Guangdong Journal of Animal and Veterinary Science

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Effects of Crude crude fat Level on Growth，Body Composition，Serum enzyme activity and Antioxidant Capacity of Procypris merus

XIE Yutong, MO Wenyan, CHEN Bing, CAO Junming, LI Shiyang, WANG Guoxia

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 1-7. DOI: 10.19978/j.cnki.xmsy.2023.01.01

Abstract （260）

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A 63?day feeding trial was conducted to investigate the effects of different crude lipid levels on growth performance，body composition and serum biochemical indices of Procypris Merus，and to explore the optimal protein requirements. A total of 525 juvenile carp with an average body weight of（4.41±0.01）g were randomly divided into 5 groups with 3 replicates per group and 35 fish per replicate. Five isonitrogenous diets were formulated with 6%、8%、 10%、12% and 14% crude lipid levels. The results showed that with dietary crude lipid level increasing，the feed conversion ratio in 10%，12% and 14% groups was significantly lower than that in 6% group（P<0.05）；Protein efficiency ratio in 10%，12% and 14% groups was significantly higher than that in 6% groups（P<0.05）；weight gain rate and specific growth rate had no significant effects（P>0.05）. The condition factor of 14% was significantly higher than that of other groups（P<0.05）；the Viscerosomatic index and Hepatosomatic index had no significant change（P> 0.05）. As dietary crude lipid level increasing，whole body crude lipid content showed an increasing trend（P<0.05）， and that of 12% and 14% was significantly higher than that of other groups；the water content of 14% was significantly lower than that of other groups（P<0.05），the contents of crude protein and ash in whole fish had no significant change （P>0.05）. With the increase of crude lipid level，serum glutamic oxalacetic transaminase was decreased（P<0.05）， 6% was significantly higher than that of other groups，albumin/globulin was firstly increased and then decreased（P< 0.05），and 12% was significantly higher than that of 14% group. There were no significant differences in the contents of amylase，protease and trypsin among different levels of fat groups（P>0.05）. There were no significant differences in total antioxidant capacity，superoxide dismutase activity and alkaline phosphatase in serum and liver among all groups （P>0.05）. There were no significant differences in blood glucose，triglyceride，cholesterol，albumin，globulin and total protein among different levels（P>0.05）. In conclusion，the appropriate dietary fat level can improve feed utilization rate，increase fish body fat content，improve liver function，without affecting digestive enzyme activity and fish body health.Combined with economic benefits，the recommended dietary crude lipid level is 10%.

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Performance comparative analysis of reciprocal cross progenies between dwarf yellow chickens and three normal type yellow chickens

ZENG Xianjun ，ZHANG Xiquan ，ZOU Yanni ，CHEN Jie ，HE Shizi

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 8-14. DOI: 10.19978/j.cnki.xmsy.2023.01.02

Abstract （356）

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The study on effects of Callicarpa Nudiflora Hook Granules on Blood Physiological and Biochemical Indexes of Target Animal Dogs

JI Yikuan, ZOU Daofu, LI Meidi

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 15-18. DOI: 10.19978/j.cnki.xmsy.2023.01.03

Abstract （358）

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This study aimed to evaluate the effect of Callicarpa Nudiflora Hook. et Am. granules on the blood physiological and biochemical indexes of target animal dogs. A total of 20 Chinese pastoral dogs were divided into 4 groups，with 5 dogs in each group. Dogs in the control group were fed a basal diet，and others in experiment groups were fed basal diet supplemented 0.1 g/kg BW and 0.3 g/kg BW Callicarpa Nudiflora Hook. et Am. Granules， respectively. The experiment lasted for 10 days. The clinical signs，body weight，and blood physiology and biochemistry of dogs were evaluated. The results showed that the clinical signs of the experimental dogs were normal after oral administration of different doses of Callicarpa Nudiflora Hook. et Am. Granules，and there was no obvious effect. There was no significant difference in the main blood physiological and biochemical indexes between the test group and the blank control group（P>0.05）. The results showed that Callicarpa Nudiflora Hook. granules had no significant effect on the clinical signs，body weight，and blood physiological and biochemical indexes of the experimental dogs.

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Effect of fermented soybean meal on the growth performance of California perch

GUO Weigan ，YUAN Minggui ，XIANG Rong ，SUN Kaihui ，WANG Xiaoshan ，TANG Xinggang

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 19-23. DOI: 10.19978/j.cnki.xmsy.2023.01.04

Abstract （306）

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This study aimed to investigated the effects of dietary supplementation with fermented soybean meal Tejiao 001（fermented soybean meal）on the growth performance of California perch. California perch fry with the body weight of about 14 g were taken as the research object and fed with circulating water. The experiment was divided into 6 groups. The diets were supplemented with 0%，5%，7.5%，10%，12.5%，and 15% fermented soybean meal， respectively，this study lasted for 6 weeks. The results showed that dietary supplementation with 5% fermentedsoybean meal significantly increased the weight gain rate（WGR）and specific growth rate（SGR）of California perch （P＜0.05），and feed conversion ratio （FCR） of 5% fermented soybean meal group and control group were significantly better than those of 12.5% and 15% fermented soybean meal groups（P＜0.05）. The feed conversion ratio in 7.5% fermented soybean meal group was significantly better than that in 15% fermented soybean meal group（P＜ 0.05），while there was no significant difference in fecal breakdown among all groups（P>0.05）. The results showed that the basal diet supplemented with 5% or 7.5% fermented soybean meal could improve the growth performance and feed efficiency of California perch，but with the increase of fermented soybean meal，the growth performance indexes and feed efficiency of California perch decreased.

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Development of a TaqMan Real��time RT��PCR Assay for detection of Enzootic Nasal Tumor Virus in Goats

LI Jiaming ，ZHENG Shuodong ，LUO Shicheng ，ZHANG Haoquan ，YAN Guangzhi ，CHEN Shengnan ， LIU Mingjie ，HUANG Liangzong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 24-28. DOI: 10.19978/j.cnki.xmsy.2023.01.05

Abstract （302）

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In order to establish a rapid detection method for Enzootic nasal tumor virus of goats（ENTV ? 2）， primers and TaqMan probes were designed according to the conserved region of ENTV?2 env gene. By optimizing the reaction conditions，the ENTV ?2 TaqMan fluorescence quantitative RT ?PCR detection method was established，and its specificity，sensitivity，repeatability and clinical detection effect were verified. The results showed that the standard curve established by this method had a correlation coefficient（R2 ）of 0.998 when the concentration of recombinant plasmid was 1.019×109 —1.019×102 copies/μL，and the Ct value had a good linear relationship with the concentration of recombinant plasmid. This approach was specific for ENTV ? 2，and there was no cross ? reaction observed against other five kinds of pathogens related to goats. The minimum detection limit was 10.19 copies/μL，andthe coefficient of variation intra ?assays and inter ?assays was within 0.46% and 1.5%. It was more sensitive than the conventional RT?PCR and gave higher ENTV?2 positive detection rate（60%，12/20）than the conventional RT?PCR （30% ，6/20）from clinical samples，the total coincidence rate of the two methods was 70%（14/20）.These data indicated that the TaqMan ? based realtime RT ? PCR assay established here was an effective method with high sensitivity，specificity and reproducibility for faster and more accurate detection and quantification of ENTV?2.

