Growth Changes in Bovine Muscle Fiber Types as Influenced by Breed and Sex

Samples of the biceps femoris were collected at 56‐day intervals from 28 days of age to slaughter from 24 Hereford, Angus, Holstein heifer and steer twin calves to define the effects of age, sex, and breed on histochemically estimated muscle fiber type patterns. Red, white, and intermediate fiber types doubled in mean cross‐sectional area during growth in all calves, while encounters of white fibers slightly increased and encounters of red fibers slightly decreased. In general, heifers had larger muscle fibers than steers, and Holstein steers had smaller fibers than Hereford or Angus steers.