Comparison of Oestrous Intensity between Natural Oestrus and Oestrus Induced with Ovsynch Based Treatments in Japanese Black Cows

Abstract

The aim of this study was to examine the possible differences of oestrous intensity between natural oestrus and induced oestrus using the walking activity measuring device. Walking activity was used as an evaluation index of oestrous intensity. A total of 27 Japanese Black cows, more than 40 days after calving and clinically normal, were randomly assigned to three groups. Walking activity was recorded using a commercially available computerized pedometer system. The treatment groups consisted of an Ovsynch (n = 8) and a controlled internal drugs releasing device (CIDR) + Ovsynch (n = 9) group. The control group (n = 10) received no treatment. Walking activity was examined in all groups. Timed artificial insemination (timed AI) was performed at 16 hours after the onset of oestrus in the control group and at 24 h after second administration of GnRH in the treatment groups. Duration of oestrus had a tendency to be shorter in both the Ovsynch and the CIDR + Ovsynch groups when compared with the control group. The time required from the onset of oestrus to the time showing the highest number of steps of walking (the time to peak) showed a tendency to be shorter in CIDR + Ovsynch group. The number of steps of walking at peak and overall walking activities were significantly lower in both treatment groups than in the control group. Both activity and super-activity periods of time in the treatment groups were shorter than the control group. No difference was observed in the conception rate between the control (50.0%; 10/20), Ovsynch (50.0%; 4/8) and CIDR + Ovsynch groups (66.7%; 6/9). This study demonstrates that the oestrous intensity of cows in oestrus was different between natural oestrus and induced oestrus and also between the methods of the synchronization, but no difference was observed in the conception rate among the three groups.