Nitrite as undesirable substances in animal feed ‐ Scientific Opinion of the Panel on Contaminants in the Food Chain

Abstract

SUMMARYNitrite is formed naturally by the nitrogen cycle during the process of nitrogen fixation and it is subsequently converted to nitrate, a major nutrient assimilated by plants. Two main nitrite salt forms occur, namely sodium and potassium nitrite.In animal tissues, nitrite is naturally present mainly as the result of endogenous nitrate conversion. Animal feed represents a natural source of exogenous nitrite and because of its potential for toxicity at excessive levels of intake, the Directive (EC) No 2002/32/EC on undesirable substances in animal feed established maximum limits for sodium nitrite in complete feedingstuffs excluding feedingstuffs intended for pets except birds and aquarium fish, and fish meal of 15 and 60 mg/kg, respectively (corresponding to 10 and 40 mg/kg for the nitrite ion). Nitrite in drinking water is regulated in Europe, with a maximum level of 0.5 mg/L. Nitrate levels in forages are naturally high and the inter-conversion of nitrate to nitrite is the largest contributor to nitrite exposure in food-producing animals. Dietary intake of nitrite per se results from the use of vegetable feeds and forages, fertilisers/manures or when used as an antimicrobial for preservation, for example in silage, processed pet food, and in former times fish meal. Additionally, water can be an important dietary source of nitrite via reduction of nitrate. The main analytical technique used to measure both nitrite and nitrate is colourimetry because of its sensitivity and specificity. Three member states provided analytical results on feedingstuffs and nitrite levels were below the maximum levels in all feed commodities.Acutely, nitrite is approximately ten-fold more toxic than nitrate and three main toxicological endpoints have been identified: methaemoglobin formation (in a wide range of species including man), hypertrophy of the adrenal zona glomerulosa (rats), and equivocal evidence In monogastric animals, most nitrite is formed and absorbed in the upper digestive tract. In contrast in ruminants, nitrite and nitrate is metabolised by the rumen flora. Reports of adverse effects after excessive nitrite exposure in livestock exist, and pigs and ruminants, as major food producing animals, are particularly susceptible: this is because of relatively low nitrite reductase activity and high levels of rumen conversion of exogenous nitrate to nitrite, respectively. Acknowledging diverse husbandry conditions between reported studies, NoObserved Adverse Effect Levels (NOAELs) for pigs and cattle have been estimated from the literature with a value of 3.3 mg/kg b.w. per day in both species. In turn, total daily nitrite intakes were estimated for pigs and cattle using the maximum exposure level in complete feed according to the current legislation (10 mg/kg), typical feeding regimens within the European Union and maximum nitrite level in forages from member states (cattle). Overall, the estimated nitrite intakes for pigs and cattle from feed were 0.37 and 0.65 mg/kg b.w. per day (excluding endogenous formation of n...

Host ecology regulates interspecies recombination in bacteria of the genus Campylobacter

“…In many bacteria, analogs of glmS have multiple downstream integration-specific sites (Tn7) ( Choi and Kim, 2009 ), which may explain the mobility of this gene. Explaining the mobility of napA is less straightforward, but this gene is known to encode a nitrate reductase in Campylobacter ( Pittman et al, 2007 ) in microaerobic conditions, which may be ecologically significant as the accumulation of nitrate in slurry, straw, and drainage water can be potentially toxic to livestock mammals ( Alexander et al, 2009 ).…”

Re‐evaluation of potassium nitrite (E 249) and sodium nitrite (E 250) as food additives

“…The EFSA Scientific Panel on Contaminants in the Food Chain (CONTAM Panel) has produced three opinions relevant to sodium and potassium nitrites (EFSA CONTAM Panel, 2008, 2009b, 2010b.…”

“…milk, meat and eggs) is only (2.9%) of the total daily dietary exposure to nitrite. The CONTAM Panel concluded that 'such low nitrite levels in fresh animal products do not raise any concern for human health' (EFSA CONTAM Panel, 2009b).…”

The antagonism effect of sodium nitrate by ascorbic acid (vitamin C) on neurobehavioral of mice

“…Nitrate poisoning has been recorded in numerous studies (1,2) and it can happen in man and animals (3). Through entero hepatic metabolism of nitrate due to nitrite being an intermediate may cause poisoning of nitrate (4).…”

“…The iron atoms in hemoglobin oxidized by nitrites converted from ferrous (Fe +2 ) to ferric iron (Fe +3 ), which leads to its inability to carry oxygen, this mechanism can lead to which is called methemoglobinemia it is a generalized deficiency of oxygen in organ tissue and a serious case, usually nitrite converts to ammonia, but if there is an increase in nitrite than can be converted, slowly the human and animal suffers from a deficiency of oxygen (5,6). In human nitrate is reduced to nitrite before ingestion in saliva and in the gastrointestinal tract (3,7). In ruminants; cattle, sheep, and goat, the conversion of nitrate to nitrite is carried out by rumen bacteria (7,8).…”