Effect of genotype and growth factors on pectoralis muscle development in chickens

• Main Author: Scheuermann, Gerson Neudi
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2003
• Subjects: Anatomy & physiology; Animal sciences; Animals; Livestock; Physiology
• ISBN: 9780496599400; 0496599402

Experiments were conducted to study the muscularity difference in chicken genotypes and its relationship to the apparent number of myofibers in the Pectoralis muscle. Attempts were also made to interfere in the myogenic process through in ovo administration of IGF-I or anti-myostatin antibody in order to impact positively the weight and yield of breast muscle by increasing the number of myofibers. Commercial broiler strain-crosses were compared by general post-hatch performance and by analyzing the growth curves using the Gompertz model. The strain-crosses showed to have different growth curves and differed in body weight, breast weight and breast yield. Males and females also showed different growth curves, with males having slower growth rate maturity parameter and reaching the maximal growth rate later than females for body weight and breast weight. Breast depth was the muscle measure with highest positive correlation to breast yield. A method was established to access the apparent number of myofibers in the Pectoralis muscle of chickens. Broiler chickens showed to have higher number and larger myofibers in the Pectoralis muscle than leghorn-type chickens. Indications were that the high breast yield of broilers might be due to increased number of myofibers. Significant negative correlation between myofiber density and production variables (BW breast weight and breast yield) indicated that chickens with higher growth rate had myofibers with larger cross-sectional area, which was age dependent. Expression of myostatin, a member of the transforming growth factor-β superfamily, was estimated during the embryonic development of broiler- and leghorn-type chickens using a semi-quantitative RT-PCR method. Results indicated that higher muscularity of broiler chickens was not due to lower expression of myostatin during the embryonic period. Finally, in ovo injection procedures were used to deliver anti-myostatin antibody and IGF-I into the albumen at early embryonic age (E). In ovo administration of different concentrations of anti-myostatin antibody at E3 or E6 did not affect post-hatch performance in broiler chickens. However, in ovo administration of 100ng IGF-I per egg at day 3 of the embryonic age improved post-hatch performance of both broiler- and leghorn-type chickens and increased the size of the myofibers, while no clear effect on Pectoralis myofiber number was observed.