Mycoplasma Gallisepticum Vaccine Research Articles

Effects of Prelay ts11-Strain Mycoplasma gallisepticum Inoculation and Time-Specific F-Strain M. gallisepticum Inoculation Overlays on Internal Egg and Eggshell Characteristics of Commercial Laying Hens ,

Mycoplasma infections are pandemic in multiage layer chicken flocks, with Mycoplasma gallisepticum being the species of greatest concern to commercial egg producers. Live M. gallisepticum vaccines are presently being used to help control M. gallisepticum outbreaks. However, vaccination of layers with F-strain M. gallisepticum may adversely affect egg production. In the present study, 2 trials were conducted to compare the effects of 2 currently available live Mycoplasma vaccines (the ts11- and F-strains), used in conjunction, on internal egg and eggshell characteristics. The following 4 inoculation treatments were used: 1) sham at 10 wk of age (control), 2) ts11 at 10 wk, 3) ts11 at 10 wk overlaid by F at 22 wk, and 4) ts11 at 10 wk overlaid by F at 45 wk. In each trial at various ages between 23 and 57 wk of age, percentage of yolk weight, percentage of yolk moisture, percentage of yolk lipid, percentage of albumen weight, Haugh unit scores, and percentage of shell weight of eggs were assessed. At wk 32, percentage of yolk lipid was increased in eggs belonging to the ts11 at 10 wk and ts11 at 10 wk overlaid by F at 22 wk treatment groups in comparison with controls. There was also a significant decrease in percentage of albumen weight in eggs in the treatment with ts11 at 10 wk overlaid by F at 22 wk, as well as a decrease in Haugh unit scores in the ts11 at 10 wk treatment in comparison with controls during post-peak lay. Percentage of yolk moisture, percentage of egg yolk weight, and percentage of eggshell weight in layers were not significantly affected by a 10-wk ts11 inoculation alone or in conjunction with subsequent overlay inoculations of F during lay. It is suggested that a 10-wk inoculation of commercial layers with ts11-strain M. gallisepticum may reduce the negative impacts of a prelay F-strain M. gallisepticum inoculation on performance while providing protection against subsequent field strain M. gallisepticum infections.

Stabilization of Live Mycoplasma gallisepticum Vaccines During Vaccination with Second-Generation Spray-Vac Vaccine Stabilizer

ABSTRACT Dilution and application of live Mycoplasma gallisepticum vaccines without the use of vaccine-stabilizing compounds may lead to significant loss of vaccine viability and loss of vaccine efficacy. Vaccine viability may decrease because of osmotic lysis of the mycoplasma as well as the presence of free chlorine or other detrimental chemicals in the water. Second-generation Spray-Vac vaccine stabilizer was developed and shown to maintain live Mycoplasma gallisepticum vaccine viability during exposure to free chlorine while protecting from the other factors that appear to decrease vaccine survival in solution. Increased vaccine survival in solution should lead to increased survival of the vaccine during vaccination. Field trial results demonstrate that second-generation Spray-Vac vaccine stabilizer yields excellent results without the need for distilled water or other vaccine-stabilizing compounds.

Effects of a Prelay 6/85-Strain Mycoplasma gallisepticum Inoculation Alone or in Conjunction with Subsequent F-Strain M. gallisepticum Inoculations During Lay on the Internal Egg Characteristics of Commercial Egg-Laying Hens

The effects of a prelay 6/85-strain Mycoplasma gallisepticum (6/85MG) inoculation alone or in conjunction with subsequent F-strain M. gallisepticum (FMG) inoculations during lay on the internal egg characteristics of commercial egg-laying hens were investigated. In the first 2 treatment groups, birds were sham inoculated or were inoculated with 6/85MG at 10 wk of age. In a third treatment group, birds were inoculated with 6/85MG at 10 wk in conjunction with a subsequent inoculation of FMG at 22 wk, and in a fourth treatment group, birds were inoculated with 6/85MG at 10 wk in conjunction with a subsequent inoculation of FMG at 45 wk. Percentage yolk weight, albumen weight, yolk moisture, and yolk lipid were determined at 24, 32, 43, 47, and 58 wk of hen age. The data from wk 24, 32, and 43 were analyzed separately from those at wk 47 and 58. Furthermore, yolk fatty acid profiles were determined at wk 58. The applied treatments affected yolk moisture and fatty acid profiles. Across wk 24, 32, and 43, yolk moisture content was higher in birds inoculated with 6/85MG at 10 wk and FMG at 22 wk when compared with control birds and those inoculated with 6/85MG at 10 wk alone. In addition, at wk 58, yolk palmitic, oleic, and linolenic acid concentrations were affected differently by treatment. A 22-wk FMG inoculation in birds previously inoculated with 6/85MG at 10 wk may increase yolk moisture content, and alterations in yolk palmitic, oleic, and linolenic acid levels with treatment may be manifested by disturbances in fatty acid synthesis.

