Genetic variability of age and weight at puberty, ovulation rate and embryo survival in gilts and relations with production traits

Age (AFE): weight (WFE) and ovulation rate (OR) at first estrus, number of embryos (NE) and embryo survival (ES = NE/OR) at 30 days of gestation of French Large White (LW), French Landrace (LF) and crossbred LW x LF gilts and their genetic relationships with average daily gain between 30 and 85 kg (ADG) and average backfat thickness at 85 kg (ABT) were analyzed. Breed differences, as well as genetic parameters in the LW breed, were estimated using a restricted maximum likelihood procedure applied to a multiple trait animal model. A total of 3 664 male and female pigs were measured for ADG and ABT between 1966 and 1979; 1 919 gilts were checked daily for puberty between 140 and 300 days of age. Most females were then bred and slaughtered at 30 days of gestation for measuring the number of corpora lutea and the number of embryos. Breed marginal means were, respectively 214.9 +/- 1.4, 197.8 +/- 3.3 and 190.1 +/- 2.1 days for AFE, 116.1 +/- 0.9. 102.5 +/- 2.2 and 97.7 +/- 1.4 kg for WFE, 14.4 +/- 0.1, 13.0 +/- 0.3 and 13.9 +/- 0.2 for OR and 9.6 +/- 0.1 9.6 +/- 0.4 and 10.5 +/- 0.3 for NE in LW, LF and LW x LF gilts. Heritability estimates were 0.29, 0.51, 0.27, 0.14 and 0.08 (se 0.03); respectively, for AFE, WFE; OR, NE and ES. Genetic correlations between AFE and WFE, between NE and OR or ES were rather large (0.84 +/- 0.05, 0.73 +/- 0.12 and 0.79 +/- 0.15 respectively). OR and ES had a low genetic correlation (-0.11 +/- 0.15). AFE was negatively correlated with ADG (-0.18 +/- 0.05), ABT (-0.21 +/- 0.05) OR (-0.36 +/- 0.09) and NE (-0.35 +/- 0.08). WFE also tended to be negatively correlated with OR (-0.26 +/- 0.11) and NE (-0.18 +/- 0.10), but exhibited low or positive genetic correlations with ABT (0.08 +/- 0.05) and ADG (0.34 +/- 0.05). OR, NE and ES had low or favourable genetic correlations with both ADG and ABT.