SERUM ANTI-ECG IMPROVES LUTEAL FUNCTION AND INCREASES OVA EMBRYOS RECOVERY IN ECG-SUPEROVULATED EWES

Superovulatory response to an eCG treatment (1200 IU) alone (Group eCG , n = 10) or with anti-eCG serum (Group AS, In = 10) given 12 h after the onset of estrus was studied during the breeding season in ewes. Bl ood samples were taken for LH and progesterone determination and on Da y 5 post-estrus all ewes were flushed and ova/embryos recovered. Mean overall interval to first signs of standing estrus for all ewes was 23 .6 +/- 1.8 h (mean +/- SEM) and peak of LH surge ranged between -11 h to 9 h after onset of estrus (2.0 +/- 1.6 h). Mean number of CL (8.8 /- 1.5 vs. 10.6 +/- 0.9 for eCG and AS groups, respectively; P = NS) a nd large anovulatory follicles (2.8 +/- 2.0 vs. 0.9 +/- 0.4, P = NS) w ere not different. A higher ova/embryo recovery was obtained in the AS group (4.1 +/- 1.0 vs, 0.9 +/- 0.5, P less than or equal to 0.05) and this was related to a lower proportion of ewes that had small (4.0 +/ - 0.1 mm in diameter, n = 75), pale and non-protruding corpora lutea a t time of embryo collection (2/10 vs, 5/10, P = 0.14). Pooled data of all ewes that displayed this CL (n = 7) show that this condition: (1) is related to the endocrine status of the ewes at time of eCG treatmen t (low endogenous levels of progesterone); (2) is characterised by a p remature luteinisation (increase of progesterone at the onset of oestr us) and a subsequent premature luteolysis (decrease of progesterone le vels at Day 3 to 5 post-estrus) and (3) is associated with a lower num ber of hems that yielded some ovum/embryo (4/14 vs. 16/24, P less than or equal to 0.01). We conclude that the administration of anti-eCG se rum at 12 h after the onset of estrus increases the ova/embryos recove ry rate because of lower number of ewes that displayed prematurely reg ressing corpora lutea in the eCG-superovulated ewes.