Eggshell penetration of hen's eggs by Salmonella enterica serovar Enteritidis upon various storage conditions

1. The survival and penetration of Salmonella enterica serovar Enteritidis (SE) inoculated on the eggshell was examined upon storage for up to 20 d at real-life conditions (15 to 25 degrees C and 45 to 75% relative humidity (RH)). 2. Penetration was assessed by emptying the egg contents and filling the eggs with a selective medium that allowed visualising Salmonella growth on the inside of the shell and membrane complex. 3. The study of survival on the eggshells was based on viable counts and showed that numbers of surviving organisms decreased over time. Survival was inversely related to storage temperature and RH. Although the average counts decreased over time, a limited proportion of shells carried high numbers of SE at all storage conditions. 4. Penetration spots were observed earlier using an increased storage temperature due to increased growth rates of SE on the agar. After 20 d of storage a similar percentage (c. 44.7%) of eggshells became penetrated, irrespective of the storage conditions tested in this study. 5. The higher the Salmonella shell contamination at the end of storage, the higher the probability that the eggshell was penetrated. Salmonella shell counts exceeding 4 log cfu yielded more than a 90% probability of eggshell penetration occurring.     

Bacteriology of washed and unwashed eggs. II. Penetration of Salmonella bacteria through the eggshell

The ability of the eggshell to resist penetration of Salmonella bacteria was studied in unwashed and in hand washed eggs, and in eggs, which had been subjected to industrial, large-scale machine washing under strictly controlled conditions.In one part of the investigation, concerning unwashed and machine washed eggs, a defined amount of a broth culture of Salmonella typhi murium was applied on the shell surface, whereafter the eggs were incubated at 4°C for eight weeks or at 30°C for 12 days. At the end of the storage period, the egg contents were examined for the presence of Salmonella. No Salmonella bacteria were detected in the 120 eggs investigated.In another part of the investigation, dealing with 200 unwashed, 200 hand washed and 200 machine washed eggs, a broth culture of Salmonella was applied on the shell surface of eggs, whose contents had been poured out through an opening. In every second egg of each kind, the shell membranes had been scraped off over an area, corresponding to the placement of the bacterial inoculum. The eggshells were filled with enrichment broth and the occurrence of Salmonella bacteria in this broth was examined after incubation.In the eggs with intact shell membranes, the frequencies of Salmonella positive enrichment broths were for unwashed eggs 0.12, for machine washed eggs 0.10, and for hand washed eggs 0.22. The corresponding frequencies in eggs with removed shell membranes were 0.27 (unwashed), 0.42 (machine washed), and 0.60 (hand washed).No statistical difference occurred between unwashed and machine washed eggs when the shell membranes were intact. When the shell membranes were removed this difference was statistically almost significant. The difference between machine washed and hand washed eggs with intact shell membranes was statistically almost significant, while the same difference was highly significant in eggs with removed shell membranes.The author assumes, from the results of the present and a preceding investigation, that the applied washing procedure in no way harms any essential storage properties of uncracked eggs. Considering the known occurrence of hand washing of eggs in Swedish farms — a treatment with documentedly unfavourable influence — it would be desirable if all eggs could be subjected to machine washing under strictly controlled conditions at the grading stations. Such an arrangement ought to result in an increase in the average bacteriologic-hygienic quality of eggs for market.     

Effect of lighted incubation on embryonic growth and hatchability performance of two strains of layer breeder eggs

