Effects of buserelin and human chorionic gonadotrophin on fertility of dairy cows with or without retained placenta

Gonadotrophin-releasing hormone (GnRH), as well as gonadotrophin hormones, control the whole reproductive cycle of mammals. GnRH analogue buserelin an d extracted hCG (human chorionic gonadotrophin) have a wide spectrum of app lication in the world. Ovarian dysfunction during early PP (post partum) pe riod, especially in cows with r.p. (retained placenta), results in prolonge d service-period and decreased rate of conception. Therefore, reproductive status of cows is expected to be improved by inducing physiological process es of ovaries by hormonal treatment. The results from various authors that have been published until now are rather contradictory. During investigatio ns, the effects of administering 20 micrograms Gn-RH analogue buserelin (Re ceptal, "Hoechst"), or 1 500 i.u. hCG (Chorulon, "Intervet") per cow betwee n d 14 and 16 PP were observed. The investigation has included 150 Holstein -Friesian cows with or without r.p. The cows were divided in six groups (n = 25), depending on hormonal treatment and placenta status: two untreated g roups - with or without r.p.; two buserelin treated groups - with or withou t r.p.; two hCG treated groups - with or without r.p. The two parameters of fertility were observed: service period (time from calving to first insemi nation) and CCI (calving-to-conception interval). Applications of mentioned hormonal prophylactics on the fixed days of PP period on a farm with manag ement deficiencies, low feed quality and low level of hygiene, did not have any significantly beneficial effects on resumption of ovulation and fertil ity after calving. Therefore, these prophylactics cannot be recommended in herds with low fertility caused by these factors.