Pregnancy and mid-term abortion rates in farmed red deer in New Zealand

Abstract

This paper describes pregnancy and mid-term abortion rate data from an investigation of sub-optimal reproductive performance in New Zealand farmed red deer. For 2 years, 87 yearling (YL) and 71 mixed-age adult (MA) herds from 85 farms were observed with 15 YL and seven MA herds observed both years. Hinds were pregnancy diagnosed using ultrasonography in the late autumn-early winter (PD1) and again late winter-early spring (PD2) and mid-term daily abortion rates (DAR) were calculated. Overall, 85.8% of 22,130YL (range, 7.0%-100% between herds) and 93.3% of 36,223 MA hinds (range, 39.8%-100% between herds) were pregnant at PD1. The mean interval between ultrasonic assessments was 90 and 87 days in YL and MA herds, respectively. Mid-term abortions occurred in 305 (2.8%) hinds from 60 (73%) YL herds and 92 (1.2%) hinds from 36 (61%) MA herds. The mean mid-term DAR, was greater (P = 0.009) in YL (mean 0.043%, range 0.005%-0.213%, 95% CI = 0.034-0.053) than MA herds (mean 0.025%, range 0.007%-0.101%, 95% CI = 0.018-0.032). In herds with hinds that aborted, the mean DAR was greater in small than large YL herds (0.055% compared with 0.033%, P = 0.023), but not MA herds. At PD1, 46 YL and 12 MA hinds had ultrasonographic evidence of abortions from 22 herds. This, combined with the 1.2% to 7.1% foetal loss in three herds pregnancy diagnosed earlier than the usual PD1 date as a pilot to test for earlier abortion, supports that abortion can occur prior to normal pregnancy assessment dates, contributing to sub-optimal pregnancy rates. Abortion rates were not consistent within herd between years for either YL or MA herds. Thus, early and mid-term abortion is prevalent in New Zealand farmed deer constituting a significant production cost, warranting further investigation into causation.

Keywords: Abortion; Pregnancy; Red deer; Ultrasonography scanning.