Phenotypic and genetic parameters for body weights and antibody response against Newcastle disease virus (NDV) vaccine for Kuchi chicken ecotype of Tanzania under extensive management.

This study was carried out to estimate phenotypic and genetic parameters for body weights and primary antibody response (Ab) against Newcastle diseases virus (NDV) vaccine for Kuchi chicken ecotype of Tanzania managed extensively. Body weight was evaluated at 8 (Bwt8), 12 (Bwt12), 16 (Bwt16) and 20 (Bwt20) weeks of age, while Ab against NDV vaccine was evaluated at 6 weeks of age (2 weeks post-vaccination). Number of birds per trait varied from 373 to 430. Mean value ± standard error (SE) over both sexes for Bwt8, Bwt12, Bwt12 and Bwt20 were 348 ± 2.8, 685 ± 5.3 g, 974 ± 6.4 g and 1,188 ± 7.3 g, respectively. Mean Ab value (HI titre in log(2)) against NDV vaccine was 4.69 ± 0.06. Heritability values ± SE for Bwt8, Bwt12, Bwt16, Bwt20 and Ab against NDV vaccine were 0.30 ± 0.13, 0.34 ± 0.12, 0.37 ± 0.11, 0.39 ± 0.12 and 0.22 ± 0.08, respectively. Genetic (r (g)) and phenotypic (r (p)) correlations were positive and high among body weights (i.e. r (g) = 0.53 to 0.74 and r(p) = 0.44 to 0.64), and were negative and low (i.e. around 0.10 and below) among Ab against NDV vaccine and body weights. Based on these estimates, it was concluded that growth performance for Kuchi chicken under extensive management is still poor. Adequate additive genetic variations exist for body weights and Ab against NDV vaccine under extensive management, thus they can be improved through selection under such environment, and further that both traits (body weight(s) and Ab) can be improved/selected simultaneously without significant reduction in genetic gain (response) for each trait.