No abstract

The impact of superovulation stimulated by FSH-P on subsequent conception in embryo donors was studied on a group of 162 cows. After the recovery of embryos 121 animals (74.68 %) conceived after three subsequent inseminations; 59 of them (48.76 %) conceived after the first insemination. The highest conception rate after the first insemination (53.19 %) was recorded in cows superovulated within 60 days of parturition.On the average the donors conceived within 67.6 days and the animals superovulated within 60 days of parturition conceived within 59.11 days. The mean service period(SP) was about 148 days. In donors flushed within 60 days parturition it did not exceed 110 days. The milk yield of the donors remained practically unaffected by the superovulation proper and by embryo removal in the experimental group of animals and the decrease of milk yield per day and per animal did not exceed 0.66 kg.

On the basis of a single clinical selection of animals, in order to synchronise oestrus according to the presence of a corpus luteum in the ovary, a single dose of Cloprostenol-based luteolytics (Estrumate from ICI and Oestrophan.from Spofa) at 500 ~gi. m. was administered to a total of 3 834 heifers of various breeds.The first group consisted of 428 heifers, of which 402 (98%) were inseminated and 298, i. e. 74.12%, became pregnant in the postsynchronisation oestrus. Foll~wing a further two inseminations in all 98% of the heifers conceived, with an insemination index of 1.24.Out of 202 control animals inseminated in the traditional manner, 54% became pregnant after the first insemination and a total of 94.05% of animals conceived, with an insemination index of 1.63.The whole experimental group of synchronised heifers which became pregnant in the 1st, lInd and IIIrd postsynchronisation oestrus conceived on average 7.37 days after the initial synchronisation insemination, which accelerated their entry into reproduction by 24.8 days compared to their conventionally inseminated counterparts.It was confirmed that clinical selection of animals for synchronisation on the basis of the presence of a corpus luteum in the ovary is highly effective and depends on the accuracy of the diagnosis of the presence of a corpus luteum.In the second experimental group, using similar criteria for selection, 3 406 heifers were synchronised, of which 2 465 animals conceived in the postsynchronisatioo oestrus, i. e. an average of 72.2%.In the third group a study was made of the onset of calving following synchronised insemination in 303 pregnant heifers of Friesian and Bohemian' Pied cattle. Calving took place from the 262nd to the 290th day of gestation at an interval of 29

A study of the contribution of the breeding bull, the work of the operator and the influence of the size of the synchronized group on the conception rate in breeding cows after a first insemination at estrus, synchronized by cloprostenol, in 21 groups of heifers, of 469 head, and 21 groups of cows (350 head), has shown that:1. Conception rate in breeding cows after a first insemination during synchronized estrus was significantly influenced by the use of a bull allotted according to a mating plan. After insemination of the breeders, carried out with frozen semen from various bulls, statistically highly significant differences in conception after the 1st insemination (P < 0.01) were ascertained.2. The conception rate in breeding cows after a 1st insemination were influenced by the work of the operators. Amongst the individual techniques, statistically highly significant differences (P < 0.01) were found in the attained conception.3. Conception rates in breeding cows were also strikingly influenced by the size of the synchronized group. A decrease in conception of 18 %'(at the limit of statistical significance) was ascertained after a 1st insemination when there were more than 30 heifers in the synchronized group, and a statistically highly significant decrease of 25 % (P < 0.01) was found when there were more than 40 heifers to a group in inseminations carried out by a sole operator. In cows a decrease of 8 % in a conception was found after a first insemination in groups with a number of breeders larger than 40 head.