Effect of Selected Water Temperatures Used in Mycoplasma gallisepticum Vaccine Reconstitution on Titer at Selected Time Intervals

Numerous methods are currently used throughout the poultry industry for the administration of vaccines. Each utilizes water for vaccine reconstitution and/or administration, including two of the three commercially available live Mycoplasma gallisepticum (MG) vaccines. Selected water temperatures were used to reconstitute and/or dilute the three commercially available live MG vaccines. Water temperatures included 4 C, 22 C (room temperature), and 32 C, and titer (color change units) was recorded at four time intervals, at point of reconstitution (time 0), 15, 30, and 60 min postreconstitution of the vaccines (time periods 15, 30, and 60, respectively). Results for F strain MG (FMG) vaccine showed significant decreases in titer from time 0 to time 15 for the 22 C and 32 C water temperatures but no significant decrease for any time period for FMG reconstituted with 4 C water. For 6/85 strain MG no significant difference in titer was noted for any of four time periods within any of the three water temperatures. For ts-11 strain MG a significant decrease was observed in titer at each of the four postdilution time periods when diluted with 32 C water. There was no significant decrease in titer at any time period for ts-11 MG vaccine when diluted with either 4 C or 22 C water.

Effects of 6/85-Strain Mycoplasma gallisepticum Inoculation Alone at Ten Weeks of Age or in Conjunction with F-Strain Mycoplasma gallisepticum Inoculation Overlays at Twenty-Two or Forty-Five Weeks of Age on the Performance of Commercial Egg-Laying Hens ,

The effects of 6/85-strain Mycoplasma gallisepticum (6/85MG) inoculation alone or in conjunction with a F-strain M. gallisepticum (FMG) overlay and its timing on the performance of commercial egg-laying hens were investigated. Control birds received sham inoculations at 10 wk of age. A second treated group of birds was inoculated with 6/85MG at 10 wk of age, a third treatment group of birds was inoculated with 6/85MG at 10 wk and received an overlay of FMG at 22 wk, and a fourth treatment group was inoculated with 6/85MG at 10 wk followed by a 45-wk overlay inoculation of FMG. Parameters investigated between 20 and 55 wk of age included BW, mortality, weekly and total egg production, egg weight, relative eggshell conductance, eggshell weight per unit of surface area, percentage shell weight, yolk/albumen ratio, and egg shape index. Hen age effects were reported for BW, egg weight, yolk/albumen ratio, and egg production. No treatment effects or hen age × treatment interactions were noted for those parameters except for yolk/albumen ratio, and no significant effects of any kind were noted for the remaining parameters examined. At wk 47, a significant treatment effect for yolk/albumen ratio was noted. The yolk/albumen ratio in the group of birds that received 6/85MG at 10 wk followed by an overlay of FMG at 22 wk was significantly lower than the sham control birds and those that were inoculated with 6/85MG at 10 wk followed by a 45-wk overlay inoculation of FMG. Prelay 6/85MG inoculations may be a suitable substitute for prelay FMG inoculations, and FMG overlays during lay on prelay 6/85MG inoculations may provide continual protection without eliciting any subsequent suppressive effects on performance.

