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IMMUNOLOGY, HEALTH, AND DISEASE |
,3
* Poultry Research Unit, Agricultural Research Service, USDA, Mississippi State, MS 39762; Department of Applied Economics and Statistics, Clemson University, Clemson, SC 29634; and Department of Poultry Science, Mississippi State University, Mississippi State 39762
3 Corresponding author: dpeebles{at}poultry.msstate.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Key Words: commercial layer • egg production • egg quality • F-strain Mycoplasma gallisepticum • ts11-strain Mycoplasma gallisepticum
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Vaccination programs are presently being used to help protect flocks from field strains of Mycoplasma. Three live vaccines are commercially available for use in the United States. The first live M. gallisepticum vaccine, referred to as the F-strain, was approved for use by the USDA in commercial table egg chickens in 1988 (Branton et al., 1999). The F-strain M. gallisepticum vaccine strain is less virulent than many of the field strains of M. gallisepticum and has a lower vertical transmission rate, yet it is able to displace the more virulent stains of M. gallisepticum (Levisohn and Kleven, 1981; Kleven et al., 1990). Continuous use of F-strain M. gallisepticum vaccines for replacement flocks in multiage commercial layer facilities has been shown to protect these flocks from field strains (Kleven et al., 1990). The F-strain M. gallisepticum vaccine, however, is pathogenic to turkeys and is not approved or licensed for use in poultry other than commercial layers. In a controlled study in biological isolation units, early vaccination of commercial layers with F-strain M. gallisepticum did not adversely affect EP (Branton et al., 1997). Anecdotal evidence from producers that have used F-strain M. gallisepticum has also shown that no adverse effects on EP occurred when F-strain M. gallisepticum vaccinations were provided prelay (personal communication, Jack Self, vice president of operations, Cal Maine Foods Inc., Jackson, MS). However, some field studies have determined that F-strain M. gallisepticum vaccination can reduce EP when compared with Mycoplasma-free birds (Carpenter et al., 1981; Mohammed et al., 1987; Branton et al., 1988). More recently, apathogenic ts11-strain M. gallisepticum and 6/85-strain M. gallisepticum live vaccines have been licensed for use in layer chickens. These vaccines show virtually no bird-to-bird transmission, but have not been proven to displace wild-type M. gallisepticum (Kleven, 1998). Furthermore, these strains may not confer continued protection, as does the F-strain throughout lay (Yoder, 1978, 1991; Mohammed et al., 1987). More testing is needed to determine whether combinations of vaccines can lessen the adverse impact of prelay F-strain M. gallisepticum vaccinations on layer performance when given alone. Therefore, the objective of the current study was to determine the effects of prelay ts11-strain M. gallisepticum inoculations and time-specific F-strain M. gallisepticum inoculation overlays administered during lay on the performance characteristics of commercial laying hens.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Two trials were performed with Hy-Line W-36 pullets that were obtained at 1 d of age from a commercial source that was monitored and certified free of both M. gallisepticum and Mycoplasma synoviae (USDA-Animal and Plant Health Inspection Service-Veterinary Services, 2003). Chickens were vaccinated at 10 d of age for infectious bursal disease via the drinking water. At 5 wk of age, 20 randomly selected chickens were tested for antibodies to both M. gallisepticum and M. synoviae by using both the serum plate agglutination (SPA) and the hemagglutination-inhibition tests (Yoder, 1975), and swabs were obtained from the choanal cleft (Branton et al., 1984) and placed into tubes containing Frey’s broth medium (Frey et al., 1968) supplemented with an additional 0.15 thallium acetate and 106 IU of penicillin-G/mL. Tubes were incubated at 37°C for 30 d or until the phenol red indicator reaction occurred in the media. A sample from those that changed color was then inoculated onto Frey’s-based agar and incubated at 37°C. Colonies with morphology suggestive of Mycoplasma species were examined by an agar plate fluorescent antibody (FA) test (Baas and Jasper, 1972) that used direct labeling of colonies stained with anti-F-strain M. gallisepticum polyclonal antibodies produced in rabbits and labeled with fluorescein isothiocyanate (Kleven, 1981).