1. Eggs from two layer-type breeder flocks (ISA-W vs Leghorn) between 30 and 45 weeks of age were used in 4 trials to study the effects of lighted incubation on embryonic growth from 5 to 18 d of age and hatchability per cent (HP). The physical dimensions, eggshell characteristics and conductance (EC) of eggs of the two strains were compared. 2. Eggs were set in an incubator on trays either in the dark-control or under two tubes of 20-watt white fluorescent light during the first 18 d of incubation. The light intensity ranged from 1230 to 1790 lux at the surface of the eggs. Eggs were transferred to dark hatching compartments at d 19 of incubation. 3. The genetic make-up of birds influenced the physical dimensions and eggshell characteristics of eggs. ISA-W eggs had higher weight, surface area (ESA), volume (EV), width, EC, shell volume and HP, and lower ESA:EV ratio, per cent shell, shell density and dead embryos than those of Leghorn eggs. 4. Lighted incubation increased daily embryonic growth (mg/d) and HP by 3.9 and 5.9%, respectively, when compared with the dark-control incubation. 5. The physical dimensions and eggshell characteristics of eggs influenced the effects of lighted incubation on embryonic growth and HP. Lighted incubation increased embryonic growth and HP of ISA-W eggs. The increase in embryonic growth and HP of the Leghorn eggs was not significant. 6. The genetic make-up of birds influenced the physical dimensions and eggshell characteristics of their eggs and these differences in the characteristics of hatching eggs influenced embryonic growth and HP when incubated under light.     

植物乳杆菌对致病性肠炎沙门氏菌感染蛋鸡的生产性能及其蛋、粪含菌量的影响

试验旨在研究植物乳杆菌（Lactobacillus plantarum,LP）对致病性肠炎沙门氏菌（Salmonella enteric,SE）感染蛋鸡的生产性能和鸡蛋、粪中病菌残留的影响。选用144只50周龄农大3号蛋鸡,分4个组,每组4个重复,每个重复9只鸡。空白对照组和阳性对照组饲喂基础日粮;土霉素组在基础日粮中添加5 mg/kg土霉素;乳杆菌组在基础日粮中添加10⁹ CFU/kg植物乳杆菌。阳性对照组、土霉素组和乳杆菌组蛋鸡在试验第22和24天口腔接种1 mL沙门氏菌（10⁹CFU/mL）,试验期50 d。结果显示：攻毒前,各组生产性能指标无显著差异（P>0.05）;攻毒后,与空白对照组相比,感染前期阳性对照组平均蛋重显著降低（P < 0.05）,料蛋比显著升高（P < 0.05）,鸡蛋中沙门氏菌带菌率和粪中沙门氏菌含菌量显著升高（P < 0.05）。与阳性对照组相比,感染前期土霉素组和乳杆菌组蛋鸡平均蛋重分别提高5.43%（P < 0.05）、9.64%（P < 0.05）,料蛋比分别降低11.51%（P < 0.05）、5.16%（P > 0.05）;感染后期乳杆菌组料蛋比降低9.96%（P < 0.05）,乳杆菌组鸡蛋中沙门氏菌带菌率和粪中沙门氏菌含菌量分别比阳性对照组降低43.17%、23.93%（P < 0.05）。空白对照组、乳杆菌组和土霉素组间生产性能和鸡蛋大肠杆菌、沙门氏菌带菌率均无显著差异（P > 0.05）。以上结果表明,日粮中添加植物乳杆菌和土霉素均可改善沙门氏菌感染蛋鸡的生产性能,降低鸡蛋和粪中的沙门氏菌含量,提高家禽抗感染能力。植物乳杆菌具有无污染、无残留的特点,可作为家禽养殖中理想的抗生素替代品。     

Effects of Lactobacillus plantarum on Production Performance,Egg and Feces Bacteria content of Salmonella enteric-Infected Hens

