[Red discolouration of the urine in a dairy cattle herd as a stock problem].

After feeding a new batch of rapeseed meal (2.5 kg/cow/day) in the total mixed ration (TMR) of dairy cows on a dairy farm in Bavaria, numerous puddles of reddish fluid were found on the floor of the cubicle housing system. These were caused by a red discolouration of the urine. Directly after urination, the urine was macroscopically yellow and bright; the discolouration developed throughout the consecutive hours. Feed intake was markedly decreased and milk yield was lowered by 10%. No disturbances of the general health and blood key parameters were evident. After feeding two other cows with rapeseed meal of this batch (three times daily 1 kg each), the phenomenon occurred in one animal on the third and fourth days. Further analyses revealed evidence that the discolouration was due to substances which were excreted via the kidney and led to reddish urine after delayed reaction with the oxygen in the air.