Effect of In Ovo Feeding of Tryptophan on Post-Hatch Production Performance and Immune Response in Commercial Broilers

In order to evaluate the post-hatch production performance, immunocompetence and muscle fibre diameter of broilers following in ovo supplementation of tryptophan on 18d of incubation, 420 fertile eggs collected from 34 weeks-old broiler breeder were randomly divided into three treatment groups: noninjected control (CON), injected control (NSS; 0.5 ml of normal saline) and tryptophan (TRP; 0.5 ml of 0.5% tryptophan). On day of hatch, 108 chicks were randomly selected from each treatment and reared on cage having six replicates in each for a period of 35d under standard management practices. Total RNA was isolated from the splenocytes of 10 birds at 4, 17 and 32d, and the cDNA was prepared. The amplification of target immune genes (IFN-γ and IL-8) was carried out in a real time PCR. Percent hatchability in the TRP group was apparently higher than the un-injected CON group. Placement weight showed significant (P<0.01) difference among treatments with the TRP chicks having significant higher weight. Though cumulative feed intake was higher in TRP group, but there was no significant difference in feed efficiency. Compared to CON group, the TRP group had higher livability. Further, in ovo tryptophan feeding resulted in higher breast yield and breast muscle fibre diameter (P<0.01). The TRP birds tended to have higher thymus weight accompanying better immune response through IFN-γ gene. The expression of IL-8 gene was more in CON followed by the TRP group. The HI titer against ND virus on 4d was more in all treatment groups as compared to CON. Additionally, the TRP groups had exhibited significantly (P<0.01) higher H/L ratio on 21 and 35d. It is concluded that in ovo feeding of TRP increased in hatch weight, livability, immunocompetence and breast meat yield.