Effects of propylene glycol drenching before and after luteolysis on blood glucose, ovarian steroids and follicular dynamics in heifers.

The effect of propylene glycol drenching on ovarian and hormonal dynamics was studied in heifers. Five cycling heifers were used twice (as control and treatment) with crossover design. After the confirmation of ovulation (day 0), the heifers in the treatment group received propylene glycol on days 6, 7 and 8 as an oral drench (250 ml of 90% propylene glycol). On day 10, prostaglandin F2α (PGF2α), 15 mg per head of dinoprost, was administered intramuscularly to induce luteal regression followed by the follicular phase and then propylene glycol was again administered twice daily (500 ml/day) on days 10, 11 and 12. Palpation per rectum and ovarian ultrasonography were performed every other day from days 0 to 10, and daily after PGF2α administration until the subsequent ovulation (second ovulation) for analysis of follicular and luteal dynamics. Blood samples were also collected every other day from days 0 to 10, and then at 6 h intervals after PGF2α administration until the second ovulation. For the samples taken at 6-h intervals after PGF2α administration, the concentrations of glucose showed clear daily fluctuations in both groups. Changes in the plasma concentration of glucose in the treatment group were significantly (P < 0.05) higher than those of the control groups during the period between 0 and 72 h after PGF2α administration. No significant difference was detected in the growth of dominant follicles, maximum diameter of the ovulatory follicles and the changes in oestradiol and progesterone during the follicular phase between treatment and control groups. This study showed the clear daily fluctuations and stimulatory changes in the blood glucose concentrations at 24-h intervals during the short-term treatment of propylene glycol drenching in heifers. However, no significant changes in ovarian and hormonal dynamics were found under such metabolic conditions.

Effect of intrauterine infusion with liquid paraffin on phagocytes migrating to mucus of external os of the cervix in cows.

The objective of this study was to investigate the effect of intrauterine infusion with liquid paraffin (LP) on phagocytic migration into the uterus of cows. Smears of swab samples of the external os of the cervix and discharges collected inside the vagina were obtained in multiparous dairy cows (n = 10) that had been infused with 50 ml of LP (LP group: n = 5) or physiological saline (PS group: n = 5) on day 10 or 11 after ovulation (day 0: ovulation). The samples were collected for cytological examination 0 (just before), 0.25, 1, 2, 3, 4, 6, 8, 12 and 24 h after LP or PS infusion and then at daily intervals until subsequent ovulation. The number of neutrophils increased significantly (p < 0.05) for 8 days compared with the pre-infusion level in the LP group and for 2 days in the PS group. The average numbers of neutrophils in the LP group were significantly (p < 0.05) greater than those in the PS group on 3, 4, 5 and 8 days after infusion. The number of monocytes from 6 h to 8 days after LP infusion was significantly higher than that before infusion (p < 0.05). The average numbers of monocytes at 4 and 6 h and 1 day after infusion in the LP group were significantly higher than those in the PS group. These findings indicate that LP stimulates phagocytic migration into the uterine lumen in cows and that LP infusion into the uterus might enhance uterine defence mechanisms during uterine infection.

Improvement of pregnancy rate in Japanese Black cows by administration of hCG to recipients of transferred frozen-thawed embryos.

Japanese Black primiparous and multiparous beef cows (n = 120) were selected as recipients and randomly divided into three groups (A, B, and C) of 40 recipients each. Group A received an intramuscular (i.m.) treatment of 1500 IU human chorionic gonadotropin (hCG) on day 1 (day 0 = onset of estrus), while Group B received an i.m. treatment of hCG on day 6. Group C received an i.m. treatment of 5 ml saline on day 6 as a control. On day 7, frozen-thawed embryo transfer was conducted in all groups, and pregnancy was diagnosed by palpated per rectum 40-50 days after the transfer. Twelve recipients were randomly selected from each group. Plasma progesterone (P) and estradiol-17beta (E2) concentrations were determined in these recipients on days 6, 7 and 14, and at the time of pregnancy diagnosis, and their ovaries were examined for a corpus luteum and follicles by palpated per rectum. The pregnancy rate in Group B was higher (67.5%. P < 0.05) than the rate in Group C (45.0%) and in Group A (42.5%). The plasma P concentration on day 14 tended to be higher although not significantly in Group B than in Groups C and A. At the time of pregnancy diagnosis, the blood P concentration of pregnant recipients in Group B was higher (P < 0.05) than that of those in Groups C and A. The plasma E2 concentrations on days 7 and 14 were lower (P < 0.05) in Group B than in Groups C and A. These results showed that administration of hCG 6 days after estrus improved the pregnancy rate for non-surgical frozen embryo transfer 7 days after estrus by enhancing luteal function and depressing E2 secretion.

