Effect of Royal Jelly in Ovo Injection on Embryonic Growth, Hatchability, and Gonadotropin Levels of Pullet Breeder Chicks

The objectives of this study were to compare the following: (1) hatchability, (2) chicks' body and internal organs weights, and (3) plasma gonadotropin levels of hatchlings after in ovo administration of royal jelly (RJ) on Day 7 of incubation. Fertile eggs (n = 270) were injected into the air sac or yolk sac with 0.5 mL normal saline solution consisting of four formulations (normal saline solution with antibiotics, ultrafiltrate RJ, pure RJ, and RJ with antibiotics). The eggs were randomly divided into nine groups of 30 eggs each: (i) C: the control eggs received no injection, (ii) ASA: air sac-injected eggs received normal saline solution with antibiotics, (iii) ARJ: air sac-injected eggs received pure RJ, (iv) ARJA: air sac-injected eggs received RJ with antibiotics, (v) ARJF: air sac-injected eggs received RJ ultrafiltrate solution, (vi) YSA: yolk sac-injected eggs received normal saline solution with antibiotics, and (vii) YRJ: yolk sac-injected eggs received pure RJ, (viii) YRJA: yolk sac-injected eggs received RJ with antibiotics, and (ix) YRJF: yolk sac-injected eggs received ultrafiltrate RJ solution. Hatchability rate was lower in ARJ (46.7%), ARJA (43.3%), ARJF (43.3%), and YRJF (46.7%) groups than in the control (80.0%; P < 0.05). Hatchability rate in ASA (70.0%), YSA (66.7%), YRJ (66.7%), and YRJA (63.3%) groups were comparable to the control (P > 0.05). In ovo injection of RJ and or RJ with antibiotics in both sacs increased chicks' body weight (CWT), heart weight (HWT), and liver weight (LWT) and FSH and LH levels compared with control (P < 0.05). CWT in YRJ (37.02 g), YRJA (37.03 g), ARJ (36.82 g), and ARJA (36.89 g) groups were higher than control (34.9 g; P < 0.05). Similarly, HWT significantly increased in YRJ (0.22 g), YRJA (0.21 g), ARJ (0.20 g), and ARJA (0.20 g) in comparison to control (0.18 g; P < 0.05). In addition, LWT were higher in YRJ (0.83 g), YRJA (0.82g), ARJ (0.81g), and ARJA (0.81g) than control (0.72 g; P < 0.05). Six hours post-hatch, the mean plasma FSH and LH levels in ARJ (1.13 and 2.80 mIu/mL), YRJ (1.32 and 3.36 mIu/mL), ARJA (1.23 and 2.95 mIu/mL), and YRJA (1.31 and 3.28 mIu/mL) groups were higher than in the control (0.56 and 1.48 mIu/mL, P < 0.05). We concluded that in ovo administration of RJ or RJ with antibiotics might be an effective method to increase CWT, chicks' internal organs weights, and LH and FSH secretion rate without deleterious effect on hatchability. However, further research should be conducted to determine the putative endocrine disruptive effects of RJ and its byproducts.