CM.(1989) Relationship between pre-partum relaxin concentrations and farrowing intervals in the pig

Summary. Gilts were treated on Day 112 of gestation with saline or a prostaglandin(PG) F-2\g=a\analogue. In control gilts there was a rise in the relaxin concentration from 48 h before the onset of delivery, peaking between 12 and 28 h pre partum followed by a steep fall. The relaxin concentrations at each 1-h time interval were analysed in relation to the farrowing interval for each gilt using correlation analysis. There was a significant(at least P < 0\m=.\05)positive correlation between the relaxin concentration and the farrowing interval at every time period from 14 to 2 h before delivery. In contrast there was little relationship between concentrations of progesterone, oestrone and oestradiol-17\g=b\and farrowing intervals. The gilts treated with PGF-2\g=a\analogues had steroid profiles indistinguishable from those in controls but differing relaxin secretion patterns. Relaxin concentrations peaked at 1\p=n-\2h after PGF-2\g=a\injection and this was followed by a second smaller increase closer to the time of delivery in 7 out of 12 gilts. The 'two-peak ' gilts had significantly higher relaxin concentrations at farrowing and took significantly longer to farrow than did the 'one-peak ' gilts (P < 0\m=.\005).These results suggest that high relaxin concentrations during the last 14 h before the onset of parturition are associated with increased farrowing times, but are not associated with any increase in neonatal mortality