Aglepristone Administration in Mid-Proestrus Reduces the LH Peak but Does Not Prevent Ovulation in the Bitch.

Piotr Socha,Katarzyna Bladowska,Sławomir Zduńczyk,Tomasz Janowski

doi:10.3390/ani11071922

Abstract

Simple SummaryThe role of preovulatory progesterone for LH release and ovulation in the bitch is not clear. The aim of the study was to evaluate the influence of administration of aglepristone in mid-proestrus on progesterone concentration, LH release, and occurrence of ovulation in the bitch. Experimental bitches (n = 7) were treated on days 4 and 5 of proestrus with aglepristone (Alizin®, Virbac) at the dose of 10 mg/kg body weight s.c. (i.e., the two treatments were 24 h apart). The progesterone concentration showed a similar pattern in both groups. The LH peak value and area under the curve for LH in bitches treated with aglepristone were significantly lower than those in control bitches. The ovulation occurred in all animals in both groups. The presented study showed that withdrawal of progesterone by administration of aglepristone in the mid-proestrus significantly reduced the preovulatory LH surge, but it had no effect on periovulatory progesterone concentration or the occurrence of ovulation.The aim of the study was to evaluate the influence of administration of aglepristone in mid-proestrus on progesterone concentration, LH release, and occurrence of ovulation in the bitch. Experimental bitches (n = 7) were treated on days 4 and 5 of proestrus with aglepristone at the dose of 10 mg/kg body weight s.c. (i.e., the two treatments were 24 h apart). Control animals (n = 7) received s.c. injections of saline. For progesterone determination, blood was collected daily until the first day of cytological diestrus. For LH determination, blood was collected daily and in the periovulatory phase every 8 h. The progesterone concentration showed a similar pattern in both groups. The LH peak value in bitches treated with aglepristone was significantly lower (p < 0.05) than that in control bitches (4.83 ± 1.20 vs. 13.66 ± 1.21 ng/mL). The area under the curve (AUC) for LH was significantly (p < 0.05) lower in treated than in control animals (6.85 ± 1.21 ng/mL/d vs. 12.25 ± 1.35 ng/mL/d). The ovulation occurred in all animals in both groups. The study showed that administration of aglepristone in the mid-proestrus significantly reduced the preovulatory LH surge, but it had no effect on progesterone concentration and the occurrence of ovulation.

Highlights

The periovulatory phase is critical in breeding management in the dog; relatively little is known about the regulation of the canine reproductive processes during this time [1]
Experimental bitches were treated with aglepristone (Alizin®, Virbac, Carros, France) at the dose of 10 mg/kg body weight s.c. on days 4 and 5 of proestrus when progesterone concentration was below 1 ng/mL and the percentage of superficial cells increased
The peak luteinizing hormone (LH) value in bitches treated with aglepristone was significantly lower (p < 0.05) than that in control bitches (Figure 2)

Summary

Introduction

The periovulatory phase is critical in breeding management in the dog; relatively little is known about the regulation of the canine reproductive processes during this time [1]. Estradiol concentrations increase from 5 to 15 pg/mL initially, reaching peak levels of 40–120 pg/mL, and begin to decline one day before the surge of luteinizing hormone (LH) [2,3]. Progesterone (P4) concentration rises very slowly throughout proestrus, from basal values of 0.2–0.4 ng/mL to 1.5–2 ng/mL before or at the start of the LH surge [2,4]. This preovulatory P4 increase results from the luteinization of ovarian follicles, visible histologically as early as 6 days before ovulation [1,5]. The determination of blood progesterone concentration is used for indirect estimation of the LH surge and of the time-point of ovulation in bitches [8,9,10]

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