The Effects of Increasing Sodium Chloride Concentration on Mycoplasma gallisepticum Vaccine Survival in Solution

Lyophilized Mycoplasma gallisepticum (MG) vaccines are generally rehydrated and diluted with distilled or chlorine-free water as per manufacturer recommendations. However, as mycoplasma species lack a cell wall, this can lead to decreased viability of live vaccine during administration. The ability of phosphate-buffered saline (PBS) to prevent losses in live vaccine viability was examined. It was shown that a concentration of 1 x PBS prevented the two-fourfold decrease in MG viability seen when the vaccines were diluted with water alone.

Effects of System Pressure and Nozzle Type on Spray Application of Avian Vaccines

Optimization of vaccine delivery via spray application of live Mycoplasma gallisepticum (MG) vaccine to commercial caged layer chickens is impacted by many factors. One of these factors is the pressure utilized to dispense the vaccine, which affects both application rate and droplet size. MG vaccine was applied using a self-propelled, constant speed vaccinator operated at two different pressures and using three different nozzles. Droplet size and as-applied coverage and deposition were measured to determine the effects of system pressure and nozzle type on spray characteristics. Vaccine viability was also assessed to determine how viability is affected by the spray application process.

Effects of Increased Dosages of the Mycoplasma Gallisepticum Vaccine MYCOVAC-L® in Layer Chickens Subsequently Challenged with Virulent M. gallisepticum: Egg Production and Serologic Response

Ten-week-old Hy-Line Commercial W-36 pullets were spray-vaccinated with MYCOVAC-L at the manufacturer's recommended dosage (1x) or at 15 times that rate (15x). At 22 or 45 wk of age, subsets of 1x- and 15x-vaccinated pullets were challenged with the virulent Mycoplasma gallisepticum (MG) strain Rlow. Percent hen-day egg production was determined through week 55. Analyses for treatment effects on overall (22-56 wk) percent hen-day egg production revealed no significant differences between nonchallenged 1x and nonchallenged 15x MYCOVAC-L treatments. Among 1x MYCOVAC-L-vaccinated groups, Rlow challenge at 45 wk corresponded to significantly (P < or = 0.01) lower overall egg production compared with the unchallenged 1x-vaccinated control (70.88% vs. 79.15%, respectively). Conversely, at the 15x MYCOVAC-L dosage level, overall egg production was not significantly affected by virulent MG challenge at 45 wk compared with its unchallenged counterpart (84.09% vs. 81.03%, respectively) and could indicate increased protection from virulent MG challenge. Serologic monitoring indicated the virulent MG challenge was consistently (100%) associated with seroconversion. Comparisons among the nonchallenged experimental treatments indicated that vaccinations at the 15x MYCOVAC-L dosage rate were associated with a greater seroconversion rate at weeks 21, 27, and 44, but not at week 50.

Effects of S6-Strain Mycoplasma gallisepticum Inoculation at Ten, Twenty-Two, or Forty-Five Weeks of Age on the Blood Characteristics of Commercial Egg-Laying Hens ,

In 2 consecutive trials of the current study, the effect of the age of application of S6-strain Mycoplasma gallisepticum (S6MG) inoculation on the blood characteristics of commercial layers housed and maintained under controlled conditions was determined. The ages of inoculation compared were those before lay at 10 wk of age, during onset of lay at 22 wk of age, and during postpeak lay at 45 wk of age. In each trial, hematocrit, plasma protein, and serum cholesterol, triglycerides, and Ca were determined at 20, 24, 32, 43, 47, and 58 wk of age. The data from both trials were pooled then analyzed together, whereas, data from wk 20 (effect of 10-wk S6MG inoculation); data from wk 24, 32, and 43 (effects of 10- and 22-wk S6MG inoculations); and data from wk 47 and 58 (effects of 10-, 22-, and 45-wk S6MG inoculations) were analyzed separately. At wk 20, hematocrit was higher in birds inoculated with S6MG at 10 wk compared with sham-inoculated birds, and across wk 24, 32, and 43, serum Ca was higher in birds inoculated with S6MG at 10 or 22 wk compared with those that were sham-inoculated. Serum Ca level across wk 47 and 58 was higher in birds inoculated with S6MG at 10 wk compared with sham-inoculated controls and birds inoculated with S6MG at 22 wk, with 45-wk S6MG-inoculated birds being intermediate. The response of serum cholesterol level at 47 wk to S6MG inoculation at either 10, 22, or 45 wk compared with controls was nearly opposite to that of the response observed at 58 wk. However, serum triglycerides were depressed only at wk 47 due to the 45-wk S6MG inoculation compared with all other treatments. Variable post-peak alterations in serum Ca and lipids occur in response to the timing of S6MG inoculation in layers housed under controlled conditions.