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Inhibition of Reuterin on Clostridium perfringens in vitro

LI Jinyan ，MA Xinyan ，XIANG Rong ，LIAO Shenquan ，LV Xiaohui ，YANG Qiao ， ZHANG Xiaoling ，YANG Xi

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 29-34. DOI: 10.19978/j.cnki.xmsy.2023.01.06

Abstract （454）

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Clostridium perfringens（Cp）is the leading pathogen of necrotizing enteritis——an acute zoonotic disease. Reuterin is a product of few probiotics in glycerol substrate，which exhibited broad spectrum antibacterial activity. The objective of this study was to observe the growth inhibition feature of Reuterin in vitro on different types of C. perfringens and to explore the stability of Reuterin under different storage temperatures. Lactobacillus reuteri was induced to synthesize Reuterin from glycerol，its concentration was determined by Acrolein ?Tryptophan method. The minimum inhibitory concentration（MIC）of C. perfringens types A，B，C，D and E were determined by 96?well plate OD600 measurement and plate titration. The antibacterial properties of Reuterin against C.perfringens was compared after 24 hours storage at - 20 ℃ ，room temperature（25 ℃）and 37 ℃ . The results exhibited that the Reuterin production concentration was 26.13 μmol/mL. Type A and D C. perfringens were the most sensitive to the Reuterin， with MIC values of 0.78 μmol/mL and 0.52 μmol/mL，respectively. Type B，C and E strains were also sensitive，MIC values were 1.57 μmol/mL，1.57 μmol/mL and 1.83 μmol/mL. In the plate titration method，all five serotype bacteria were inhibited under 0.26 μmol/mL Reuterin treatment. The bacteriostatic effect of Reuterin were measured after different storage temperatures. For C.perfringens type A and C，the growth inhibition capacity did not change，and the MICs were 0.78 μmol/mL and 1.57 μmol/mL. This study proved that Reuterin has the grow inhibitory ability on C. perfringens in vitro as one of the probiotic metabolits，and its antibacterial ability is not affected by storage temperature.

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Diagnosis and treatment of porcine proliferative enteritis

XU Minsheng ，KE Haiyi ，YANG Dongxia ，SONG Shuai ，GOU Hongchao ，ZHANG Kunli ， JIANG Zhiyong ，LI Yan ，CHU Pinpin ，ZHAI Shaolun ，JIAN Yunhua ，LI Chunling

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 35-38. DOI: 10.19978/j.cnki.xmsy.2023.01.07

Abstract （370）

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Diarrhea and bloody stool occurred on a pig farm in Guangdong Province. Necropsy reveled the swelling and bleeding in the intestinal tissues. The feces of dead pigs has the black coal tar appearance. The feces were collected for laboratory test. With the pathogenesis symptoms and PCR results，porcine proliferative enteritis caused by intracellular Lawsonella was diagnosed. Tiamulin combined with other adjuvant therapy was given，which solve the case in this herd.

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Comparative study on the detection of African Swine Fever virus between the commercial kit for viral DNA extraction

YANG Yunlong, FENG Yongzhi, GAO Qi, WU Xiaoyi, GONG Lang, ZHANG Guihong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 39-43. DOI: 10.19978/j.cnki.xmsy.2023.01.08

Abstract （255）

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In order to establish a rapid and accurate detection method for African swine fever（ASF），a standarddetection of ASFV，it was found that the primers and probes provided by CADC were more sensitive to the detection of ASFV，and the DNA extraction kit of Axygen brand was more cost?effective for the detection of ASFV. plasmid and a standard curve were constructed for the late translation protein p72 gene of ASFV. The sensitivity of primers and probes provided by OIE and CADC was compared by fluorescence quantitative PCR technology，and the detection efficiency of ASFV DNA extracted by various DNA extraction kits was evaluated，providing data reference for the efficient detection of ASFV. The results showed that p72 standard plasmid had better detection efficiency and sensitivity among the standard plasmid and standard curve of p72 gene of ASFV constructed. Through the use of primers， probes and various DNA extraction kits provided by OIE and CADC for fluorescence quantitative PCR

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Research progress on common factors and their interaction associated with reproductive performance and gut microbes of livestock and poultry

DONG Menglin, CHEN Peng, YAN Xia, DONG Shangzhi, LUO Xuehui, GUO Zhaowen, LUO Chenglong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 44-50. DOI: 10.19978/j.cnki.xmsy.2023.01.09

Abstract （302）

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Many factors can affect the composition of gut microbes and reproductive performance of livestock andthe compositions of gut microbes were different between genders and reproductive stages. This paper mainly elaborates on these two points from the perspective of differences in the hormone，intestinal microorganism，and reproductive performance：the differences in gut microbes richness and diversity of livestock and poultry under different reproductive performances；the differences in reproductive performance caused by intestinal microbial changes. It also provides a reference for further study on the interactive mechanism between intestinal microbial and reproductive performance. poultry. At the same time，there is an interaction between the composition of gut microbes and reproductive performance. Gut microbes can affect reproductive performance and sex hormone levels of livestock and poultry，while

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Research progress on GEM��PA surface display system

LU Ruiqing，JIAO Cuicui，ZHANG Mengyao，WANG Hualei，ZHANG Haili*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 51-56. DOI: 10.19978/j.cnki.xmsy.2023.01.10

Abstract （478）

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The GEM?PA surface display system is composed of gram?positive enhancer matrix（GEM）and protein anchor（PA）. It uses GEM particles as its display core，and heterologous proteins are expressed by fusion with PA to achieve their display on the surface of GEM particles. GEM particles have many advantages such as high biosafety， ability to bind heterologous proteins，and autologous adjuvant effect. The GEM ?PA surface display system has been developed rapidly in recent years and becomes one of the new research hotspots of surface display system. At present， this system has been used in several fields including immobilizing enzymes，protein and virus purification，and development of novel vaccines. In this paper，the composition and applications of this system will be reviewed.

