Effects of caponization and age on the histology, lipid localization, and fiber diameter in muscles from Leghorn cockerels.

Poultry researchers seek general and native lines of birds for capon production. The primary aim is to find high-quality meat with valuable sensory attributes. Castration decreases androgen levels and changes lipid metabolism, resulting in the accumulation of abdominal, subcutaneous, and intramuscular fat, which changes the flavor, texture, and tenderness of the meat. Histological analysis of selected skeletal muscles from Leghorn capons and cockerels was the main aim of the present study, along with examination of lipid localization in muscle tissue. We also assessed fiber type and diameter in the pectoral muscles (pectoralis major). The experiment was performed on 200 Leghorn cockerels; testes were removed at 8 wk of age. At 12, 16, 20, 24, and 28 wk of age, 6 cockerels and 6 capons were slaughtered, and samples from the pectoral and thigh muscles were evaluated. Differences in the focal necrosis of the fibers with infiltration of lymphoid cells (P < 0.05) were observed in thigh muscles, with higher numbers in cockerels than in capons. All examined locations in the pectoral and thigh muscles of capons (around the blood vessels, in the perimysium, in the endomysium, and in the sarcoplasm) showed higher concentrations of lipids compared to levels in cockerels. The analysis of fiber type in pectoralis major muscles revealed that all fibers were type IIB. The diameters of the fibers of the pectoral muscles were different (P < 0.05) at 28 wk of age, and the diameters of the giant fibers were different (P < 0.05) at 16 wk of age. The high concentration of lipids in the skeletal muscles of Leghorn capons is remarkable. Thus, ethical reasons as well as economic reasons should be considered when one-day-old cockerels are eliminated.