Effect of GnRH at Estrus and 12-Day Post Matting and Propylene Glycol on Sera Metabolites Concentrations and Ewe Conception Rate
*Gholamali Moghaddam Department Of Animal Sciences, University Of Tabriz, Tabriz, Iran, Islamic Republic Of
*Corresponding Author: Gholamali Moghaddam
Department Of Animal Sciences, University Of Tabriz, Tabriz, Iran, Islamic Republic Of Email:Ghmoghaddam@tabrizu.ac.ir
Published on: 2018-06-28
In this study GnRH and propylene glycol respectively used as hormonal treatment and to supply precursor material of glucose. Animals (56 crossbred ewes, Arkhamerino-Ghezel (AG) and Arkhamerino-Moghani (AM), 2.5 years old) were classified to 1 control and 3 treatment groups randomly. After estrus detection and before mating, one milliliter of physiological saline (0.9% NaCl, placebo) was administered to each ewe in control group, group 1 were injected with 2.5 ml GnRH and after 2 hours they were mated by ram, group 2 were injected with 5 ml GnRH 12 days after mating, group 3 were received 30 ml propylene glycol for 5 days after mating. Blood samples were taken on 6 d after mating by using vacuum tube. Glucose, urea, phosphorus, total protein, β-hydroxybutyrate (BHBA) and progesterone concentrations in blood serum were measured. Results shows that glucose in AM was significantly higher than AG (P<0.01). Urea and BHBA in AM were significantly (P<0.01) lower than AG. In repeat breeder ewes, progesterone concentration in estrus 2 was significantly (P<0.05) higher than estrus 1, and urea and BHBA concentrations in estrus 2 were significantly (P<0.05) lower than estrus 1. Administration 5 ml of GnRH on day-12 after mating was effective on reproductive performance than others. In conclusion, results showed that only one sheep in GnRH-2.5 ml treatment at estrus and five sheep in GnRH-5 ml on day-12 after mating showed repeat estrus and suggested that using 2.5 ml of GnRH before mating had better effect to prevent of repeat breeder.
There are a number of factors (including the method of insemination, type of estrus (neutral or controlled), age, season, genetic, stress, embryonic and fetal mortality) that can influence fertility in a breeding program. The time of mating or artificial insemination is important point to increase the fertility in animals. Insemination too early or too late in relation to ovulation is determinately to fertility. The reduction in fertility may reflect failure of conception or embryonic mortality. Pervious study showed that reproduction of crossbred sheep could be improved by using of hormonal treatments and GnRH or its analogues have a positive effect on fertility. Improvement of conception rates following GnRH treatment during estrus has been attributed to the prevention of ovulation failure or to reduced variation in the interval to ovulation. It has also been suggested that GnRH induced increase in progesterone concentrations during the subsequent estrous cycle may have an effect on conception.