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Recombination analysis of PRRSV epidemic strains and vaccine strains over the years in Guangdong

KANG Pu ，CHEN Qiang 2 ，LIN Mu ，WANG Xiaohu ，WANG Gang ，LU ZongJi ，CHEN Jing

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 57-62. DOI: 10.19978/j.cnki.xmsy.2023.01.11

Abstract （321）

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The complete genome sequences of 42 PRRSV strains derived from Guangdong and completerecombination events occurred in the parental strain of JXA1?R?CN?2009 from 2010 to 2018. Vaccine strains Ingelvac ATP?US?2006 and CH?1R?CN?2008 appeared as secondary parental strains in event 10，the recombinant strain of this event was Guangdong strain isolated from 2018. Recombination between vaccine strains can be seen in events 18，25， but the software also shows that this event may have evolved naturally rather than recombined. This paper has certain significance for the scientific and standardized use of modified live vaccines in Guangdong pig farms. sequences of 6 PRRSV vaccine strains were selected from all 424 PRRSV complete sequences available on GenBank database to carry out recombination analysis using RDP4(Recombination detecting program 4，RDP4) software. Recombination events between Guangdong strains were found to be concentrated in 2010，2011 and 2015. 12

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Molecular epidemiological investigation of transmissible viral proventriculitis in poultry farms located in western Guangdong

PAN Xiaoting, LI Xiu, QI Nanshan, LIAO Shenquan, LI Juan, LV Minna, LIN Xuhui, CAI Haiming, HU Junjing, ZHONG Yaoguang, ZHUO Fuqiu, ZHANG Jianfei, SUN Mingfei, LI Guoqing

Guangdong Journal of Animal and Veterinary Science 2023, 48 (1): 63-70. DOI: 10.19978/j.cnki.xmsy.2023.01.12

Abstract （272）

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In order to investigate the prevalence and main causes of transmissible viral proventriculitis（TVP）in chickens in western Guangdong，we collected a total of 910 glandular gastric samples（every 10 mixed into 1 pool sample，a total of 91 pool samples）from some chicken farms in western Guangdong province，and detected 8 kinds of TVP ? related viruses using real ?time PCR method. The results indicated that 42 out of the 91 samples were positive， with a positive rate of 46.2%，and a total of 6 kinds of TVP ? related viruses were detected，and double or multiple infection were found. There is no breed specificity for infected chickens in this area，but infection rate among different age groups varies significantly. It suggests that TVP infection is widespread in chicken farms in western Guangdong province，and our data will provide basic information for the epidemic characteristics as well as prevention and control of TVP in Western Guangdong.

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Development trends and suggestion for swine nutrition and feed science in 2023

WANG Li, XIAO Hao, HU Shenglan, MA Xinyan, JIANG Zongyong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 1-4. DOI: 10.19978/j.cnki.xmsy.2023.02.01

Abstract （302）

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In 2022，pig production capacity was stably increased，coupled with the continuous rise in feed raw material prices and emission reduction and carbon reduction in animal husbandry，that had brought enormous pressure to pig breeding entities. Pig industry faced severe pressure，however，new energy has been injected into healthy pig farming by the research and development of various technologies in the front ??end，mid??range，and back??end of pig farming. This paper proposed the direction for the development of the pig industry in 2023，such as accelerating the promotion of intelligent breeding technology，improving the precision level of feed preparation，strengthening precision feeding technology，increasing the development of non ?? grain feed raw materials，researching new anti ?? microbial products，adopting low??protein feed source emission reduction and so on，which aimed to provide direction reference for the healthy development of the pig industry.

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Iodine Requirement for Yellow��Feathered Chickens from 1 to 21 Days of Age

TAN Shujun, JIANG Zongyong, LI Long, JIANG Shouqun

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 5-10. DOI: 10.19978/j.cnki.xmsy.2023.02.02

Abstract （171）

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The purpose of this experiment was to investigate the effects of different dietary iodine levels on growth performance，immune organ index，blood T3，T4 content and T3/T4 ratio of yellow ? feathered broilers，in order to explore the appropriate level of iodine for yellow?feathered broilers during 1 to 21 days old. A total of 1440 1?day?old healthy and well?developed fast?growing Lingnan yellow?feathered male broilers were randomly divided into 6 groups with 6 replicates per group and 40 chickens in each replicate. The basal diet was supplemented with different doses of Ca（IO3）2，and the dietary iodine supplemental levels were 0.00，0.20，0.40，0.60，0.80 and 1.00 mg/kg， respectively. The results showed that the level of dietary iodine had no significant effect on daily gain，daily feed intake and ratio of feed to gain of chickens（P>0.05）. Using one?slope broken?line analysis，taking the average daily gain asthe evaluation index，the suitable dietary iodine level of chick was determined to be 0.80 mg/kg. Different dietary iodine levels had no significant effect on immune organ index，blood T3，T4 content and T3/T4 ratio of birds. To sum up，the appropriate iodine level of corn?soybean meal diet for 1?21?day?old yellow?feathered male broilers was 0.80 mg/ kg，that is，the optimum level of dietary iodine was 0.91 mg/kg.

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Study of Energy Requirement of Sows during Pregnancy and Lactation and Its Application in Animal Husbandry

AN Xiaokai, GAO Kaiguo, WANG Wence, XIAO Hao

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 11-17. DOI: 10.19978/j.cnki.xmsy.2023.02.03

Abstract （254）

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Energy is the most important nutrient in the gestation stage of sows，providing fuel for sow maintenance growth，reproduction and lactation processes as well as physical activity. Accurate determination of the energy utilization of feed ingredients in sows at different growth stages can better meet the energy needs of pigs at different growth stages. This paper reviews the energy requirements of sows during gestation and lactation from four databases e.g. the Nutrient Requirements of Swine（NRC，2012），and effects of different energy substance additions on reproduction performance and physiological function of sows at different stages，to provide a theoretical reference for future research on the dynamic energy requirements of sows during reproduction.

