Effect of ovarian stimulation by different gonadotrophin treatments on in vivo and in vitro reproductive efficiency of r
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Effect of ovarian stimulation by different gonadotrophin treatments on in vivo and in vitro reproductive efficiency of rabbit does under high ambient temperature I. T. El-Ratel 1
&
A. E. Abdel-Khalek 2 & Sara F. Fouda 3
Received: 6 January 2020 / Accepted: 6 October 2020 # Springer Nature B.V. 2020
Abstract Non-lactating multiparous NZW rabbit does (n = 227) were used in two experiments. In the 1st experiment (n = 87), does were i.m. injected with 0.1-ml saline/doe in day 0 (control, n = 29). Other does were injected with 25 IU equine chorionic gonadotrophin (eCG), followed by 0.2-ml gonadotrophin-releasing hormone (GnRH, n = 29) or 75 IU human chorionic gonadotrophin (hCG, n = 29) per doe 48 h later. After 60 h of day 0, does in all groups were artificially inseminated (AI). In the 2nd experiment, does (n = 140) were mated (AI) after synchronization of estrus/ovulation with 25 IU eCG, and 75 IU hCG 48 h later. On day 5 post-AI, does were injected with saline (control), 75 IU hCG, 0.2 ml GnRH, or 25 IU eCG per doe. Injection of eCG with GnRH or hCG pre-AI significantly increased corpora lutea number, ovulation rate, total number/doe and recovery rate of embryos, viable embryos, hatched blastocysts, in vivo reproductive parameters, and concentration of progesterone and progesterone/ estradiol 17-β ratio. Injection of eCG on day 5 post-AI significantly improved large and total follicle number, and in vivo reproductive efficiency. The corpora lutea number and impantation sites were significantly increased in the hCG and eCG groups. Fetal loss rate significantly increased only in the GnRH group. Under high ambient temperature, administration of eCG with hCG or GnRH injection pre-AI could be synchronized estrus/ovulation for improving in vivo and in vitro embryo production. In addition, pregnancy outcomes could be enhanced in rabbit does induced to ovulation by a single eCG or hCG dose on day 5 post-AI. Keywords Rabbits . Gonadotrophins . Ovulation . Pregnancy . Embryonic loss
Introduction There are a variety of physiological factors causing a decrease in the reproductive activity of intensively farmed rabbits (Castellini 2007). Exposing to the environmental stressor such as high ambient temperature (AT) is considered one of the main factors affecting the oxidative stress that leads to impaired physiological and reproductive features in rabbit does
* I. T. El-Ratel [email protected] 1
Present address: Department of Poultry Production, Faculty of Agriculture, Damietta University, Damietta 34517, Egypt
2
Department of Animal Production, Faculty of Agriculture, Mansoura University, Mansoura 35516, Egypt
3
Department of Poultry Production, Faculty of Agriculture, Mansoura University, Mansoura 35516, Egypt
(El-Ratel et al. 2020). Under high AT, disturbances in metabolism, energy, water, mineral, and hormonal balances had been reported in rabbits (Ondruska et al. 2011). Reproductive hormones in females were found to be affected by high AT, in terms of decreasing levels of luteinizing hormone
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