Effect of genetic strains ( Ross 308 , Cobb 500 and Hubbard F 15 ) on immune response against Newcastle disease vaccine in broiler chickens

Copyright © 2016 The Author(s); Published by Alborz University of Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited. Background IGenetic selection would seem to have some effects on immunological memory. Studies have shown that a line of broilers selected for high antibody level to SRBC antigen responded better to vaccination against viruses than a line selected in the opposite direction.1 Poultry breeders evaluated some major genes such as the MHC or B complex that affect resistance to Marek disease (MD). If a gene is shown to reduce a commercially important disease, then selection for the resistance gene is useful.2 A resaerch showed that while Ross 308 gained 3.9 times more weight than the Athens Canadian Randombred Control, it had a lower humoral immune response to SRBC.3 The effect of genetic background on the immune system has been studied in some animals, and it has been reported that some innate and specific immune response features are heritable.4,5 In meat type chickens, humoral responses are lower than egg-type chickens, so it can concluded that cell-mediated immunity has more important role in meat type strains).6

paramyxovirus 1 (APMV-1).This virus can spread through exposure to fecal and other excretions of infected birds to others.Newcastle disease has been reported in domestic birds and wild birds.This virus can cause diarrhea, respiratory problems, circulatory and central nervous system disorder. 7

Objectives
The objective of this study was to compare the immune response against NDV of 3 commercial broiler strains (Ross 308, Cobb 500 and Hubbard F15).

Materials and Methods
Chickens A total of 36 000 one-day-old broiler chicks including 12 000 one-day-old Hubbard F15, 12 000 one-day-old Cobb 500, and 12 000 one-day-old Ross 308 strains were purchased.

Experimental Design
A total of 36ooo one-day-old broiler chicks Hubbard F15, Cobb-500 and Ross 308, were divided into 3 equal groups with 2 replicates and 6000 birds per replicate.The birds were reared under similar conditions from one-dayold to 49 days of age.All groups were vaccinated against Newcastle disease.Blood samples were collected before vaccination and on 7, 17, 27, 35, 42, 48 days of age and antibody titer against NDV was determined by Hemagglutination inhibition (HI) test.

Blood Collection and Serological Tests
Thirty chicks from each group were bled randomly and blood samples were collected before vaccination and on 7, 17, 27, 35, 42, 48 days of age and antibody titer against NDV was determined by hemagglutination inhibition (HI) test.Brachial vein was drained to collect blood samples and until performing the serological tests, sera were frozen at -20˚C.HI test was performed to detect antibodies against NDV in serum samples. 7croplate Hemagglutination Inhibition Test Beta method of micro-plate HI test was carried out in U-bottomed 96-well µL plates to determine the antibody level of the sera of different groups.One percent of chicken erythrocytes was used in this test.The test was carried out using constant 4HA unit NDV as antigen.

Statistical Analysis
The SPSS version 18.0 was used to analyze the titers obtained by HI test.After vaccination, the significant differences in HI titres of chickens of each group were determined by one-way analysis of variance (ANOVA) LSD test.Means were compared at a significance level of 5%.

Results
The Cobb 500 and Hubbard F15 strains had the highest and the lowest immune responses against Newcastle disease vaccine, respectively.Ross 308 had the second status among strains.
As shown in Table 2, the results indicated that at the age of 7, there was a significant difference between groups A and B and between groups B and C. At the age of 17, 27, and 35, there was not any significant difference between all groups.At the age of 42, there was a significant difference between groups B and C and antibody titers in group B were higher than those in group C. At the age of 48, there was a significant difference between groups A and C and between groups B and C.Then, at the end of this period, the Cobb 500 and Hubbard F15 strains had the highest and the lowest antibody titers against Newcastle disease vaccine, respectively.Ross 308 had the second status among strains.Moreover, at the last three ages, Cobb 500 and Ross 308 strains had higher antibody titers, respectively.

Discussion
2][13] Genetic selection would seem to have some effects on immunological memory.Researches have shown that a line of broilers selected for high antibody level to SRBC antigen responded better to vaccination against viruses than a line selected in the opposite direction. 1Some studies have indicated that primary and secondary immune responses are under different genetic control. 13Studies indicated that the disease resistance and antibody response of fast-growing birds is fairly weaker than the slower-growing birds, and fast-growing birds had high mortality, because high growth rate may lead to metabolic diseases or infections. 14A chicken line that had been experimentally selected for higher body weight, had a significant decrease of antibody response to sRBC. 15enetic selection for higher production performance in poultry negatively affected antibody response to sRBC, but had either no effect or a positive effect on cell-

Conclusion
The results of this study showed that at the last three ages, Cobb 500 and Ross 308 strains respectively had higher antibody titers.Therefore on the basis of present study, Cobb 500 and Ross 308 chickens had better immune responses against Newcastle disease vaccine and so are recommended for rearing, respectively.It is concluded that genetic strain could affect immune response against Newcastle disease vaccine in broiler chickens.And in Hubbard F15 strain, antibody response to Newcastle disease vaccine (as antigen) was negatively affected.

Table 1 .
Program of Vaccination Against Newcastle DiseaseThe results of the current study indicate that at the end of this period, the Cobb 500 and Hubbard stains respectively had the highest and the lowest antibody titers against NDV.Ross 308 had second status among strains.Also, at the last three age, Cobb 500 and Ross 308 stains respectively had higher antibody titers and we can say that in this study, in Hubbard stain , antibody response to Newcastle vaccine (as antigen), was negatively affected.