The aim of the present study was to compare first-service conception rates after inclusion of either hCG or GnRH in Double Ovsynch to anestrous dairy cows. The animals with follicle size ≥10 mm and no corpus luteum in ovaries were allotted into 2 groups. At the start of the programme, follicle sizes were 13.7±1.5 mm and 13.9±1.2 mm respectively (р=0.5). Higher percentage of ovulations (72.7%) were established in cows treated with hCG vs those treated with GnRH (64.4%, р<0.2094). Follicle sizes at the time of AI were 15.9±0.5 mm and 16.2±0.4 mm (р=0.5). Pregnancy was detected in 38.6% of cows treated with hCG and 42.2% of cows treated with GnRH (р<0.3501)
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