The experiment was conducted to study the influence of Lactobacillus plantarum (LP) on production performance, egg and feces Salmonella enteric (SE) residues of SE-infected hens. 144 fifty-week-old Nongda No.3 hens were randomly allocated to 4 treatments with 4 replicates of 9 hens each. The hens in blank control and positive control groups were fed the basal diet, terramycin group, the basal diet with terramycin (5 mg/kg), LP group, the basal diet with Lactobacillus plantarum (10⁹CFU/kg). The hens in positive control, terramycin and LP groups were oral inoculated with 1 mL SE (10⁹CFU/mL) on 22 and 24 d. The experiment lasted for 50 d. Before being vaccinated, the production performance of each group showed no significant difference (P > 0.05); After being vaccinated, in early period, compared with blank control group, the average egg weight significantly decreased (P < 0.05), the feed-egg ratio significantly increased (P < 0.05), and the SE content of eggs and feces significantly increased (P < 0.05) in positive control group. Compared with positive control group, the average egg weight in terramycin group and LP group increased by 5.43% and 9.64% respectively (P < 0.05), while the feed-egg ratio decreased by 11.51% (P < 0.05) and 5.16% (P > 0.05) respectively. In later period, the feed-egg ratio in LP group decreased by 9.96% (P < 0.05), SE content of eggs and feces in LP group decreased by 43.17% and 23.93% respectively (P < 0.05). The production performance and E. coli, SE-carrying rates of eggs had no significant difference among the blank control, LP and terramycin groups (P > 0.05). The results indicated that, supplemented with Lactobacillus plantarum or terramycin could improve the production performance, reduce the SE content in eggs and feces, and improve the ability to resist infection in hens. Because Lactobacillus plantarum had the characteristics of no pollution and no residue, it could be used as a kind of ideal substitute for antibiotics in poultry production.     

规模化鸡场种蛋蛋壳、蛋内容物的总菌数、大肠杆菌数、沙门氏菌数测定

用稀释滴种法对四川四个万只以上父母代种鸡场送检新鲜种鸡蛋，每个鸡场随机抽检20枚进行了蛋壳、蛋内容物总菌数、大肠杆菌数、沙门氏菌数的定量计数测定。结果表明：不同鸡场的不同种蛋的蛋壳、蛋内容物的总菌数、大肠杆菌、沙门氏菌检出率有较大变化范围，但不同鸡场间带菌对数值平均数和检出率差异都不显著（P＞0.05）。各规模化种鸡场的种蛋所带大肠杆菌在蛋壳上及蛋内容物中均为优势菌。     

The influences of SE infection on layers’ production performance,egg quality and blood biochemical indicators

Background： Salmonella enterica serovar Enteritidis （SE）, as a major cause of foodborn illness, infects humans mainly through the egg. However, the symptom of laying hens usually is not typical and hard to diagnosis. In the present study, it is studied that the influences of SE infection on layers＇ performance, egg quality and blood biochemical indicators. It will help us to improve the strategy to control SE infection in commercial layers. One hundred layers at 20 wk of age were divided into 2 groups, 60 hens for experiment and others for control. The experiment group was fed with the dosage of 108 CFU SE per hen. The specific PCR was used to detect the deposition of SE. On the 8 d after SE infection, 10 hens from the control group and 30 hens from the experimenta group were slaughtered to detect the SE colonization. The production performance, egg quality and blood biochemical indices were also analyzed. Results： The results showed that the colonization rate of SE was highest in caecum contents （55.17%） and lowest in vagina （17.24%）. For the eggs the detection rate of SE was highest on the eggshell （80.00%） and lowest in yolk （18.81%）. SE infection had no significant influence on production performance and egg qualities （P 〉 0.05）. The difference of laying rate between the experimental and control groups was less than 0.30%, and both were approximately equal to 82.00%. The blood analysis showed that the aspartic aminotransferase （AST） and alanine aminotransferase （ALT） of experimental group was significantly higher than those of control group （P 〈 0.05）. For experimental and control groups AST values were 236.22 U/I and 211.84 U/I respectively, and ALT values were 32.19 U/I and 24.55 U/I. All of coefficients were less than 20%. The colonization of SE in organs increases the enzyme activities of AST and ALT in blood. Conclusions： SE in feed could invade the oviduct and infect the forming eggs. It significantly increased the concentration of ALT and AST in blood. Ho     

Growth of Salmonella typhimurium and Salmonella enteritidis in egg yolks from highly immunized hens.