The effect of a live vaccine on the horizontal transmission of Mycoplasma gallisepticum

The effect of a live Mycoplasma gallisepticum vaccine on the horizontal transmission of this Mycoplasma species was quantified in an experimental animal transmission model in specific pathogen free White Layers. Two identical trials were performed, each consisting of two experimental groups and one control group. The experimental groups each consisted of 20 birds 21 weeks of age, which were housed following a pair-wise design. One group was vaccinated twice with a commercially available live attenuated M. gallisepticum vaccine, while the other group was not vaccinated. Each pair of the experimental group consisted of a challenged chicken (10(4) colony-forming units intratracheally) and a susceptible in-contact bird. The control group consisted of 10 twice-vaccinated birds housed in pairs and five individually housed non-vaccinated birds. The infection was monitored by serology, culture and quantitative polymerase chain reaction. The vaccine strain and the challenge strain were distinguished by a specific polymerase chain reaction and by random amplified polymorphic DNA analysis. In both experiments, all non-vaccinated challenged chickens and their in-contact 'partners' became infected with M. gallisepticum. In the vaccinated challenged and corresponding in-contact birds, a total of 19 and 13 chickens, respectively, became infected with M. gallisepticum. Analysis of the M. gallisepticum shedding patterns showed a significant effect of vaccination on the shedding levels of the vaccinated in-contact chickens. Moreover, the Cox Proportional Hazard analysis indicated that the rate of M. gallisepticum transmission from challenged to in-contact birds in the vaccinated group was 0.356 times that of the non-vaccinated group. In addition, the overall estimate of R (the average number of secondary cases infected by one typical infectious case) of the vaccinated group (R = 4.3, 95% confidence interval = 1.6 to 49.9) was significantly lower than that of the non-vaccinated group (R = infinity, 95% confidence interval = 9.9 to infinity). However, the overall estimate of R in the vaccinated group still exceeded 1, which indicates that the effect of the vaccination on the horizontal transmission M. gallisepticum is insufficient to stop its spread under these experimental conditions.

Effects of S6-Strain Mycoplasma gallisepticum Inoculation at Ten, Twenty-Two, or Forty-Five Weeks of Age on the Egg Yolk Composition of Commercial Egg-Laying Hens

Commercial laying hens maintained under controlled conditions were experimentally inoculated with the S6 strain of Mycoplasma gallisepticum (S6MG) at 45 wk of age. This resulted in depressed liver lipid concentration, and inoculations at 20 and 45 wk affected the size of various portions of the reproductive tract. In 2 consecutive trials of the current study, the effect of age of application of S6MG inoculation on the egg yolk characteristics of commercial layers similarly housed and maintained under controlled conditions was determined. The ages of inoculation compared were prior to lay at 10 wk of age, during onset of lay at 22 wk of age, and during postpeak lay at 45 wk of age. In each trial, yolk moisture and total lipid content were determined at 24, 32, 43, 47, and 58 wk of age. Yolk cholesterol concentration and yolk fatty acid profiles at wk 47 and 58 were also examined. Data from wk 24, 32, and 43 (effects of S6MG inoculations at 10 and 22 wk) and data from wk 47 and 58 (effects of S6MG inoculations at 10, 22, and 45 wk) were analyzed separately. The data of both trials were pooled then analyzed together. Across wk 47 and 58, percentage yolk lipid was significantly lower in eggs laid by birds inoculated at 10 wk compared with those inoculated at 45 wk. Sham-inoculated control and 22-wk inoculated groups had intermediate percentage yolk lipids. Compared with sham-control and 10-wk S6MG inoculation groups across wk 47 and 58, yolk myristic, oleic, and linolenic acid concentrations were reduced, whereas yolk stearic and arachidonic acid levels were increased by either 22- or 45-wk S6MG inoculations. In comparison with all other treatment groups at wk 47, yolk linoleic acid concentration was reduced by S6MG inoculation at 45 wk. Variable postpeak alterations in yolk total lipid and fatty acid content occur in response to the timing of S6MG inoculation in layers housed under controlled conditions.

