Two experiments assessed the efficacy of in ovo administration of insulin-like growth factor-I (IGF-I) to enhance skeletal muscle development and improve feed efficiency of broilers. Hatching eggs were divided into three groups: uninjected control, vehicle-injected control, and recombinant human (rh) IGF-I (100 ng per embryo). Eggs in Experiment 1 were injected on Day 1, 4, or one of Day 7 through 18 of incubation. Growth rates for Days 1 and 4 resulted in the greatest response to treatment (P < 0.01, P < 0.06 respectively). Based on these results, Experiment 2 focused on Days 1 to 4 of incubation. Results from Experiment 2 showed that there was no significant difference in hatchability among control and rh IGF-I treatment groups. Injection on Day 3 resulted in the greatest response for increased live (P < 0.035) and leg (P < 0.02) weights in both sexes. Feed efficiencies of all rh IGF-I groups were significantly (P < 0.01) improved for the first 3 wk. In ovo administration of rh IGF-I on Day 3 increased feed efficiency (6.65%; P < 0.009) in pens of mixed-sex broilers. In addition, live weights (12.3%; P < 0.002), leg weights (11.7%; P < 0.01), breast weights (9.9%; P < 0.04), and heart weights (11.4%; P < 0.02) were increased in males. These results demonstrate that in ovo administration of rh IGF-I alters feed efficiency, growth, and tissue development. This finding lends itself to significant improvements in broiler production efficiency and profitability.
The effect of in ovo administration of chicken growth hormone (cGH) on growth rate and efficiency of gain, organ, and long bone growth of 42-d-old broiler chickens was investigated. Eggs were injected once with 100 microL vehicle (0.03 M NaHCO3, 0.15 M NaCl, pH 8.3) per embryo or vehicle containing 100 ng cGH/100 microL per embryo (n = 630 eggs total) on one of the following Days: 1, 4, or 7 through 18 of embryogenesis. There was no significant difference in hatchability between control and cGH treatment groups on any given injection day. Cumulative feed conversion of all treatment groups was improved relative to their respective control groups (P < 0.05). In ovo administration 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 were 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 treatment 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 difference between control and treatment groups, in terms of heart or leg weights, or in Warner-Bratzler shear force of Pectoralis profundus muscle. Hydroxyproline concentration and cross-sectional area of female broiler tibias from 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.
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