凝结芽孢杆菌对感染沙门氏菌蛋鸡生产性能、蛋品质和血浆生化指标的影响

本试验旨在研究凝结芽孢杆菌对感染沙门氏菌前后蛋鸡生产性能、蛋品质的影响,并探究其对感染沙门氏菌蛋鸡血浆生化指标的影响。将400只沙门氏菌阴性、体况健康的京红商品代蛋鸡根据产蛋率无显著差异(P0.05)原则随机分成4组(A组、B组、C组和D组),每组5个重复,每个重复20只鸡。对照组(A组和C组)饲喂基础饲粮,凝结芽孢杆菌组(B组和D组)在基础饲粮中添加2.5×1010CFU/kg凝结芽孢杆菌;饲喂1周后,C组和D组连续2 d定量口服肠炎沙门氏菌悬浮液(1×108CFU/mL),A组和B组口服等量无菌磷酸盐缓冲液(PBS),继续饲养3周。结果表明:1)感染沙门氏菌前,凝结芽孢杆菌对蛋鸡生产性能无显著影响(P0.05)。感染沙门氏菌后,沙门氏菌显著降低了蛋鸡平均日采食量(P0.05);凝结芽孢杆菌极显著降低了蛋鸡料蛋比(P0.01),显著降低了平均日采食量(P0.05)。2)感染沙门氏菌前,凝结芽孢杆菌极显著增加了蛋鸡蛋壳重/蛋重(P0.01)。感染沙门氏菌后,沙门氏菌和凝结芽孢杆菌对蛋鸡蛋品质指标均无显著影响(P0.05)。3)感染沙门氏菌后,凝结芽孢杆菌显著降低了血浆总胆固醇和甘油三酯含量(P0.05);沙门氏菌显著降低了血浆总胆固醇、甘油三酯和钙含量,显著提高了血浆谷草转氨酶活性(P0.05),极显著提高了血浆碱性磷酸酶活性(P0.01);凝结芽孢杆菌与沙门氏菌对血浆总蛋白含量、钙/磷及谷草转氨酶活性有显著交互作用(P0.05)。综上,凝结芽孢杆菌可改善蛋鸡生产性能和蛋品质,在蛋白质代谢、脂质代谢、肝功能和钙磷吸收上都具有一定程度的改善作用。     

植物乳酸杆菌对感染肠炎沙门氏菌蛋鸡生产性能、蛋品质及血浆生化指标的影响

为研究植物乳酸杆菌对感染肠炎沙门氏菌蛋鸡生产性能、蛋品质及血浆生化指标的影响,本试验选用400只沙门氏菌阴性蛋鸡,随机分成4个处理组,每处理组5个重复,每个重复20只试鸡。试验第1周,对照组（T1、T3组）饲喂基础日粮,试验组（T2、T4组）在基础日粮添加2×10⁸ CFU/g植物乳酸杆菌。饲喂1周后,T3、T4组试鸡连续2 d灌服1 mL肠炎沙门氏菌悬浮液（1.0×10⁸ CFU/mL）,T1、T2组试验鸡口服等量无菌PBS溶液。结果显示：①蛋鸡感染肠炎沙门氏菌后可极显著降低产蛋率（P_SE=0.02）及平均日采食量（P_SE=0.01）。添加植物乳酸杆菌可显著提高产蛋率（P_LP=0.02）,显著降低料蛋比（P_LP=0.04）。②蛋鸡感染肠炎沙门氏菌后,添加植物乳酸杆菌可显著增加蛋壳厚度（P_LP=0.01）和蛋壳强度（P_LP=0.02）,显著降低蛋黄颜色（P_LP=0.02）。③蛋鸡感染肠炎沙门氏菌后可极显著提高蛋鸡血浆中碱性磷酸酶（ALP）含量（P_SE<0.01）,植物乳酸杆菌干预可显著提高谷草转氨酶（AST）（P_LP=0.02）、钙（P_LP=0.04）和磷（P_LP=0.04）的含量。综上所述,植物乳酸杆菌可显著改善蛋鸡生产性能和蛋品质,维持蛋鸡生理生化指标稳定,同时可缓解沙门氏菌带来的病理损伤,保障蛋鸡机体健康。     