Changes of ovarian structures, plasma LH, FSH, progesterone and estradiol-17 beta in a cow with ovarian cysts showing spontaneous recovery and relapse.

In a cow diagnosed as having ovarian cysts, we observed changes in the ovarian structures by ultrasonography for 71 days and examined plasma concentrations of sex hormones. The cow had 2 regressing cysts at the start of this study and 3 new follicles subsequently developed into cysts. With regression of these cysts, 2 new follicles developed and ovulated spontaneously, followed by the formation of 2 corpora lutea. On the day prior to ovulation, a preovulatory luteinizing hormone (LH) surge was detected. With regression of the corpora lutea, a new follicle developed and underwent atresia. Meantime, another follicle developed and became a cyst without ovulation. No preovulatory LH surge was observed during the period from regression of the corpora lutea to cyst formation. The results indicate that absence of the preovulatory LH surge is associated with occurrence of ovarian cysts and this endocrine aberration is reversible.

Ultrasonic observations on the turnover of ovarian follicular cysts and associated changes of plasma LH, FSH, progesterone and oestradiol-17 beta in cows.

Changes in the diameters of individual follicular structures on ovaries were measured by transrectal ultrasonography for 29 to 40 days and the plasma concentrations of luteinising hormone (LH) follicle-stimulating hormone (FSH), progesterone and oestradiol-17 beta were determined in four cows with ovarian cysts. When these structures decreased in size, new follicular structures appeared and developed into cysts. Progesterone concentrations in plasma were below 1.0 ng ml-1 during the experimental periods. Plasma concentrations of oestradiol-17 beta fluctuated. The mean concentration of oestradiol-17 beta in plasma differed (P < 0.01) depending on the stage of the cyst. No preovulatory surges of LH were detected during the developmental stage of the cysts.

Recombinant human activin A stimulates development of bovine one-cell embryos matured and fertilized in vitro.

The effects of recombinant human activin A on the development of bovine one-cell embryos matured and fertilized in vitro were investigated. In experiment 1, one-cell embryos were cultured in a chemically-defined medium, of modified synthetic oviduct fluid supplemented with 1 mg/ml polyvinyl alcohol (mSOF-PVA), containing different concentrations of activin (0, 0.1, 1, 10, and 100 ng/ml) until 240 hr after in vitro fertilization. The addition of > or = 1 ng/ml activin to mSOF-PVA improved development to the blastocyst stage (14.5-17.1%), compared with no addition of activin (5.6%). However, there was no significant difference in hatching rate of embryos among treatments. In experiments 2 and 3, the embryos were also cultured in mSOF-PVA at various periods of exposure to 10 ng/ml activin, to evaluate development to the morula and blastocyst stages, respectively. The proportion of morulae was significantly higher in culture with activin at 20-120 hr postinsemination (37.2%) than with control (25.7%). Total number of cells in morulae at 120 hr postinsemination significantly increased by the addition of activin at 20-72 hr (26.1 cells) and 20-120 hr (24.2 cells) postinsemination, compared with control (20.1 cells). When activin was added to the medium during 20-120 hr and 20-192 hr postinsemination, the percentages of blastocysts (18.0% and 18.7%, respectively) were significantly higher than in the control (9.6%). However, the total number of cells in blastocysts was not significantly different. These results demonstrate that activin stimulates the development of bovine one-cell embryos to the morula and blastocyst stages in vitro.

Application of anti-bovine CD2 monoclonal antibody to the rosette inhibition test for detection of early pregnancy factor in cattle.

To reliably detect early pregnancy factor (EPF) in cattle, monoclonal antibody specific for bovine CD2 molecule, which is the sheep red blood cell (SRBC) receptor on bovine T cell surface, was applied to the rosette inhibition test. The rosette inhibition titers (RITs) were significantly higher in pooled sera from early pregnant cattle than in those of non-pregnant cattle using two anti-bovine CD2 monoclonal antibodies, B26A4 (P < 0.001) and BAQ95A (P < 0.01). The dissociation value of RITs between pregnancy and non-pregnancy with B26A4 was greater than that with BAQ95A. The B26A4 monoclonal antibody was therefore applied to the rosette inhibition test in subsequent experiments. The RITs in serum of individual pregnant and non-pregnant cows 8 days after estrus were significantly different (P < 0.001) by three or more dilutions. When the rosette inhibition test was carried out in sera from individual pregnant and non-pregnant cows at estrus and at 24, 72 and 168 hr after ovulation, the RITs of pregnancy sera increased significantly at 24 hr after ovulation as compared with non-pregnancy sera (P < 0.001). These results indicate anti-bovine CD2 monoclonal antibody can be utilized with the rosette inhibition test to detect EPF in cattle, and that this assay detects bovine EPF for pregnancy serum at least 24 hr after ovulation.