Pullets were placed on clean dry litter in a conventional house until 10 wk of age. A daily artificial lighting schedule followed a 13 L:11 D cycle. One 75-W incandescent light bulb was used to illuminate each 8.4 m2 of floor space, providing a calculated intensity at bird level of 35.5 lx. Feed and water were provided for ad libitum consumption in each trial. At 10 wk of age, 11 pullets were randomly selected and placed in each of 16 negative-pressure fiber-glass biological isolation units (1.16 m2). The units were housed in a previously described poultry disease isolation facility (Branton and Simmons, 1992). Hen numbers were reduced to 10 per unit at point of lay (22 wk of age) so that bird density was 0.116 m2/bird for the duration of each trial. At 18 wk of age, the length of the artificial lighting schedule was increased by 15 min/d until a cycle of 16 h and 15 min of light per 7 h and 45 min of dark was achieved. Chickens were maintained on that schedule through the remainder of each of the trials. For the entirety of each trial, chickens had ad libitum access to feed and water. Pullet and layer diets were formulated to meet or exceed NRC (1994) recommendations. Ingredient percentages and calculated analyses of the diets were as described by Burnham et al. (2002). No medications were administered during either trial.
Treatments
Four experimental treatment groups were used. Each treatment group consisted of 4 isolation units containing 10 birds each for a total of 40 birds per treatment group. Treatment 1 (controls) received no M. gallisepticum inoculation but were sham-inoculated via eye drop in the right eye with sterile Frey’s media. Treatment 2 contained birds that were eye-drop vaccinated in the right eye with ts11-strain M. gallisepticum at 10 wk of age (ts11/10). Birds belonging to treatment 3 received ts11-strain M. gallisepticum via eye drop at 10 wk of age followed by a 22-wk overlay vaccination via eye drop in the left eye with F-strain M. gallisepticum (ts11/10-F/22). Treatment 4 consisted of birds given ts11 strain M. gallisepticum at 10 wk of age via eye drop in the right eye followed by a 45-wk overlay vaccination of F-strain M. gallisepticum via eye drop in the left eye (ts11/10-F/45).
Data Collection
All data collected before wk 22 were designated as belonging to age interval I; all data collected from wk 22 to 44 were designated as belonging to age interval II; and all data collected from wk 45 to 57 were designated as belonging to interval III. Individual BW was recorded at 20 wk (interval I), at 24, 32, and 43 wk (interval II), and at 47 and 56 wk of age (interval III) in both trials 1 and 2. Egg production was recorded daily and analyzed weekly (weekly EP) from wk 23 (when control treatment EP reached approximately 10%) through wk 44 (interval II) and from wk 45 through 55 (interval III), and was expressed as percent hen-day EP. Furthermore, the total number of eggs produced per hen (total hen EP) from onset of lay through 55 wk (across all 3 intervals), and within interval II (wk 22 to 44) and interval III (wk 45 to 55) separately, were likewise determined. To include all eggs that were laid before 10% EP, the calculation of total hen EP across all 3 intervals was initiated when the first egg was laid (onset of lay). Age of onset of lay ranged between 18 and 21 wk. Total hen EP was calculated as the total daily numbers of eggs produced as a percentage of the total daily numbers of hens for each replicate group.
Beginning on wk 23 (when control treatment EP reached approximately 10%), eggs were collected 2 d/wk to determine egg weight (EW), eggshell breaking strength (ESS), and percentage incidences of eggshell pimpling (ESP), egg blood spots (EBS), and egg meat spots (EMS). Egg weight, ESS, ESP, EBS, and EMS determinations were recorded weekly in both trials from 23 to 57 wk of age. These determinations were made on all the same eggs that were produced within the 2-d time period. The ESS of each egg was determined by the technique described by Reece and Lott (1976), and ESP, EBS, and EMS incidences were determined by using the methods described by Branton et al. (1997). For determination of eggshell weight per unit of eggshell surface area (SWUSA), a total of 10 eggs per pen were weighed at 20, 24, 32, 43, and 46 wk of age in both trials. The eggs used for SWUSA measurements were different from the eggs used for determination of EW, ESS, ESP, EBS, and EMS. Determination of SWUSA was according to the procedure described by Peebles et al. (1994). All the above egg and eggshell determinations were recorded on the same day that the eggs were collected.
