Effect of in ovo Injection of L-Threonine on Hatchability Followed by post-hatch Extra Level of Dietary Threonine on the Performance of Broilers

The aim of this study was to examine the effect of in ovo injection of L-threonine (L-Thr) on hatchability, growth performance, antioxidant capacity, carcass traits, immune organs weight, and intestinal histomorphology of Ross 308 broilers chicks. On day 18 of incubation, 258 fertile eggs were randomly allotted into 3 sets: non-injected group (NC group), saline injected group (sham control SC group), and (Thr group) L-Thr injected group. After hatch, each set was allocated into 2 groups (3 replicates of 10 birds/ replicate) and were fed on a basal diet (calculated Thr content, 0.87 %) supplemented with 0 (CON group), and 3 g/kg L-Thr, respectively. The groups were divided as follows: G1, G2, G3, G4, G5 and G6 where G1 is non injected group and fed basal diet, G2 saline injected and fed basal diet, G3 threonine injected and fed basal diet, G4 non injected and fed threonine supplemented diet, G5 saline injected and fed threonine supplemented diet and G6 threonine injected and fed threonine supplemented diet. Growth performance parameters were measured during different periods of the trial. At the end of rearing period serum antioxidative parameters (SOD and MDA) were measured, carcass traits and relative immune organs weight were calculated, in addition to intestinal histomorphology. Addition of Thr positively affected the FCR, and feed intake of broiler chicks compared to sham and control (p < 0.05) groups. Dietary Thr supplementation increased relative weight of spleen and thymus compared to the control non supplemented group and improved intestinal histomorphology. In conclusion, in ovo injection and dietary supplementation of L-Thr can improve growth performance, immunity of broiler chickens that may be mediated by the development of immune organs and improving the intestinal morphology of broilers as demonstrated by higher ratio of villus height to crypt depth.