卵黄性腹膜炎、鸡白血病对种鸡死亡率、产蛋率影响的初步调查

为了探讨卵黄性腹膜炎和鸡白血病对种鸡死亡率和产蛋率的影响，在2016年1月至2017年4月中旬，对江苏省常州市某种鸡场岭南黄鸡、花鸡（金茅花鸡）、草鸡（金茅草鸡）、黄脚麻鸡4个品种鸡的发病及死亡情况进行临床症状观察及病理剖解；同时记录鸡场每日的鸡死亡数、产蛋数、每日免疫和用药情况，分析不同时期的死亡率和产蛋率，比较不同品种鸡的产蛋率及产蛋高峰期产蛋率与正常蛋鸡产蛋高峰期产蛋率（参考值80%）之间的差异。从死亡鸡的剖解结果来看，腹腔内卵黄凝固黏连在肠道上，输卵管肿大，充满白色或淡黄色干酪样物，初步诊断为卵黄性腹膜炎；肝脏和脾脏肿大，肠系膜或胸壁有肿瘤状物体，初步诊断为鸡白血病。岭南黄鸡产蛋后期的死亡率极显著高于产蛋上升期和高峰期（P<0.01），黄脚麻鸡产蛋后期的死亡率极显著低于产蛋高峰期（P<0.01）；花鸡、草鸡、黄脚麻鸡产蛋高峰期产蛋率平均值均低于60%，与参考值（80%）差异极显著（P<0.01）。综合试验结果，卵黄性腹膜炎和鸡白血病对鸡场影响严重，导致鸡死亡率上升，产蛋率下降；抗应激药和营养药可以起到缓解预防的作用，但无法根治，尚无有效的治疗方法。     

Observations on the distribution and persistence of Salmonella enterica serovar enteritidis phage type 29 on a cage layer farm before and after the use of competitive exclusion treatment

1. A continuously occupied cage layer house, which had been linked with a human outbreak of Salmonella Enteritidis PT29, was investigated to assess the distribution of contamination and the options for control. 2. The presence and persistence of Salmonella before and after application of competitive exclusion (CE) treatment was investigated by culturing samples from faeces, the environment, spent hens and eggs, and use of an ELISA to detect egg yolk antibodies. 3. A high prevalence of Salmonella was found in faecal and environmental samples before CE treatment was used but this reduced to minimal levels after treatment. 4. Egg yolk antibody assay suggested that although treated birds showed reduced excretion of Salmonella there was no difference between these and non-treated birds in terms of seroprevalence. 5. Contamination of the egg packing plant disappeared following CE. 6. Chicks and pullets in separate accommodation on site remained Salmonella free throughout despite no precautions being taken to avoid transmission of infection from the laying flock. 7. The rapid and substantial reduction in Salmonella in faeces, birds and the environment following the introduction of CE treatment suggests that further controlled field studies would be justified.     

Effect of electrostatic space charge on reduction of airborne transmission of Salmonella and other bacteria in broiler breeders in production and their progeny

Salmonella in birds is a concern because of the human foodborne illness associated with the consumption of poultry meat and eggs. One of the methods of transmission of Salmonella within a flock can be by the air. Therefore, we used reduction of transmission of Salmonella to monitor the effectiveness of the electrostatic space charge system (ESCS). During the average broiler breeder laying cycle of 40 wk, a large amount of dust becomes airborne and accumulates on walls, ceiling, and equipment. Many microorganisms adhere to these dust particles, making dust an excellent vector for horizontal disease transmission between birds.We used two environmentally controlled rooms containing commercial broiler breeders to evaluate the effectiveness of an ESCS that produced a strong negative electrostatic charge to reduce airborne dust and, subsequently, microorganism levels. The ESCS caused the dust to become negatively charged, therefore moving to the grounded floor in the treatment room. The use of the ESCS resulted in a significant reduction (P < 0.0001, 61% reduction) in airborne dust concentration levels, which resulted in a significant reduction (P < 0.0001, 76% reduction) in total airborne bacteria and gram-negative bacteria (48% reduction) in the treatment room. Significant reductions (P < 0.05) of gram-negative bacteria (63% reduction) on the egg collection belts were also recorded in the treatment room, which resulted in a significant reduction (P < 0.0001) of gram-negative bacteria (28% reduction) on the eggshell surface. The ESCS treatment resulted in fewer Salmonella enteritidis-positive hens and their progeny from the treatment room due to reductions of dust and airborne bacteria. In addition, this significant reduction in bacteria on the eggshell surface should result in less bacteria in the day-old chicks, therefore better early chick livability. There was no significant difference (P > 0.05) in egg production, male or female body weights, mortality, or reproductive performance in the ESCS room compared with the control room.     

