The effect of GnRH on the pregnancy ratio in low-yielding local race cows: comparison of different injection times.

The objective of this article was to investigate the efficiency of GnRH administrations at different time points after induced luteolysis on pregnancy rates in low-yielding subfertile cows. One thousand six hundred and ten healthy and subfertile dairy cows of different ages and races were used in this study. Cows were randomly divided into 4 groups. Estrus cycles were synchronized by two, with 11-day intervals, injections of the prostaglandin F2α-analogue (PG). The artificial inseminations (AIs) of all animals were achieved at the 72nd and 96th hours following the last PG injection. The animals in groups I (n 257), II (n 337), and III (n 675) were used for the administration of a single dose of GnRH at different time points. Accordingly, GnRH was applied at 48th, 64th, and 72nd hours following the last PG injection in groups I, II, and III, respectively. Group IV was accepted as a control without GnRH injection (n 341). The pregnancy rates in groups I, II, III, and IV after transrectal pregnancy examinations were found to be 89.88%, 91.09%, 83.25%, and 77.12%, respectively. In our study, maximal pregnancy rates could be obtained with GnRH injections performed at 48th and 64th hours following luteolysis induction (P < 0.001). There was a 6-8% decrease in pregnancy rates due to the injection of GnRH in the 72nd hour (P < 0.001). These dramatic losses and gains in pregnancy rates in our study emphasized the necessity of taking the time of injection into account when using GnRH to stimulate ovulation. It can be said that the success of GnRH stimulation of ovulation is directly related to the follicle wave dynamics at the time of injection point and the character of a dominant follicle.

Effect of chrysin on methotrexate-induced testicular damage in rats.

This study was conducted on 28 male Wistar albino rats to determine the effects of chrysin on methotrexate-induced damage to testicular tissue. Rats were grouped into four groups of seven rats reach: Group 1 (n = 7) was the control group to which no drugs were administered; this group was only provided with food and water. Group 2 (n = 7) was administered 20 mg/kg of methotrexate once intraperitoneally. Group 3 (n = 7) was administered 50 mg/kg of chrysin for 7 days orally. Group 4 (n = 7) was administered 20 mg/kg of methotrexate once intraperitoneally, followed by oral administration of 50 mg/kg of chrysin for 7 days. At the end of the experiment, rats were anaesthetised, rat testes were removed, and spermatozoon was obtained from the cauda epididymis. It was determined that sperm count and motility, glutathione peroxidase, superoxide dismutase and catalase activities decreased in the methotrexate group, whereas malondialdehyde, tumour necrosis factor-α, interleukin-1ß and nuclear kappa factor B expression levels increased. Furthermore, damage to tubulus seminiferus structures and affusion in germ cells was identified. In the methotrexate + chrysin administered group, sperm count improved, biochemical enzyme levels increased, and structural improvements were observed in testicular tubules. These findings demonstrated that chrysin plays a protective role in testicular damage in rats.