الفهرس 
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Abstract
Two experimental trials were conducted to study the effect of in ovo injection of L-Threonine or Lavender essential oils on performance of broilers. The first trial was conducted to study the effect of in ovo injection of L-threonine (L-Thr) on hatchability, growth performance, antioxidant capacitity, 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) 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 was 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 improvement of intestinal morphology of broilers demonstrated by higher ratio of villus height to crypt depthThe second experimental trial was conducted to examine the impact of route of supplementation of lavender essential oil either in ovo and /or dietary addition on fertile hatchability, growth performance, serum antioxidant capacity, intestinal histomorphology and carcass traits of broiler chickens. Two hundred fifty-eight fertile ross 308 eggs, on day 18 of incubation, were randomly allotted into 3 sets: non injected set (NC group), a 0.5 ml saline injection set (SC Sham control group) and lavender essential oil enriched saline 20% set (LEO). After hatch, each set of hatchlings was divided into 2 new groups 3 replicates (10 birds each). The two groups received different diets, a basal diet without essential oil (control diet), and a basal diet supplemented with LEO (600 mg/kg). The groups were designated as follows: G1, G2, G3, G4, G5 and G6 where G1 were chicks hatched from non-injected group fed on basal diet, G2 non-injected group and fed on LEO supplemented diet, G3 saline injected and fed on basal diet, G4 saline injected and fed on LEO supplemented diet, G5 LEO injected and fed on basal diet and G6 LEO injected and fed on LEO supplemented diet. Daily feed intake (FI), body weight (BW), and feed conversion ratio (FCR) were calculated weekly. At the end of rearing period serum antioxidant parameters (SOD and MDA) were evaluated, immune organs relative weight and carcass traits (dressing %, breast and thigh yield) were calculated, in addition to intestinal histomorphology. Pre hatch (in ovo) injection of LEO improved fertile hatchability accompanied with reduction of chick’s mortality, improve growth performance parameters of hatched chicks and enhancing total weight gain and improving FCR, and augment the intestinal health of the chicks through increasing villus height to crypt depth ratio. Post hatch dietary supplementation of LEO, in ovo injection of LEO had a positive effect on growth performance of supplemented chicks, enhanced the antioxidant capacity of serum by increasing SOD, increased relative weight of thymus and improved the structure and health of intestine.
It could be concluded that the use of Pre hatch (in ovo) injection of either Threonine or LEO followed by dietary supplementation had a better effect not only on chick’s hatchability and growth performance but also alleviated oxidative stress, potentiated the immune response and improved gut health through enhanced intestinal histomorphology of Ross 308 broilers.