Differences in skeletal muscle fibre growth in broiler and layer chickens: Association with myopathy?

Vicky E Cooke*, Sally Gilpin, Michael Mahon, DA Sandercock, MA Mitchell

*Corresponding author for this work

Research output: Contribution to journalMeeting Abstractpeer-review


Genetic selection for improved production traits in poultry may be associated with an increased incidence of spontaneous and stress induced myopathies. Increased muscle fibre diameter and reduced oxidative capacity of specific muscles may be linked with increased incidence of myopathology in broilers. This study compared the growth of skeletal muscles of differing fibre type composition in commercial broilers (B) and layers (L). In the latter, selection strategies have not focused upon increased muscle growth and altered
conformation. 4 birds per line were weighed and euthanised at intervals between 4 and 22 weeks of age. Samples of Pectoralis major (Pm) (breast) and Biceps femoris (Bf ) (thigh) muscles were frozen for cryostat sectioning and stained using histocytochemical techniques. The minimum fibre diameter (MFD) of 100 fibres was measured for each muscle sample. Qualitative analysis of fibre type
composition demonstrated that in both lines and at all ages Pm consisted almost entirely of glycolytic fibres, whereas Bf had a large population of oxidative fibres. Body weight and mean MFD of both muscles increased with age (P≤0.05) in both lines, and were greater in broilers at all ages (P≤0.05). In B, mean MFD of Pm was greater than that of Bf at all ages (P≤0.05) except for at 20 wks (P=0.064). In L there was no difference in mean MFD of the two muscles at any age. The larger muscle fibre diameters in B compared to L may reflect increased rates of hypertrophy in B from hatch or before. Previous studies in turkeys have demonstrated a threshold muscle fibre diameter, above which further hypertrophy is associated with an increased incidence of spontaneous myopathy. Genetic selection for increased breast meat yield in broilers may have caused the
divergence in Pm and Bf fibre size and the commercially desirable high degree of muscle fibre hypertrophy may be associated with a predisposition towards spontaneous or idiopathic myopathy
Original languageEnglish
Article numberabstract 55
Pages (from-to)14
Number of pages1
JournalPoultry Science
Issue number1
Publication statusPrint publication - 2003
Externally publishedYes
Event92nd Poultry Science Association Annual Meeting 2003 - University of Wisconsin, Madison, United States
Duration: 6 Jul 20039 Jul 2003


  • Skeletal muscle
  • Muscle fibre growth
  • Myopathy
  • Broiler chicken
  • Layer chicken
  • Mean fibre diameter
  • Idiopathic myopathy
  • Histology
  • Hypertrophy


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