This experiment was conducted to ascertain whether the growth of Salmonella Enteritidis (SE) or Salmonella Typhimurium (ST) would be suppressed in the presence of antibodies contained in egg yolks. Specific pathogen-free chickens (102 days of age) were subcutaneously immunized with oil-adjuvanted bacterin of SE or ST, twice within a four-week interval. During 160 to 170 days of age, eggs were collected, the yolks were removed and mixed with an equal volume of physiological buffered saline, inoculated with ten colony forming units (CFU) of SE or ST, and incubated at 37 degrees C or 20 degrees C for 23 hr. The growth of organisms in each yolk solution was examined. The egg yolk derived from non-immunized hens was examined in the same manner as the controls. There was no difference in the growth titer between the antibody-positive yolk and the negative yolk. The result suggests that the antibodies in the yolk do not influence the growth of each organism, even if the hens are highly immunized.     

Evaluation of the efficacy of Salmonella enteritidis oil-emulsion bacterin in an intravaginal challenge model in hens.

The efficacy of Salmonella enteritidis (SE) oil-emulsion bacterin (a commercially available vaccine) was evaluated in an intravaginal challenge model in hens producing a high rate of SE-contaminated eggs. Hens were vaccinated at 38 wk of age. A second (booster) bacterin injection was administered 4 wk later. Two weeks after the second vaccination, all hens were challenged intravaginally with 10(7) colony-forming units of SE. After challenge, 36 of 189 eggs (19.0%) in the vaccinated hens were positive for SE, and this contamination rate was significantly (P < 0.01) lower than that in the unvaccinated hens (61 of 165 eggs, 37.0%). SE was highly recovered from the cloacal and vaginal swabs of the unvaccinated and vaccinated hens, but the number of SE from the cloaca of the vaccinated hens was significantly (P < 0.05) lower than that in the unvaccinated hens at 7 days post-challenge (PC). The recoveries of SE from the spleen and ovary in the vaccinated hens were significantly (P < 0.05) lower than those in the unvaccinated hens at 7 days PC. At necropsy, SE was recovered from 2 of 15 forming eggs (13.3%) taken from the oviducts of the unvaccinated hens, whereas no SE was recovered from 17 forming eggs in the vaccinated hens. After vaccination, serum antibodies for SE in the vaccinated hens were significantly higher than those in the unvaccinated hens. Antibodies from the oviductal washing, especially immunoglobulin G isotype, in the vaccinated hens were higher than those in the unvaccinated hens after challenge. This intravaginal challenge model produced frequent contaminated eggs and clearly demonstrated the ability of the bacterin to protect against egg contamination. The present model may be a useful tool for further studies to evaluate the protective effect against SE contamination of eggs by potential vaccine candidates.     

Colonization of a marker and field strain of Salmonella enteritidis and a marker strain of Salmonella typhimurium in vancomycin-pretreated and nonpretreated laying hens

This study was conducted to evaluate the influence of a vancomycin pretreatment on the ability of marker (nalidixic-acid resistant) Salmonella Enteritidis (SE(M)), field Salmonella Enteritidis (SE(E)), and marker Salmonella Typhimurium (ST(M)) strains to colonize within the intestinal and reproductive tracts and translocate to other organs of leghorn laying hens. In each of three trials, caged laying hens (76, 26, and 33 wk ofage) were divided into six groups designated to receive SE(M), SE(F), or ST(M), and half were pretreated with vancomycin (n = 11-12 hens). Vancomycin-treated hens received 10 mg vancomycin in saline/kilogram body weight orally for 5 days to inhibit Gram-positive bacteria within the intestines. On Day 6, all hens were concurrently challenged by oral, intravaginal, and intracolonal routes with Salmonella and placed into separate floor chambers by Salmonella strain. Two weeks postinoculation, all hens were euthanatized and the ceca, spleen, liver/gall bladder (LGB), upper (URT), and lower (LRT) reproductive tracts, and ovarian follicles were aseptically collected, and analyzed for Salmonella. Results did not differ for the three hen's ages and were therefore combined. The vancomycin pretreatment also had no significant effect on the colonization ability of SE(M), SE(F) or ST(M), and therefore results were combined within Salmonella strain. The marker strain of Salmonella Enteritidis was recovered from 21% of ceca, 4% of LGB, 9% of LRT, and 17% of the fecal samples. The field strain of Salmonella Enteritidis was recovered from 88% of ceca, 96% of spleen, 92% of LGB, 30% of LRT, 4% of URT, 13% of follicle, and 42% of the fecal samples. The marker strain of Salmonella Typhimurium was recovered from 100% of ceca, 74% of spleen, 91% of LGB, 30% of LRT, 9% of URT, 9% of follicle, and 100% of the fecal samples. Among ceca, spleen, LGB, and fecal samples, SE(F) and ST(M) colonization was significantly greater than SE(M) colonization. Overall prevalence of Salmonella in the reproductive tracts of challenged hens was relatively low, ranging from 4% to 30%.     