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Research progress of Newcastle disease virus vector vaccines

ZHANG Guoli，XU Shaozhu，KUANG Zhenjie，PAN Chengzhi，XIAO Jie，QI Dongmei*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 18-23. DOI: 10.19978/j.cnki.xmsy.2023.02.04

Abstract （453）

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Newcastle Disease Virus（NDV）has been successfully used as a vaccine carrier in a variety of human and animal diseases to develop vaccines. Studies have shown that recombinant Newcastle disease virus (rNDV) vector vaccines have better performance in humoral immunity，mucosal immunity，and challenge protection compared with traditional vaccines. NDV vector has become a ideal tool for the development of safe，efficient，low toxicity，and better immunogenicity vector vaccines. The advances of novel vaccines for poultry，mammals，and humans using NDV as a vaccine vector are reviewed，to provide new ideas for the development of more epidemic vaccines using NDV vector.

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Advance in Pharmacokinetics/Pharmacodynamics Models of Veterinary Antimicrobial Drugs

WEI Haitao, FANG Qiuhua, YANG Weicong, ZHANG Bingshun, LIU Shuojia

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 24-29. DOI: 10.19978/j.cnki.xmsy.2023.02.05

Abstract （263）

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The remarkable progress of veterinary antimicrobial drugs （AMDs） pharmacokinetics/ pharmacodynamics（PK/PD）models has been made in recent years. Understanding the basic concept of PK/PD model and optimizing the dosage regimen can improve the antibacterial effect of AMDs and reduce the occurrence of drug resistance. This paper introduces the research methods and progress of PK/PD model，as well as the challenges and application prospects of PK/PD model in veterinary AMDs and its future development trend，and provide a theoretical basis for the research of PK/PD model for veterinary AMDs.

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Progress in the Diagnosis and Treatment of Arterial Thromboembolism Secondary to Feline Hypertrophic Cardiomyopathy

ZHOU Shuilian1，2，QU Yanyan1，BAI Yuman2，HUANG Jianjia3，XIE Wenting3，YU Yibo2，GONG Xiaopei2，QIU Wenyue2，PANG Xiaoyue2，ZHANG Xinting2，ZHANG Xin1*，SU Rongsheng2

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 30-35. DOI: 10.19978/j.cnki.xmsy.2023.02.06

Abstract （593）

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Hypertrophic cardiomyopathy（HCM）is the most common heart disease in cats. HCM in cats is characterized by centripetal thickening of ventricular walls and papillary muscle hypertrophy. The incidence of HCM followed by thromboembolism（ATE）in cats is increasing year by year. The overall survival rate of HCM was as low as 35%. This article reviewed the diagnosis and treatment of HCM and ATE in cats focusing on the main therapeutic drugs and their efficacy. It is suggested to file the predisposed breeds as soon as possible，conduct regular physical examination and screening，provide timely treatment，perform breed selection，improve the techniques of surgical treatment and integrated traditional Chinese and western medicine，use drugs prudently for treating thrombosis，try to use new antithrombolytic drugs，and so on.

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Analysis of Serum Steroid Hormone Metabolism in Broiler Breeders in Different Laying Weeks

LIU Jiaxin, XIN Wentao, JIANG Xiaolong, YANG Baohe, YUAN Mingfeng, TIAN Yunbo

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 36-40. DOI: 10.19978/j.cnki.xmsy.2023.02.07

Abstract （188）

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The purpose of this experiment was aimed to compare the follicular development and serum steroid metabolism in broiler breeders of different laying weeks. Six broiler breeders were randomly selected at the beginning of preinitiation（24 weeks of age），at the peak of laying（28 weeks of age），and at the late stage of laying（47 weeks of age）. Liquid chromatogram?tandem mass spectrometry（LC?MS/MS）was used to detect serum steroid hormone levels in broiler breeders at different laying weeks of age. The results showed that the number of small yellow follicles was significantly higher at the late stage than those detected at thepeak stage（P<0.01）. The progesterone concentration in the perinatal period was highest，and significantly higher than that in the peak of egg production（P<0.01）. The levelsof 11?deoxycortisol and testosterone were the highest at the peak of egg laying.Meanwhile，the content in the opening perinatal period was the second，and the content in the late laying period was the lowest. Progesterone and estradiol levels were the lowest in the peak laying period but increased in the late laying period. In the late laying period，the content of estradiol was significantly higher than that in the peak laying period（P<0.01），and the level of progesterone was significantly higher than that in the peak laying period（P<0.05）；The level of estradiol in late laying period was significantly higher than that in the opening period（P<0.05）. The content of 17 ? hydroxypregnenolone increased gradually with the increase of laying week age，but there was no significant difference between different weeks of age. Overall，our results indicated that the low reproductive performance of broiler breeders may be related to the retardation of the development of small yellow follicles recruited into the preovulatory hierarchy and the significant increase of estradiol and progesterone in serum.

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Effects of deoxynivalenol on chickens infected with Mycoplasma gallitatis and avain pathogenic Escherichia coli

LIU Jiaxu, HAN Qian, GUO Sitao, QI Zhenxiong, WANG Yongqiang, （.

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 41-45. DOI: 10.19978/j.cnki.xmsy.2023.02.08

Abstract （195）

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Mycoplasma gallitatis（MG）which often co?infect with Avian pathogenic Escherichia coli.（APEC）is an important pathogen for avian air saccultitis and put poultry industry in serious risks. In the meantime，mycotoxins as secondary metabolites produced by fungi or molds bring serious challenges to poultry health. In order to understand the correlation between mycotoxin and MG infection，7?day?old chickens were inoculated with MG S6 strain at 1×1010 CCU/mL for 3 days. Chickens were inoculated with avain pathogenic Escherichia coli（APEC）O78 strain at 1×107 CFU/mL 6 days later to induce the symptoms of diseases. During the experiment，8 mg/kg deoxynivalenol（DON）was fed through daily diet. The results showed that，at the condition of DON exposure，chickens did not show clinical symptoms of respiratory disease by MG and APEC infection，but the exposure of DON could significantly reduce the antibody level of MG and increase the detection rate of the MG in chicken blood. This study evaluated theimmunosuppressive ability of DON and confirmed that other pathogenic factors may be needed for the occurrence of multi etiological air saccultitis in chicks.

