Relationship Between Dose of Cloprostenol and Age of Corpus Luteum on the Luteolytic Response of Early Dioestrous Mares: A Field Study

Effects of repeated embryo flushing without PGF2α administration on luteal function, percentage of unwanted pregnancy and subsequent fertility in mares

BACKGROUND

PGF2α is commonly given at the end of embryo flushing (EF) to shorten the interval to the next oestrus and ovulation.

OBJECTIVES

To determine the effect of repeated EF on plasma progesterone concentration, percentage of mares with endometritis, unwanted pregnancy and subsequent fertility in mares flushed without the use of PGF2α.

STUDY DESIGN

Controlled experiments.

METHODS

Nine mares were inseminated in seven consecutive cycles (n = 63), to either perform an EF (n = 54) 7-9 days after ovulation or left pregnant (n = 9). PGF2α was not used to induce oestrus. Ultrasound examination and blood sampling were performed just before the EF and 72 h later to determine changes in progesterone concentration and signs of endometritis.

RESULTS

The overall percentage of positive EF/pregnancy was 55.5% (30/54) and 66.7% (6/9), respectively. The likelihood of pregnancy/positive EF in the first three cycles was 55.5% (15/29). This was not different (p > 0.1) from the fertility of the last four cycles (69.4%, 25/36). In five EF cycles (9.3%), mares had signs of endometritis and early luteolysis (progesterone <2 ng/mL) 72 h after EF. The reduction in progesterone concentration by 72 h after EF was greater (p < 0.05) for Day 9 (-2.3 ± 0.7 ng/mL) than Day 7 (-1.0 ± 0.8 ng/mL) or Day 8 (-1.3 ± 1.1 ng/mL) cycles. The progesterone concentration in non-flushed mares did not vary significantly during the sampled period (Day 7-12). There were 5 cycles in which the donor mare remained pregnant after the EF, although four were from a single mare.

MAIN LIMITATIONS

The mare population was limited to barren and maiden mares. The cycle order and operator allocation to each EF were not randomised.

CONCLUSIONS

EF induces a subtle, but significant reduction in progesterone concentrations compared with non-EF cycles. However, the percentage of mares with EF-induced full luteolysis is low (9.3%). The fertility of mares after repeated EF without administration of PGF2α was unaffected; however, there is a considerable risk of unwanted pregnancy (5/27 = 18.5%) in donors from which an embryo was not recovered.

Luteal tissue blood flow and side effects of horse-recommended luteolytic doses of dinoprost and cloprostenol in donkeys

This study assessed luteolysis and side effects in jennies receiving standard horse-recommended doses of cloprostenol and dinoprost. Sixteen cycles of eight jennies were randomly assigned in a sequential crossover design to receive dinoprost (5 mg, i.m.) and cloprostenol (0.25 mg, i.m.) at 5-d post-ovulation. B-mode and Doppler ultrasonography were employed to assess luteal tissue size and blood flow before (-15 min and 0h) and after (0.5, 1, 2, 3, 4, 5, 6, 7, 8, 12, 24, and 48h) administering PGF2α. Immunoreactive progesterone concentrations were assayed at similar timepoints via RIA. Side effects such as sweating, abdominal discomfort, and diarrhea were scored at 15-min-intervals for 1h after PGF2α. Data normality was assessed with the Shapiro-Wilk's test. Luteal tissue size and blood flow were analyzed using PROC-MIXED and post-hoc by Tukey. Non-parametric tests analyzed side effect variables. The luteal blood flow increased overtime by 27% at 45 min and peaked by 49% at 3 h for dinoprost, and conversely, it increased by 14% at 30 min and peaked at 39% at 5h for cloprostenol (P<0.05). Luteal blood flow was reduced by 50%, 25%, and 10% on both groups at 8, 12, and 24h (P<0.05). Immunoreactive progesterone concentrations decreased in 0.5h for dinoprost and 1h for cloprostenol and gradually decreased by 48h (P<0.05). Dinoprost induced greater sudoresis scores, while cloprostenol resulted in greater abdominal discomfort and diarrhea scores (P<0.05). In conclusion, dinoprost and cloprostenol effectively induced luteolysis with distinct side effects; this could guide practitioners' case selection to use one or another PGF2α.

