Comparison of luteinizing hormone and steroid hormone secretion during the peri- and post-ovulatory periods in Mangalica and Landrace gilts

The objective of this study was to determine plasma concentrations of luteinizing hormone (LH), progesterone (P4) and estradiol-17β (E2) in Mangalica gilts (M), a Hungarian native breed, and compare them with Landrace gilts (L) during the peri- and post-ovulatory periods. The estrous cycle of gilts was synchronised by Regumate® feeding, and ovulation was induced with a gonadotropin-releasing hormone (GnRH) agonist. Blood sampling was carried out via indwelling jugular catheters three times a day and in 2-h intervals during a 16-h period after the GnRH application. The concentrations of LH, E2 and P4 were determined by immunoassays. Gilts of both breeds showed a typical gonadotropin and gonadal hormone secretion pattern. Preovulatory E2 peaks were observed on day 2 (M) and day 4 (L) after the last Regumate® feeding. Highest E2 concentration was different between M and L breeds (46.5 ± 5.7 vs. 26.0 ± 6.8 pg/ml, P < 0.05). Maximum LH levels measured up to 6 h after GnRH were not different between M and L breeds (11.5 ± 4.1 vs. 6.6 ± 2.3 ng/ml). Both LH amounts during surge (41.1 ± 15.9 vs. 27.5 ± 6.1 ng/ml) and total over LH release (73.4 ± 22.2 vs. 50.0 ± 8.7 ng/ml) did not differ significantly between M and L breeds. P4 concentrations started to rise on day 6 after Regumate® feeding and increased significantly from 0.6 ± 0.3 and 0.7 ± 0.4 ng/ml to maximal 14.0 ± 2.4 and 11.3 ± 2.1 ng/ml in M and L breeds, respectively. Mean P4 secretion was higher in M on days 10-15 (12.9 ± 2.6 vs. 9.3 ± 2.2 ng/ml; P