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Comparative Study on Four Hydrodynamic Determination Methods of Systems in Pork

LI Hao1，3，ZHENG Enqin3，WANG Sutian1，2，XIN Haiyun1，2，YAO Zekai1，3，LI Baohong1，2，WANG Ying4， HU Bin1，2，CHENG Leiyan1，2，LI Jianhao1，2，MENG Fanming1，2*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 46-51. DOI: 10.19978/j.cnki.xmsy.2023.02.09

Abstract （428）

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This study aimed to using 4 methods to determine the hydraulic power of pork，and combined with the actual operation to improve and evaluate the hydraulic power of pork，and then provide a theoretical basis for the identification of pork hydraulic power and meat quality. Using the 4 methods mentioned in the Ministry of Agriculture standard NY/T 1333-2007 to determine the hydraulic power，the pressure method，centrifugation method，drip loss， and cooking loss were used for parallel determination of more than 100 fresh pork samples. Moisture content（direct drying）was used as the fifth index to evaluate the water ??holding power. The water ??holding power measured by different methods of each sample was calculated by formula，and the differences of different methods were compared and analyzed. Compared with other methods，the drip loss method had the smallest error，and the average loss rate was 1.984%；the average value of the pressure method was 68.377%，and the calculation formula of the centrifugal method and the pressure method were the same，and the average value was 65.098%. However，the coefficient of variation of the centrifugation method is the largest among several methods，reaching 10.633%，the average value of the cooking method was 66.888%，and the average value of the moisture content was 68.022%，which is similar to the average value of the pressure method. The results show that drip loss was the least affected by human factors，but it was suitable for the determination of meat quality difference；the moisture content in meat can replace pressure method and centrifugation method in production，but it takes a long time；in the market Preliminary identification of meat quality could be carried out by using the cooking method，which was quicker and convenient for consumers to taste and feel the meat quality more intuitively.

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Effects of Eight Plant Extracts on Antioxidant Capacity of MODE⁃K Cells

LIANG Mei，SUN Xinyi，GUO Mengru，WU Huining，ZHANG Jin，ZHAO Linlu，LIU Xiaoxi*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 52-58. DOI: 10.19978/j.cnki.xmsy.2023.02.10

Abstract （273）

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The aim of this study was to evaluate the antioxidant capacity of eight plant extracts based on the oxidative stress model of MODE?K cells induced by lipopolysaccharide（LPS）. CCK8 method was used to detect cell viability and screen modeling conditions. The levels of IL?6，reactive oxygen species（ROS），lactate dehydrogenase （LDH），superoxide dismutase（SOD），malondialdehyde（MDA）and reduced coenzyme I（NADH）were detected by ELISA. The expression of HO?1 mRNA was detected by QPCR. The results showed that compared with the control group，the cell viability（P<0.01）was significantly reduced after 1 h of LPS treatment with 40 μg/mL. The expression of IL?6，ROS，LDH and MDA（P<0.05）was significantly increased，the expression of HO?1 mRNA（P<0.01）was significantly increased，and SOD（P<0.01）and NADH activity（P<0.05）were significantly reduced. Compared with the model group，the expression of MDA（P<0.05）and the expression of NADH and HO?1 mRNA were significantly increased（P<0.05）in the perilla seed and knotweed extract groups，while the remaining six extracts did not show significant differences. In summary，among the eight plant extracts，perilla seed and knotweed extract（20 μg/mL） improved the antioxidant effect of MODE?K cells, and the effect of perilla seed was better than that of knotweed.

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Protective Effect of Chitosan ⁃ Gentamycin Conjugate on DSS ⁃ induced Ulcerative Colitis in Mice

WANG Xinchen1，2，HU Canyin1，2，YONG Yanhong1，2，LI Chengpeng3，JU Xianghong1，2*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 59-64. DOI: 10.19978/j.cnki.xmsy.2023.02.11

Abstract （254）

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To observe the protective effect of Chitosan ? Gentamicin conjugate（CS ? GT）on Dextran Sulfate Sodium（DSS）? induced colitis in mice. Thirty healthy SPF male C57BL / 6J mice were randomly divided into 5 groups：Control group，DSS group and low，medium and high dose CS?GT group. Taking daily clinical observation and recording of mice activity，diet，body weight and fecal occult blood. All animal were euthanized and blood，colon tissues were collected on the 14th day. The changes of intestinal mucosal，the concentration of serum biochemical indexes and inflammatory factors were determined by optical microscope，biochemical analyzer，and ELISA，respectively. The results showed that compared to the control group，the body weight，and colon length were decreased in DSS?treated mice（P<0.01）. Meanwhile，we observed serious bloody stool and intestinal villus dropped in this animal. The concentration of serum ALB and TP significantly decreased（P<0.01），as well as the decrease of anti? inflammatory factors IL?4 and IL?13. But the concentration of pro?inflammatory factor IL?6 was significantly increased （P<0.01）. Compared with DSS group，the body weight and colon length of mice in medium and high dose CS?GT groups were significantly increased（P<0.05），the bleeding was improved，and the level of serum ALB and TP increased significantly（P<0.05）. The expression level of pro?inflammatory factor IL?6 decreased significantly（P< 0.05），and the anti?inflammatory factors IL?4 and IL?13 trend to increase trendy. Our results suggested that CS?GT has a significant protective effect on DSS?induced colitis in mice and is valuable to development as a functional feed additive for animal intestinal protection.

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Epidemiological Investigation of Lawsonia Intracellularis in Large scale Pig Farm under the Scenarios of Antibiotic⁃Free Feed Policy

ZHI Kangfa1#，LI Fukun1，2，ZHONG Menglong1，WANG Hongcai1，LI Bo1，OU Lanxin1，HUNAG Fuqiang1， YU Xingang1，QI Dongmei2，ZHANG Haoji1*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 65-69. DOI: 10.19978/j.cnki.xmsy.2023.02.12

Abstract （305）

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In order to provide evidence for precise prevention and control of Porcine proliferative enteropathy， the prevalence of Lawson Intracellularis in large?scale pig farms under the background of antibiotic?free feed and restricting the use of antibiotics in pig breeding industry was investigated. In this study，nested PCR and indirectELISA were used to detect fecal and serum samples from different pig farms. Under the background of antibiotic?free feed，nested PCR detection was conducted on 695 fecal samples collected from different pig farms. the overall infection rate was 23.88%. The infection rates of nursery pigs，finishing pigs and boars were 16.56%，29.58% and 24.63%，respectively. The results of the follow?up survey of the pig herds with antibiotic?free feed and under the background of restricting the use of antibiotics in pig breeding industry were as follows：the infection rate of nursery pigs at 30，44，58 and 72 days of age was 16.67%，20.00%，50.00% and 70.00%，respectively. The infection rate of gilts ranged from 44.44% to 66.67%. As for the ELISA test results，the positive rate of lawsonia intracellularis was 42.6% in 338 serum samples and the positive rate of Lawsonia Intracellularis range from 10% to 75.90% in pig farms from different provinces. The aboved results showed that the prevalence of Lawsonia Intracellulare in large?scale pig farms in China were at a high level at present. The highest infection rates of nursery pigs and gilts were 70% and 66.67% respectively. The infection rate of nursery pigs increased significantly with the increase of age. Therefore，it is necessary to pay more attention to the prevention and control of porcine proliferative enteropathy in large?scale pig farms under the background of antibiotic?free feed.