Effects of S6-Strain Mycoplasma gallisepticum Inoculation at 10, 22, or 45 Weeks of Age on the Digestive and Reproductive Organ Characteristics of Commercial Egg-Laying Hens

Experimental inoculation of commercial laying hens with the S6-strain of Mycoplasma gallisepticum (S6MG) at 20 wk of age, while being maintained under ideal conditions, has previously been shown to affect the lengths and weights of various portions of the reproductive tract. Two trials were conducted in the current study to compare the effects of S6MG inoculation prior to lay at 10 wk of age, during onset of lay at 22 wk of age, and during lay at 45 wk of age on the digestive and reproductive organs of commercial layers similarly housed and maintained under ideal conditions. In each trial, liver weight, liver moisture and lipid concentration, incidence of fatty liver hemorrhagic syndrome, ovary weight, ovarian mature follicle numbers, weights and lengths of the oviduct and oviductal regions, and weights and lengths of the small intestine and small intestinal regions were examined at 60 wk of hen age. At 60 wk, liver lipid concentration was depressed, and isthmus weight, as a percentage of total oviduct weight, was increased in birds that had been inoculated with S6MG at 45 wk. Alterations in liver lipid content and weight of the isthmal portion of the oviduct may occur in response to S6MG inoculation during the later stages of production in layers housed under ideal conditions.

Initial Proteomics Analysis of Differentially Expressed Proteins from Mycoplasma gallisepticum Vaccine Strains ts-11 and F Detected by Western Blotting

Mycoplasma gallisepticum (MG) is the causative agent of chronic respiratory disease in laye r chickens. The live MG vaccine strains that are available for use in layer chickens include F, ts-11 and 6/85. The MG vaccine strains ts-11 and 6/85 are safer than F and they have little or no potential of spreading from bird to bird. However, ts-11 and 6/85 appear to be less efficacious than F-strain. Results from studies suggest that the use of MG vaccine strain F in replacement flocks over a period of time results in th e displacement of the original field strain. Also, reports of MG breaks in layer flocks previously vaccinated with ts-11 or 6/85 have resulted in revaccination of these flocks with F. The continued use of F-strain in displacement and revaccination regimens necessitates the development of more rapid and sensitive field tests that will differentiate between wild-type and vaccine strains of MG. In the present study, ts-11 and F- strain whole cell extracts were analyzed by Western blotting and proteomic methodologies. Differentially expressed protein bands were excised, in-gel digested with trypsin, and analyzed by mass spectrometry. The proteins were identified as internal proteins and were predicted to be involved in such cellular processes as carbohydrate transport and metabolism, energy production and conversion, posttranslational modification, protein turnover, chaperone activity, transcription, and translation. The results of this study suggest that proteomics may aid in the characterization of proteins that could contribute to the development and improvement of current MG diagnostic tests.

Effects of S6-strain Mycoplasma gallisepticum inoculation at ten, twenty-two, or forty-five weeks of age on the performance characteristics of commercial egg laying hens

Experimental inoculation of commercial laying hens, maintained under controlled conditions, with the S6-strain of Mycoplasma gallisepticum (S6MG) at 10 wk of age has previously been shown to affect the lengths and weights of various portions of the reproductive tract without affecting subsequent performance. Two trials were conducted to compare the effects of S6MG inoculation at 10 wk of age (prior to lay), 22 wk of age (onset of lay), and 45 wk of age (during lay) on performance characteristics in commercial layers housed and maintained under controlled conditions, as in previous studies. In each trial, BW, mortality, egg production, egg weight, eggshell weight per unit of surface area, percentage eggshell weight, percentage albumen weight, percentage yolk weight, and yolk weight per albumen weight ratio were examined at various ages throughout an entire laying cycle. Across wk 47 and 58 (age periods after the last 45 wk inoculation), eggshell weight per unit of surface area and percentage eggshell weight were significantly reduced in birds that had received an S6MG inoculation at 45 wk of age when compared with birds that had not received an S6MG inoculation or had been inoculated with S6MG at either 10 or 22 wk of age. Alterations in eggshell quality in response to S6MG may become evident only in older birds that are experiencing declines in production when housed under controlled conditions.

