The effect of the intravenous injection of 100 mcg (2 ml)
gonadotropin-releasing hormone (Ovarelin, Ceva) from the 1st to the 20th day
after calving of beef cows was monitored in the article, in regard to the
occurrence of the first oestrus and the possibilities for its controlling. It
was established that in the first minutes of intravenous application of
Ovarelin the concentration of luteinizing hormone (LH) increased. By
increasing the number of days increased the amount of secreted LH. Maximum
effect of the injection of 100 mcg GnRH occurred between the 10th and 15th
day. The physiological dose (100 mcg) GnRH injected intravenously on the 1st
day after birth of cows led to increased content of LH in blood circulation.
The experiment included 20 ewes of the Tsigai breed, allocated in two groups of 10 animals each. Inducing of oestrus synchronisation was performed during anoestral season (April-May) through vaginal sponges containing gestagens, and administration of Gravohormon (Vetbiopharm, Bulgaria)-500 UI in group 1 ewes and 1000 UI in group 2 ewes. Macromorphological study of the ovaries was carried out by means of laparoscopy after the adopted methods-on the 56 th hour, 72 nd hour and 5 th day following sponge withdrawal and injection of gonadotropin. The levels of the steroid hormones progesteron and 17ß-oestradiol were recorded in three ewes per each group at different times according to the experiment scheme. The histological structure of the ovaries was determined in seven animals subjected to ovariectomy.
Different schemes of PMSG treatment on some reproductive parameters in sheep were studied. Two groups of 6 sheep each at the end of the non breeding season were treated with vaginal sponges Chrono-gest (Intervet, Holland) containing 30 mg fluorogeston acetate (FGA). The sponges were removed 12 days after insertion. Sheep of the experimental group were injected with 500UI Folligon (Intervet, Holland) 48 hours before sponge removal whilst the corresponding control sheep were treated with the same dose Folligon at the day of of sponge withdrawal. The clinical signs of oestrus, plasma progesterone concentrations and changes in the ovarian morphology during the observation period were registered. The conception rate, fertility and twinning rate were also recorded. The results show that the earlier application of the gonadotropin influence positively the reproductive traits in ewes.
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