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Consistency Analysis of Three ELISA Methods to Fluorescent Antibody Virus Neutralization for Detection of Rabies Antibodies

HONG Weibin，MO Zuanlan，YIN Sanhong，YE Yifei，LI Min，XU ZhenNa，HUANG ShiPin

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 70-73. DOI: 10.19978/j.cnki.xmsy.2023.02.13

Abstract （331）

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In order to select suitable kits for the detection of rabies antibodies，the FAVN method was used as the reference and compared with three ELISA kits for consistency analysis. The results showed that kit A had the best consistency and coincidence rate（86%）with Fluorescent Antibody Virus Neutralization（FAVN），its kappa value was 0.605；the Kappa value of kit B was 0.485，which was moderate consistent，the coincidence rate was 80%；the Kappa value of kit C was 0.310，indicating poor consistency between the results of the two reagents. The sensitivity and specificity of the three kits were calculated. Kit A had the highest sensitivity（92.1%）and Kit B had the highest specificity（72.7%）. This study provides a scientific basis for screening kits in clinical practice.

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Comparison of Detection Sensitivity for Mycoplasma Hyorhinis Between Liquid Culture and qPCR

XUE Shaohua1，2，LÜ Zixin1，2，ZHANG Xinjie1，2，DAI Ailing1，2，YANG Xiaoyan1，2，YU Guohua1，2*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 74-80. DOI: 10.19978/j.cnki.xmsy.2023.02.14

Abstract （236）

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To Compare the detection sensitivity between liquid culture and real ??time qPCR for the samples collected at different growth phases of Mycoplasma hyorhinis（included in the Chinese Pharmacopoeia but very time?? consuming）（not included in the Chinese Pharmacopoeia but rapid），samples were collected at three different growth phases of Mycoplasma hyorhinis ：log phase（48 h），stationary phase（96 h）and dead phase（144 h）. Then the samples were diluted 10 times serially，and the detection sensitivity was tested by liquid culture and qPCR. The results showed that the detection sensitivity of liquid culture was about 100 times higher than that of the qPCR method in the log phase and stationary phase with a high proportion of viable mycoplasma. In the dead phase when theproportion of dead mycoplasma increased significantly，the detection sensitivity of qPCR was about 1000 times higher than that of liquid culture. When the log phase sample was concentrated（about 100 times）by centrifugation，they were detected again by qPCR. Compared with the sample before concentration，the detection sensitivity of the sample was increased by 100 times. In conclusion，the main factors affecting the relative detection sensitivity of liquid culture and qPCR are the sample addition volumes in their respective systems and the proportion of viable and dead mycoplasma cells in the samples. The difference in sensitivity between the two methods caused by the former factor can be reduced by high??speed centrifugal concentration，so that the sensitivity of the two methods is the same.

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Diagnosis and Treatment on a Case of Feline Sublingual Mass Removed by Ultrasonic Scalpel

DAI Jinghong1，HUANG Ruiwu2，QIU Wenyue3，SU Rongsheng3*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (2): 81-84. DOI: 10.19978/j.cnki.xmsy.2023.02.15

Abstract （913）

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In order to better promote the application of ultrasonic scalpel in the clinical diagnosis and treatment of pets，this paper reviewed the diagnosis and treatment process of a feline sublingual tumor treated with ultrasonic scalpel，analyzed its clinical symptoms，diagnosis，treatment，postoperative care and recovery，and discussed the difference between ultrasonic scalpel sublingual tumor resection and traditional surgery. The results showed that the sublingual mass was diagnosed as collagen fiber hyperplasia by histopathology；Compared with traditional sublingual tumor resection，ultrasonic scalpel resection has the advantages of less damage，less bleeding，accurate cutting and better prognosis. It is recommended that ultrasonic scalpel should be promoted in veterinary surgery.

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The epidemic of Piglet Diarrhea and Research Progress in Prevention and Control Technology

LIU Shiyu, LI Bin

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 1-7. DOI: 10.19978/j.cnki.xmsy.2023.03.01

Abstract （324）

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Piglet diarrheal diseases have acute onset，large scale，rapid onset and high annual average incidence in swine herd，posing a huge threat to the global pig industry and leading to heavy economic losses. The causes of piglet diarrhea are complex and the main pathogens，causing piglet diarrhea，have the characteristics of natural recombination，continuous variation，a wide host spectrum and a variety of serotypes. With the emergency of more mutated pathogens，serious co ? infection and reduced vaccine protection，there is an urgent need to develop more sensitive and accurate tools，safer and more effective vaccines and to upgrade existing integrated prevention and control technologies. In this review，we summarize the causes of piglet diarrhea，the epidemic status，the key technologies research progress of integrated prevention and control，and propose to accurate diagnosis，rational selection of vaccines and strict feeding management，providing a basis and reference on the diagnosis and control of the disease.

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Research and Application Progress of Natural Alternatives to Antibiotics for Animal

JU Xianghong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 8-17. DOI: 10.19978/j.cnki.xmsy.2023.03.02

Abstract （456）

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The huge consumption of antibiotics by human and animal industry in the world has resulted in severe problems of bacterial resistance and drug residue，the rate and probability of the occurrence of“superbacteria” increased significantly，presenting threat to human and animal health. Although developed countries such as the Europe union and the United States of American，and our country，have successively issued a series of policies to decrease the consumption of antibiotics，its use in some developing countries such as Africa and Southeast Asia，still is insufficiently supervised and excessive used，and the long?term threat of bacterial resistance still exists. Therefore， the search of effective natural products to reduce the use of antibiotics is vital. Now，Chinese herbal medicine， probiotics，antimicrobial peptides，acidifiers，enzyme，and animal used marine drugs，all showed excellent antibacterial，anti?inflammatory，immunity enhancement，and growth?promoting functions. A green，antibiotics?free breeding technology in animal industry is of tendency in future. This paper reviewed the current situation of antibiotics used in China，as well as the antibiotics replacement products，focused on their function and acting mechanism， problems occurred in usage，and possible solutions for dealing with these problems.