Line differences in resistance to salmonella enteritidis pt4 infection

1. Four groups of hens, each of a different line, were inoculated at peak of lay, per os in the crop with 1 ml of a suspension containing 10⁹ cfu/ml Salmonella enteritidis PT4 (SE). The kinetics of SE contamination in the environment, egg shell and yolk were studied during the first 28 d post inoculation. On the day of slaughter, intestines, caeca, spleen, liver, ovary, oviduct and content were investigated for SE contamination.

2. The commercial egg‐type line L2 was found to be the most susceptible to SE. It laid many SE‐positive yolks (13.8%) and internal and faecal organs were frequently infected.

3. Certain lines are found to exhibit a degree of resistance to SE; the cause of which is unknown and might be attributed to major genes.     

Differences in abilities to colonize reproductive organs and to contaminate eggs in intravaginally inoculated hens and in vitro adherences to vaginal explants between Salmonella enteritidis and other Salmonella serovars

In Experiment 1, mature laying hens were inoculated intravaginally with 10(6) colony-forming units of Salmonella enterica serovar enteritidis (S. enteritidis), Salmonella typhimurium, Salmonella infantis, Salmonella hadar, Salmonella heidelberg, or Salmonella montevideo to compare their abilities to colonize the reproductive organs of chickens and to contaminate eggs. Salmonella enteritidis was more frequently recovered (from 11 of 40 eggs, 27.5%) than the other serovars, and especially the inner shell was contaminated with these organisms in 10 of 40 eggs (25.0%). The contamination rates and the viable counts in cloaca were significantly (P < 0.05) higher in hens inoculated with S. enteritidis than in those inoculated with the other serovars at 4 days postinoculation (PI). In the vagina, the positive rates were 90%-100% in hens inoculated with S. enteritidis, and the viable counts of the organisms in this portion were significantly (P < 0.05) higher than those of the other serovars at 2, 4, and 7 days PI. The ceca were colonized similarly by each serovar at 7 days PI. The spleen and ovary were infected with S. enteritidis in three and one hen, respectively. No Salmonella was recovered from liver and peripheral blood in any hen. Salmonella enteritidis was recovered from other oviductal portions than the vagina (10%-20%), whereas no forming egg was contaminated in the oviduct. In Experiment 2, the in vitro adherence of these six serovars to the vaginal epithelium was compared with vaginal explants. The mean number of S. enteritidis attaching to the secondary villi in the vaginal lumen was significantly (P < 0.05) higher than those of the other serovars. These results suggest that S. enteritidis has a specific advantage over the other Salmonella serovars by its capacity to colonize the vaginal tissues of hens, and this higher affinity of S. enteritidis to the vagina may play a significant role in the production of many S. enteritidis-contaminated eggs.     

Salmonella Enteritidis: the egg and I

SUMMARY: The world-wide clinical incidence of Salmonella Enteritidis has increased markedly. The increase is associated with the enhanced ability of the bacterium to systemically colonise layer chickens. Subsequent contamination and consumption of intact shell eggs from colonised layer hens, either directly or in foods containing raw or lightly cooked eggs, causes human disease. Despite investigation, no change in the biology of the bacterium has been correlated with increased colonisation in chickens. To date, no method of control at the production level has proven effective; consumer education is the best means of minimising the public health risk.     

