Source: MISSISSIPPI STATE UNIV submitted to NRP
MYCOPLASMA GALLISEPTICUM INFECTION, IMMUNITY, AND BLOOD AND ORGAN CHARACTERISTICS IN COMMERCIAL LAYING HENS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0183446
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 1999
Project End Date
Sep 30, 2004
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
MISSISSIPPI STATE UNIV
(N/A)
MISSISSIPPI STATE,MS 39762
Performing Department
POULTRY SCIENCE
Non Technical Summary
A comprehensive investigation of blood and organ characteristics associated with immunity and reproductive performance in commercial egg-laying chickens infected with mycoplasma gallisepticum.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3013210102060%
3113210110040%
Knowledge Area
311 - Animal Diseases; 301 - Reproductive Performance of Animals;

Subject Of Investigation
3210 - Egg-type chicken, live animal;

Field Of Science
1100 - Bacteriology; 1020 - Physiology;
Goals / Objectives
In uninfected birds and birds vaccinated with MG throughout lay, the objective is to determine differences in various blood and tissue components which are important to immunity and egg formation. The association between these changes and those in reproductive performance will be monitored. Further studies to investigate the effects of immunomodulation on performance, and the blood and tissue variables important to immunity and egg formation are planned.
Project Methods
A series of similarly designed trials will be conducted in an effort to better determine the physiological and biochemical means by which MG infection alters reproductive performance in layers. Birds will be innoculated with MG prior to lay, and reproductive and blood parameters will be monitored at regular intervals throughout a complete production cycle. Successive trials will be designed based on results of previous trials.

Progress 10/01/99 to 09/30/04

Outputs
The potential mechanisms responsible for alterations in production parameters and physiological characteristics of birds inoculated with either the S6 (S6MG), TS-11 (TS-11MG), or F (FMG) strains of Mycoplasma gallisepticum were examined. All parameters selected for examination had a potential role in influencing the uptake, metabolism, and deposition of materials necessary for egg production (EP) in infected chickens. In isolation units, 12 wk FMG-inoculation delayed onset of lay 1 wk, decreased EP 34 wk post-inoculation, decreased overall EP, and resulted in a higher incidence of fatty liver hemorrhagic syndrome, ovarian follicular regression, and decreased isthmal and vaginal proportions of the reproductive tract. Serum lipoprotein characteristics and concentrations were, nevertheless, not impacted. Increases in hematocrit, serum triglycerides, and plasma protein between 8 and 10 wk post FMG-inoculation, suggest that the initial weeks of EP are stressful, and post-peak decreases in both serum triglycerides and plasma protein suggest a more chronic inhibition on lipid and protein synthesis in the liver. Decreased blood lipid concentration may be directly responsible for the reductions in yolk lipid, cholesterol, and fatty acid deposition in 12 wk FMG-inoculated hens. In the caged layer facility, onset of lay was also delayed 1 wk in birds inoculated with FMG at 12 wk and total egg mass was decreased by 1000 g. Feed conversion was also increased by 0.5 g feed/g egg in 22 wk FMG-inoculated birds. However, as in the isolation units, the lipoprotein profiles of the birds in the caged layer facility were not affected by FMG inoculation. In isolation units, TS11MG vaccination at 10 weeks of age followed by FMG inoculation at 22 weeks of age had no effect on EP, egg weight, eggshell breaking strength, Haugh unit scores, pimpling incidence, or blood/meat spot incidence over the initial 15 weeks of production. However, in another study comparing the effects of S6MG administered at 10, 22, and 45 weeks of age, across Weeks 47 and 58 (age periods after the last 45 wk inoculation), both eggshell weight per unit of surface area (SWUSA) and percent eggshell weight were significantly reduced in birds that had received an S6MG inoculation at 45 wk when compared to birds that had either not received an S6MG inoculation or had been inoculated with S6MG at either 10 or 22 wk of age. Nevertheless, 10 week S6MG inoculations had no apparent effect on the leukocytic profiles of commercial layers housed in the biological isolation units.

