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The objective of the examinations performed on 230 cows and 36 embryo recipients was to establish if 1—3 doses of progesterone applied between the 17th and 19th day after insemination or on the 10th day after embryo transfer help the stabilization of pregnancy. After one dose of P4 (250 mg) 51,1% of conceptions were noted, after 2 doses 63,8% and after 3 doses 76,6% of conceptions were observed. In a control group 30,3% of the cows became pregnant. In embryo recipients after one anpplication of an exogenous progesterone at a dose of 125 mg the pregnancy rate was 44,4% as compared to a control group in which the rate was 27,8%. In pregnant cows initial levels of progesterone varied from 1,96 to 8,1 ng/ml. In the group of cows receiving 1 dose of P4 an average increase of the level of progesterone was by 1,1 ng/ml, in the group receiving two injections by 3,36 ng/ml, and in the group receiving three injections of P4 by 4,9 ng/ml. In the control group on the 19th day after insemination in 37,2% of pregnant cows the level of progesterone in blood plasma decreased by an average of 1,65 ng/ml. It can be assumed that the application of exogenous progesterone in inseminated cows with subclinical disturbances of endometrial functions and in embryo recipients positively affects the stanilization of pregnancy.
The purpose of the work was to confirm the possibility of embryo transfer to protect offspring of leukaemic cows of high breeding value from infection with EBLV. The studies were carried out on 229 donors of embryos infected with the EBLV. Heifers free from enzootic leukaemia were receivers of the embryos. The disease was diagnosed both in the donors, receivers and new-born calves by the gel precipitation test or ELISA. From 152 donors 1390 embryos were obtained and only 676 (48.6%) were qualified as suitable. There were transfered 585 embryos resulting in 278 pregnant cows (the efficacy of the transfer was 47.5%). There were born 274 calves free from leukaemia and 4 died during parturition. The transferes and new-born calves were housed in isolation under conditions which protected them against EBLV. The studies showed that the transfer of embryos was an effective method allowing to get healthy offspring from leukaemic cows on condition that strict prophylactic measures during the operation and pregnancy and after calving were applied.
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