0023-6152

AA00697606

24013

査読無

0023-6152

AA00697606

Behavioural observation was made on a herd of 6 dehorned Japanese Black Cows and their calves during 3 consecutive days (0900-1700 h, exclusive of 1500-1530 h) to investigate the cow-calf relationships and the social interactions between cows within the herd when kept together in a dry-lot. The intensive nursing incidents and maternal lickings occurred between 0900 and 1000 h and between 1530 and 1700 h. It appeared that such a relatively high-level behavioural synchronization was related to feed delivery time. The average number of nursing events per cow was 5.1; the average time spent nursing 32.2 min; the average nursing time per bout 7.9 min and the average number of maternal lickings 10.4. Older calves suckled less frequently, spent relatively less time suckling and more suckling time per bout. Dams of older calves also licked their own calves less frequently. Cows had a significantly higher frequency of lickings toward their own calves than that toward other cows (P=O.O5). A total of 35 interruptions of nursing (vs 92 nursing events) induced by agonistic encounters between dams ujas observed. Interrupted nursing occurred more frequently between 1400 and 1500 h. There was a close negative association between social order and the number of interrupted nursings (r=-0.966, P <O.Ol), suggesting that cows lower in the order suffered more interruptions of nursing and their calves were in relatively stressful condition.