| Summary: | Objective: To investigate some blood biochemical parameters in anoestrous dairy cows with cystic ovarian follicles (COF) during the first two months post partum and the effect of hCG-PGF2α -GnRH treatment on their reproductive response.
Methods: The investigation was performed on 20 lactating Holstein cows, divided into two groups: control group (n=8) and treated group (n=12). All animals had cystic ovarian follicles, detected during the two consecutive transrectal ultrasound examinations at 7-day interval. Blood samples from each animal were collected on the day of second ultrasonography (Day 0) and subjected to a hormonal and biochemical analysis. Treated cows were subjected to another ultrasound examination on day of prostaglandin injection and the presence of corpus luteum was recorded. The control animals were not treated, while the treated group received 1 500 IU hCG on day 0, PGF2α 500 mg on day 7 and 100 μg GnRH 48 hours latter. Eighteen hours after GnRH administration animals bearing corpus luteum on Day 7 were artificiallly inseminated. The last ultrasound examination was made forty days after start of the threapy. On the base of the obtained results, cumulative oestrous activity, cumulative ovulation rate, pregnancy rate and COF persistence were determined.
Results: The blood analysis in the both groups on Day 0 showed significantly (P<0.05) lower mean concentration of progesterone, glucose and inorganic phosphate compared to the reference range values for cyclic dairy cows. Cumulative oestrous activity (91.7%) and cumulative ovulation rate (75.0%) were considerably higher (P<0.05) in treated group than control group, whereas the cystic follicle persistence (25.0%) was lower (P<0.05) in the treated group than control group.
Conclusions: The present study confirmed the thesis for low blood levels of glucose and inorganic phosphate in cows presenting cystic ovarian follicles. It also indicated significant improvement of cumulative oestrous activity and ovulation rate in animals subjected to hCG-PGF2α -GnRH administration than non-treated animals. The used hormonal protocol could decrease cystic ovarian follicle persistence in dairy cows.
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