Abstract
To clarify the significance of milk-ammonia levels in dairy-herd health surveillance, ammonia, creatinine, and urea (MUN) levels were determined in 291 milk samples and 26 colostrum samples taken from186 lactating cows. The milk ammonia-N level was 1.4±9 ppm (mean±SD), nearly the sameas previously reported blood ammonia-N levels. The colostrum ammonia-N level, however, was much higher (11.4±6.7 ppm). Higher ammonia levels were observed in some samples thereafter. The colostrum creatinine-N level (14.4±1.6 ppm) was slightly higher than that of milk samples (13.0±1.2 ppm). Great fluctuation occurred in MUN levels at all lactation stages. Positive relations were observed between ammonia levels and creatinine or MUN levels in colostrum samples.
