GENETIC-PARAMETERS OF BODY-WEIGHT, EGG-PRODUCTION AND SHELL QUALITY TRAITS IN THE BROWN TSAIYA LAYING DUCK

Heritabilities and genetic correlations were estimated for 5 575 layin g Brown Tsaiya ducks on performance data from 5 generations of a selec tion experiment, by means of a multivariate, multimodel, restricted ma ximum likelihood method (MM-RFML) applied to an animal model on the 12 traits: feather length at 20 weeks of age (FL20); body weight at 20 a nd 40 weeks of age (BW20; BW40); age at first egg (AGE1EGG); number of eggs laid up to 40 and 52 weeks of age (NEGG40; NEGG52); eggshell str ength at 30 and 40 weeks of age (ES30; ES40); egg weight at 30 and 40 weeks of age (EW30; EW40); egg yolk weight at 40 weeks of age (EYW40); and the proportion of egg weight to body weight at 40 weeks of age (E W40/BW40). Adult females were heavier than adult males (BW40: 1391 g v s 1310 g). ES40 was lower than ES30 (3.5 kg/cm(2) vs 3.8 kg/cm(2) Heri tabilities were found to be low (0.094, 0.107, 0.118, 0.160, 0.169, 0. 191 and 0.201 for ES40, ES30, NEGG52, NEGG40, FL20, EYW40 and AGE1EGG respectively), to medium (0.327, 0.329, 0.353, 0.425 and 0.499 for EW4 0/BW40, EW40, EW30. BW20 and BW40, respectively). Fifty genetic correl ations were tabulated. The pattern of the genetic correlations for the traits to be selected showed that NEGG52 was highly positively correl ated with NEGG40 (rg = 0.948), uncorrelated with the body weight and w as negatively correlated with AGE1EGG (rg = -0.749), EW40 (rg = -0.323 ), EW30 (rg = -0.200), EYW40 (rg = -0.340), ES30 (rg = -0.194), ES40 ( rg = -0.203), FL20 (rg = -0.131) and EW40/BW40 (rg = -0.259). Egg weig hts, body weights and eggshell strength traits were positively genetic ally correlated among themselves. The results suggest that a linear se lection index for NEGG52 with constraints for EW40, BW40 and ES40 coul d be an efficient tool for improving the efficiency of egg production with this small body type laying duck.