Impacts
Inoculation with FMG at 12 wk of age appeared to be more desirable and cost efficient than an FMG inoculation at 22 wk of age, and higher degrees of physiological stress experienced by hens in a caged layer facility may exacerbate the effects of FMG-inoculation seen in the isolation units. Overall, these data demonstrated that alterations in performance and egg characteristics of commercial layers inoculated with FMG at either 12 or 22 wk of age and housed in either isolation units or caged layer facilities are related to mutual functional disturbances in the blood, liver, ovary, and oviduct without concomitant intestinal changes. Furthermore, although TS11MG vaccination at 10 weeks of age followed by FMG inoculation at 22 weeks of age did not influence subsequent production, alterations in eggshell quality in response to S6MG may become evident in older birds that are experiencing declines in production when housed under ideal conditions.

Publications

  • Peebles, E. D., T. A. Parker, S. L. Branton, K. O. Willeford, M. S. Jones, P. D. Gerard, G. T. Pharr, and W. R. Maslin, 2004. Effects of an S6 strain of Mycoplasma gallisepticum inoculation before beginning of lay on the leukocytic characteristics of commercial layers. Avian Dis. 48:196-201.
  • Peebles, E. D., M. R. Burnham, R. L. Walzem, S. L. Branton, and P. D. Gerard, 2004. Effects of fasting on serum lipids and lipoprotein profiles in the egg-laying hen (Gallus domesticus). Comp. Biochem. Physiol., Part A. 138(3):305-311.
  • Vance, A. M., S. D. Collier, S. L. Branton, E. D. Peebles, and J. D. Evans, 2004. Infection by the TS-11-strain of Mycoplasma gallisepticum in commercial egg-laying hens persists in conjunction with a subsequent infection by the F-strain. Proc. SPSS, Poultry Sci. 83(Suppl, 1):21(Abstr. #83).
  • Branton, S. L., E. D. Peebles, P. D. Gerard, J. D. Evans, S. C. Collier, W. R. Maslin, and A. M. Vance, 2004. Effect of overlaying F-strain Mycoplasma gallisepticum on TS-11 vaccinated laying hens. Proc. SPSS, Poultry Sci. 83(Suppl. 1):21(Abstr. #84).
  • Basenko, E. Y., S. W. Park, E. D. Peebles, S. L. Branton, D. V Maurice, S. K. Whitmarsh, and P. D. Gerard, 2004. Egg characteristics of commercial egg laying hens between 20 and 58 weeks of age when inoculated with S6-strain of Mycoplasma gallisepticum at 10, 22, or 45 weeks of age. Poultry Sci. 83(Suppl. 1):108.


Progress 01/01/03 to 12/31/03

Outputs
The potential mechanisms responsible for alterations in production parameters and physiological characteristics of birds inoculated with the F-strain of Mycoplasma gallisepticum (FMG) at 12 wk in fiberglass isolation units and at 12 and 22 wk in a caged layer facility were examined. All parameters selected for examination had a potential role in influencing the uptake, metabolism, and deposition of materials necessary for egg production (EP) in chickens infected with FMG. In isolation units, 12 wk FMG-inoculation delayed onset of lay 1 wk, and decreased EP 34 wk post-inoculation and overall EP, and resulted in a higher incidence of fatty liver hemorrhagic syndrome, ovarian follicular regression, and decreased isthmal and vaginal proportions of the reproductive tract. Ovarian regression may be related to retarded production (liver), transport (blood), and/or uptake (ovary) of yolk particles. Changes in blood (i.e. lipid) characteristics with FMG colonization of the liver may become manifest through changes in egg constituents. Liver FMG colonization significantly affects EP through alterations in yolk lipid and fatty acid concentrations. As evidenced through changes in the relative weights of various reproductive organs, colonization of these organs by FMG, in addition to the liver, may also be a cause of the effects observed on EP. Increases in hematocrit, serum triglycerides, and plasma protein between 8 and 10 wk post FMG-inoculation, suggest that the initial weeks of EP are stressful, and post-peak decreases in both serum triglycerides and plasma protein suggest a more chronic inhibition on lipid and protein synthesis in the liver. Decreased blood lipid concentration may be directly responsible for the reductions in yolk lipid, cholesterol, and fatty acid deposition in 12 wk FMG-inoculated hens. In the caged layer facility, onset of lay was also delayed 1 wk in birds inoculated with FMG at 12 wk and total egg mass was decreased by 1000 g and feed conversion was increased by 0.5 g feed/g egg in 22 wk FMG-inoculated birds. Inoculation with FMG at 12 wk of age, therefore, appears to be more desirable and cost efficient than an FMG inoculation at 22 wk of age. Lower percentages of undersized, peewee, and small sized eggs laid during pre-peak by 12 wk FMG-inoculated hens is indicative of a delay in EP. Higher degrees of physiological stress experienced by hens in a caged layer facility may exacerbate the effects of FMG-inoculation seen in the isolation units. These data demonstrate that alterations in performance and egg characteristics of commercial layers inoculated with FMG at either 12 or 22 wk of age and housed in either isolation units or caged layer facilities are related to mutual functional disturbances in the blood, liver, ovary, and oviduct without concomitant intestinal changes. Research in caged layer facilities may be more appropriate than that attained from isolation units from a practical perspective. On the other hand, isolation units may be more suitable for research at the cellular and molecular levels, because environmental factors influence the severity of mycoplasma infections.

