Some Factors Influencing the Results of Conception in Cows and Heifers in Estrus Synchronized by the Synthetic Analogue of PGF2α Cloprostenol

Abstract

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.