Epidemiology of bovine abortions in Israeli dairy herds.

Routine monitoring of abortions is carried out on most Israeli Kibbutz dairy herds. The reports include both descriptive epidemiology and multivariable analysis. Data are presented according to parity, trimester, abortion curves and sire. Results are produced in the form of abortions per 10000 cows-days-at risk, proportion of aborted cows by 260 days of gestation, abortion per confirmed pregnancy, and adjusted odds ratios. For 58048 pregnancies from 111 herds in 1995, the respective abortion density, proportion of aborted cows, and abortions per confirmed pregnancy were 4.2, 5.9%, and 10.2%. Among parities, heifers had the lowest, and cows of second parity the greatest risk of fetal death (respective odds ratios 0.6 and 1.3) compared to all other parities pooled together. The greatest risk of fetal death was observed in the first, and the lowest in the second trimesters of pregnancy (odds ratios 1.9 and 0.6, respectively). Recurrent risk ratio for abortion in the same lactation was high (odds ratio 2.7). Respective proportions of aborted cows with and without a previous abortion were 17.5% and 5.9%. Odds of aborting after twinning in multiparous cows was 1.3 greater than for those having a single calf. Risk of abortion in the autumn and early winter was greater than that in the summer months. Increased risks of abortion were associated with eight sires out of the 233 used (odds ratios of mates to abort ranged from 1.9 to 3.9). One, two and three peaks of abortions were established in 53.2%, 24.3%, and 0.9% of the 111 herds studied in 1995. None were detected in 21.6% of the herds.