Introduction: The aim of this study was to investigate the relationship between body condition score (BCS) determined on the dry-off day, calving day, and in the first month of lactation, its changes during the dry period and early lactation, and periparturient indices and fertility in high-producing dairy cows. Material and Methods: The experiment was conducted in two herds: A and B, located in Western Poland. The studies were conducted on 116 and 108 Polish Holstein-Friesian dairy cows respectively, with an average milk yield of >10 000 kg/305-day lactation. The experiment included the dry period (-56 d to the calving day), the calving day, and early lactation (from +1 to +56 d). The experimental factor was BCS (0 to 5-point scale). The BCS was performed by one person on day -56, on parturition day (in the first 12 h after calving) and on day 30 of lactation. Results: A decrease in BCS (≥-0.25) in herd A during the dry period accelerated the planned calving period by 7.3 d. In the group of cows with BCS <3.25 on the dry-off day, the lowest artificial insemination index (1.80), the shortest period of insemination services (25 d), and days open (87 d) were recorded. Moreover, cows with BCS < 3.25 at calving had the shortest days open (91 d). BCS >3.50 in the first month of lactation (30 d) resulted in the extension of uterine involution period (56 d). Improvement of BCS during the dry period shortened the anoestrus (60 d) in herd A and the period of insemination service (60 d) in herd B. However, in this group (IM BCS ≥ 0.25) of cows the day of the highest artificial insemination index (2.50) in herd B was analysed. Conclusion: The body condition on the dry-off day and at calving, as well as its deterioration in the first month of lactation, have a considerable effect on fertility indices in dairy cows, thus confirming the advisability of its regular monitoring during routine operations connected with the management of a dairy cattle herd.

The effect of metoclopramide (MC), a dopamine antagonist on luteinizing hormone (LH), was examined in anestrous primaparous cows. Metoclopramide has been found to be beneficial in overcoming fescue toxicosis; increasing LH secretion stimulates return to ovulatory function after parturition. Consequently, if MC had negative effect on LH secretion, it would indicate that administration of MC to reproducing animals might be limited. Of 14 postpartum (47 to 66 days) cows, 7 were given MC (4 mg/kg of body weight, IV), and 7 served as controls. Blood was obtained via jugular cannulas at 15-minute intervals for 8 hours; MC was given at the end of the first hour, and gonadotropin-releasing hormone (GnRH, 7 mg/kg), was given IV at the end of hour 7 as a challenge stimulus for LH secretion. Prior to GnRH administration, MC did not have significant effect on LH secretion, as judged by mean serum LH concentration, LH pulse frequency, and LH pulse amplitude. Administration of MC resulted in greater (P < 0.05) LH response to GnRH, indicating enhanced secretory ability when the pituitary gland was challenged. Serum prolactin concentration was increased (P < 0.01) by MC administration. Therefore, MC did not have adverse effect on LH secretion in postpartum cows.

The effect of glucocorticoids on early follicular growth in sows undergoing normal estrous cycles was evaluated by administration of dexamethasone during the middle of the luteal phase. Plasma specimens were obtained for measurement of luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone, and estradiol-17 beta concentrations. Fifteen sows were used. Control sows (n = 5) were given physiologic saline solution twice daily from day 9 to day 14 of the estrous cycle. Sows of the second group (n = 5) were given dexamethasone (30 microgram/kg of body weight, IM) similarly, and those of the third group (n = 5) were given dexamethasone plus gonadotropin-releasing hormone (GnRH+ 50 microgram at 6-hour intervals, IV). Plasma specimens, obtained twice daily from day 8 through day 26, indicated that progesterone production and luteal regression were not inhibited by any of the 3 treatment regimens. Although preovulatory plasma estradiol concentration increased in control sows, such was not observed in the sows treated with dexamethasone or dexamethasone plus GnRH (P less than 0.01). Ovulation, with formation of corpora lutea, occurred in gilts given saline solution. Dexamethasone administration resulted in persistence of 19 to 41 follicles/ovary (2 to 4 mm in diameter), and dexamethasone-plus-GnRH treatment resulted in 6 to 18 follicles/ovary (5 to 6 mm in diameter). Plasma was obtained at 15-minute intervals for 12 hours to compare the effect of treatmenton hormone concentrations on day 12 of the estrous cycle with the values on day 8. Glucocorticoid administration had no significant effect on mean concentration, final concentration excluding those hormone concentrations that constituted part of a pulse (referred to as base line), number of pulses, pulse amplitude, and area under the pulse for either gonadotropin. Addition of GnRH to dexamethasone treatment significantly (P less than 0.01) increased all plasma LH values, but only base-line concentration of FSH. For estradiol, pulse amplitude and mean pulse area were increased (P less than 0.05), and although the frequency of pulses was not significantly altered, base-line concentration in glucocorticoid-treated sows was significantly reduced, compared with that of control sows. In sows treated with GnRH plus dexamethasone, the pulse frequency of estradiol was significantly (P less than 0.01) increased, but pulse area and amplitude were similar to those of sows given saline solution. Dexamethasone treatment was associated with an increase in mean and base-line concentrations of progesterone. The results suggest that high midcycle glucocorticoid concentrations (1) do not inhibit luteal function or regression, (2) have little influence on LH and FSH secretion during the middle of the luteal phase, (3) alter the pattern of estradiol secretion, (4) are associated with the persistence of small ovarian follicles, and (5) result in the development of fewer but larger follicular structures when GnRH is administered concurrently.

The potential of a gonadotropin-releasing hormone (GnRH) agonist (goserelin acetate), delivered constantly for 28 days via a subcutaneous depot, to induce ovulation in seasonally anestrous mares, was investigated. Two experiments were conducted, in which a range of doses (30 to 240 micrograms/mare/d) was examined. Mares were selected on the basis of lack of substantial follicular development (follicle diameter < 20 mm determined ultrasonically) and low serum concentrations of luteinizing hormone (LH) and progesterone. Constant administration of the GnRH agonist-induced ovulation in anestrous mares, but a dose-response relation was not observed. Furthermore, with identical doses tested in consecutive or alternate years, considerable variation was observed in the ovulatory response. In general, ovulation in all treated mares was accompanied by increased circulating concentrations of LH and a decrease in follicle-stimulating hormone values. Ovulation was preceded by an increase in estradiol and LH concentrations. In mares in which ovulation did not occur, concentration of LH increased during agonist treatment, whereas that of follicle-stimulating hormone either increased or did not change. It was concluded that constant administration of GnRH agonists may induce ovulation in mares during seasonal anestrus; however, percentage of mares ovulating and the lack of reproducibility of effect indicate that this approach is inappropriate for use as a reliable method to manipulate breeding activity in commercial broodmares.