined via microbroth dilution method and colony counting method. Bacterium solution conductivity and DNA amount were detected to investigate the effect of thymol on USA300 cell membrane. SDS-PAGE was used to detect the effect of thymol on USA300 soluble protein synthesis. The ultra structure of USA300 cell treated by thymol was observed through transmission electron microscope. The effect of thymol on USA300 biofilm formation was investigated via crystal violet staining method.【Result】Thymol had definite inhibitory activity on USA300, both MIC and MBC of thymol to USA300 were 256 mg·L^-1. Compared with the control group, after treating the strain with 512 mg·L^-1 thymol for 1 h, the conductivity of bacterium solution was improved by 18.08%±1.80%, and DNA exosmosis amount increased by (123.40±8.06) mg·L^-1; after treating for 24 h, the soluble protein content of USA300 was reduced 68.20%±0.15%. Thymol destroyed cytoderm and cytomembrane of USA300, disturbed its normal binary fission, and inhibited biofilm formation at subinhibitory concentration.【Conclusion】Thymol can inhibit bacterium growth by changing its cytomembrane permeability and disturbing protein synthesis and normal binary fission, and depress biofilm formation at subinhibitory concentration in the premise of not affecting bacterium growth. Thymol has the potential of developing as anti-MRSA medicine.

Abstract:【Objective】To determine the effect of sulfadimidine (SM₂) applied with manure in soil on microbial community, and provide a basis for reasonably conducting environment quality evaluation and fertilization management of soil around the farm.【Method】Manure and soil around the farm that were not contaminated by antibiotics were collected to construct the manure-soil model. Different SM₂ adding dosages were setted, including the control group (0), low dosage group (5 μg·kg^–1), medium dosage group (500 μg·kg^–1) and high dosage group (5 000 μg·kg^–1), and the soil samples were collected on 1, 7, 14 and 50 days respectively after SM₂ application. Biolog technology and phospholipid fatty acid (PLFA) labelling were used to compare and analyze the capacities of carbon source utilization, and the structural and functional diversities of soil microbial communities in different treatments.【Result】The application of SM₂ improved the overall carbon source utilization capacity of soil microbial community. After applying SM₂ for 50 days, the utilization capacities of medium and high dodage groups to all carbon sources except esters were significantly stronger than those of the control group. The capacities of low dodage group utilizing all carbon sources after applying SM₂ for 7 days were obviously enhanced. The applications of medium and high SM₂ dosages might affect the propagation and quantity distribution of some dominant flora in soil community. With the extension of SM₂ application time, the responses of soil microbial community to SM₂ at different dosages was different. The quantity changes of Gram-positive bacterium, Gram-negative bacterium and fungi were significant, while the change of actinomycetes number was not obvious.【Conclusion】The application of SM₂ will affect the structural and functional diversities of soil microbial communities for a long time. The farm should dispose animal excrements in time to eliminate antibiotic residues, and reduce the ecological damages to soil environment.

Abstract:【Objective】To establish a reliable HPLC-MS/MS (High performance liquid chromatography-tandem mass spectrometry) method suitable for determing tildipirosin residues in swine tissues.【Method】Swine tissue samples, including muscle, liver, kidney and skin-fat were extracted with 0.1 mol·L^–1 KH₂PO₄ buffer solution. The supernatant fluids were enriched and purified using HLB solid-phase extraction column, and gradiently eluted by Phenomenex Luna Omega C18 liquid chromatography column. The analytes were then detected using triple-quadrupole mass spectrometry in positive electrospray ionization and multiple reaction monitoring (MRM) mode. The matrix-matched method was used to calibrate tildipirosin content.【Result】Tildipirosin contents presented good linear relationships (r²>0.99) with characteristicion peak area in the ranges of 25–2 400 ng·g^-1 in muscle, 25–2 500 ng·g^-1 in liver, 25–2 000 ng·g^-1 in kidney and 25–1 600 ng·g^-1 in skin-fat. All the limits of detection and quantitation in muscle, liver, kidney and skin-fat samples added tildipirosin were 10 and 25 ng·g^-1, respectively. The recovery experiments of tildipirosin in swine tissues were setted in four dosage levels, including limit of quantitation, 1/2 maximum residue limit (MRL), MRL and 2MRL, and the mean intra-batch recoveries of tildipirosin in all analytes ranged from 85.6% to 105.0%. The relative standard deviations of intra-batch and inter-batch recoveries were in the ranges of 2.3%–9.5% and 4.7%–7.6%, respectively.【Conclusion】The established method is simple, practicable, and with high sensitivity and specificity. It can be applied to determine tildipirosin residues in swine tissues.

