Al-Qadisiyah Journal of Veterinary Medicine Sciences

Abstract Broiler breast muscle development is strongly affected by nutritional quality, particularly the source and biological value of dietary protein. Dietary protein source may influence muscle fiber growth, connective tissue organization, glycogen deposition and the transcriptional activity of myogenic regulatory genes. The aim of the present study was to evaluate the effect of dietary protein source on muscle structure, glycogen content and myogenic gene expression in the pectoralis major muscle of broiler chickens. A total of 9000 one-day-old broiler chicks were raised under field conditions and divided into two dietary groups: an animal protein-based diet containing fish meal and a plant protein-based diet based on corn-soybean meal. Samples of pectoralis major muscle were taken at 42 days of age and analyzed using morphological, histological, histochemical and molecular techniques. Birds fed the animal protein diet had significantly larger muscle fiber area and muscle bundle area than birds fed the plant protein diet (P < 0.05), whereas birds fed the plant protein diet exhibited thicker connective tissue layers. Periodic acid-Schiff staining showed greater glycogen deposition in the animal protein group. RT-qPCR analysis showed that MYF6 (MRF4) and MYOG were significantly more expressed in the animal protein group than in the plant protein group (P < 0.05). In conclusion, animal protein enhanced muscle hypertrophy, glycogen storage and myogenic gene expression in the pectoralis major muscle, indicating the importance of protein quality in improving broiler production and meat quality.

Abstract This study aimed to investigate the histological growth and Myoz1 gene expression and evaluated the level of glycogen in the iliofibularis muscle of broiler chickens at 2, 4, and 5 weeks of age. By investigating the structural changes in muscle fibers and the corresponding alterations in Myoz1 gene levels, this research sought to elucidate the relationship between age, muscle growth, and gene expression in the iliofibularis muscle group. Understanding these developmental processes is crucial for optimizing broiler production and potentially providing insights into muscle growth and development in other species.  In this study, fifteen broiler chickens were examined to investigate the histological structure and evaluate the level of the Myoz1 gene in the iliofibularis muscles at three different ages: 2 weeks, 4 weeks, and 5 weeks. The muscle fibers are cylindrical and multinucleated, with elongated nuclei beneath the sarcolemma. The muscle fibers are surrounded by a very thin layer of endomysium, which is composed of fibroelastic connective tissue. Each fascicle of muscle fibers is surrounded by a dense, irregular connective tissue called the perimysium. A cluster of muscle fascicles is surrounded by a layer of dense, irregular connective tissue called the epimysium. The size and organization of muscle fibers increase with age. At 5 weeks, the muscle fibers become larger and more uniform. The mean areas of muscle fibers at 2 weeks, 4 weeks, and 5 weeks were 233.1± 0.0099, 492.32± 0.0079, and 1177.56± 0.0098 µm2, respectively. Our results show the muscle fibers in the third group had a highly significant difference from the muscle fibers of the iliofibularis muscle in the first and second groups. The highest average expression was found in the third group (5 weeks old), while the lowest was in the first group (2 weeks old). Our findings indicate statistical analysis confirmed iliofibularis muscle in the third group had a highly significant difference with iliofibularis muscle in the first and second groups (Ƿ=0.0000269) and (Ƿ=0.000025), respectively. Overall, the findings suggested an age-dependent rise in myzo1 gene expression within the iliofibularis muscle in the third group of broiler chickens.