The relationship between the duration of fecal shedding and the production of contaminated eggs by laying hens infected with strains of Salmonella enteritidis and Salmonella Heidelberg

Egg contamination by Salmonella Enteritidis has remained a significant public health problem for nearly two decades, and Salmonella Heidelberg has also been recently implicated in egg-transmitted human illness. Colonization of the intestinal tract is a necessary precursor to the invasion of reproductive organs and subsequent deposition inside eggs laid by infected hens, but the relationship between the persistence of Salmonella in the intestinal tract and the likelihood of egg contamination has been uncertain. In this study, groups of laying hens were inoculated with large oral doses of strains of Salmonella Enteritidis and Salmonella Heidelberg, including variants of the original parent strains that had been reisolated from eggs laid by infected hens in a prior study. The shedding of Salmonella in voided feces was monitored for 6 wk postinoculation, and all eggs laid by infected hens between 5 and 22 days postinoculation were cultured for Salmonella in their contents. The mean duration of fecal shedding was significantly longer for the previously passaged Salmonella strains (26.7 days) than for the original parent strains (17.5 days), and the passaged strains caused a significantly higher frequency of egg contamination (6.4%) than did the parent strains (3.3%). However, the duration of fecal shedding and the frequency of egg contamination were not correlated for any of the Salmonella Enteritidis or Salmonella Heidelberg strains.     

Evaluation of laying-hen feed with varied vitamin E and antioxidant supplementation

In two experiments with 1,250 laying hybrids the influence of the elimination of vitamin E and antioxidant supplements to the laying hen feed was tested. With mixed feed according to official quality requirements but without vitamin E and antioxidant supplements laying hens achieved the same laying performance and individual weight as the control group. There was no influence on feed consumption, feed expenditure per 100 g egg, mortality, development of body weight, the tensile strength of the eggs and the fat quality of the body either. Vitamin E content in the yolk increases with the growing vitamin E content in the feed. The vitamin E requirement norm of laying hens for consumer egg production is achieved at a native vitamin E content of 7 mg/kg laying hen feed. The supplement of synthetic antioxidant is unnecessary.     

Colonization of specific regions of the reproductive tract and deposition at different locations inside eggs laid by hens infected with Salmonella enteritidis or Salmonella heidelberg

Internal contamination of eggs by Salmonella Enteritidis has been a significant source of human illness for several decades and is the focus of a recently proposed U.S. Food and Drug Administration regulatory plan. Salmonella Heidelberg has also been identified as an egg-transmitted human pathogen. The deposition of Salmonella strains inside eggs is apparently a consequence of reproductive tissue colonization in infected laying hens, but the relationship between colonization of specific regions of the reproductive tract and deposition in different locations within eggs is not well documented. In the present study, groups of laying hens were experimentally infected with large oral doses of Salmonella Heidelberg, Salmonella Enteritidis phage type 13a, or Salmonella Enteritidis phage type 14b. For all of these isolates, the overall frequency of ovarian colonization (34.0%) was significantly higher than the frequency of recovery from either the upper (22.9%) or lower (18.1%) regions of the oviduct. No significant differences were observed between the frequencies of Salmonella isolation from egg yolk and albumen (4.0% and 3.3%, respectively). Some significant differences between Salmonella isolates were observed in the frequency of recovery from eggs, but not in the frequency or patterns of recovery from reproductive organs. Accordingly, although the ability of these Salmonella isolates to colonize different regions of the reproductive tract in laying hens was reflected in deposition in both yolk and albumen, there was no indication that any specific affinity of individual isolates for particular regions of this tract produced distinctive patterns of deposition in eggs.     

