The Effect Of F Strain Vaccine Of M.gallisepticum On Growth Performance And Immunity Of Broiler

Mycoplasma gallisepticum (MG) is the main pathogenic, which causes chronicrespiratory disease (CRD) of chickens and infectious sinusitis of turkeys. Theinfective rate of MG is very high in our country, chickens’ health was maintained byusing drug to control at most of farms except the breeders’ farms, but it is diffcult tocontrol completely, thus it lead to economic losses largely in poultry industry.Therefore, it has the practical significance for preventing and controlling the diseaseof CRD through application of F vaccine of MG (F MG). In the study, the aim was toestablish duplex PCR method for distinguishing the virulent strain R and the vaccinestrain F of MG; To investigate into the influence of the broiler’s growth performanceand immunity arise from vaccinating the F MG, and the reasonable immunizationprograms of it were explored. The following parts were conducted in the study:Experiment1: Establishment of duplex PCR method for distinguishing thevirulent strain R and the vaccine strain F of M. gallisepticumThe internationally recognized virulent strain R and the vaccine strain F of MGwere choosed, then the two primers were designed according to sequence of the pvpAgene of the R strain and putative alpha-phosphotrehalase gene of the F strain of MGfrom GenBank, named as R1, R2and F1, F2respectively. Based on the single PCR,the duplex PCR assay was made to determinate the two strains of MG. The resultindicated that it had high specificity and sensitivity, and the0.45ng DNA from Rstrain and0.25ng DNA from F strain could be detected. Compared to the traditionalidentification methods, it was easy to be operated and the clinical samples were testeddirectly, meanwhile the strong and weak strains of MG also could be distinguished byit. The conclusion could be made that the larynx and tracheal swabs should be usedfirstly, and it would provid a technical support for establishing MG negative groups ofchicken flocks eventually. Hence, it had the significant value in practical application.Experiment2: Effect of the F strain vaccine of M. gallisepticum on the growthperformance and immunity of commercial broilerIn the experiment,200three yellow broiler chickens at1day age were selected,and divided into4groups:1) vaccination of F MG at1day and16day age andchallenging R MG at24day age;2) challenging R MG at24day age;3) vaccinationof F MG at1day and16day age;4) sham vaccination and challenging. The bodyweight again and feed of consumption of trial animals from1to42day age werecounted; five chickens per group were treated after challenged every7days, then the duplex PCR method was appled to determine MG from throat swabs, air-sac swabsand the organizations of larynx, lung, liver, and so on, meanwhile the serum calcium(SCA), serum phosphorus (SP), serum total cholesterol (SCHOL), total protein (TP)and serum urea nitrogen (SUN) of the blood also were detected and analyzed; HA-HItest was used to determine the serum antibody titers to newcastle disease vaccine foreach groups at31and38day age.The results showed that the detected R strain numbers in the first trial was lower60%than that of the second. The total increased weight of the third trial was higherthan that of the others, which raised14.2%,19.66%and10.38%, the difference wassignificant (p<0.05), and the feed/gain ratio decreased0.37,0.12and0.14respectively; Higher antibody titer was maintained, there was significant differencesbetween the third gourp and the second group (p<0.05). Compared with the fouthgroup, it had significant difference in the early (p<0.05), but in the later there was nosignificant difference (p>0.05), equally there was no significant difference betweenthe first tiral and the third tiral (p>0.05); There also was no significant difference onblood indexes at different periods among them (p>0.05). It indicated that there was noimpact of the body’s metabolic balance by vaccinating the F MG, but it can inhibit thefollow-up infection, improve the growth performance, strengthen the immune effectof NDV vaccine and improve economic benefits eventually.Experiment3: Effect of the F strain vaccine of M. gallisepticum on the growthperformance and immunity of breeder chickensIn this experiment,3000three yellow breeder chickens at1day age wereselected and divided into2trials:1) vaccination of F MG at1old age;2) shamvaccination at1old age. The duplex PCR method was applied to determine MG fromthe throat swabs of each trials at5day,30day and40day age. The body weight again,the feed of consumption and the mortality at22,22-32,32-40and0-40days of agechickens of each trials were counted. The serum antibody titers to newcastle diseaseand H9subtype avian influenza vaccines of the each trials at31and38day agechickens were analyzed by HA-HI test.The results showed that the detected numbers of the field-strain in the first trialwas lower than that of the second, and the total increased weight also was higher3.6%than that of the second, the feed/gain ratio was decreased0.14, the defferencewas significant (P<0.05), and the differences was also kept at different stage (P<0.05).The titer of antibody of the first trial were higher than that of the second, with significant difference (P<0.05). It indicated that it can inhibit the follow-up infection,improve the growth performance, strengthen the immune effect of NDV and AIV byvaccinating the F MG, and improve economic benefits eventually.