Statistical Analysis
A completely randomized experimental design, with trial as a block, was used. Data before wk 22 (age interval I), from wk 22 to 44 (age interval II), and from wk 45 to 57 (age interval III) were analyzed separately. The data of both trials were pooled and then analyzed together. Therefore, the results from both trials were not reported independently but were reported over both trials. Trial was considered as a random effect. All data within each age interval were subjected to a repeated measures analysis if parameters were examined at multiple age periods in an age interval. Otherwise, data (i.e., total hen EP) obtained within and across age intervals was subjected to 1-way ANOVA.
In the first age interval, the control group and the ts11/ 10 treatment group were compared. In the second age interval, control birds and those having had ts11/10 and ts11/10-F/22 inoculations were compared. In the third age interval, the control, ts11/10, ts11/10-F/22, and ts11/10-F/ 45 groups were compared. Individual sample data within each of these replicate units were averaged before analysis. Least squares means were compared in the event of significant global effects (Steel and Torrie, 1980). Global effects and differences among least squares means were considered significant at P 
0.05. All data were analyzed by using the MIXED procedure of SAS (SAS Institute, 2003).
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RESULTS AND DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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In large commercial multiage layer facilities, where depopulation followed by disinfection is impractical, vaccination programs are the best protection (Bermudez and Kalbac, 1988). Vaccination for diseases in animals is commonly practiced where the disease is endemic (Barile, 1985). Furthermore, early vaccination allows for the early development of immunity to Mycoplasmas before EP begins. Therefore, in 1 of the treatment groups of this study, an early prelay vaccination was used, and in 2 of the other treatments, the early vaccination was used in conjunction with later overlay vaccinations to confer continued protection during lay. Despite these treatment applications, only a main effect (P 0.04) attributable to hen age for BW was observed in interval II; hen BW at wk 24, 32, and 43 were 1.34, 1.40, and 1.45 kg, respectively (pooled SEM = 0.022). Hen BW at wk 23 and 43 were significantly greater than that at wk 24, but BW at wk 32 and 43 were not significantly different. There was no treatment effect at wk 20 in interval I, and there was no significant treatment main effect or age by treatment interaction in interval II. In addition, there were no significant age or treatment main effects or an age by treatment interaction for BW in interval III. These BW data are consistent with those reported by Burnham et al. (2002), Peebles et al. (2007), and Viscione et al. (2008). Burnham et al. (2002) found no effect of a 12-wk F-strain M. gallisepticum inoculation on subsequent BW, Peebles et al. (2007) showed that BW was not affected by inoculation of F-strain M. gallisepticum at either 12 or 22 wk of age, and Viscione et al. (2008) noted no significant effects of F-strain M. gallisepticum inoculation at either 22 or 45 wk of age on layer hen BW. No previous research has reported the effects of prelay ts11-strain M. gallisepticum vaccinations on layer BW.
A hen age main effect was observed for weekly EP in interval III (wk 45 to 55; P 0.01; data not shown); however, no significant treatment main effect or age by treatment interaction was observed for weekly EP in interval III. In addition, no significant effects of any kind were observed for weekly EP in interval II. Furthermore, total hen EP across lay (intervals I to III) and total hen EP within interval II and within interval III were not significantly affected by treatment. Although total hen EP within intervals II and III and across all 3 intervals was not affected by treatment, treatment means within interval II and interval III are provided in Table 1
for observation. In addition, means for total hen EP across lay for the control, ts11/10, ts11/ 10-F/22, and ts11/10-F/45 treatments were 76.8, 76.8, 70.8, and 72.2%, respectively (pooled SEM = 2.36). In trials conducted by Branton et al. (1997), no negative effects were noted in EP or EW for birds that were challenged with F-strain M. gallisepticum before lay, when compared with control birds. The results of Branton et al. (1997) support other research previously conducted by Yoder (1978, 1991) and Mohammed et al. (1987), who reported that F-strain M. gallisepticum vaccination can reduce the negative impact of natural M. gallisepticum infections in layer flocks. However, in studies reported by Burnham et al. (2002), in which egg-laying hens were inoculated at 12 wk of age with F-strain M. gallisepticum, it was reported that there was a decrease in total EP and that birds laid their first eggs approximately 1 wk later than controls that received only sham inoculations. Furthermore, Peebles et al. (2008) noted that F-strain M. gallisepticum inoculations given at either 12 or 22 wk of age decreased EP at the beginning of lay.