强制换羽对蛋鸡生产性能和蛋品质的影响

旨在研究强制换羽对蛋鸡生产性能和蛋品质的影响。选取80周龄海兰褐蛋鸡4 500只,分为A、B、C组,每组1 500只,于试验组Ⅰ区饲养;选取60周龄海兰褐蛋鸡3 000只,分为D、E组,每组1 500只,于试验组Ⅱ区饲养;另选取60周龄海兰褐蛋鸡1 500只（F组）,于对照组Ⅲ区饲养。试验组Ⅰ区和试验组Ⅱ区位于同一栋鸡舍,对照组Ⅲ区位于另外一栋鸡舍。采取饲料、饮水、光照控制的方式对A~E组鸡群进行强制换羽处理;F组不进行强制换羽处理。试验包括7 d的预试期和56 d的正试期。在正试期内,测定各组鸡群的产蛋率、蛋品质指标、死亡率。结果表明：与换羽前相比,强制换羽后A、B、C组的平均产蛋率的提高幅度为27.1%,强制换羽后D、E组的平均产蛋率的提高幅度为16.1%,换羽后F组的平均产蛋率的降低幅度为5.5%;5个接受强制换羽处理的试验组（A~E组）与对照组（F组）相比,蛋重增加2.5%,蛋壳强度提高11.8%,蛋白高度提高8.8%,蛋形指数提高3.3%,蛋壳尖端的厚度提高14.8%;5个接受强制换羽处理的试验组（A~E组）的平均死亡率为2.5%,对照组（F组）的死亡率为1.5%。综上所述,强制换羽技术的应用可以明显提高海兰褐蛋鸡的产蛋率,并提升蛋品质。     

Occurence of salmonellae in laying hens in different housing systems and inferences for control

As eggs represent now as ever the most important source for Salmonella infection in human beings and because of the currently occurring shift in housing conditions for laying hens from conventional cages to alternative systems it was studied whether the Salmonella prevalence in layers is influenced by the housing system. Following systems were considered: organic farming with free range management systems, floor management systems with free range, floor management systems without free range, conventional cages. 453 pooled faecal samples as single or double examination per herd from 329 flocks in different housing systems for table egg production from three Federal Lander were examined bacteriologically. The share of layer flocks which were Salmonella positive at least once independently of the housing system amounted to 32.2%. Analysis of the Salmonella findings in the single housing systems revealed that the share of Salmonella positive flocks was higher in conventional cage systems (46.3%) than in alternative housing systems (32.996% in organic farming with free range management systems, 21.9% in floor management systems with free range, 23.4% in floor management systems without free range).The results of the study clearly show that Salmonella Enteritidis (mostly phage type 4, other phage types rarely) presents with a share of 78% the dominant serovar in laying hens.The total number of all other serovars (apart from Salmonella Enteritidis and subspecies I rough) reached a share of ca. 14%, however, no other single serovar was dominant. As Salmonella Enteritidis is the predominant serovar in laying hens it is strongly recommended to use Salmonella Enteritidis vaccines for immunisation programmes of chickens during the rearing period. Because of the high prevalence of Salmonella organisms in the different housing systems, detailed information on the epidemiology of Salmonella in laying hens are needed to introduce effective control measures. Of particular interest is the question whether the Salmonella findings in laying flocks are the result of multiplication of already existing Salmonella organisms in the animals or whether the bacteria are introduced only during the laying period.     

Effects of vaccination and other preventive methods for Salmonella enteritidis on commercial laying chicken farms

The effect of introducing vaccinated commercial laying chickens on to farms, which previously had laying flocks that were infected with Salmonella Enteritidis, was investigated by sampling faeces and environmental samples, and in some cases spent hens. In 15 of 17 free-range flocks vaccination eliminated any evidence of infection. In 11 barn egg production flocks, vaccination produced similar results in four flocks on one farm but infection persisted in seven flocks on other farms. Vaccination of two consecutive cage layer flocks led to a gradual disappearance of the infection, but in 18 other flocks there was evidence of infection after vaccination. In one continuously occupied cage layer house, treatment by competitive exclusion was followed by a gradual disappearance of S Enteritidis in faeces and a substantial reduction in its levels in the environment. On four barn egg production sites disinfection with a formaldehyde, glutaraldehyde and quaternary ammonium compound disinfectant eliminated Salmonella species even though birds housed subsequently were not vaccinated. In three flocks that had been vaccinated for four years, S Enteritidis was still present. In most cases the poor performance of the vaccine was associated with severe rodent control problems and a poor standard of cleaning and disinfection.     

