Influence of stage of lactation and milk production on conception rates after timed artificial insemination following Ovsynch

Conception rates after timed artificial insemination (TAI) are of paramount importance for the success of protocols based on synchronization of ovulation. Stage of lactation and milk production level are known factors that influence dairy cow fertility. It was the objective of this study to analyse the effect of stage of lactation and milk production level on conception rates and pregnancy rates by 200 days in milk (DIM) in dairy cows synchronized with the Ovsynch protocol (Day −10, Day −1: 0.1 mg of D-Phe6-gonadorelin, Day −3: 0.5 mg of cloprostenol, Day 0: AI). A total of 1288 dairy cows were assigned to two groups and classified in three production levels (high, average, low). Cows of all milk production levels in Group 1 (Simultaneous Ovsynch, SO) were synchronized with the Ovsynch protocol simultaneously for TAI between 73 and 81 DIM. In Group 2 cows with average milk production were synchronized at the same time as Group 1, while low producing cows were synchronized 3 weeks earlier and high producing cows were synchronized 3 weeks later than Group 1, respectively. First service conception rates (FSCRs) were lower ( P