THE EFFECTS OF MATERNAL IMMUNIZATION AGAINST MYOSTATIN ON POST-HATCH CHICKEN GROWTH

Date
2021
Authors
Mishra, Rajeev Kumar
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Kim, Yong-Soo
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Animal Sciences
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Myostatin (MSTN) is a negative regulator of skeletal muscle growth. A previous study showed that in-ovo administration of monoclonal anti-MSTN antibody increased post-hatch body weight and muscle mass, demonstrating the potential of in-ovo MSTN suppression to improve the growth performance of chicks. Therefore, we hypothesized that active immunization of hens against MSTN will produce anti-MSTN antibodies, and this antibody will be passively transferred into fertilized eggs, leading to improvement of skeletal muscle growth of the first-generation chicks. Recombinant myostatin (chMSTN) was produced from transformed E. coli and was processed for hen immunization. Two experiments examined the effects of maternal immunization against chMSTN and Myo2, a synthetic MSTN fragment, on the growth performance and muscle mass of chicks from immunized hens. In Experiment 1, twelve 18 weeks old Hy line brown hens were randomly allocated into four pens with a breeder’s feeding program plus freely available water, each pen with 3 hens and 1 White Leghorn rooster of the same age. At 24 weeks of age, the 4 pens were randomly divided into two groups with two pens in each group: Control and chMSTN. Hens in the Control and chMSTN groups were immunized by subcutaneous injection of 0, and 0.5 mg of chMSTN emulsified with adjuvant on days 0, 7, and 21, respectively. The peak antibody titer was seen around day 35 from the first immunization, and the peak egg yolk antibody titer was day 41. About 60 eggs were collected from each group between day 38 to 48 after the first immunization and were incubated under standard conditions. Chicks were reared under a deep litter system for 7 weeks with weekly bodyweight monitoring. At sacrifice, viscera were removed, breast muscle and bone-in legs were separated and weighed. There was no difference in the body weight and carcass parameters between the two groups. In Experiment 2, the two pens of the chMSTN group used in Experiment 1 were divided into chMSTN and Myo2 groups while the two pens of the Control group remain as the Control group. At 43 weeks of age, Control and chMSTN groups were immunized in the same way as the experiment 1 on days 0 and 7. The Myo2 group was immunized with 2 mg of Myo2 peptide (synthetic MSTN fragment) conjugated to KLH /100 μl of PBS emulsified with the same volume of adjuvant. The peak serum antibody titer was seen around day 21 from the first immunization, and the peak egg yolk antibody titer was day 28. Thirty-three eggs were collected from each group between days 24 to 34 after the first immunization and were incubated and chicks were reared for 11 weeks and sacrificed in the same manner as was performed in Experiment 1. The body weight of the chMSTN was not different from that of the Control, but the body weight of the Myo2-KLH was significantly lower than that of the Control. The dressing % and breast muscle mass of the chMSTN and Myo2 were significantly lower than those of the control, and the breast muscle mass of Myo2 was significantly lower than that of the chMSTN, indicating that maternal immunization against chMSTN or Myo2 suppressed muscle growth of offspring with immunization against Myo2 being more suppressive than immunization against chMSTN. In Western blot analysis, IgY from the chMSTN and Myo2 groups showed binding affinity to the chMSTN, Myo2, and commercial MSTN. However, the binding affinity of egg yolk IgY to commercial MSTN was much lower than to chMSTN, Myo2-KLH, or Myo2-BSA. The weak binding affinity to bioactive MSTN of the IgY partly explains the reason why the maternal immunization against chMSTN and Myo2 did not increase the muscle mass of offspring, but the reason for reduced muscle mass of the offspring from immunized hens is not clear. In summary, the maternal immunization against chMSTN and Myo2 did not increase but decrease the body weight and muscle mass of offspring from the immunized hens. The results are not as expected since the inhibition of MSTN via maternal immunization could not enhance the body weight and muscle mass of offspring. However, the results show that the body weight and muscle mass of offspring could be controlled by maternal immunization against molecules having physiological functions.
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Animal sciences, antibody, immunization, maternal immunization, muscle growth, myostatin, poultry
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95 pages
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