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In a study reported by Branton et al. (1988), in which layer hens were inoculated with F-strain M. gallisepticum at 45 wk of age, there was a significant decrease in EP compared with control birds that were not vaccinated. This was in agreement with earlier work published by Carpenter et al. (1981), who found that layers maintained free from M. gallisepticum infection laid an average of 8.7 eggs/hen housed more than did flocks that were vaccinated with F-strain M. gallisepticum at 45 wk of age. The results of Branton et al. (1988), Carpenter et al. (1981), and Peebles et al. (2008) demonstrate further potential negative impacts of 22- and 45-wk F-strain M. gallisepticum inoculations on performance. Because EP was not affected by the use of ts11/10-F/22 or ts11/10-F/45 vaccine treatments in the current 2 trials, it is also suggested that a prelay ts11/ 10 vaccination may help to prevent a significant drop in hen day EP when F-strain M. gallisepticum vaccination overlays are given at either 22 or 45 wk. A prelay ts11/10 inoculation might serve to reduce the negative impacts of F-strain M. gallisepticum inoculations given during lay.
An age by treatment interaction was observed for EW (P 0.04) in interval II (Table 2). At wk 27, EW was significantly larger in the ts11/10-F/22 treatment group compared with the control and ts11/10 treatment groups. This was opposite that at wk 38, where the control and ts11/ 10 treatment birds had greater EW than the ts11/10-F/22 birds. At wk 37, the control and ts11/10-F/22 birds had a higher EW than the ts11/10 treatment group. There were no significant age or treatment main effects or age by treatment interactions in interval III. It has been noted that EW was unaffected by inoculations with ts11-strain M. gallisepticum at 10 wk (Branton et al., 2000), F-strain M. gallisepticum at 12 wk (Burnham et al., 2002), F-strain M. gallisepticum at 12 and 22 wk (Peebles et al., 2008), and F-strain M. gallisepticum at 22 and 45 wk (Viscione et al., 2008). Branton et al. (1988) did find that F-strain M. gallisepticum inoculated at 45 wk increased EW over a 15-wk period, but this was noted in only 1 of 2 trials. In addition, Burnham et al. (2002) found that the percentage of eggs belonging to the USDA undersized egg category decreased at 19 wk but later increased at 20 and 21 wk after a 12-wk F-strain M. gallisepticum inoculation. The inconsistent results of these aforementioned studies do not convincingly demonstrate that EW is susceptible to the various inoculation regimens described involving the ts11- and F-strains of M. gallisepticum. However, despite the apparent innocuousness of a ts11/10 vaccination on EP, consideration should be given to possible subsequent effects that a ts11/10 vaccination might have on EW. This is suggested in this study because of the reduction in EW of the ts11/10 treatment group relative to the control group at wk 37. Furthermore, the current data indicate that an overlay of F-strain M. gallisepticum at 22 wk may lead to respective increases and decreases in EW at 27 and 38 wk in birds that had been given ts11-strain M. gallisepticum vaccinations at 10 wk.
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0.05; Table 3) and EBS (P 0.05; Table 4) in interval III. At wk 53, ESP was significantly higher for the ts11/ 10-F/45 treatment group than for the control or ts11/10-F/22 treatment groups. The ESP of the ts11/10 treatment group was not significantly different from the other 3 treatment groups. At wk 56, the ts11/10-F/45 treatment group had a significantly higher ESP than the control, ts11/10, or ts11/10-F/22 treatment group. Conversely, at wk 57, the ts11/10-F/45 treatment group was significantly lower than the control or ts11/10 treatment group; however, the ts11/10-F/22 group was not significantly different from the other 3 groups. For EBS at wk 54, the incidence was higher for the ts11/10-F/22 treatment group when compared with the control, ts11/10, and ts11/10-F/45 treatment groups. However, at wk 56, the ts11/10-F/45 treatment group had a significantly higher incidence of EBS than did the other 3 groups. There were no significant effects of any kind for ESP or EBS in interval II, for ESS or EMS in interval II or III, or for SWUSA in any of the 3 time intervals. The egg and eggshell quality parameters selected for these trials reflected the functionality of the ovary and specific segments of the oviduct as described by Branton et al. (2000). However, ESS, EMS, and SWUSA were not affected, and EW, ESP, and EBS were affected inconsistently by the combined vaccine treatments.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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2 Use of trade names in this publication does not imply endorsement by the Mississippi Agricultural and Forestry Experiment Station of these products, nor similar ones not mentioned.