Impacts
The F-strain of Mycoplasma gallisepticum (FMG) was used in various trials in order to gain a better understanding of the mechanisms responsible for altered egg production (EP) and egg quality in commercial layers, as these alterations can cause economic loss to the U.S. layer industry. An understanding of the pathogenic and physiological processes associated with Mycoplasma gallisepticum (MG) infections may lead to new approaches to the treatment and control of MG. It is clear that eradication of MG is the best solution in terms of maximizing EP and reducing vaccination and/or medication costs. However, it is equally important to realize that on some multi-age farms, MG eradication is not currently practical. Vaccination programs using FMG can provide significant protection against decreased EP caused by field strain MG infection. Numerous citations have reported alterations in EP due to FMG inoculation, but previous information in the literature is controversial concerning the degree of effects on EP under different housing conditions and the timing of administration. Certainly, the effects of MG are due to type and degree of tissue colonization. This may vary under the different environmental conditions (i.e. facility, disease, etc.) imposed on the birds and may thus have an enormous impact on the performance of commercial laying hens.

Publications

  • Peebles, E. D., S. L. Branton, M. R. Burnham, and P. D. Gerard, 2003. Influences of supplemental dietary poultry fat and F-strain Mycoplasma gallisepticum infection on the early performance of commercial egg laying hens. Poultry Sci. 82:596-602.
  • Burnham, M. R., E. D. Peebles, S. L. Branton, M. S. Jones, and P. D. Gerard, 2003. Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on the blood characteristics of commercial egg laying hens. Poultry Sci. 82:1397-1402.
  • Burnham, M. R., E. D. Peebles, S. L. Branton, R. L. Walzem, and P. D. Gerard, 2003. 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. Poultry Sci. 82:1630-1636.
  • Basenko, E. Y., 2003. Effects of S6-strain Mycoplasma gallisepticum inoculation at either 10, 22, or 45 weeks of age on performance, egg, blood, and visceral characteristics of commercial egg laying hens. M.S. Thesis, Mississippi State, MS 39762.
  • Burnham, M. R., E. D. Peebles, and S. L. Branton, 2003. Reproductive organ characteristics of commercial layer hens inoculated with F-strain Mycoplasma gallisepticum and housed in a caged layer facility. Proc. SPSS, Poultry Sci. 82(Suppl. 1):97.
  • Burnham, M. R., E. D. Peebles, R. L. Walzem, S. L. Branton, and P. D. Gerard, 2003. Age of F-strain Mycoplasma gallisepticum inoculation affects the lipoprotein profiles of commercial layer hens housed in a caged layer facility. Proc. SPSS, Poultry Sci. 82(Suppl. 1):100.
  • Basenko, E. Y., E. D. Peebles, S. L. Branton, P. D. Gerard, M. R. Burnham, and S. K. Whitmarsh, 2003. Blood characteristics of commercial egg laying hens between 20 and 58 weeks of age when inoculated with S6-strain of Mycoplasma gallisepticum at 10, 22, or 45 weeks of age. Proc. SPSS, Poultry Sci. 82(Suppl. 1):91.
  • Burnham, M. R., E. D. Peebles, R. L. Walzem, S. L. Branton, and P. D. Gerard, 2003. Inoculation of F-strain Mycoplasma gallisepticum at twelve weeks of age alters the effects of fasting on plasma protein and percentage serum LDL cholesterol concentrations in commercial laying hens. Poultry Sci. 82(Suppl. 1):30.
  • Peebles, E. D., M. R. Burnham, S. L. Branton, K. O. Willeford, J. R. Richardson, and P. G. Gerard, 2003. Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on serum vitellogenin concentrations in commercial egg laying hens. Poultry Sci. 82(Suppl. 1):84.
  • Basenko, E. Y., E. D. Peebles, P. D. Gerard, S. L. Branton, and S. K. Whitmarsh, 2003. Demonstrated effects of S6-strain Mycoplasma gallisepticum inoculation on hematocrit and serum calcium in two different flocks of commercial layers between 20 and 58 weeks of age. Poultry Sci. 82(Suppl. 1):34.
  • Parker, T. A., S. L. Branton, M. S. Jones, E. D. Peebles, P. D. Gerard, K. O. Willeford, G. T. Pharr, and W. R. Maslin, 2003. Effects of an S6 strain of Mycoplasma gallisepticum challenge at onset of lay on digestive and reproductive tract characteristics in commercial layers. Avian Dis. 47:96 100.
  • Burnham, M. R., E. D. Peebles, S. L. Branton, D. V. Maurice, and P. D. Gerard, 2003. Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on egg yolk composition in commercial egg laying hens. Poultry Sci. 82:577-584.


