THE INTERACTION EFFECT OF STRAIN , SEX AND LIVE BODY WEIGHT ON ANTIBODY RESPONSE TO SRBC S IN BROILER CHICKENS

An experiment was designed to evaluate the effect of both strain and sex against of SRBCs antigen on live body weight, at different ages in broiler chickens. The experimental extended from June to July 2007, in order to investigate the relationship between the general immune response to SRBCS antigen on body weight traits in broiler chicks at one cycle. Two different commercial strains (ISA Hubbard and Ross 308) were used. Chicks were brooded and reared under similar environmental condition and raised on deep litter up to marketing age (7 weeks). The feed and water were provided ad libitum. Individual body weight of 500 chicks was recorded for each strain (250 per each) separately at 0, 1, 2, 3, 4, 5, 6 and 7 weeks of age. Prepared antigen (SRBC 2.5%) was injected individually in all birds with 0.13 dose at 28 day of age. Then, chickens were bled from the wing vein at 7, 14 and 21 day postinjection for anti-body (Ab) levels determination. Means of Ab – titers were 6.91 and 5.66 at 7-d post – injection in ISA Hubbard and Ross 308, respectively, with highly significantly differences (p≤ 0.001) between strains. While, females had higher Ab – titers than males, but the difference were not significant. On other hand, Ab titers at 7, 14 and 21 d post injection in both broiler strains had negative phenotypic correlations with body weight at 7Wks of age, being – 0.049, – 0.008 and – 0.041, respectively. INTRODUCTION One of the concerns of commercial poultry farmers is the protection of their flocks against disease challenge. This objective could be achieved through selecting birds that are resistant against particular pathogens, and/or those displaying better immunocompetence, i.e., the general quality of host’s immune system to launch sufficient defense against infections (Knap and Bishop, 2000). Previous studies have linked genetic makeup of poultry to disease resistance and/or susceptibility(Lamont et al., 1987; Lakshman et al., 1997; Poulsen et al., 1998; Yonash et al., 2001). Furthermore, genetic improvement for growth performance over the years has been seen to negatively influence immune performance of chickens. High An 2 Annals of Agric, Sc, Moshtohor, Vol,48(2),2010 growth rate in broiler chickens has also been linked to increased susceptibility for Marek’s Disease Gebriel et al., 1979 and Presently, the aim of commercial poultry breeding is to achieve higher body weight and maximum egg production per unit of feed intake. However, there is a negative correlation between production traits and immunity in chickens because of the conflict between some production and immunity, i.e. maturation and function of the immune system. The genotypes with the maximum body weight exhibit lower immunity (Gebriel, 1990 and Nestor et al., 1996) Mortality due to Marek’s Disease challenge showed higher in males than in females of B 13 B 21 Cornell Random bred White Leghorn chickens divergently selected for low antibody response to SRBC signifying a sex effect in disease susceptibility (Martin et al., 1989). Furthermore, age of the chickens also has an effect on immune performance. Due to immunological immaturity, young chickens have a greater incidence of diseases such as infectious bursal disease, avian encephalomyelitis, Marek’s Disease, E. coli and Salmonella infections (van der Zijpp, 1983). MATERIALS AND METHODS 1.Genetic stocks and management: The experiment of this study was carried out at Private Breeding Farm of poultry production Toukh city, Kaluobia Governorate, Egypt, during 49 days in summer 2007, in order to investigate the relationship between the general immune response to SRBCS and some productive traits in broiler chicks. Two different commercial strains, named ISA Hubbard and Ross 308, were used. Data collected from 500 chicks (250 chicks from each strain) were used. All chicks were brooded and reared under similar environmental conditions and raised on deep litter up to marketing age (7 weeks). Feed and water were provided ad libitum. They were fed a diet containing 23% crude protein and 3000 k.cl ME/kg in starter formula, 21% crude protein and 3050 k.cl ME/kg in grower formula and 19% crude protein and 3150 k.cl ME/kg in finisher formula. The load number was (intensity numbers 10 birds /m 2 ). All chicks exposing to similar environmental condition during experimental period. 2. Immunization with SRBCS antigen: Sheep red blood cells (SRBCS) were chosen as natural immunizing antigen to elicit the antibody response in the chicks. The prepared SRBCs antigen (2.5%) was injected individually in the wing vein with 0.13 ml at 28day of age according to the method of Van der Zijpp and Leenstra (1980).