Abstract. Data on 29,411 quails of two selected lines along with a control line were examined over nine generations. Significant genetic gains/generation for 4-week body weight were realized in the two strains (3.70 and 3.10 g). Significant correlated genetic changes were also observed in early body weights (day-old to 3-weeks) as well as in 16-week body weight. Egg number and sexual maturity did not show any significant response while egg weight and egg mass showed desirable genetic gains. Natural selection did not seem to exert any effect. Inbreeding levels of 0.32 to 0.43 % per generation did not appear to be of any significance in affecting the response. Realized heritabilities (0.21–0.24) were reasonably consistent between sexes and matched fairly well with the nine-generation pooled sire-component heritabilities of 0.20 ± 0.04 and 0.25 ± 0.04 in the two lines. There was evidence of maternal effects as indicated by excess of dam- over the sire-component heritability. Time-trend in heritabilities was non-significant. There was good agreement between the predicted and realized genetic gains.

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1. A total of 39,280 eggs obtained from two selected White Leghorn strains over 4 generations representing 290 sires were incubated. 2. The unhatched eggs were broken open for examination of embryonic developments and classified as early-dead (0-11 d), late-dead (12-22 d) and pips. 3. The sire-component heritability estimates (%) pooled over years in the two strains, respectively were 8.5 +/- 1.5 and 7.6 +/- 1.4 for total mortality; 0.5 +/- 0.5 and 6.3 +/- 1.2 for early-dead; 5.8 +/- 1.2 and 5.5 +/- 1.1 for late-dead and 5.0 +/- 1.1 and 3.1 +/- 0.9 for pips.

Abstract. A total of 1,33,507 eggs obtained from 7864 pullets of two selected White Leghorn strains over four generations representing 304 sires and 1669 dams were incubated. The unhatched eggs were broken-open for examination of embryonic development and classified as early-dead (0-11d), late-dead (12-22d) and pips. The sire component heritabilities (%) pooled over years in the two strains, respectively were 10.5±3.4 and 11.0±3.2 for total incubation mortality; 2.2 ± 2.2 and 5.1 ± 2.4 for early-dead; 6.8 ± 3.0 and 8.0 ± 3.0 for late-dead and 8.7 ± 3.1 and 4.8 ± 2.4 for pips. Total embryonic mortality as well as its three components had high genetic correlations amongst each other. However, the genetic correlations of pipping mortality with early and late mortality were weaker as compared with those of early and late mortality.