DELAYED-EFFECT OF PROGESTERONE ON ENDOMETRIAL MORPHOLOGY IN DAIRY-COWS

Two experiments were conducted to investigate the effect of vaginal pr ogesterone (P-4,) administered during the luteal phase, on endometrial morphology during the subsequent oestrous cycle. In experiment 1, lac tating Holstein cows were allotted to three groups: (1) Control group in which cows remained untreated; (2) The CIDR group in which cows wer e treated with two P-4-containing controlled intravaginal-drug releasi ng devices (CIDR) during days (d) 6-12 of the cycle; and (3) The PG CIDR group of cows that received two prostaglandin F-2 alpha (PGF(2) a lpha) injections on d 6 and 7 of the oestrous cycle, to regress the co rpus luteum (CL), and were treated with CIDRs on d 6-12, like the CIDR group. All cows were slaughtered on d 3 of the subsequent oestrous cy cle. In experiment 2, cows were allotted to three groups: (1) Control cows that remained untreated; (2) CIDR cows that were treated with two CIDRs from d 6 to 15; and (3) Early PG cows that received three i.m. injections of PGF(2) alpha on d 3 and 3 of the oestrous cycle to reduc e plasma P-4.,, All cows were slaughtered on d 15 of the subsequent cy cle, In both experiments, blood was collected during the treated and s ubsequent cycles to determine P-4, and oestradiol(E-2,) concentrations , and tissue samples from the uterine horn ipsilateral to the CL were collected on the day of slaughter to evaluate endometrial morphology. In both experiments, plasma P-4, differed between treatments during th e treated cycle but no differences in P-4, and E-2, concentrations wer e recorded during the subsequent cycle, In experiment 1, the endometri al morphology of the cows from CIDR and PG + CIDR groups differed from that found in the control group: The surface epithelium was medium to high and the glands were round and tortuous, as compared with low epi thelium and oblong glands in the control. In addition, the density of blood vessels and the level of edema. was higher in the CIDR-treated c ows than in the control cows. Zn experiment 2, the endometrial morphol ogy of the CIDR-treated group differed from that of the control and ea rly PG groups: Low surface epithelium and oblong glands in the former compared with high epithelium cells and tortuous glands in the latter. in summary, P-4, supplementation during the luteal phase had a delaye d effect on endometrial morphology at different stages of the subseque nt oestrous cycle. (C) 1997 Elsevier Science B.V.