Estrus reaction of gilts as selection criteria for litter size

The analysis of estrus symptoms has been done on 656 purebred and 884 crossbred gilts. Heritability estimates for estrus reaction in purebreds were low, 0.12 and 0.14 for crossbreds. The heritability for number of ovulation egs in purebred and crossbreds were 0.40. Genetic correlations between estrus reaction and litter size in first litter were high:0.88 than estrus reacion and life production 0.76. Correlation between same traits for crossbreds were higher: 0.93 and 0.87. In carantin room we measured age and weight of gilts together with estrus. The first estrus showed 90.8% and second 90.2% in purebred and 94.7% and 93.8% at F1 gilts. The gilts which did not show regular first and second estrus get born between 2 and 9, average 6.23 for purebred and 7.11 F1 alive piglets. Later on they had longer interval between birth and next estrus, 17- 48, average 32 empty days for purebred and 28 crossbreds gilts. Those animals had significant lover life production. In conclusion, it is necessary to note estrus reaction in carantin room at the beginning of production life of gilts. Gilts with irregular oestrus is necessary to get out of production imediately from carantin room to decrease economical losess in production.