THE EFFECT OF SIRES ON THE RESULTS OF SUP EROVULATION AND EMBRYO-TRANSFER IN CATTLE

Data were acquired by our experimental work and from the records of op erative teams for embryo transfer. Fifty sires were evaluated in set 1 , the semen of which was used for A.I. of embryo donors (minimally of five donors) at least in two herds, and/or for insemination of four do nors minimally in three herds. The acquired data were processed by the method of analysis of variance and covariance. In set 2 data were eva luated on the percentage of transferable embryos and livable embryos a ccording to DG in the third month after ET in 160 sires used for insem ination of embryo donors. The conditions of sire's inclusion was recov ery of 12 embryos minimally from 4 donors in two herds. Data on the fe rtility of tested sires were added from the records of the State Anima l Breeding Enterprise in Prague. In set 1 the effect of sires on the r esults of superovulation and embryo transfer was investigated in 611 d onors inseminated with the semen of 50 sires. On average, 8 804 eggs w ere obtained, out of this amount 5 093 transferable embryos (58%), 2 3 98 degenerated embryos (27.4%) and 1 284 unfertilized oocytes (14.6%). A total of 4 239 embryos (56.6%) were transferred on average, 2131 ca lves were born (50.3% out of ETs and 83.3% out of livable embryos). Th e loss of conception rate (11.7%) involves the donors with abortions ( 0; 173; 7%) and still-born calves (0; 121; 4.7%). The differences in t he percentage of transferable and livable embryos between the sires ar e statistically highly significant (P < 0.01, Tab. 1). A significant e ffect of lactation number on the number of donors with abortions was d etermined during pregnancy (P < 0.05). An overall evaluation showed th at it was best to stimulate for embryo transfer the donors in 2nd to 7 th lactation as they produced the highest number and ratio of transfer able embryos and embryos with high livability. The differences in the number of recovered eggs are statistically significant between the dis tricts and/or herds (P < 0.05); it also applies to the conception rate of donors and to the number of born calves (P < 0.01), which reflect numerous effects (the deviation from the mem values am not indicated d ue to the scope of the paper). The value of coefficients of determinan cy for the indicators of the effect of sires on the results of superov ulation and embryo transfer range from 34.8 to 48% (Tab. II). Signific ant correlation relationships were found between the dependent variabl es at a various significant level (P < 0.05, P < 0.01 - Tab. III). In 160 sires of set 2 the percentage of transferable embryos is 52.7% and the differences in the percentage of transferable embryos between the sires are statistically highly significant (P < 0.01, Tab. IV). The v alues of correlations and regression coefficients for the ratio of tra nsferable and livable embryos and of the indicators of sires' fertilit y depending upon reproductive figures of daughters show that the testi ng of sire suitability to the use for donor insemination is necessary and realistic when ET data are processed from one center (Tab. V).