DETERMINATION OF PREGNANCY AND ESTIMATION OF LITTER SIZE IN GILTS BASED ON CONCENTRATION OF ESTRONE GLUCURONIDE AND ESTRADIOL GLUCURONIDE IN PLASMA

Three experiments were conducted to determine the concentration of est radiol glucuronide (E(2)G), and estrone glucuronide (E(1)G) in the blo od of gilts after mating (Day 0). Blood samples were taken from 20 mat ed gilts at weekly intervals from Day 14 to Day 34 and analyzed by rad ioimmunoassay (RIA) for concentration of E(2)G and E(1)G. The concentr ations of both hormones rose from about Day 19 to a peak at Day 26 and then declined. The concentration of E(2)G rose to 1700 pg ml(-1) and E(1)G rose to 8000 pg ml(-1) at Day 26. Eleven mated gilts in a second study were bled on Days 20, 22, and 24 and plasma analyzed for E(2)G and E(1)G. At slaughter on Days 29-35, gilts with more than 100 pg ml( -1) of E(2)G or more than 1000 pg ml(-1) of E(2)G on Day 20 or later w ere pregnant. In a third study, 31 gilts were bled at 48 h intervals f rom Day 20 to 28 and plasma was analyzed for concentration of E(2)G an d E(1)G. All gilts with over 100 pg ml(-1) of E(2)G and 30 of 31 with over 1000 pg ml(-1) of E(2)G were pregnant when killed at Days 30-35. When gilts were classified according to the concentration of E(2)G at Day 20, 86% of gilts with over 200 pg ml(-1) had eight fetuses or more and at Day 24, 77% of gilts with over 1100 pg ml(-1) had eight or mor e fetuses. When gilts were sorted on the basis of over 1500 pg ml(-1) on Day 20 and on Day 22 for over 3400 pg ml(-1) of E(1)G, the percenta ges of correct classification for eight or more fetuses were 87% and 8 1% respectively. Concentration of E(2)G or E(1)G from Day 20 to 28 aft er mating can be used to detect pregnancy and estimate litter size at the time of analysis.