| Popis: |
Three unselected control strains and four strains selected for high egg production were studied. Semen weight (SW), packed sperm volume (PSV), and total sperm weight (TSW) were evaluated on two consecutive days. The female traits were age at first egg (AFE), hen-housed egg number (HHEN), hen-day rate of egg production (HDREP), egg weight (EW), and four egg-quality traits. Wattle and testes size were also measured in the males. Sire-plus-dam component heritabilities ± SE of SW, PSV, and TSW in the selected strains, were .36 ± .08, .42 ± .08 and .32 ± .06. The full sibling component heritabilities for the control strains were: .42 ± .15 for SW, .50 ± .15 for PSV, and .41 ± .15 for TSW. The heritabilities of wattle and testes weights computed by regression of son on father were: .54 ± .10 and .58 ± .11, respectively. The genetic correlations between semen and egg-production traits, estimated by intraclass and regression procedures were generally consistent in sign. The mean genetic correlations of SW, PSV, and TSW with EW were .23, .06 and .17, respectively. Semen traits were unfavorably correlated with HHEN (mean −.23, range −.60 to .04), HDREP (mean −.10, range −.36 to .14), and AFE (mean .27, range .03 to .40). Wattle size measured on 14-mo-old males was favorably correlated with HHEN (mean .36, range .26 to .55), HDREP (mean .23, range .05 to .44), and AFE (mean −.31, range −.17 to −.43). Semen traits as well as size of the testes and wattle appeared to be unrelated to egg-quality traits. Hence, wattle size, measured at an early age, could be useful in selecting for high egg production; and selection for semen production could increase egg size. |