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The Formation and Decomposition Mechanism of typical Odor Components Indole and 3��methylindole of Livestock and Poultry Farms

Deng Dun, Yu qin, Wen Guangying, Ma Xinyan, LU Yusheng, Ma Xianyong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 18-23. DOI: 10.19978/j.cnki.xmsy.2023.03.03

Abstract （327）

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Due to frequent environmental cases caused by the foul odor of farming, the reduction of odor emissions in farms has become increasingly urgent. This article focuses on the formation mechanisms, degradation methods, and problems in the prevention and control process of typical odor components such as indole and 3?methylindole in livestock and poultry farms. Tryptophan is the source of indole and 3?methylindole formation, and using fermented feed, acidifiers, and probiotics can control the formation of indole at the source. Changing the intestinal pH can significantly reduce thegeneration of 3?methylindole. Adding microorganisms and enzyme preparations can effectively control the formation of indole and 3?methylindole during manure storage. When designing pig pens, consider using environmental control equipment and enhancing physical odor elimination methods to further reduce the generation and spread of indole class malodorous substances, and achieve systematic control of their formation and transmission. This article provides a reference for scientific prevention and control of malodorous pollutants in farms.

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Processing Technology Requirements of Meat Prepared Dishes Based on Traditional Cooking

LIU Mengzhu, KANG Huahua, TU Du, HAN Yixin, TAN Shu, ZHEN Rui, XU Zhihong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 24-29. DOI: 10.19978/j.cnki.xmsy.2023.03.04

Abstract （333）

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Livestock and poultry meat prepared dishes refer to the finished or semi ?? finished cooking products with livestock and poultry meat as the main raw materials，which are used as staple dishes after processing. Based on the basic characteristics and development status of prepared dishes，this paper compares the characteristics of the industrialization of traditional livestock and poultry meat cooking dishes and meat prepared dishes，summarizes the Chinese and Western traditional processing technology of livestock and poultry meat products，and proposes the technical requirements and suggestions for the development of prepared dishes accordingly. We aim to provide reference for scientific and technological innovation to promote the rapid industrial development of livestock and poultry meat prepared dishes.

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A Genome��wide Association Study in Landrace Sows during Weaning��to��service Interval

CHEN Xinyou, LIN Qing, ZHANG Xiaoke, LI Tingting, WAN Pengchong, LIN Changguang, HUAGN Zhen, XIE Shuihua, ZHANG Hao, LI Jiaqi

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 30-34. DOI: 10.19978/j.cnki.xmsy.2023.03.05

Abstract （201）

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The aim of this study was to detect candidate genes affecting the weaning ? to ? service interval of Landrace sows through the genome?wide association analysis（GWAS），in order to provide theoretical references for swine breeding in China. In this study, the weaning?to?service interval records and 50K gene data of 1 063 Landrace sows in a core breeding farm in China were used as research materials, and genome ? wide association analysis was performed by mixed linear models of GEMMA software to identify important loci. The results showed that there were 5significant SNPs in the first and third parity of Landrace sows. Haplotype analysis was performed on the 5 significant locus and 4 haplotype blocks were obtained. The screened genes of BTG1, FUT1, FUT2, SCNN1G, and CBLB may be the important genes affecting the weaning?to?servce interval traits. The results of this study can provide the reference for future practice of swine breeding.

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Effect of Dietary Tryptophan Level on Antioxidant Ability in Laying Duck Breeders

ZHANG Yanan, HUANG Xuebing, JIN Yongyan, LAI Yue, LI Kaichao, ZHENG Chuntian

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 35-41. DOI: 10.19978/j.cnki.xmsy.2023.03.06

Abstract （235）

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This study aimed to determine the effect of dietary tryptophan（Trp）levels on antioxidant ability and Trp requirement for laying duck breeders. A total of 504 Longyan breeding ducks（body weight：1.20 ± 0.02 kg）aged 22 weeks were randomly allocated to 6 treatments，each with 6 replicates of 14 ducks. During the following 16 weeks，birds of differenttreatments were fed the basal diet with total Trp contents of 1.00，2.00，3.00，4.00，5.00 and 6.00 g/kg，respectively. The results showed that the dietary Trp level of 2 g/kg could result in the highest T?SOD activity in plasma（P<0.05），and the plasma serotonin content increased linearly and quadratically with dietary Trp supplemental levels（P<0.05）. The content of T?SOD and T?AOC in liver increased linearly and quadratically，and hepatic MDA content was lowest with dietary Trp level being 2 g/kg（P<0.05）. The gene expression of hepatic GPx1，SOD and Nrf2 increased linearly and quadratically， and the highest values was with Trp level of 4，2 and 1 g/kg，respectively（P<0.05）. The content of T?SOD and T?AOC in jejunum increased linearly and quadratically，and jejunal MDA content was lowest with the dietary Trp level of 3 g/kg（P< 0.05）. The gene expression of jejunal HO?1 and Nrf2 increased linearly and quadratically（P<0.05）. Collectively，dietary Trp level of 2 to 3 g/kg could improve the antioxidant ability in plasma，liver and jejunum in laying breeding ducks.

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Development and Clinical Pathogenic Characterization of Bovine Mastitis Models Caused by Escherichia coli

FAN Junwen ，TIAN Chongyu ，LI Huabin ，SHI Bochang ，LI Xinyu ，LI Chunhe ，TAN Lingyun ，HE Wei ， LIU Yuan ，YAN Fang ，ZHAO Zhongpeng

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 42-48. DOI: 10.19978/j.cnki.xmsy.2023.03.07

Abstract （309）

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In order to better evaluate the effectiveness of preventative vaccines and therapeutic drugs，we aimed to establish a stable dairy cow mastitis model，which may provide a reliable way to verify the concept of“human disease and animal prevention”for extensively infectious diseases. Milk samples from dairy cows with clinical mastitis were collected from different regions of China. Different strains of E.coli were used to infect 6-8 weeks old Balb/c mice and 2- 6 years old healthy susceptible cows in late stage of lactation respectively after bacterial isolation and identification. The infectivity and pathogenicity of the different strains against mice and dairy cows were determined， and strong virulent strains with high pathogenicity for both species were chosen for in vivo infection. The susceptible cows were inoculated with the selected candidate virulent strains，and the differences of clinical manifestations，daily milk yields，milk bacterial counts and somatic cell counts were recorded. Meanwhile，the mice were infected by the same strains，and the clinical symptoms and death of mice were recorded to establish a stable animal model of E.coli infection. Results：Three virulent E.coli strains（LZ06，ESH05，EHL11） of different serotypes were obtained，which could induce typical clinical mastitis in dairy cows and death in mice. The mastitis models in dairy cows and a lethal model in mice were finally established using virulent strain LZ06. Conclusion：The virulent strains of E.coli causing mastitis were successfully screened，and the animal mastitis model was successfully established，which could be used to evaluate the protective effects of vaccines or medicine. This study provided the new method and strategy for evaluating the concept of“human disease and animal prevention”for zoonosis.