Abstract:【Objective】To investigate the effects of different addition levels of maize straw on organic carbon pool of black soil with different organic carbon contents, and provide important references for improving the quality of degraded black soil and repairing with straw.【Method】Different amounts (0.5%, 1.5%, and 2.5%) of maize straw were added to black soils with two different organic carbon contents by outdoor culture method to study the content changes of total organic carbon (TOC), readily oxidizable organic carbon (ROC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC), light fraction organic carbon (LFOC), mineral-bound organic carbon (MOC), high fraction carbon soil (HFOC) and inert organic carbon (IOC), and correlations among each component of the soil.【Result】All three straw amounts applied increased the contents of TOC, ROC, MBC, DOC, POC, LFOC, MOC, and IOC in two black soils. The enhancing effects were more obvious on the soil with low organic carbon content than the soil with high organic carbon content. The HFOC contents of the two black soils decreased. All the components of soil organic carbon pool except LFOC and HFOC had highly significant positive correlations with TOC. Also the correlation relationships between ROC, MBC, DOC contents and POC content in each treatment were highly significant.【Conclusion】All three straw adding amounts have certain effects on the black soils with two kinds of organic carbon contents. The application of high straw adding amount can effectively enhance the carbon pool component contents of two soils, especially the soil with low organic carbon content. In the range of straw adding amount, the best treatment is mass ratio 2.5%.

Abstract:【Objective】To examine the effects of different organic loading rate (OLR) and effluent recirculation rate on acid and gas productions during the two-phase anaerobic digestion of food waste.【Method】The effects of acid and gas productions of the two-phase anaerobic digestion of food waste were investigated by setting different organic loading rate and reflux ratio.【Result】Effluent recirculation significantly increased the pH of acidogenic reactor and accelerated the acidification of food waste. The concentrations of volatile fatty acid (VFA) in the acidogenic reactors were 11 598.48, 12 998.41 and 14 967.64 mg·L^-1, increased by 9.06%, 22.23% and 40.74% compared with CK when the recirculation rate was 10%, 30% and 50% at the 11.33 g·L^-1·d^-1 of OLR (based on volatile solid content, the same below), respectively. Under the condition of non-recirculation, the optimum OLR of methanogenic reactor was 6.38 g·L^-1·d^-1, but when it enhanced to 8.50 g·L^-1·d^-1, the system showed acid suppression phenomenon. The reflux ratio of 50% could help the system buffer and stabilize. The average methane production under the reflux ratio of 50% was 486.14 mL·g^-1 (based on volatile solid content), which was 29.84%, 20.80% and 9.13% higher than those under the reflux ratios of 0% (CK), 10% and 30%, respectively.【Conclusion】During the two-phase anaerobic digestion process of food waste, the optimum OLR of the methanogenic phase is 6.38 g·L^-1·d^-1 when the biogas slurry is not refluxed, and the system will appear acid inhibition when the OLR continuously increases. The optimum OLR of methanogenic phase could be increased to 8.50 g·L^-1·d^-1 when biogas reflux ratio is 50%.

Abstract:【Objective】To determine the effects of polycyclic aromatic hydrocarbons (PAHs) stress on the growth of Chinese flowering cabbage (Brassica parachinensis), and explore the physiological toxicity of PAHs.【Method】The PAHs solution mixing naphthalene, phenanthrene, fluoranthene, benzopyrene and indenopyrene was applied to soil to stress the growth of B. parachinensis. The changes of malondialdehyde(MDA),H₂O₂ and proline contents and antioxidase activites in leaves of B. parachinensis were analyzed on the 10th, 17th, and 24th day after planting, and the growth was measured on the 24th day after planting.【Result】The plant height of B. parachinensis was increased by PAHs treatments, and it was highest under 10.0 mg·kg^-1 PAHs treatment. The treatments of 0.4 and 0.8 mg·kg^-1 PAHs had little effects on stem diameter of B. parachinensis, but had some promotions on individual plant fresh weight and root fresh weight. The stem diameter, individual plant fresh weight and root fresh weight of B. parachinensis were decreased by 2.0, 5.0 and 10.0 mg·kg^-1 PAHs treatments for different degrees. The contents of MDA, H₂O₂ and proline in leaves of B. parachinensis increased with the stress time and PAHs content increasing. With the PAHs content increasing, the activity of superoxide dismutase(SOD) increased, and the activities of peroxidase(POD), catalase(CAT) and ascorbic acid peroxidase(APX) increased firstly and then decreased.【Conclusion】Stress from low content of PAHs has little effect on the growth of B. parachinensis, while stress from high content of PAHs can inhibit plant normal growth as it decreases stem diameter, individual plant fresh weight and root fresh weight and also causes earlier blooming. B. parachinensis could alleviate the disadvantageous effects from increasing contents of H₂O₂ and MDA under PAHs stress by increasing proline content and antioxidant enzyme activities.