Luteotropic effect of pregnant mare serum gonadotropin in cattle.

Pregnant mare serum gonadotropin (PMSG) is a long acting luteotropin with follitropin activity. Cattle were used to examine whether a smaller dose of PMSG has substantial luteotropic effect without excessive follitropic effects. Eleven Japanese Black heifers were randomly assigned to two groups. Animals were administered 500 IU PMSG on the day of ovulation (Day 0) to promote the formation of corpus luteum (group A; N = 5) or Day 7 to stimulate the luteal function (group B; N = 6). Four of them were given injections of saline on Days 0 and 7 of the preceding estrous cycle for control. All animals were examined by palpation per rectum every other morning and bled every day for steroids analyses. The length of estrous cycle was shortened by the treatment in group A compared with the previous cycle, whereas it was extended in group B (P < 0.05). Progesterone secretion was not enhanced in group A, but it was significantly elevated and sustained on higher levels in group B (P < 0.05) as compared with the control. Although estradiol-17 beta concentrations were significantly increased in both PMSG-treated groups (P < 0.05), no excessive follicular development was observed. It is concluded that 500 IU PMSG administered on Day 7 enhances luteal function without excessive follicular development, whereas the administration on Day 0 has an adverse effect on luteal function.

Activation of quiescent ovaries by administration of PMSG after LH-RH analogue treatment in heifers.

The effect of pregnant mare serum gonadotrophin (PMSG) treatment on activation of quiescent ovaries was examined in heifers. Groups of thirteen, twenty and twelve heifers which showed ovulation within 2 d and corpus luteum (CL) development after injection with a luteinizing hormone releasing hormone analogue (LH-RH-A) were supplementally injected with 500 IU of PMSG (Group I); 500 IU of PMSG and 500 mug of Prostaglandin F(2alpha) analogue (PGF(2alpha)-A; Group II); and 500 mug of PGF(2alpha)-A (Group III) on Day 6 after the injection of 200 mug of LH-RH-A (Day 0), respectively. Estrus appeared in 33.3 to 45.0% of the heifers of the respective groups after the treatment. Ovulation occurred at a significantly (P<0.01) higher rate in Groups I (100%) and II (90.0%) than in Group III (41.7%). The ovarian cyclic activity was initiated in all the heifers that ovulated. Plasma progesterone levels decreased significantly (P<0.05) to about 1 ng/ml on Day 8 and Day 7 in Group I and Groups II and III, respectively. Plasma estradiol-17beta (E(z)) levels increased significantly (P<0.05), reaching a peak on Days 7 to 7.5 in Groups I and II but not in Group III. It is concluded that PMSG treatment stimulates maturation and E(z) secretion of a follicle, thus promoting ovulation and the onset of ovarian cyclic activity.

Blood LH level and induced ovulation after hCG and PMSG treatment in ovarian quiescent cattle.

Ovarian quiescent cattle bearing follicle with palpable size were treated with single intramuscular injection of 750-6,000 IU of human chorionic gonadotrophin (hCG) in 13 cases and 1,000-2,000 IU of pregnant mare serum gonadotrophin (PMSG) in 5 cases. Changes of blood luteinizing hormone (LH) level, estrus and ovulation after the treatments were examined. After the hCG treatment LH level became slightly high from 0.2-0.6 ng/ml of pre-treatment to 0.3-1.9 ng/ml of post-treatment and maintained the level up to ovulation without the ovulatory LH surge. Ovulation was induced about 36 hr after the treatment in 12 cases. The ovulations were all silent ovulations. After the PMSG treatment LH level became slightly high from 0.6 ng/ml of pre-treatment to 1.3 ng/ml of post-treatment and the level lasted until the ovulatory LH surge. The ovulatory LH surge occurred about 39 hr after the PMSG treatment in 4 cases with a peak of about 32 ng/ml. Ovulation was induced about 74 hr after the treatment in all 5 cases. Four cases showed estrus but one in which the LH surge could not be confirmed did silent estrus preceding the induced ovulations. It was demonstrated that hCG induced ovulation without the LH surge but PMSG induced the ovulatory LH surge and the subsequent ovulation in ovarian quiescent cattle.