Genetic and environmental factors influencing first service conception rate and late embryonic/foetal mortality in low fertility dairy herds

Abstract The objective of this study was to identify factors affecting variation in conception rate to first artificial inseminations (AI) (CR: number of pregnant cows on D80–100/inseminated cows) and the incidence of embryonic/foetal loss (LEM) between 21 and 80 days of pregnancy (number of cows non-pregnant on D80–100/pregnant on D21) in 44 low fertility dairy herds of the west-central region of France. Reproductive status was assessed using progesterone milk concentration on D0 = Day of AI and D21–24, plasma PSPB concentration on D30–35, rectal palpation on D80–100 and observed return to oestrous. The final data set contained 1285 Prim’Holstein cows, 5.0% (64/1285) were inseminated in the luteal phase (progesterone ≥3 ng/ml on D0), 61.3% (787/1285) were pregnant on D21–24 (progesterone  p p p p  = 0.11). LEM incidence was affected by period of AI ( p p p