OVULATION RATE AT FIRST MATING AND REPRODUCTIVE PERFORMANCE OF GILTS

Abstract
Laparoscopy was used to estimate ovulation rate at 1st mating in 460 Large White/Landrace gilts. For 385 gilts which farrowed litter size was recorded, and the relationships between age and mating, maternal litter size, ovulation rate and reproductive performance were examined. The mean ovulation rate of the gilts which farrowed was 10.9 .+-. 0.14 corpora lutea, and the mean 1st litter size was 8.0 .+-. 0.12 piglets born with 7.5 .gtoreq. .+-. 0.13 born alive. Ovulation rate was related to 1st litter size (r= 0.29, P < 0.001) but embryo loss was the major factor determining litter size, accounting for about 58% of the variation. Any variation at the time of mating was not sufficiently correlated with litter size to be useful as selection criteria for improving reproductive performance.