There was no significant difference in plasma progesterone or oestradiol concentration,
luteal weight or CL progesterone content between pregnant (n = 11) and non-pregnant
(n=6) cows (Table 1). In pregnant cows, however, both plasma progesterone concentration
(P < 0.01) and total luteal weight (P < 0.001) were significantly greater in those animals with
embryos beyond the 8-cell stage of development (Table 1). Furthermore, plasma progesterone
concentration in cows with morulae (1.94±0.06 ng ml−1; n = 3) tended to be higher
(P = 0.065) than in cows with 16 cell embryos (1.40±0.21 ng ml−1; n = 3).
embryos were recovered from 4 cows. In all four cases, both embryos were at the same
stage of development (morula stage (n = 1 cow), 9–16 cell (n = 2 cows) and 8 cell (n=1
cow).