Methods for pregnancy determination and the effects of body condition on pregnancy status in Rocky mountain elk ([formula omitted

Abstract

The objective of this study was to determine the effectiveness of transrectal ultrasonography and serum progesterone (P4), estrone sulfate (E1S) and pregnancy-specific protein B (PSPB), without prior knowledge of reproductive status, in detecting pregnancy in elk cows. In addition, body weight and body condition score (BCS) were determined to assess whether body condition affects pregnancy status in elk cows. Twenty-five elk cows were sampled during the early rut (Period 1) and after the rut (Period 2), an interval of 120 d. Age, weight, BCS and blood samples, for P4, E1S and PSPB determinations, were taken at Periods 1 and 2. Ultrasonography was performed at Period 2. The younger elk cows weighed less (P<0.05) than older cows. However, pregnancy status was not affected (P> 0.10) by age or weight of the cow. Elk cows that calved had higher (P<0.02) BCS at Periods 1 and 2 than cows that remained open. Serum P4 and E1S were higher (P<0.0001) in pregnant cows at Period 2 than in open cows. Progesterone was 85.8% accurate in detecting pregnant versus open cows at Period 1, while E1S and PSPB were not effective. Elk cows at Period 1 were <20 d pregnant with the exception of 1 cow at 46 d. Ultrasonography was 92% accurate, P4 was 95% accurate, and E1S and PSPB were both 100% accurate in determining pregnant versus open cows at Period 2. Pregnant cows at Period 2 were all > 100 d pregnant. Ultrasonography, serum E1S and PSPB all may provide a reliable means for pregnancy diagnosis in elk cows at > 100 d of gestation, while serum P4 may be effective when multiple samples are compared during or after the rut, or when used in combination with the other diagnostic methods described. Further research is needed to determine the optimum time period after breeding in elk cows for accurate pregnancy detection through hormonal analysis.