Nitrate or nitrite can be ingested or endogenously produced from nitric oxi
de. They can cause intoxication and are of general concern for health becau
se they relate to various diseases. Our goal was to study ontogenetic and n
utritional effects on the nitrate + nitrite (NOx-) status in cattle, partic
ularly calves. NOx- concentration in blood plasma, cerebrospinal fluid, sal
iva, and urine was measured based on nitrate conversion by added nitrate re
ductase to nitrite, which was then determined by the Griess reaction. Conce
ntrations of nitrate were the result of the difference between NOx- and nit
rite 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 leng
ths 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 mea
surable 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 NO
x- decreased postnatally from 600 to 200 mu mol/l at 2 days and to 25 mu mo
l/l at 4 weeks. Urinary NOx- excretion decreased from 125 or 16 mu mol/l pe
r 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 in
take by 24 h after birth or feeding at different feeding intensity had no e
ffect on the NOx- status. In conclusion, the high plasma, salivary and urin
ary NOx- concentrations especially in newborn calves, ingesting but insigni
ficant amounts of nitrite or nitrate, indicated marked endogenous formation
of nitrate, which decreased with age. The high nitrate status may contribu
te to enhanced susceptibility of young calves to exogenous nitrite + nitrit
e ingestion. (C) 2001 Elsevier Science Inc. All rights reserved.