Received for publication December 3, 2007. Accepted for publication January 3, 2008.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Barile, M. F. 1985. Immunization against Mycoplasma infections. Pages 451–492 in The Mycoplasmas. S. Razin and M. F. Barile, ed. Acad. Press, New York, NY.
Bermudez, A. J., and M. Kalbac. 1988. Control of Mycoplasma gallisepticum infection in commercial layers: A field study. J. Am. Vet. Med. Assoc. 192:1783.
Branton, S. L., H. Gerlach, and S. H. Kleven. 1984. Mycoplasma gallisepticum isolation in layers. Poult. Sci. 63:1917–1919.[Web of Science][Medline]
Branton, S. L., B. D. Lott, J. W. Deaton, J. M. Hardin, and W. R. Maslin. 1988. F strain Mycoplasma gallisepticum vaccination of post-production-peak commercial leghorns and its effect on egg and eggshell quality. Avian Dis. 32:304–307.[CrossRef][Web of Science][Medline]
Branton, S. L., B. D. Lott, J. D. May, W. R. Maslin, C. R. Boyle, and G. T. Pharr. 1997. The effects of F-strain Mycoplasma gallisepticum, Mycoplasma synoviae, and the dual infection in commercial layer chickens over a 44-week laying cycle when challenged before beginning of lay. I. Egg production and selected egg quality parameters. Avian Dis. 41:832–837.[CrossRef][Web of Science][Medline]
Branton, S. L., B. D. Lott, J. D. May, W. R. Maslin, G. T. Pharr, S. D. Bearson, S. D. Collier, and D. L. Boykin. 2000. The effects of ts-11 strain Mycoplasma gallisepticum vaccination in commercial layers on egg production and selected egg quality parameters. Avian Dis. 44:618–623.[CrossRef][Web of Science][Medline]
Branton, S. L., B. D. Lott, J. D. May, W. R. Maslin, G. T. Pharr, J. E. Brown, and D. L. Boykin. 1999. The effects of F-strain Mycoplasma gallisepticum, Mycoplasma synoviae, and the dual infection in commercial layer hens over a 44-week laying cycle when challenged before beginning of lay. II. Egg size distribution. Avian Dis. 43:326–330.[CrossRef][Web of Science][Medline]
Branton, S. L., and J. D. Simmons. 1992. Design of a poultry disease isolation facility with programmable environmental control. Appl. Eng. Agric. 8:695–699.
Brown, J. E., S. L. Branton, and J. D. May. 1995. Effect of isolation and sanitation on the recovery of F-strain Mycoplasma gallisepticum from chronically infected hens held in biological isolation units. Avian Dis. 39:263–268.[CrossRef][Web of Science][Medline]
Burnham, M. R., S. L. Branton, E. D. 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.
Carpenter, T. E., E. T. Mallinson, K. F. Miller, R. F. Gentry, and L. D. Schwartz. 1981. Vaccination with F-strain Mycoplasma gallisepticum to reduce production losses in layer chickens. Avian Dis. 25:404–409.[CrossRef][Web of Science][Medline]
Domermuth, C. H., W. B. Gross, and R. T. DuBose. 1967. Mycoplasmal salpingitis of chickens and turkeys. Avian Dis. 11:393–398.[CrossRef][Web of Science][Medline]
Frey, M. C., R. P. Hanson, and D. P. Anderson. 1968. A medium for the isolation of avian Mycoplasma. Am. J. Vet. Res. 29:2164–2171.
Kleven, S. H. 1981. Transmissibility of the F-strain of Mycoplasma gallisepticum in Leghorn chickens. Avian Dis. 25:1005–1018.[CrossRef][Web of Science][Medline]
Kleven, S. H. 1998. Mycoplasmas in the etiology of multifactorial respiratory disease. Poult. Sci. 77:1146–1149.