Abstract:【Objective】To understand the rules of starch accumulation during development of Chinese yam (Dioscorea spp.) tuber,and provide theoretical references for breeding and cultivation of Chinese yam with high yield and quality.【Method】Using ‘GH16’ as material, starch accumulation during development process of Chinese yam tuber was measured. The changes of tuber tissues, cells and starch grains were studied through paraffin sectioning. The key proteins related to tuber development were discovered by two-dimensional electrophoresis.【Result】There was no starch accumulation in early stage of tuber formation (April to May). In the early expansion stage (June), starch grains distributed uniformly in parenchyma cells. With the development of yam tuber, tuber cells and starch grains enlarged gradually, and starch accumulated rapidly. In the mid and late expansion stages (after September), substantial starch grains distributed near parenchyma cells around vascular bundle. In the late expansion stage, tuber cell size reached the maximum in November with cell longitudinal diameter and transverse diameter reaching 121.685 and 89.572 μm respectively, and starch accumulation reached the peak with longitudinal diameter of starch grain being up to 27.608 μm (December), and transverse diameter being up to 16.450 μm (November). There were 179 differentially expressed proteins to be found. Among them, Fifty-two proteins with relatively larger differences in expression were analyzed by mass spectra, and 31 differentially expressed proteins were identified. Most of them were enzymes related to sugar metabolism and starch synthesis, such as glucose 6-phosphate acid dehydrogenase, fructose-bisphosphatealdolase cytoplasmic isozyme-like, ATP synthetase alpha subunit, UTP-glucose-1-phosphate uridylyltransferase and phosphoglycerate kinase 1, and these were up-regulated after the early stage of tuber formation. Chinese yam tuber specific protein, Dioscorin, was accumulated in the late stage of tuber expansion.【Conclusion】The expansion of Chinese yam tuber is the results of cell division, cell amplification and starch accumulation. The main differentially expressed proteins during development of Chinese yam tuber play the key roles of sugar metabolism and starch synthesis.

Abstract:【Objective】To investigate responses of litterfall carbon (C) and nitrogen (N) fractions to atmospheric N deposition in a monsoon evergreen broad-leaved forest.【Method】Three levels of N addition, including low N (LN, 35 kg·hm^-2), medium N (MN, 70 kg·hm^-2) and high N (HN, 105 kg·hm^-2), were conducted for two years, with a control without extra N addition (CK). Fresh litterfall samples were collected in the dry and wet seasons, respectively. C and N fraction contents were analyzed.【Result】N additions significantly increased the contents of total organic carbon (TOC) and water-soluble organic carbon (WSOC) in the wet season, with the WSOC/TOC ratio presenting a rising trend. N additions did not significantly alter acid-insoluble fraction carbon (AIFC) content and its proportion to TOC, although a decreasing trend was observed compared with the control. Different N addition treatments did not significantly change the contents of litterfall total nitrogen (TN), water-soluble nitrogen (WSN) and acid-insoluble fraction nitrogen (AIFN). The proportions of WSN and AIFN to TN were not altered significantly either. The short-term N additions did not significantly affect litterfall C/N ratio and AIFC/AIFN ratio, but significantly increased WSOC/WSN ratio in the dry season.【Conclusion】The atmospheric N deposition promotes labile C accumulation and therefore is beneficial for litterfall decomposition to transfer nutrients into soil, which will further affect nutrient cycling in the tropical forest.