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Application of Manganese in Broiler Production

LIU Yu，CHEN Lixue，CUI Xiaoyan*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 49-51. DOI: 10.19978/j.cnki.xmsy.2023.03.08

Abstract （93）

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Manganese is one of the essential trace elements for livestock and poultry，and plays an important role in the breeding of livestock and poultry，especially in poultry. Manganese is an important component or activator in the biosynthesis of various enzymes，which is closely related to broilers’growth，bone development，reproduction，and immunity. Both the deficiency and excess of manganese will have a greater negative impact on broilers. Manganese is mainly added in the form of inorganic manganese（manganese sulfate，manganese oxide，manganese chloride and manganese carbonate，etc.）and organic manganese（protein manganese and amino acid manganese，etc.）. Studies have shown that organic manganese has a higher biological availability than inorganic manganese but is expensive. In broiler chicken production，how to efficiently select different forms of manganese according to the appropriate amount of manganese in broiler feed is particularly important，to improve the growth performance of broiler chickens. At the same time，reduce the adverse impact on the ecological environment caused by excessive manganese discharge. In the present article，the biological characteristics，added forms，added amounts，and application prospects of organic manganese were reviewed，to provide theoretical support for the efficient and reasonable application of manganese in broiler production.

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Research Progress of Aquaponics Technology

LI Zhenmming ，YU Miao ，RONG Ting ，LIU Zhichang ，LI Shuhong ，MA Xianyong ，CHEN Weidong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 52-56. DOI: 10.19978/j.cnki.xmsy.2023.03.09

Abstract （374）

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With the development of aquaculture，large ? scale，intensive and high ? density aquaculture not only bring huge economic benefits，but also bring many environmental problems. At present，aquaculture not only consumes a lot of water resources and nutrients，but also brings a great burden to the ecological environment. The fish and vegetable symbiosis technology has effectively solved many problems by aquaculture. Aquaponics is a new type of compound farming system with low?carbon，simple and convenient，high yield and no secondary pollution. This paper discusses the development history，system components，and functional applications of aquaponics technology，and provides an outlook on the future development direction of aquaponics technology.

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An Overview on the Application of the Combined Farming and Breeding Model in Aquaculture

RONG Ting ，LI Zhenmming ，YU Miao ，CUI Yiyan ，LI Yuanfei ，TIAN Zhimei ， MA Xianyong， CHEN Weidong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 57-62. DOI: 10.19978/j.cnki.xmsy.2023.03.10

Abstract （74）

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Aquaculture consumes a large amount of freshwater resources and nutrients，which is very likely to cause environmental damage and water pollution，and seriously restrict the development of aquaculture industry.Therefore，it is urgent to develop a green recycable and sustainable aquaculture model. The application of the combined farming and breeding model can effectively alleviate many related problems and promote the rapid development of aquaculture. There are various models for the application of combined farming and breeding in aquaculture，including the“aquaponics”，“rice?fish”，and“mulberry?based fish pond”model. The main applications of the combined farming and breeding model in aquaculture are to improve water quality，regulate the temperature of the water environment，enrich biological diversity，beautify the ecological environment，and improve the economic benefits. This paper provides an overview，including the current application and problems，and presents an outlook on the future research directions of the combined farming and breeding model，in order to provide a reference and basis for the application of the combined farming and breeding model in the aquaculture industry.

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Exploration on Construction of African Swine Fever Free Community in Small and Medium��sized Swine Production Enterprises

LIU Jinfang ，LUO Lixia ，LI Chi ，LUO Shunhui ，RONG Biao ，WANG Aimin ，SU Huilong ， XU Wenyuan ，ZHANG Yilong

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 63-67. DOI: 10.19978/j.cnki.xmsy.2023.03.11

Abstract （90）

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The construction of African swine fever ?free plots is an important initiative implemented in China to combat the African swine fever epidemic. This paper discusses the implementation，supporting，and institutional issues facing the construction of African swine fever?free plots in small and medium?sized pig farms. From the actual plant planning，decontamination prevention and control，and system construction，we analyze the key points of African swine fever epidemic?free plot construction，common problems in applying for African swine fever epidemic? free plots，and summarize the initiatives suitable for small and medium?sized pig breeding enterprises in the process of building African swine fever epidemic?free plots.

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Effect of Heat Stress on Beef Cattle Production and its Regulating Measures

LI Yilin，LI Yaokun，GUO Yongqing*

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 68-75. DOI: 10.19978/j.cnki.xmsy.2023.03.12

Abstract （117）

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In order to understand the effects of heat stress on beef cattle production and take measures to prevent heat stress，this paper mainly expounds the influence of heat stress on beef cattle from the aspects of various biochemical indexes，production performance，reproductive performance and so on. Meanwhile，based on this，the regulation measures on heat stress of beef cattle are summarized. Various studies have found that heat stress conditions have great negative effects on various physiological behaviors， biochemical indexes， production performance，reproductive performance and immune function of beef cattle. In addition，various studies have put forward various regulatory measures for the prevention of heat stress in beef cattle，including prevention and control of physical facilities，regulation of feed nutrition and regulation of feeding management，so as to solve the problem of heat stress in key beef cattle breeding in southern China. Based on this，this paper summarized the influence of heat stress on beef cattle production under high temperature in summer and the regulation measures of heat stress，in order to provide reference for beef cattle breeding under heat stress conditions in southern China.

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Experience on the Treatment of Two Pyometra Cases

ZHENG Yongfeng ，FU Anjing ，HUANG Mingying

Guangdong Journal of Animal and Veterinary Science 2023, 48 (3): 76-79. DOI: 10.19978/j.cnki.xmsy.2023.03.13

Abstract （211）

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There are two types of pyometra: open pyometra and atretic pyometra. Pyometra is an obstetric disease of female dogs with the highest incidence rate in clinic，which is commonly seen in the middle and late stages of estrus in female dogs， and adult non ? sterilized female dogs. Through the comprehensive analysis and diagnosis of epidemiological inquiry，clinical examination，blood work and diagnostic imaging，the disease can be confirmed. Generally，it cannot be cured by conservative treatment，and surgery is needed. This paper analyzed two cases of pyometra treated in clinic，and the patients recovered well after hysterectomy and ovariectomy，aiming at providing reference for colleagues.

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