Progress 01/01/02 to 12/31/02

Outputs
Three separate collaborative trials have recently been completed. In these trials, various performance, egg, organ, and blood characteristics of egg laying chickens infected with Mycoplasma gallisepticum (MG) were examined. The first two trials were conducted on birds housed in isolation units, and the third trial was conducted on birds housed in a caged layer facility. In the first trial, the effects of the S6 strain of MG administered at either 10, 22, or 45 weeks of age were examined. In the second trial, the effects of an inoculation with the F strain of MG (FMG) at 22 and 45 weeks of age after inoculation with the TS-11 strain of MG at 10 weeks of age were determined. In the third trial, the effects of a diet supplemented with both phytase and vitamin D3 on birds that had been inoculated with FMG at 12 and 22 weeks were determined. Work is currently underway to complete sample and data analyses, and present abstracts, write theses, and publish journal manuscripts from trials in the previous year. Furthermore, the collection of data from two new trials is also underway. The first trial will be a replicate trial to that conducted for the determination of the effects of an inoculation with FMG at 22 and 45 weeks of age after inoculation with the TS-11 strain of MG at 10 weeks of age. The second trial will be similar to the previous trial conducted to determine the effects of supplemental phytase and vitamin D3 on birds that had been inoculated with FMG at 12 and 22 weeks. However, in this trial, phytase and vitamin D3 will be provided separately.

Impacts
Results of published results from this project showed that commercial Single Combed White Leghorn chickens, housed in biological isolation units, experienced a decrease in total egg production and delays in onset of lay and in production of undersized eggs after being inoculated at 12 weeks of age with FMG. These data further showed that these alterations in performance and egg characteristics are related to mutual functional disturbances in the liver, ovary, and oviduct, changes in yolk composition, and changes in blood hematocrit. It has previously been estimated that losses due to field strain MG infections in layers may cost egg producers up to $140 million (16 eggs/hen) per year. When administered during the pullet period, FMG can prevent field strain MG infections and greatly reduce the impact of these more virulent strains on layer performance. Gaining a better understanding of the types and degrees of changes in the performance of layers in response to FMG as well as its underlying mechanism of action, will allow for appropriate adjustments to be made in FMG vaccination programs. These adjustments would minimize the negative impacts of FMG while preventing field strain infections, and could greatly reduce profit losses by millions of dollars per year in the industry.

