PREDICTION OF GENETIC GAINS IN BODY-WEIGHT, EGG-PRODUCTION AND SHELL QUALITY TRAITS IN THE BROWN TSAIYA LAYING DUCK (ANAS-PLATYRHYNCHOS)

An evaluation was made of the expected genetic gain and predicted gene tic responses for egg weight and body weight at 40 weeks of age (EW40, BW40), number of eggs laid up to 52 weeks of age (NEGG52);, eggshell strength at 30 or 40 weeks of age (ES30 or ES40) in Brown Tsaiya layin g ducks selected for five generations by independent culling levels, f irst on a linear phenotypic index for the first three traits, and then on ES30 or ES40. The genetic parameters estimated in the base populat ion were used to calculate the expected genetic gains in one generatio n of selection. The genetic responses per generation were evaluated by averaging the multitrait best linear unbiased prediction (BLUR) anima l model predictors and regressing them on generation number. The per g eneration genetic responses were + 0.177 g (EW40); + 8.029 g (BW40); 0.935 eggs (NEGG52); + 0.017 kp/cm(2) (ES30); + 0.014 kg/cm(2) (ES40) . These values fit the expected genetic gains for NEGG52, but they are higher than those for BW40 and lower than those for ES30 and ES40. It was shown that, compared to the selection method which has been used and with the same selection intensity in female ducks (i = 1.271), con strained selection based on a phenotypic selection index or a genetic index could increase the expected genetic gains in NEGG52 by a factor of 3.5 or 5.7, respectively, while maintaining constant EW40 and BW40.