Comparative effectiveness of different methods of using the analogue of gonadotropin-releasing hormone for ovulation stimulation in rabbit does

Abstract

Modern reproductive technologies require artificial insemination (AI) protocols that are safe for the health of animals and do not violate their welfare. Stress factors arising in the reproduction process of industrial rabbit breeding negatively affect the sexual function and reproductive performance of rabbits and their offspring. In recent years, researchers have focused on alternative methods of ovulation stimulation, including intravaginal introduction of hormonal means of its induction. Therefore, the aim of our study was a comparative evaluation of the effectiveness of the intramuscular method of administration of the gonadotropin-releasing control (GnRH) analogue and its addition to the sperm dose for AI on Hyplus rabbit (n = 30), which were randomly divided into three groups. For this, buserelin acetate was administered intramuscularly at a dose of 1 μg per rabbit immediately after artificial insemination (control group). Experimental animals were inseminated with sperm doses with the addition of a GnRH analogue in the amount of 25 μg (experimental group 1) and 15 μg (experimental group 2). The influence of the method of administration of GnRH analogue on reproductive function was evaluated by indicators of the effectiveness of AI, fertility, and the dynamics of the progesterone level during pregnancy. A decrease in fecundity was observed in females; for example, in experimental group 1, the effectiveness of AI in terms of the number of rabbits was 64.3 %; in animals of experimental group 2 – 41.2 %, and the number of inseminations in this group of rabbits was 41.7% higher compared to control data. The fertility of rabbits of all groups was high, reaching the maximum value in the control group (10.42 ± 0.52 heads/female). Fertility according to live newborns in experimental group 1 was the highest among all groups of rabbits and was 9.67 ± 0.49 heads/female, which showed an increasing trend compared to the control. Also, in the animals of experimental group 1, an increase in the level of progesterone in blood serum was observed (on the 7th day of pregnancy by 13.2 %, on the 14th day by 14.3 %, on the 21st day by 16.4 %). In contrast, in experimental group 2, a significant decrease in the progesterone level was noted. Thus, 25 μg of GnRH analogue added to the extender is optimal. It is worth noting that there were no advantages of intravaginal administration over intramuscular administration in terms of reproductive performance. However, the number of live births and progesterone levels were improved.