REPEATED SUPEROVULATION AND ITS USE IN CA TTLE-BREEDING

The objective of the present paper is to evaluate the position and suc cessful application of repeated superovulation with respect to its use in cattle breeding. Repeated superovulation of embryo donors - high-p erformance dairy cows at the end of their productive life (6th to 13th lactation) - was evaluated for the purposes of embryo transfer in the first part of the study. In the second part, repeated superovulation of high-performance donors was evaluated in various calving intervals (mothers of bulls and elite dams C1 to C3 in the 5th to 14th lactation ) within an experimental program MOET. Estrous cycles of donors were s ynchronized by two applications of the analog prostaglandin F2 alpha ( Oestrophan, Leciva Praha) in an eleven-day interval. The preparation F SH Folicotropin, Spofa Praha, was applied i.m. to cows from the 9th to the 11th day of the estrous cycle, in the morning and in the evening (at 7.00; 19.00 hours) for four days at doses of 2.3; 3.2; 1.1; 1.1 am poules of the preparation (total batch of 14 ampoules, i.e. 560 i.u. F SH), and in the same way to heifers, 2.2; 1.1; 1.1; 1.1 ampoules of th e the preparation (total batch of 10 ampoules, i.e. 400 i.u. FSH). The analog of prostaglandin F2 alpha (Oestrophan, Leciva Praha) was admin istered on day 3 of superovulation treatment in the morning at a dose of 500 to 750 mu g. Insemination and reinsemination were done on days 5 and 6 of superovulation treatment. Tab. I shows data on the recovery of transferable embryos and on embryo quality after repeated interven tions in order to recover embryos from high-performance donors. The hi ghest number of eggs in total (14.25 +/- 0.05) and of transferable emb ryos was obtained from 10 and 8 donors after the fifth and sixth treat ment. The average number of eggs and transferable embryos recovered af ter the first and second treatment is at the level of mean values dete rmined by Riha (1990) for donors. Average numbers were insignificantly increasing (P > 0.05) after the third and next treatment to the eight h one. Repeated stimulations of mothers of bulls within one lactation and within several successive lactations suggested small and statistic ally insignificant differences in the number of recovered eggs (8.30 /- 7.05 and 8.60 +/- 6.38, respectively; P > 0.05) and transferable em bryos (5.20 +/- 5.58 and 4.04 +/- 4.34, resp.; P > 0.05). The percenta ge of transferable embryos out of recovery percentage was higher in do nors that were stimulated and applied repealed interventions within th e same calving interval (62.6%) in comparison with different calving i ntervals (51.2%, P > 0.05 - Tab. II).