Peri-oestrous hormone profiles, embryonic survival and variation in embryonic development in gilts and primiparous sows.

The primary objective of this study was to determine whether embryo survival in gilts and primiparous sows is related to variations in the peri-oestrous profiles of oestradiol, progesterone and LH. A secondary objective of the present work was to compare embryo development and certain endocrine characteristics in gilts and primiparous sows. Sows (n = 6) and gilts (n = 6) were catheterized in the jugular vein on the day after weaning or on day 14 of the oestrous cycle, respectively. Additional females (one gilt and seven sows) were examined only for characteristics of embryonic development. Embryos were recovered on day 11.5-11.75 of gestation, and size and volume of individual embryos were recorded. Minimal differences were observed between sows and gilts for endocrine and embryo data. Embryo recovery was 71.38 +/- 4.77% based on the number of corpora lutea. However, endocrine differences were noted for pigs with high embryo survival (> 71% recovery) compared with those with low survival. Peak oestradiol concentration occurred closer (P < 0.05) to the onset of oestrus in pigs with high embryo survival than in pigs with low embryo survival (3.3 +/- 4.6 h after oestrus versus 13.0 +/- 5.5 h before oestrus) and peak LH concentration occurred later (P < 0.05) after the onset of oestrus for pigs with high embryo survival. Peak oestradiol concentration tended (P = 0.07) to be higher in pigs with low embryo survival (35.21 +/- 2.56 pg ml-1) compared with pigs with high embryo survival (28.17 +/- 2.14 pg ml-1).(ABSTRACT TRUNCATED AT 250 WORDS)