Postnatal growth of broilers in response to in ovo administration of chicken growth hormone

The effect of in ovo administration of chicken growth hormone (cGH) on grow th rate and efficiency of gain, organ, and long bone growth of 42-d-old bro iler chickens was investigated. Eggs were injected once with 100 mu L vehic le (0.03 M NaHCO3, 0.15 M NaCl, pH 8.3) per embryo or vehicle containing 10 0 ng cGH/100 mu L per embryo (n = 630 eggs total) on one of the following D ays: 1, 4, or 7 through 18 of embryogenesis. There was no significant diffe rence in hatchability between control and cGH treatment groups on any given injection day. Cumulative feed conversion of all treatment groups was impr oved relative to their respective control groups (P < 0.05). In ovo adminis tration of cGH on Day 15 or 16 of incubation increased body weights (P < 0. 01) of female broilers. On the other hand, body weights of male broilers we re significantly increased by treatment on Day 1 (P < 0.04). Breast weights of female broilers from treatment groups Day 15 or 16 were increased (P < 0.01, P < 0.05, respectively). Liver weights of female broilers from treatm ent groups Day 1 and 15 were increased (P < 0.05, P < 0.01, respectively). In contrast, in ovo administration of cGH on Day 11 of incubation increased liver weights of male broilers (P < 0.03). There was no significant differ ence between control and treatment groups, in terms of heart or leg weights , or in Warner-Bratzler shear force of Pectoralis profundus muscle. Hydroxy proline concentration and cross-sectional area of female broiler tibias fro m treatment groups Day 11 or Day 16 were increased (P < 0.05), and ultimate breaking strength (stress) of tibias from the same groups was reduced (P < 0.05). In ovo administration of cGH altered growth and tissue development of broiler chickens in a time by sex dependent fashion.