Are reproductive traits impaired by selection for egg production in hens
1998
Sewalem, A. | Johansson, K. | Carlgren, A.-B. | Wilhelmson, M. | Lillpers, K.
SUMMARY: The data consisted of information on egg production traits (age at first egg, egg number and egg weight), and reproduction traits such as percentage fertile eggs (PF), percentage hatched of fertile eggs (PHF) and percentage hatched of total egg set (PHT) were also recorded for the selected parents. The experiment was carried out for 10 generations of selection for increased egg number (EN), egg weight (EW), egg mass (EM) along with a control line (C). Although line C had high PF, PHF and PHT in most generations compared to the selected lines, it was not significantly better than the EN and EM lines at the last generation. Differences in PF, PHF and PHT were also observed among the selected lines. The lowest performances of PF, PHF and PHT was observed in line EW. (Co)variances and resulting correlations were estimated between egg production and reproduction traits using a multivariate animal model. The result showed that the estimates of heritability values for egg production traits were moderate to high and low for reproduction traits. The genetic correlation between PF and egg weight traits in line EW was negative and positive in line EM. PHF was positively correlated with egg number in line EN and negatively correlated with egg weight in line EW. Genetic trends calculated from the animal model showed that direct selection for increased egg number in line EN, egg weight in line EW and egg mass in line EM has resulted in substantial genetic gain over generations. Moreover, in lines selected for egg number and egg mass there were consistent positive genetic trends of PHF and PHT along with the selected trait. Selection for increased egg weight, however, negatively affected PF, PHF and PHT over generations.
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