Desired-gain selection indices for improving performance of two Tanzania local chicken ecotypes under intensive management
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A study was carried out to evaluate various desired-gain selection indices (Yamada index) in improving performance of two chicken ecotypes of Tanzania viz. Kuchi and Tanzania Medium (Medium). The indices for Kuchi ecotype were geared at improving body weight at 16 (Bwt16) weeks of age while those for Medium ecotype were geared at improving egg production and related traits. These traits included age at first egg (AFE), egg production in the first 90 days after sexual maturity (EN-90) and egg weight (EW). Apart from production traits, antibody responses (Ab) against Newcastle disease virus vaccine was also included in some selection indices in both ecotypes. Furthermore, correlated responses to some egg quality traits namely egg shape index (ESI) and eggshell thickness (STH) were also studied. Results indicated that it would take between 5 to 6 generations of selection in Kuchi to improve Bwt16 either singly or together with Ab from their current levels of 1394 g and 5 (HIlog2) to the desired averages of 1800 g and 6 (HIlog2), respectively. On the other hand results indicated that it would take between 8 to 11 generations of selection in Medium ecotype to improve either AFE and EN-90 or together with EW or Ab or both of them from their current averages of 168 days, 49 eggs, 42 g and 5 (HIlog2) to the desired averages of 154 days, 68 eggs, 50 g, and 6 (HIlog2), respectively. Based on the number of generations required to achieve desired gains and correlated responses, some selection indices were recommended.
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