Abstract:【Objective】To investigate the effects of NaCl stress on element contents and accumulations of Hibiscus rosa-sinensis, Ixora chinensis, Schefflera arboricola and Cordyline fruticosa, and provide a scientific basis for nutrient management of plants under NaCl stress.【Method】The above four landscape plant species were selected as materials and treated by three NaCl concentrations (0, 0.3% and 0.6%) to analyze the contents and accumulations of Na, Cl, N, P, and K in these plants.【Result】The contents of Na, Cl, N, P, and K in different organs of above landscape plants ranged from 0.30 to 19.66, 0.12 to 25.79, 5.72 to 23.86, 0.92 to 2.86 and 6.77 to 26.67 g·kg^-1, respectively. NaCl stress greatly increased Na and Cl contents in different organs of four species. N contents in all organs of H. rosa-sinensis and I. chinensis significantly increased with the increase of NaCl stress concentration. N contents in all organs of S. arboricola and C. fruticosa, P contents in all organs and K contents in leaves and stems of four species varied irregularly. K contents in roots of four species decreased. NaCl stress increased Na accumulations in all organs of four species (except that in roots of S. arboricola), and Cl accumulations in all organs of H. rosa-sinensis, I. chinensis and C. fruticosa, and decreased N accumulations in all organs of four species except that in roots of H. rosa-sinensis, and P and K accumulations of four species. The change ranges of Na and Cl accumulations were greater than those of N, P and K under NaCl stress, and Na and Cl mainly accumulated in leaves and stems. The ratios of K⁺/Na⁺ in all plant organs decreased with the increase of NaCl stress concentration except that in roots of C. fruticosa. The decrease ranges of K⁺/Na⁺ ratio in leaves and roots of H. rosa-sinensis, S. arboricola and C. fruticosa were less than those in stems, while those in all organs of H. rosa-sinensis and S. arboricola were less compared with I. chinensis and C. fruticosa. 【Conclusion】In these four landscape plants, H. rosa-sinensis and S. arboricola have relatively stronger salt-resistance abilities.

Abstract:【Objective】To provide a basis for wastepaper recycling and create important economic, ecological and environmental benefits.【Method】Composite particleboard was manufactured using waste newspaper and wood particles of mixed wood species with adhesives under hot pressing. Effects of the addition amount of wastepaper, amount of urea formaldehyde resin (UF), and hot pressing parameters on physical and mechanical properties including the modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IBS) and thickness swelling rate (TSR) of composite particleboard were studied.【Result】The optimal manufacture parameters were 11% UF, 10% wastepaper and 1.0% self-made wax emulsion under 190℃ of hot pressing temperature and pressing 34 s·mm^-1. The formaldehyde emission from the manufactured composite particleboard was 0.002 4 mg·g^–1 using the perforator method, which was much lower than the threshold value of 0.009 0 mg·g^–1 for E1 level based on the GB 18580-2001 standard. The MOR, MOE and IBS were 20.43, 3 431 and 0.57 MPa respectively, and the TSR was 1.7%. These properties exceeded the requirements of P2-type particle board at dry condition according to GB 4897-2015 standard.【Conclusion】It is an effective way to utilize wastepaper and wood particles for producing composite particleboard.

Abstract:【Objective】To design a kind of trenching depth control system based on laser sensor,so as to solve the problem that it is difficult to adjust accurately the trenching depth of chain trencher.【Method】The laser triangular-reflecting displacement sensor was used to detect the trenching depth in real time, which was compared with the target value. The closed-loop control of trenching depth was realized by the control system making decision and driving hydraulic system and actuator. The field experiment was conducted to compare the control precision and stability before and after enabling the system.【Result】The result of static test showed that when the different values between the detection depth and the target depth were ±50 mm, the response time of the system were 0.19 and 0.31 s respectively, and the maximum control error was 3 mm. The field test showed that when the trenching depths were 200, 300 and 400 mm respectively at the speed of 3 km·h^-1, the control precision and stability for trenching depth of the chain trencher were improved after starting the control system. Compared with closing the system, the control precision and stability coefficients increased by 2.3% and 4.3% respectively after opening the system.【Conclusion】This control system responds quickly with a high control accuracy, and the control error satisfies the set requirements. The result provides a solution for controlling the trenching depth of the chain trencher.