BACTERIAL PENETRATION IN FLOOR AND NEST BOX EGGS FROM MEAT AND LAYER BIRDS

A method similar to that used by Board and Board (1967) was used to determine the numbers of eggs penetrated by bacteria on 3 poultry farms in south-east Queensland. Significant differences in the percentages of penetrated eggs between the eggs of layer birds (9.7%) and the eggs of meat birds (16.1%) and between nest eggs (10.5%) and floor eggs (15.3%) were detected. The distribution of the numbers of penetration points was similar for nest and floor eggs for both types of bird and was independent of shell surface area or thickness.     

The effect of killed Salmonella enteritidis vaccine prior to induced molting on the shedding of s. enteritidis in laying hens

Effects of administering killed Salmonella enterica serovar enteritidis (SE) vaccines to laying hens prior to induced molting on egg production and on shedding of SE were investigated. Forty hens were vaccinated with one of two SE vaccines available commercially in the United States and Japan. Twenty-five days after vaccination, feed was withdrawn for 2 wk from 20 vaccinated plus 10 unvaccinated hens to induce molt. Four days after molt induction, all hens were challenged with a dose of 2.4 X 10(9) of SE. For the 25 days following administration of the SE bacterins, egg production in vaccinated hens showed approximately a 15% decrease. After molt induction, egg production in molted hens ceased and then returned to normal levels 8 or 9 wk postvaccination. Through the 3-mo experimental period, the decreases in numbers of eggs laid in the unvaccinated/molted group and two vaccinated/molted groups were 225 (26.2%), 245 (28.4%), and 274 (31.9%), respectively, compared with 860 in the unvaccinated/unmolted group. There was no significant difference in egg lay at the P < 0.05 level among the former three groups. Hens in the vaccinated/molted groups shed about two logs less SE than hens in the unvaccinated/molted group 3 14 days postchallenge (P < 0.05 or 0.01). These results indicate that vaccination prior to induced molting might be effective in preventing the exacerbation of SE problems within flocks in which the potential for SE contamination may exist.     

Salmonella enteritidis in chicken eggs

After an outbreak caused by salmonella enteritidis (SE) of which home-made mayonnaise and remoulade sauce were found to be the cause, SE was detected in ten of the remaining eggs. Subsequently 409 eggs of the next shipment from the same outlet were examined bacteriologically. Of 70 of the eggs examined, SE was found in 5 egg yolk samples and in 3 egg white samples as well as in 2 of 7 pooled shell samples. Five out of 35 pooled whole egg samples comprising a total of 349 eggs were likewise positive for SE. The isolates belonged to the phage types 4 and 7 carried the virulence plasmid pRQ29.     

Application of Ionized Reactive Oxygen Species for Disinfection of Carcasses,Table Eggs,and Fertile Eggs

We evaluated the effect of ionized reactive oxygen species created using Binary Ionization Technology (BIT) for disinfection of broiler carcasses, table eggs, and treatment of fertile eggs. Previous research has indicated that BIT creates a high concentration of reactive oxygen species (ROS) that lyse bacterial cells on contact. Application of BIT to broiler carcasses that had been intentionally inoculated with 1.58 × 10⁶ Salmonella enterica Enteritidis (SE) caused a 1 to 3 log reduction in recoverable SE, depending on the duration of the treatment. Additionally, after inoculation of table eggs with 6.8 × 10⁸ cfu of SE, we recovered SE from 95% fewer eggs following enrichment and found significantly fewer (7.77 and 7.41 log reduction) colony-forming units recovered from eggs treated with BIT compared with nontreated control eggs. We also evaluated whether application of the BIT treatment had any effect on hatchability of broiler breeder eggs to determine whether use of this technology could be feasible in a hatchery environment for disinfection of eggs. There were no significant effects of BIT on the hatchability (of total set) of treated eggs as compared with nontreated control eggs; however, there was a slight numerical increase in hatchability, between 5 and 10% in 2 trials. These data suggest that application of BIT technology to carcasses and table eggs could reduce contamination with pathogens and that the application to fertile eggs may not have effects on hatchability of eggs set.     

