Effects of genetic control of subcutaneous fat deposition via using restricted selection indexes on live Performance and carcass characteristics of Pekin ducklings
Abstract. Estimates of phenotypic and genetic parameters for live Performance and detaiied dissection traits of body components and carcass tissues in Pekin ducks were calculated and used to construct selection indexes. The expected reduction in potential gain in live weight, dressing percentage and carcass characteristics resulting from restricting change in subcutaneous fat level to zero were assessed. The aggregate genotype measurements were weight at slaughter, dressing percentage and percent subcutaneous fat. The index measurements were weight at hatching, weight at slaughter, weight gain, breast width, breast length and breast circumference. The restricted indexes as compared with the unrestricted would lead to minimum reduction in potential gain of 29.4% in total net merit, 96.4% in weight at slaughter, 49.0% in dressing percentage, 74.0% in dissected side weight and 75.0% in muscle to bone ratio. The potential reduction in percent abdominal fat and percent bone in side was decreased by at least 38.5% and 80.2%, respectively. Absolute genetic response results showed that selecting for breast width alone (rTI = 0.79) would be recommended for birds with substandard levels of SCF, whereas use of the restricted index containing weight at hatching and breast width (rTI = 0.54) would be advised for individuals with Standard fatness.