Floor Pen Study to Evaluate the Serological Response of Broiler Breeders After Vaccination with ts-11 Strain Mycoplasma gallisepticum Vaccine

To determine the Mycoplasma gallisepticum (MG) rapid serum plate agglutination (RSPA) test response of broiler breeders after ts-11 strain vaccination, 55 Cobb pullets derived from a nonvaccinated, MG-negative, commercial, broiler breeder grandparent flock were monitored from 8 to 20 wk of age (over a 12-wk trial period). To evaluate the effect of lateral spread of the ts-11 vaccine strain on RSPA test results from commingled and adjacently penned birds, treatment groups included (A) birds vaccinated with ts-11strain MG at 8 wk of age, (B) commingled nonvaccinates in the same pen as the vaccinated birds, (C) nonvaccinates in a second pen separated from the first pen by a distance of 2 m, and (D) birds vaccinated with ts-11 strain MG at 8 wk of age and kept in a separate room. Rapid serum plate agglutination tests were performed once a week for 6 wk and then every 2 wk for 6 more wk, postvaccination. A polymerase chain reaction (PCR) assay specific fbr ts-11 strain MG was used to confirm vaccination, and a second PCR specific for non-ts-11 strain MG was used to confirm the absence of field infection. Seroconversion was first detected by the RSPA test 2 wk postvaccination and attained maximum positive rates of 58% at 12 wk postvaccination in treatment A and 60% at 8 wk postvaccination in treatment D. Seroconversion rates in nonvaccinated, commingled pullets was 10% at 5 wk and 30% at 12 wk after the vaccination of pen mates. The ts-11-specific PCR detected the vaccine strain in 80%-100% of the vaccinated birds 2 wk after vaccination. One of 15 nonvaccinated birds penned 2 m from vaccinated birds yielded ts-11 by PCR assay 12 wk after vaccination, which indicates that the spread of ts-11 over short distances may be possible in situations in which there is a common caretaker. PCR on tracheal swabs taken 12 wk postvaccination detected ts-l1 in 50% and 60% of the vaccinated birds in treatments A and D, respectively; in 30% of the commingled nonvaccinates; and in 6.6% of the separately penned nonvaccinates. In contrast, choanal swabs collected from vaccinated birds at 12 wk were 21% and 40% PCR positive for ts-11 strain MG, while those from nonvaccinates were negative. All samples were PCR negative for field strain MG. The pattern of seroconversion as measured by RSPA test in small groups of broiler breeders was different from that previously reported for leghorns. Lateral spread of the ts-11 strain to commingled pen mates occurred rapidly, causing RSPA seroconversion patterns that mimicked those of the vaccinated pen mates.

Safety of Mycoplasma gallisepticum Vaccine Strain 6/85 After Backpassage in Turkeys

The objective of this research was to evaluate the safety of the 6/85 strain vaccine strain of Mycoplasma gallisepticum in turkeys by backpassing the vaccine strain up to 10 times by contact infection in turkeys and challenging turkeys with the resulting backpassaged strain. The vaccine strain, however, did not spread to in-contact turkeys, and it was necessary to reisolate the organism before challenging turkeys for the next passage. The challenge strain, therefore, was one that had been backpassaged four times in turkeys, with a total in vivo time in turkeys of 66 days. The backpassaged 6/85 vaccine strain was no different in pathogenicity than the original vaccine strain, except that at 10 days postchallenge, it was isolated in higher numbers from air sacs. Both the original 6/85 vaccine strain and the backpassaged strain were apathogenic in turkeys, except for a slightly increased diameter of the tracheal mucosa at 10 days postchallenge; at 20 days postchallenge the tracheal mucosal thickness was no different from that of controls.