Efficacy and Side Effects of Low Single Doses of Cloprostenol Sodium or Dinoprost Tromethamine to Induce Luteolysis in Donkeys

Due to the limited literature available evaluating doses of Prostaglandin F2α in donkeys, doses for horses have been extrapolated and used as guidelines. This study aimed to assess the efficacy and side effects of four different cloprostenol sodium and dinoprost tromethamine doses to induce luteolysis in jennies. Sixty-three cycles of seven Jennies (nine cycles per jenny) were used in this study. Seven days after ovulation, jennies randomly received one of the treatments in a crossover design as follows: Control, no treatment was administered; C1, 250 µg of cloprostenol sodium (CS, Estrumate , Merck Animal Health, USA); C2, 125 µg of CS; C3, 65.5 µg of CS, C4, 37.5 µg of CS; DT1, 5 mg of dinoprost tromethamine (DT, Lutalyse, Zoetis, USA); DT2, 2.5 mg of DT; DT3, 1.25 mg of DT; DT4, 0.625 mg of DT. Jennies were monitored for 30 minutes following treatment, and adverse effects were recorded. The measurement of the corpus luteum (CL) and the length of the estrous cycle were recorded. All DT and CS treatment doses were effective (P < .0001) in reducing the estrous cycle length compared to jenny's Control cycle. The CL volume was decreased in all treated groups one day after treatment (P < .05). The adverse effects were reduced as the dose of both Prostaglandin F2α analogs were reduced. In conclusion, a single low dose of dinoprost tromethamine (0.625 mg) or cloprostenol sodium (37.5 µg) can induce luteolysis and shorten the estrous length in jennies producing fewer adverse effects.

Hemodynamics of the corpus luteum in mares during experimentally impaired luteogenesis and partial luteolysis

The aim of the current project was to characterize the luteal vascularity and the plasma concentrations of progesterone (P4), prolactin (PRL) and 13,14-dihydro-15-keto-PGF_2α (PGFM) in mares with luteal disturbances during early and mid-diestrus. In Experiment 1, twenty-one mares were treated with 2 mL of 0.9% NaCl, or 1 mg Dinoprost, or 10 mg Dinoprost on day two after ovulation (Control-D2, 1/10PGF-D2 and PGF-D2 groups, respectively; n = 7 mares/group). In Experiment 2, similar treatments were performed eight days post-ovulation using a different cohort of 21 mares (Control-D8, 1/10PGF-D8 and PGF-D8 groups, respectively; n = 7 mares/group). Blood samples were collected hourly and power-Doppler examinations of the corpus luteum (CL) were performed every 6 h from H0 (moment immediately before treatment) to H48. Data collection was also done once a day from D0 (day of ovulation) to D20. In Experiment 1, the PGF-D2 and 1/10PGF-D2 groups had lower increase of plasma concentration of P4 until H48 and reduced maximum P4 concentrations on D8-D11 than mares from the Control-D2 group. However, no differences among groups were detected for luteal vascularity during early and mid-diestrus. In Experiment 2, complete and partial luteolysis were detected in mares from the PGF-D8 and 1/10PGF-D8 groups, respectively. Luteal vascularity and plasma P4 concentrations differed among Control-D8, PGF-D8 and 1/10PGF-D8 groups on H48. Partially regressed CLs (1/10PGF-D8 group) generated more Doppler signals than completed regressed CLs (PGF-D8 group) between D10 and D13. In both experiments, a transient increase in PRL activity was observed in parallel to the PGFM pulse in mares receiving 1 or 10 mg Dinoprost. The use of prostaglandin on D2 at conventional or 1/10 of the dose impaired the luteal development in mares. Moreover, the low dose of prostaglandin lead to partial regression of mature CLs. The blood supply was reduced in partially regressed CLs, but not in CLs undergoing impaired luteogenesis.

The effect of dose and type of cloprostenol on the luteolytic response of dairy cattle during the Ovsynch protocol under different oestrous cycle and physiological characteristics

The objective of this study was to characterize the effect of dose and type of cloprostenol (CLO) on the luteolytic response of dairy cattle during the Ovsynch protocol under different oestrus cycle and physiological characteristics. Twelve non-lactating dairy cows and 111 lactating dairy cows were used in three experiments. In Experiment I, cows were synchronized so that they had only a 5.5- to 6-day-old corpus luteum (CL) at the time of the prostaglandin F2α (PGF2α ) treatment of Ovsynch. In Experiment II, cows were synchronized so that they had at least a CL of approximately 14 days old at the time of PGF2α treatment and an accessory CL if they had responded to the first GnRH of Ovsynch. Furthermore, in each experiment, cows received either a standard or a double dose of d-CLO as the luteolytic treatment. In Experiment III, lactating cows were blocked by parity and assigned to one of three luteolytic treatments during Ovsynch: 500 μg d,l-CLO, 150 or 300 μg of d-CLO. In Experiment I, the dose of d-CLO had an effect (p = 0.08) on the percentage of cows with full luteolysis, but not in Experiment II (p > 0.1). More cows in Experiment II had full luteolysis than did cows of Experiment I (87% vs 58%, respectively; p = 0.007). In Experiment III, 87.1%, 84.4% and 86.2% lactating dairy cows had full luteolysis and 37.8%, 36.8% and 36.1% of cows became pregnant after treatment with 500 μg d,l-CLO, 150 or 300 μg of d-CLO, respectively (p > 0.05).