Publications

  • Parker, T.A., S.L. Branton, M.S. Jones, E.D. Peebles, P.D. Gerard, K.O. Willeford, M.R. Burnham, and W.R. Maslin, 2002. Effects of an S6 strain of Mycoplasma gallisepticum challenge before beginning of lay on various egg characteristics in commercial layers. Avian Dis. 46:593-597.
  • Burnham, M.R., S.L. Branton, E. David Peebles, B.D. Lott, and P.D. Gerard, 2002. Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on performance and egg characteristics of commercial egg laying hens. Poult. Sci. 81:1478-1485.
  • Burnham, M.R., E.D. Peebles, S.L. Branton, M.S. Jones, P.D. Gerard, and W.R. Maslin, 2002. Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on digestive and reproductive organ characteristics of commercial egg laying hens. Poult. Sci. 81:1884-1891.
  • Burnham, M.R., 2002. Physiological factors potentially associated with the alteration of reproductive performance of commercial egg laying chickens infected with the F-strain of Mycoplasma gallisepticum. Ph.D. Dissertation, Mississippi State, MS 39762.
  • Burnham, M.R., E. D. Peebles, S.L. Branton, and P.D. Gerard, 2002. Age of inoculation with F-strain Mycoplasma gallisepticum affects the performance and eggshell characteristics of commercial egg laying hens. Proc. SPSS, Poult. Sci. 81(suppl 1): 126.
  • Burnham, M.R., E. D. Peebles, S.L. Branton, and P.D. Gerard, 2002. Influences of various dietary factors on egg quality responses to age of inoculation with F-strain Mycoplasma gallisepticum in commercial egg laying hens. Proc. SPSS, Poult. Sci. 81(Suppl. 1): 123.
  • Burnham, M. R., S.L. Branton, E.D. Peebles, P.D. Gerard, and S. K. Whitmarsh, 2002. Age of inoculation with F-strain Mycoplasma gallisepticum affects the hematology of commercial egg laying hens. Proc. SPSS, Poult. Sci. 81 (Suppl. 1): 155.
  • Basenko, E.Y., E.D. Peebles, S. L. Branton, P.D. Gerard, M.R. Burnham, and S.K. Whitmarsh, 2002. Comparative effects of 10 and 22 week inoculations of S6-strain Mycoplasma gallisepticum on performance of commercial egg laying hens. Proc. SPSS, Poult. Sci. 81(Suppl. 1): 126.
  • Peebles, E.D., M.R.Burnham, S.L. Branton, and P.D.Gerard, 2002. Influences of supplemental dietary poultry fat and F-strain Mycoplasma gallisepticum infection on the early performance of commercial egg laying hens. Poult. Sci. 81(Suppl. 1): 33.
  • Basenko, E.Y., E.D. Peebles, S.L. Branton, P.D. Gerard, M.R. Burnham, and S.K. Whitmarsh, 2002. Performance of commercial egg laying hens between 32 and 60 wk of age after inoculation with S6-strain of Mycoplasma gallisepticum at 10, 22, or 45 wk of age. Poult. Sci. 81(Suppl. 1): 32.


Progress 01/01/01 to 12/31/01

Outputs
A third trial has been completed and a fourth trial has been initiated as part of this project. Data collection is currently underway in Trial 4 in an effort to determine the effects of the S6 strain of MG administered at 10 and 22 wk of age on the performance and associated physiological characteristics of layers housed in biological isolation units. In the third trial, the effects of challenges of the F strain of MG (FMG) (12 and 22 wk) in conjunction with added dietary poultry fat, phytase, and vitamin D3 on the performance and associated physiological characteristics of layers in a caged layer facility were determined. The inoculation of layers with FMG at 12 rather than at 22 wk of age reduced pre-peak and post-peak egg production, and caused shifts in egg size distribution. Furthermore, timing of inoculation affected layer performance through asociated changes in hematological characteristics. Birds inoculated with FMG at 12 or 22 wk of age may be less likely to perform as adequately as non-infected birds in a caged layer facility. In these birds, age dependent effects of poultry fat, phytase, and vitamin D3 modified responses in percentage yolk weight and percentage yolk moisture to FMG inoculation at 12 or 22 wk. These studies will provide layer industry personnel information to develop more precise programs for the elimination of virulent field strains of MG in flocks by the timely inoculation of the mild F-strain. The adoption of this technology by the commercial egg industry may result in millions of dollars of savings per year in production costs. These production savings may further be realized through increased numbers of total eggs produced along with increased numbers of eggs within those size classes most desired by the customer.

Impacts
These data provide potential means by which FMG may be used in commercial egg laying flocks to displace more virulent field strains of MG while alleviating some of the negative effects of FMG on layer performance through dietary manipulation. Also, physiological parameters have been identified which may allow producers to better predict the long term effects of FMG and these dietary additives on flock performance.

