Estrous detection in dairy cows using a multiple pedometer reading system in a freestall barn

牛群の繁殖成績を向上させるためには発情発見率を高め適期での授精が不可欠である。本発情発見システムは,牛舎内の横断通路等に活動量データ収集用のアンテナを設置し,乳牛がこの上を通過する毎に活動量を収集する方式である。フリーストール牛舎における試験では,供試牛延べ47頭のうち44頭で活動量が増加し,このうち正常発情牛は41頭であった。各乳牛の積算活動量は直線的に変化し,マウンティングおよびスタンディングの発情行動出現時には急激に増加した。発情行動終了後はもとの直線の傾きで変化した。1時間あたりの平均活動量は,非発情時で5.2カウント/hで発情時に23.0カウント/hとなり,非発情時の4.4倍となった。活動量の増加出現時間は平均約12.7時間で,スタンディングおよび,マウンティングはこの時間内でみられた。排卵は活動量の増加から平均で28.5時間後に発生した。これらのことから,頻回収集システムでは発情行動出現にともなう活動量の増加をほぼ確定でき,授精適期は活動量の増加開始から4〜24時間の範囲となった。さらに,1 時間あたりの活動量の変化には日変化はなく,発情行動出現時と非発情時とを明確に区分できる閾値の設定が可能であることが明らかとなった。この発情発見システムを用いて,搾乳ロボット牛舎において発情発見状況を検討したところ,発情検出率(発情牛のうち何%検出できたか)は91.4%で,発情発見精度(発情と判定したうち,何%の牛が真の発情であったか)は83.5%と非常に高いシステムであった。An important factor in obtaining high levels of pregnancy in dairy cows is to accurately detect estrous in order to inseminate at the optimal time. The present study installed in a freestall barn an estrous detection system for dairy cows that utilizes pedometer reading antennas (e.g., in the cross alleys) that read the number of steps when cows walk passed them. The system can read the pedometer data produced by voluntary cow movement. Data from all 47 cows housed in our old freestall barn were analyzed in the study. An increase in pedometer readings occurred in 44 cows, of which 41 showed normal estrous cycle. During non-estrous, all additional integration of pedometer readings showed changes in a straight line, while during estrous a dramatic increase in pedometer readings occurred. Further, the average number of steps during non-estrous was 5.2 counts per hour, but was increased during estrous, to 23.0 counts per hour. Cows were about 4.4 times as active during estrous as they were during non-estrous. The duration of increased walking activity occurs for approximately 12.7 hours on average, and standing and/or mounting behavior was observed during this period. Ovulation was defined as occurring 28.5 hours after the start of increased walking activity. Using the multiple pedometer reading system, the start time of increased walking activity could be clearly determined, and the optimum time for artificial insemination was defined as between 4 and 24 hours after this time. Further, while there is no diurnal rhythm in the number of steps per hour, there is a clear threshold level easily separating the number of steps in estrous and non-estrous. Testing of this estrous detection system in our robot milking freestall barn showed very high system efficiency for estrous detection at 91.4%, and very high system accuracy at 83.5%