Effet de l'incorporation à la ration de bromure de Potassium sur les comportements de repos et de chevauchement de taurillons culards en stabulation libre.

A high incidence of broken legs being observed in a fattening unit, the farmer decided to feed the animals with a concentrate containin 2 kg/T of potassium bromide. This compound was supposed to quiet the animals. Broken legs were indeed occuring after mounting activities. Two groups of 7 fattening bulls were observed in adjacent pens in a littered loose house. One group was fed with a control diet and the other with the KBr supplemented diet. Resting and mounting behaviours were recorded, using a video equipment, before (period 1), 4 days (period 2) and 4 months (period 3) after the beginning of the experiment. Observations were performed during 3 days in periods 1 and 2 and during 5 days in period 3. The mean percentage of lying time was 63%. 'The difference between groups was not significant. The mean numbers of standing bouts per 24 h were 18, 20 and 15 during the 3 periods respectively. The difference between periods 2 and 3 was significant but not between the two goups. Peaks of mounting activity were observed during the two feeding periods and one occured during the night. The incidence of mounting behaviour was very different from day to day. Treatment with potassium bromide had no effect on this behaviour. For example, in period 3, mounting occured 13.1 +- 9. 1 and 9.5 +- 11.3 times per animal and per day, respectively with the two groups. No broken leg was observed in the stable during the 4 months from period 1 to period 3.