Productivity and Immune Response of Broiler Chickens Vaccinated with Different Avian Influenza Vaccines at One or Seven Days of Age

This study was carried out to investigate the effect of different Avian Influenza "AI" vaccines (H5N1, H5N2, combinant AI H5N2 + Newcastle Disease "ND", and Egyptian H5N1) and vaccination programs (at 1 or 7 days-old) on broiler productivity and immunity. A total number of 1,350 day-old Hubbard broiler chicks were divided into 9 groups. Eight groups of chickens (3 replicates per group) were vaccinated with H5N1, H5N2, AI+ND and the Egyptian vaccine H5N1 at 1 or 7 days-old. The Egyptian vaccine was prepared from the isolated H5N1 AI virus from the Egyptian infected chickens in 2006. The chickens of group 9 were kept as negative control. All chicks had ad libitum access to water, corn-soy-based starter diet from 1 to 21 days-old, grower diet from 21 to 30 days-old and finisher diet from 30 to 42 days-old. Productive traits were measured weekly and calculated globally from 1 to 42 days-old. Serum samples were collected at 4, 7, 14, 21, 28, 35, and 42 days-old from 5 chickens per replicate. During the experimental period, results indicated that neither different vaccines nor vaccination programs affect broiler productivity (final body weight (2,212 g), body weight gain (51.6 g/bird/d), feed intake (91.7 g/bird/d), feed conversion ratio (1.74 g feed : g gain) or mortality rate (6.6 %)), ND titer (ranged from 3 to 7) and relative spleen (ranged from 125 to 197 mg/100 g BW) or bursa (ranged from 51 to 159 mg/100 g BW) weights. On the other hand, this study revealed that, H5N2 and AI + ND vaccines were more protective than H5N1 or the Egyptian AI vaccines as indicated by the geometric mean of HI titer against AI virus of experimentally broiler chicks (5.71 to 8.20 vs. 0 to 4.91, respectively). However, no differences were detected among the vaccinated chicks at 1 or 7 days-old for HI titer against AI virus in most ages. It could be concluded that, both H5N2 and AI + ND vaccines were more preferable for Hubbard broiler flocks in Egypt than H5N1 or the Egyptian AI vaccines.