[Concentration of ammonia in the urine of dairy cows given green feed rations and winter feed rations]

The concentration of ammonia in urine at a known level of energy yielding nutrients offered in feed rations was determined in 987 dairy cows in four summer feeding seasons and 1420 cows in three winter feeding seasons. The long-term average ammonia levels in urine showed no significant variation with the two types of feed rations. Different feed rations in the feeding seasons had no significant influence on ammonia concentration in the urine of lactating cows. On a long term-average as well as in the overwhelming majority of the winter and summer feeding seasons, high-pregnant cows had significantly higher ammonia contents in urine than the cows in the first and second lactation stage. At feeding rations complying with Czechoslovak Standard CSN 46 7070 the content of ammonia in the urine of lactating cows was lower than the recorded long-time averages and averages for individual stages; on the other hand, in high-pregnant cows the ammonia level was higher in both types of feed rations and the difference from lactating cows increased 3.25 times. This suggests that neither do the feed rations currently used in practice nor those strictly adhering to the Czechoslovak Standard meet the biological demand of high-pregnant cows and often lead to the injury of hepatal parenchyma. Ammonia concentration of 11.7 to 58.7 mmol per litre of urine is considered as a tolerable limit.