不同季节蛋种鸡产蛋性能的测定分析

以海兰褐蛋种鸡为观察对象,从122日龄开始到429日龄结束,收集7 520只蛋种鸡1个产蛋年（2014年1月—12月）的产蛋资料,分析得出每月的产蛋率、破蛋率等相关数据,对12个月的数据进行统计分析。结果表明,产蛋率以春季最高,秋季最低;种蛋合格率冬季最高,秋季最低;料蛋比以冬季最高,春季最低;破蛋率以夏秋两季最高,冬季最低;死淘率以秋季最高,冬季最低。     

Prevention of fatal cage-layer osteoporosis

Regular necropsy of samples of laying hen mortality at a large cage-layer ranch revealed significant loses due to osteoporosis. The feeding program consisted of feeding a pullet-growing diet until egg production commenced followed by a change to a laying diet. Literature review and experimental results have demonstrated a requirement for 2% dietary calcium for about 2 wk before first egg is anticipated followed by transfer to a higher calcium level during lay. A nutritional regimen of this design was tested on two paired sister flocks of hens. Necropsy of mortality during the tests showed a striking reduction in mortality due to osteoporosis.     

Differences among six Salmonella serovars in abilities to colonize reproductive organs and to contaminate eggs in laying hens

The abilities of Salmonella serovars to colonize the reproductive organs of chickens and to contaminate eggs were compared. Mature laying hens were inoculated intravenously with 10(5) colony-forming units of Salmonella enteritidis, Salmonella typhimurium, Salmonella infantis, Salmonella hadar, Salmonella heidelberg, or Salmonella montevideo to cause the systemic infection. Salmonella enteritidis was recovered from three yolks of the laid eggs (7.0%), suggesting egg contamination from the transovarian transmission of S. enteritidis. The liver, spleen, and cecum were colonized by each serovar similarly at 4 or 7 days postinoculation (PI), whereas the ovary and preovulatory follicles were colonized by S. enteritidis with significantly (P < 0.05) higher levels than by the other serovars at 4 and 7 days PI. Salmonella enteritidis was recovered from the cloaca and vagina at 2, 4, and 7 days PI and from the other portions of the oviduct at 4 and 7 days PI. In addition, S. enteritidis had been persistent in the peripheral blood for 7 days PI. These results suggest that S. enteritidis is the predominant serovar to colonize the reproductive organs of mature laying hens among six serovars used in this study, reflecting the field situatibn in which the predominant outbreaks of human salmonellosis were caused by S. enteritidis-contaminated eggs recently. The ability of S. enteritidis to colonize the reproductive organs may be one of the reasons that egg contamination with S. enteritidis has increased.     

日粮添加甜菜碱对夏季高温蛋鸡生产性能、蛋品质及血液理化特征的影响

本研究旨在评估夏季高温时日粮添加甜菜碱对蛋鸡生产性能、蛋品质及骨骼和血液理化特性的影响.试验将480只产蛋性能一致的罗曼粉壳蛋鸡随机分为2组,每组240只,每组10个重复(24只/重复).对照组饲喂基础试验日粮,处理组蛋鸡饲喂基础试验日粮+150?mg/kg甜菜碱,试验为期8周.结果:日粮添加150?mg/kg甜菜碱对...     

The clinical course of the Infectious Laryngotracheitis (ILT) field case in hens and estimation of immunoprophylaxis efficiency

The ILT case was observed in laying hen farm where birds of different age (from 40 to 107 weeks) were kept in 10 flocks. A rapid spread of the disease, the decrease in egg production (in flock No. 1 it reached 58%) and higher mortality (the highest in 76 and 77 week-old birds, accounting for 0.11% and 0.36%, respectively ) was recorded during first 2 weeks of disease. Antibodies against ILT virus were detected in serum of the examined birds during the whole observation period (50 weeks after the disease outbreak). The laying hens were vaccinated at 8 weeks of age and boosted after 5 weeks. The vaccine was applied in drinking water, in a dose twice as high as usually recommended per one bird. Immunopropylaxis efficiency was estimated on the basis of immunological response in birds (serum samples, ILT ELISA kit, Guildhay Ltd.) and general health status of hens in flocks. Postvaccinal immunity, the presence of specific antibodies against ILT, was observed in all birds during the observation period (51 weeks). During that time GMT value ranged from 8261,3 (week 10) to 5196 (week 51) after the second vaccination, and CV amounted in this period to 41.1% and 51%, respectively. Subsequently, clinical symptoms of the disease disappeared and the egg production, as well as mortality, returned to the level of technological norms for laying hens.     

