Comparison of mean serum progesterone levels and luteal period following anestrous bitches implanted with GNRH agonist, deslorelin, short or long-term

Abstract

To investigate the effect of short or long-term GnRH agonist deslorelin implantation on duration of luteal period and serum progesterone concentrations in bitches. Eighteen healthy anestrous bitches and two fertile male dogs were used in this study. All bitches were randomly divided into 4 groups. Group 1 (n=4), bitches received 4.7 mg deslorelin which was removed at the first day of estrus. Group 2 (n=6), received 4.7 mg deslorelin which was removed at the end of experiment. Group 1 and 2 were mated and inseminated during estrous period and detected pregnant by ultrasonography. The same protocol as group 2 was used for group 3 but without insemination. And group 4 (n=4), bitches process a spontaneous estrous cycle which were used as control. All bitches were examined for the stage of estrous cycle by physical and behavioral signs, vaginal cytology and serum progesterone concentrations on required dates. Statistic analytical process using ANOVA for evaluated a mean interval of day in luteal period (mean±SEM) in each group. Mean concentrations of progesterone were analyzed using descriptive statistic. The results showed that all bitches came into estrous stage and ovulated except 1 bitch in group 3. Mean diestrous period in group 3 (31.7±2.7 days) was significantly shorter than group 1, 2 and 4 (56.3±3.1 days, 45.3±5.0 days and 54.8±1.7 days, respectively) (P<0.05). Progesterone profiles in group 1 and 2 resemble natural estrous dogs. Mean serum progesterone concentrations in group 3 exhibited a low peak and premature declined compared with other groups. Three bitches in group 1 and 2 were found to be a pregnant. All pregnant bitches in group 1 had a normal pregnancy and whelping. In group 2, 2/3 pregnant bitches started aborting on day 51 and 53, respectively and aborting was completed within 3 days. In conclusion, the results of this present study clearly revealed that short-term implantation of 4.7 mg deslorelin in anestrous bitches is effective and practical method for estrous induction. Bitches processed normally estrous cycle as natural cyclic dogs if the implants were removed at the first day of estrus. In contrast, long-term implantation to generate contraception produced premature luteal failure, resulting shortened diestrus or interrupted pregnancy but this effect may be incomplete. Therefore, a mating in flare-up period should be avoided.