High constitutional nitrate status in young cattle

Nitrate or nitrite can be ingested or endogenously produced from nitric oxide. They can cause intoxication and are of general concern for health because they relate to various diseases. Our goal was to study ontogenetic and nutritional effects on the nitrate + nitrite (NOx-) status in cattle, particularly calves. NOx- concentration in blood plasma, cerebrospinal fluid, saliva, and urine was measured based on nitrate conversion by added nitrate reductase to nitrite, which was then determined by the Griess reaction. Concentrations of nitrate were the result of the difference between NOx- and nitrite values. Nitrate in blood plasma, saliva and urine was greater than or equal to 97% and in cerebrospinal fluid of calves was approximately 35% of NOx-. Preprandial plasma NOx- in calves born after shortened or normal lengths of pregnancy (277 and 290 days) was 470 and 830 mu mol/l, respectively, decreased within 4-7 days to 40-60 mu mol/l, remained in this range up to 4 months, was less than or equal to 5 mu mol/l in heifers and no longer measurable in 3-8-year-old cows. Cerebrospinal NOx- in 8-day-old calves was 14 mu mol/l and approximately 11-fold lower than in blood plasma. Salivary NOx- decreased postnatally from 600 to 200 mu mol/l at 2 days and to 25 mu mol/l at 4 weeks. Urinary NOx- excretion decreased from 125 or 16 mu mol/l per kg X 24 h in 5-day-old calves to 45 or 8 mu mol/kg X 24 h between 10 and 115 days of life and was undetectable in urine of heifers and cows. Feeding neonatal calves no or variable amounts of colostrum, delaying colostrum intake by 24 h after birth or feeding at different feeding intensity had no effect on the NOx- status. In conclusion, the high plasma, salivary and urinary NOx- concentrations especially in newborn calves, ingesting but insignificant amounts of nitrite or nitrate, indicated marked endogenous formation of nitrate, which decreased with age. The high nitrate status may contribute to enhanced susceptibility of young calves to exogenous nitrite + nitrite ingestion. (C) 2001 Elsevier Science Inc. All rights reserved.