Vaccination of turkey breeder hens and toms for fowl cholera with CU strain

Unvaccinated laying breeder hens and semen-producing toms were susceptible to the CU strain of Pasteurella multocida and highly susceptible to a virulent strain of P. multocida. Laying breeders vaccinated with CU strain when environmental temperatures were low ceased egg production during the first week after vaccination and had 29% mortality, whereas those vaccinated when temperatures were moderate had only a 25% decrease in egg production and 17% mortality. Comparable nonlaying breeders vaccinated during moderate temperatures did not die. Although few semen-producing toms died postvaccination and the quantity and quality of semen was not affected, 21.7% developed torticollis. Laying breeders were protected against CU vaccine and challenge with virulent P. multocida if vaccinated every 4 weeks beginning when 7 weeks old. Potential breeders vaccinated before laying with combinations of 3 vaccinations via drinking water, wing-web puncture, or inoculation into the air spaces of the head through the auditory tube were protected against challenge after the onset of laying. However, vaccination via wing-web puncture at 25 weeks of age resulted in abscesses that failed to resolve. The combination of vaccinations most effective in protecting laying breeders was vaccination in the drinking water at 7 and 11 weeks and inoculation into the air spaces of the head at 15 weeks.     

不同日粮组成对蛋鸡生产性能及鸡蛋品质的影响

选用５７６只１５４日龄海赛克斯蛋鸡探讨不同日粮组成对蛋鸡生产性能及鸡蛋品质的影响。共计３个处理，每个处理４个重复，每个重复４８只鸡，全阶梯三层笼养，自由采食、饮水，进行产蛋率大于８０％的饲养试验。试验期为４周。试验结束后，对各处理的产蛋率、只日产蛋量、料蛋比、破蛋率、每千克蛋耗料成本及蛋的品质指标进行统计分析。试验结果表明，采食３种日粮的试鸡在产蛋量、破蛋率、采食量等指标差异不显著（Ｐ＞０．０５），但采食无鱼粉日粮的试鸡料蛋比、死淘率最低，每千克蛋饲料成本最低（Ｐ＜０．０５），且产蛋率最高（Ｐ＜０．０５）。蛋形指数、蛋壳厚度、蛋壳强度、哈氏单位４项指标上３个处理间无明显差异（Ｐ＞０．０５）。     

An outbreak of avian urolithiasis on a large commercial egg farm

A significant outbreak of avian urolithiasis was observed on a large commercial egg farm. From the initial outbreak site (a single laying house), the incidence of urolithiasis slowly spread in the ensuing months to numerous other laying houses. Increasing mortality associated with urolithiasis commenced during late growout to early lay and then leveled off when egg production peaked. At the height of the outbreak, mortality was typically 0.5% per week; 75% of this mortality was due to urolithiasis. The clinical and pathologic features of this condition are described. Both infectious bronchitis virus (IBV) and fowl adenoviruses were isolated from organ homogenates of sampled birds. A clone of the IBV strain was found to induce nephritis in specific-pathogen-free white leghorns.     

Review of induced molting by feed removal and contamination of eggs with Salmonella enterica serovar Enteritidis

As laying hens age, egg production and quality decreases. Egg producers can impose an induced molt on older hens that results in increased egg productivity and decreased hen mortality compared with non-molted hens of the same age. This review discusses the effect of induced molting by feed removal on immune parameters, Salmonella enterica serovar Enteritidis (SE) invasion and subsequent production of SE-contaminated eggs. Experimental oral infections with SE show molted hens are more susceptible to SE infection and produce more SE-contaminated eggs in the first few weeks post-molt compared with pre-molt egg production. In addition, it appears that molted hens are more likely to disseminate SE into their environment. Molted hens are more susceptible to SE infection by contact exposure to experimentally infected hens; thus, transmission of SE among molted hens could be more rapid than non-molted birds. Histological examination of the gastrointestinal tracts of molted SE-infected hens revealed more frequent and severe intestinal mucosal lesions compared with non-molted SE-infected hens. These data suggest that induced molting by feed deprivation alters the normal asymptomatic host-pathogen relationship. Published data suggest the highest proportion of SE-positive eggs is produced within 1-5 weeks post-molt and decreases sharply by 6-10 weeks and dissipates to the background level for non-molted hens by 11-20 weeks. Appropriate treatment measures of eggs produced in the fist 5 weeks post-molting may decrease the risk of foodborne infections to humans.