Kleven, S. H., M. I. Khan, and R. Yamamoto. 1990. Fingerprinting of Mycoplasma gallisepticum strains isolated from multiple-age layers vaccinated with live F-strain. Avian Dis. 34:984–990.[CrossRef][Web of Science][Medline]
Levisohn, S., and S. H. Kleven. 1981. Vaccination of chickens with nonpathogenic Mycoplasma gallisepticum as a means for displacement of pathogenic strains. Isr. J. Med. Sci. 17:669–673.[Web of Science][Medline]
Mohammed, H. O., T. E. Carpenter, and R. Yamamoto. 1987. Economic impact of Mycoplasma gallisepticum and M. synoviae in commercial layer flocks. Avian Dis. 31:477–482.[CrossRef][Web of Science][Medline]
NRC. 1994. Nutrient Requirements of Poultry. 9th Rev. ed. Natl. Acad. Press, Washington, DC.
Patterson, P. H. 1994. Coping with Mycoplasma gallisepticum. Internews 7:1–3.
Peebles, E. D., S. L. Branton, M. R. Burnham, S. K. Whitmarsh, and P. D. Gerard. 2007. Effects of supplemental dietary phytase and 25-hydroxycholecalciferol on the blood characteristics of commercial layers inoculated before or at the onset of lay with the F-strain of Mycoplasma gallisepticum. Poult. Sci. 86:768–774.
Peebles, E. D., S. L. Branton, M. R. Burnham, S. K. Whitmarsh, and P. D. Gerard. 2008. Effects of supplemental dietary phytase and 25-hydroxycholecalciferol on the performance characteristics of commercial layers inoculated before or at the onset of lay with the F-strain of Mycoplasma gallisepticum. Poult. Sci. 87:598–601.
Peebles, E. D., E. H. Miller, C. R. Boyle, J. D. Brake, and M. A. Latour. 1994. Effects of dietary thiouracil on thyroid activity and eggshell quality in commercial layers. Poult. Sci. 73:1829–1837.[Web of Science][Medline]
Reece, F. N., and B. D. Lott. 1976. The effect of loading rate on the breaking force deformation and stiffness modules of eggs. Poult. Sci. 55:349–358.[Web of Science]
SAS Institute. 2003. SAS Proprietary Software Release 9.1. SAS Inst. Inc., Cary, NC.
Steel, R. G. D., and J. H. Torrie. 1980. Principles and Procedures of Statistics: A Biometrical Approach. 2nd ed. McGraw-Hill, New York, NY.
USDA-Animal and Plant Health Inspection Service-Veterinary Services. 2003. National poultry improvement plan and auxiliary provisions. Fed. Regist. 68:28169–28175.
Viscione, K. A., S. L. Branton, A. M. Vance, P. D. Gerard, S. K. Whitmarsh, and E. D. Peebles. 2008. Effects of 6/85-strain Mycoplasma gallisepticum inoculation alone at 10 weeks of age or in conjunction with F-strain Mycoplasma gallisepticum inoculation overlays at 22 or 45 weeks of age on the performance of commercial egg laying hens. Poult. Sci. 87:588–593.
Yoder, H. W., Jr. 1975. Mycoplasmosis: Isolation and Identification of Avian Pathogens. Am. Assoc. Avian Pathol., College Station, TX.
Yoder, H. W., Jr. 1978. Mycoplasma gallisepticum infections. Pages 236–250 in Diseases of Poultry. 7th ed. M. S. Hofstad, B. W. Calnek, C. F. Helmboldt, W. M. Reid, and H. W. Yoder Jr., ed. Iowa State Univ. Press, Ames.
Yoder, H. W., Jr. 1991. Mycoplasmosis. Pages 198–212 in Diseases of Poultry. 9th ed. B. W. Calnek, H. J. Barnes, C. W. Beard, W. M. Reid, and H. W. Yoder Jr., ed. Iowa State Univ. Press, Ames.
Yoder, H. W., Jr., and M. S. Hofstad. 1964. Characterization of avian Mycoplasma. Avian Dis. 8:481–512.[CrossRef][Web of Science]
Zander, D. V. 1984. Principles of disease prevention. Pages 1–37 in Diseases of Poultry. 8th ed. M. S. Hofstad, H. J. Barnes, B. W. Calnek, W. M. Reid, and H. W. Yoder Jr., ed. Iowa State Univ. Press, Ames.
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