Abstract:【Objective】To realize the rapid and nondestructive identification of rice sheath blight at the early stage using hyperspectral imaging technology, and establish the corresponding identification model.【Method】Healthy rice seedlings and rice seedlings infected with sheath blight were used as the research samples. A total of 360 hyperspectral curves of 180 samples were collected separately from leaves and canopy at the wavelength of 380 to 1 030 nm. After eliminating the obvious noise part, the spectra of rice samples were reserved at the wavelength of 440 to 943 nm, and the spectral curves were preprocessed with different treatments. Partial least squares-discriminant analysis (PLS-DA) was used to model different preprocessed spectra. The feature information was extracted from the original canopy spectral data using the MNF algorithm, and a linear discriminant analysis (LDA) model and a back-propagation neural net-work (BPNN) discriminant model were established based on the feature information.【Result】The prediction accuracy of PLS-DA model after preprocessing by standard normal variate transformation (SNV) was the highest (92.1%). The discriminant results of LAD and BPNN model based on feature information were superior to the PLS-DA discriminant model based on all bands. The BPNN model based on feature information from minimum noise fraction transformation had optimal results. The accuracies of the model set and prediction set were 99.1% and 98.4% respectively.【Conclusion】It is feasible to identify nondestructively rice sheath blight using hyperspectral imaging technology. Our research provides a new method for identifying rice sheath blight.

Abstract:【Objective】To enhance the effects of litchi fruit pericarp defect extraction and satisfy the accuracy requirements of quality detection and classification.【Method】A fully convolutional neural network was built up based on AlexNet (AlexNet-FCN) using Tensorflow framework, with ReLU as the activation function, Max-pooling as the down-sampling method and loss function of Softmax regression classifier as the optimization target. Mini-batch stochastic gradient descent (Mini-batch SGD) was used to optimize the model.【Result】When the model was converged, the intersection-over-union of dehiscent area (IoU_d) of litchi fruit cracking was 0.83 for the validation set, the intersection-over-union of brown area (IoU_b) was 0.60, and the intersection-over-union of both dehiscent and brown area (IoU_a) was 0.68. Compared with linear-support vector machine (SVM) and Naïve Bayes classifier, AlexNet-FCN had a stronger defect extraction ability.【Conclusion】Fully convolutional networks (FCN) have a good prospect for application of fruit pericarp defect extraction.

Abstract:【Objective】To realize non-contacting and low-cost pig contour extraction under the piggery scene. 【Method】We took individual pig in the real culture environment as the research object, and proposed a full convolutional neural network model based on the combination of VGG16 and UNET (VGG-UNET model). We adopted the batch processing method in this model to transfer and learn the parameters of VGG16 model. We achieved semantic level segmentation of the image by combining the deep abstract feature and shallow feature in depth via building the duplicate channel. The model was verified on 1 815 datasets of 30 Large White×Landrace pigs. Comparison experiments of different batch sizes were performed, and three groups with the best results were selected to explore the relationship between batch size and the evaluation index.【Result】Through comparison experiments on datasets, the pixel accuracy and mean intersection-over-union of VGG-UNET model were 94.32% and 86.60% respectively, which were 0.89% and 1.67% higher than those of the UNET model. The experiments showed different relationship between the change of different index values and batch size. Batch size had no obvious impact on the convergence rate of the model under this experimental environment. Through comprehensive analysis of PA and MIoU index values under different batch sizes, the VGG-UNET model showed the highest stability and robustness, and it was found to be the best when the batch size was 8.【Conclusion】The VGG-UNET model is effective for accurate and stable extraction of pig contour. Such segmentation result is relatively complete and the model has higher robustness, which can provide a reference for follow-up identification of individual pigs.

Abstract:【Objective】To screen the best mathematical model of laying curves for layer breeders in layer breeder houses installed natural mating cages with four overlap tiers.【Method】All the experimental Hy-Line Brown parent stock layers were fed in the closed layer breeder houses installed natural mating cages with four overlap tiers, and laying records from the 19th to 61th week were collected. The laying rates were fitted using Wood model, McMillan model and Yangning model respectively, and their fitting effects were compared.【Result】All three mathematical models were available for laying rate fitting. The R values of Yangning model, McMillan model and Wood model were 0.997 87, 0.964 63 and 0.764 57 respectively, which showed that Yangning model was the best, followed by McMillan model and Wood model successively. Yangning model was more suitable for actually observed data, and the suitability degree was 1.160 37×10²⁶ times of McMillan model, 1.599 31×10⁴² times of Wood model. The laying rate curves showed different characteristics in different periods. Compared with the standard laying rates of Hy-Line Brown stock layers in the same age, the experimental laying rates of layer breeders during early rising stage were lower.【Conclusion】Yangning model is most suitable for laying rate fitting of layer breeders in layer breeder houses installed natural mating cages with four overlap tiers. The feeding management should be carried out scientifically and reasonably according to fitting model and egg production curve to maximize the benefits in production process.