Hot air treatment for surface decontamination of table eggs experimentally infected with Salmonella,Listeria, and Escherichia coli

Hot-air pasteurization was investigated in the EU-funded project “Reducing Egg Susceptibility to Contaminations in Avian Production in Europe (RESCAPE)” as an innovative treatment for surface bacterial decontamination of table eggs. Possible side effects of the treatment on egg quality traits were also studied. The decontamination power of hot air was evaluated over 1 month on shell eggs that were experimentally inoculated with Salmonella enteritidis, Escherichia coli, or Listeria monocytogenes. The S. Enteritidis and L. monocytogenes populations on the surfaces of treated eggs showed a significant reduction compared with untreated eggs. No statistically significant results were obtained comparing E. coli loads on treated and untreated eggs. No detrimental effects on quality traits either immediately after treatment or after 28 days of storage at 20°C were recorded.

     

Comparison of prophylactic or therapeutic dietary administration of capsaicin for reduction of Salmonella in broiler chickens

In three experiments the effects of prophylactic or therapeutic dietary inclusion of capsaicin, the pungent component of peppers, were evaluated as a nonantibiotic alternative for reduction of Salmonella in broiler chickens through culture and morphologic assessment of cecal tissue. Expt. 1 evaluated the effects of 0 or 10 ppm purified capsaicin (CAP) in the starter phase (days 1-16) on chicks challenged with Salmonella Enteritidis (SE) on day of age. Therapeutic inclusion of 10 ppm purified CAP increased (P < 0.05) liver/spleen (L/S) and ceca positive results for SE. In Expt. 2, capsaicin oleoresin (CO) was included in the finisher diet (days 30-37) at 0, 5, or 20 ppm with SE challenge on day 31. Inclusion of 5 ppm CO increased ceca positive results for SE, and a linear decrease in cecal lamina propria thickness of SE-challenged birds was observed with increased CO concentration in the diet. Expt. 3 evaluated prophylactic CO treatment at 0, 5, or 20 ppm in starter, grower, and finisher diets for resistance to SE or Salmonella Typhimurium (ST) challenge on day 14 or 29. With challenge on day 14, 5 and 20 ppm prophylactic CO feeding reduced ceca SE positive results by 37% and 26%, respectively, and ST culture rate was reduced similarly with 5 ppm CO. Lamina propria thickness of the ceca increased with 5 ppm CO feeding in SE-challenged birds, whereas a decrease was observed in nonchallenged birds fed 5 ppm CO. Challenge on day 29 of birds fed 20 ppm CO resulted in reduced L/S positive results for SE. Lamina propria thickness decreased with 5 ppm CO and SE or ST challenge compared with nonchallenged birds fed 5 ppm. An increase was observed in ST- or SE-challenged birds fed 20 ppm CO compared with nonchallenged birds fed 20 ppm CO. No differences were observed in mast cell number in either Expt. 2 or 3. These data provide evidence that prophylactic or therapeutic dietary capsaisin differentially affects broiler susceptibility to Salmonella.     

蛋壳胶护膜研究进展

蛋产品安全一直是人们重点关注的问题,也是研究的热点。随着福利养殖的推广,鸡蛋被微生物污染的机率增大。除了加强饲养管理之外,强化鸡蛋自身保护屏障从而抵抗细菌入侵也十分重要。胶护膜是蛋壳最外层覆盖的无色透明膜,鸡蛋产出前1.5~2.0 h于子宫部形成,是蛋抵御微生物污染的重要屏障,研究表明胶护膜较厚的蛋不易被细菌入侵。鸡蛋蛋壳胶护膜主要由糖蛋白（90%）、多糖（4%）、脂质（3%）和以羟基磷灰石晶体形式存在的无机磷（3%）组成。胶护膜中含有溶菌酶C、卵转铁蛋白、ovocleidin-32等多种抗菌蛋白,可有效地阻碍细菌跨壳污染。此外,胶护膜能终止蛋壳矿化、帮助蛋产出前在子宫中翻转、调节水气交换以延长鸡蛋的保存时间。本文对胶护膜的结构、生物学功能、胶护膜品质评价方法及胶护膜质量的影响因素等方面进行了阐述,并对尚待解决的问题展开了探讨。