Publications

  • Burnham, M.R., S.L. Branton, E.D.Peebles, R.L Walzem, S.K. Whitmarsh, and P.D. Gerard, 2001. Effects of F-strain Mycoplasma gallisepticum on serum lipids and lipoprotein profiles in commercial laying hens. Proc. SPSS, Poultry Sci.80(Suppl.1):15.
  • Burnham, M.R., R.L. Walzem, E.D. Peebles, S.L. Branton, S.K. Whitmarsh, and P.D. Gerard, 2001. Effects of fasting on serum lipids and lipoprotein profiles in commercial laying hens. Proc. SPSS, Poultry Sci.80(Suppl.1):19.
  • Jones, M.S., E.D. Peebles, S.L. Branton, K.O. Willeford, T. Pharr, R. Montgomery, T.A. Parker, S. Whitmarsh, and W. Maslin, 2001. Effects of an immunomodulator and phasic challenges of S6 strain Mycoplasma gallisepticum and Escherichia coli on egg production and egg characteristics of commercial laying hens during peak and post-peak lay. Proc. SPSS, Poultry Sci.80(Suppl.1):16.
  • Burnham, M.R., S.L. Branton, E.D. Peebles, M.S. Jones, B.D. Lott, J.B. Yeatman, S.K. Whitmarsh, and P.D. Gerard, 2001. Digestive and reproductive organ characteristics in commercial laying hens as affected by F-strain Mycoplasma gallisepticum. Poultry Sci.80(Suppl.1):136.
  • Jones, M.S., 2001. Use of a Caprine serum fraction as an immunomodulator in Single Comb White Leghorn chickens. M.S. Thesis, Mississippi State, MS 39762.


Progress 01/01/00 to 12/31/00

Outputs
Two trials as part of this project have been completed. In Trial 1, onset of lay was delayed 1 wk in F-strain Mycoplasma gallisepticum (FMG)infected birds. However, FMG significantly reduced rate of egg production after 45 wk of age. Although total egg production and egg mass at the end of the lay cycle were not affected by FMG, FMG inoculation at 12 wk caused a forward shift in egg production away from the mid post-peak production period. Furthermore, FMG decreased percentage egg albumen weight across bird age and yolk lipid content was increased at Week 44 and decreased at Week 48. Increased serum cholesterol, serum triglycerides, and plasma protein levels preceded numerical increases in egg production between 22 and 45 wk, and decreased levels of these same blood parameters were coincidental with significant decreases in egg production after 45 wk of age. Data from Trial 2 revealed that at 16, 24, 28, 34, 40, and 46 wk of age, hematocrit was lower in birds inoculated with FMG at 12 wk. Serum VLDL particle diameter distributions(10th, 50th, and 90th population percentiles); mean VLDL particle diameter; percentage of serum cholesterol recovered in VLDL, LDL, and HDL; plasma total protein; and serum concentrations of cholesterol, triglycerides and calcium were not affected by FMG inoculation.

Impacts
Mycoplasma gallisepticum (MG) has long been recognized as economically important to the poultry industry. Within the commercial egg laying industry, losses attributable to MG may be reduced with an increased knowledge of the mechanisms by which MG affects layer performance as a result of this work. Furthermore, changes in management practices based on these data may help circumvent the immediate effects of this disease at various points in the production cycle.

Publications

  • Burnham, M. R., E. D. Peebles, S. Whitmarsh, and S. L. Branton, 2000. Effects of F-strain Mycoplasma gallisepticum on blood characteristics in commercial laying hens. Poultry Sci. 79(Suppl. 1):22.
  • Jones, M. S., S. L. Branton, E. D. Peebles, K. O. Willeford, T. Pharr, R. Montgomery, T. A. Parker, S. Whitmarsh, and W. Maslin, 2000. Effects of an immmunomodulator and phasic challenges of S6 strain Mycoplasma gallisepticum and Escherichia coli on egg production and egg characteristics of commercial laying hens during pre-peak lay. Poultry Sci. 79(Suppl. 1):23.
  • Willeford, K. O., T. A. Parker, E. D. Peebles, C. Wang, and E. W. Jones, 2000. Reduction of mortality in specific-pathogen-free layer chickens by a caprine serum fraction after infection with Pasteurella multocida. Poultry Sci. 79:1424-1429.