This study aimed to investigate the effects of pre-incubation in ovo injection with different levels of L- carnitine (L-Car) on hatchability traits of Bronze Turkey eggs, blood plasma constituents and subsequent growth performance of hatched chicks. A total of 300 hatching eggs of Bronze Turkey were chosen (averaged 80.0 g) and randomly divided into four main groups each of three replicates (25 eggs each). The 1st group was used as a control (C) without injection, while the 2nd, 3rd and 4th groups were injected with 0.1 ml distilled water contained 6, 8 or 10 mg L-Car/egg, respectively. Hatchability (%), Early and late embryonic mortality (%) were calculated. After hatch, 33 chicks were taken from each treatment group then distributed into three replicates (11 chicks, each), then reared up to 84 d-old to evaluate their growth performance. The results indicated that, in- ovo L-car injection (with 6.0 mg/egg) before incubation had significantly (P≤0.01) increased hatchability (%) of fertile eggs and decreased (P≤0.01) both early and late embryonic mortality compared with the control group (non-injected). Hatched chicks from injected eggs with 6.0 mg L-car /egg recoded a significant (P≤0.01) improvement of all studied growth traits during the entire period after hatch as compared with the other treatment groups. Blood PlasmaIGF-1, triiodothyronine and total antioxidant capacity constituents were significantly elevated for chicks at hatch by in ovo L-car injection compared to control group. Histological examination explained an improvement in small intestine and lymphoid organs development by in ovo L-car injection compared to the control group. So, we concluded the in ovo L-car injection (6 mg/egg) before incubation could be used as a promising technical method to improve hatchability and decrease embryonic mortality (%), obtain better immunity and subsequent growth performance of Bronze turkey chicks after hatch.
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