Abstract. The objective of this study was to investigate the efficiency of estrus detection and determination of the time of ovulation in Japanese Black cows by a real-time radiotelemetric pedometer. A herd of Japanese Black cows was housed in a loose-housing barn. This pedometer system and a pressure-sensing radiotelemetric device, which detects standing events, were concurrently compared in regard to their availability for detection of estrus events. Pedometer estrus and standing events were observed for all cows (n=20), and the duration of increased walking activity was 15.8 ± 0.9 h, which was longer (P<0.0001) than the duration of standing events (9.0 ± 1.3 h). Ovulation was observed 30.2 ± 0.6 h after the onset of pedometer estrus and 29.0 ± 0.6 h after the first standing event. There was a high correlation (r=0.89, P<0.0001) between the intervals from the onset of pedometer estrus and onset of standing event to ovulation. The animals of the pedometric group (n=20) were inseminated 10 to 18 h after the onset of pedometer estrus and had a higher conception rate (90.0%, P<0.05) than those inseminated according to the a.m. /p.m. method (58.4%, n=24). In conclusion, the pedometer system is an excellent tool for precise estrus detection and insemination at the appropriate time, which ensure a high pregnancy rate in Japanese Black cows.

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Walking activity of cattle changes at estrus, and in this study, we measured the walking activity of Japanese black cattle in a loose-housing barn. Recently, a system (Gyu-Ho; Comtec, Miyazaki, Japan) for determining estrous activity has been developed. This system uses a pedometer equipped with a transmitter, which makes it possible to measure walking activity over a period of time. The objectives of the present study were to compare the walking activity at an induced estrus in superovulating cattle (SOV group, n = 10) to natural estrus in nonstimulated cattle (Natural group, n = 10), and to determine whether there is a correlation between estrus behavior and superovulatory response. A pedometer equipped with a transmitter was placed on the front of the metatarsal bone of each cow. In addition, a sensor (Hatujo-Pitari; Comtec), which determined the duration and frequency of standing estrus by mount pressure, was placed on the tail head of each cow. The walking activity and times of standing estrus were recorded through a receiver every h on a personal computer. In the SOV group, superstimulation was initiated on Days 9 to 13 (Day 0 = day of estrus) with a total dose of 28 mg FSH (Antrin R-10; Kawasaki-Mitaka, Kawasaki, Japan) via twice-daily IM injections in decreasing doses for 4 days. At 72 h after the first FSH injection, 750 µg cloprostenol (PGF; Cropromate-C; Dainippon Sumitomo Pharmaceuticals, Osaka, Japan) was administered. The donors were artificially inseminated at 60 h after PGF. Embryos were collected nonsurgically 6 days after estrus. Walking activity and duration of standing estrus were compared in the SOV and Natural groups. Data were analyzed by t-test (walking activity) and regression analysis. There were no differences between the Natural and SOV groups for the endpoints measured. Mean CL number was 15.7 ± 6.9, mean number of recovered ova/embryos was 10.3 ± 9.9, and mean number of normal (IETS grades 1 and 2) embryos was 6.9 ± 7.1. A significant (P &lt; 0.02) correlation was found between the number of CL and the duration of estrus (r = 0.7). Data suggest that walking activity at estrus did not differ between superstimulated Japanese black cattle and those experiencing a natural estrus. However, superovulatory response appears to be related to the duration of estrous behavior. Table 1. Walking activity at estrus of SOV and Natural groups