Effect of Embryonic and Post-Hatch Thermal Challenge on Turkey Muscle Development

Exposure of newly hatched turkey poults to hot or cold thermal stress often results in detrimental effects on breast muscle growth and development. Typical changes include increased lipid deposition and damage to muscle ultrastructure, leading to inferior meat quality with consequent economic losses to producers and processors. Likewise, exposure of market-weight turkeys to acute heat stress immediately prior to harvest, frequently results in a high incidence of inferior meat quality characterized by pale color, reduced marinade uptake and water-holding capacity, and poor protein functionality. Thermal manipulation of embryonic development has met with some success as a strategy to improve thermotolerance of broilers. We hypothesized that exposure of turkey eggs to a mild heat challenge at a critical developmental stage would alter muscle growth and development, thereby setting the stage for improved thermotolerance of the growing bird. Eggs from RBC2 (slow-growing) and F (fast-growing) turkey lines were exposed to a control temperature of 38C throughout 28 days of incubation or 12h of 39.5C between days 21-25. Following hatch, birds were brooded at temperatures of 31C, 35C (control), or 39C for 3d, followed by brooding at 35C until 14d of age when the birds were sacrificed. Breast muscle (P. major) was collected for analyses including muscle weight and fiber diameter. Results from this preliminary study suggest that mild thermal manipulation of turkey eggs results in changes to muscle ultrastructure that may be associated with altered thermotolerance in the growing bird.