Effects of an S6 Strain of Mycoplasma gallisepticum Inoculation Before Beginning of Lay on the Leukocytic Characteristics of Commercial Layers

A clinical study was conducted on commercial layers housed in biological isolation units, within which exogenous stress factors potentially affecting bird performance were minimized. This set-up was devised in order to assess how a pre-lay inoculation of S6 strain Mycoplasma gallisepticum affects the leukocytic properties of laying chickens. Previous studies have demonstrated relative decreases in lymphocyte and relative increases in heterophil percentages in birds infected with other strains of Mycoplasma gallisepticum. However, current results showed that the differential percentages of lymphocytes were decreased, whereas those of heterophils were increased, in both sham-inoculated control birds and birds inoculated with S6 Mycoplasma gallisepticum between 19 and 26 wk of age. This study clearly shows that a pre-lay inoculation of S6 Mycoplasma gallisepticum alone had no apparent effect on the leukocyte profile of commercial layers housed in biological isolation units.

Effects of F-strain Mycoplasma gallisepticum inoculation on serum very low density lipoprotein diameter and fractionation of cholesterol among lipoproteins in commercial egg-laying hens

Experimental inoculation with the F-strain of Mycoplasma gallisepticum (FMG) at 12 wk of age has been shown to affect the performance, liver, reproductive organs, and yolk lipid characteristics of commercial layers. Therefore, this study was conducted to determine the serum lipoprotein characteristics of commercial egg-laying hens at 16 wk of age and throughout lay after inoculation with FMG at 12 wk of age. Mean diameters of very low density lipoproteins (VLDL) were determined for the 10th, 50th, and 90th percentiles of serum total VLDL of each hen. Percentages of total serum cholesterol recovered in VLDL and low and high density lipoprotein particle classes were also determined. Inoculation of birds with FMG at 12 wk did not change the physical properties or relative concentrations of their circulating lipoproteins. However, the age of the bird had significant differential effects on all the parameters examined. These data demonstrate that FMG-inoculation at 12 wk of age does not affect the lipoproteins of laying hens, but because these birds were housed in biological isolation units, these results do not preclude the possibility that these yolk precursors may be affected in FMG-infected birds that are housed in facilities in which there are increased levels of environmental stress. These data further suggest that alterations in liver, reproductive organs, and yolk lipid characteristics in response to FMG, as noted in previous reports on commercial layers, are not mediated through changes in circulating VLDL diameters.

Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on the blood characteristics of commercial egg laying hens

In two trials, the effects of an F-strain Mycoplasma gallisepticum (FMG) inoculation at 12 wk of age on the blood characteristics of commercial Single Combed White Leghorn laying hens were investigated throughout lay. Variables measured in both trials were whole blood hematocrit, plasma protein (PP), and serum cholesterol, triglycerides (ST), and calcium. In both trials, hematocrit at 20 wk of age was significantly increased in birds inoculated with FMG. In trial 1, ST and PP were significantly increased at 22 wk of age by FMG, while ST and PP were significantly decreased in FMG-inoculated birds at wk 54 and 52, respectively. When combined with the establishment of an FMG infection, the initial weeks of egg production become particularly stressful to the bird. Increases in these independent blood parameters between 8 and 10 wk postchallenge are suggestive of compensatory responses in these birds to an FMG challenge. Postpeak decreases in both ST (54 wk) and PP (52 wk) in FMG-infected birds may be the result of a more chronic effect of FMG on lipid and protein synthesis in the liver. These data are the first to suggest that alterations in egg production in response to FMG-infection in commercial layers, as noted in a previous report, may be associated with changes in hematocrit. However, because ST and PP were not affected by FMG in both trials, the responses of these blood parameters to FMG-infection may be inconsistent among flocks.

Phenotypic and antigenic variation of Mycoplasma Gallisepticum vaccine strains

Phenotypic and antigenic variations among Mycoplasma gallisepticum vaccine F and Ts-11 strains were investigated by SDS-PAGE and serological methods (hemagglutination-inhibition and immunoblot assays). The SDS-PAGE system followed by densitometer analysis showed weak phenotypic variability between the strains, being the major difference close to the 75 kDa level where a prominent peptide band was detected only in the F vaccine strain. Polyclonal antibodies to the M. gallisepticum antigens produced in chickens were used in serological tests for this antigenic variability study. There were strong cross-reactions between the strains and homologous/ heterologous antibodies. The most evident characteristic was the specific response of the vaccine-type F polyclonal antiserum to the 75 kDa peptide band of the homologous strain.