Dietary nitrate and presence of protozoa increase nitrate and nitrite reduction in the rumen of sheep.
J Anim Physiol Anim Nutr (Berl)
; 104(5): 1242-1255, 2020 Sep.
Article
em En
| MEDLINE
| ID: mdl-32333622
ABSTRACT
Nitrate ( NO 3 - ) supplementation is an effective methane (CH4 ) mitigation strategy for ruminants but may produce nitrite ( NO 2 - ) toxicity. It has been reported that rumen protozoa have greater ability for NO 3 - and NO 2 - reduction than bacteria. It was hypothesised that the absence of ruminal protozoa in sheep may lead to higher NO 2 - accumulation in the rumen and a higher blood methaemoglobin (MetHb) concentration. An in vivo experiment was conducted with defaunated (DEF) and faunated (FAU) sheep supplemented with 1.8% NO 3 - in DM. The effects of rumen protozoa on concentrations of plasma and ruminal NO 3 - and NO 2 - , blood MetHb, ruminal volatile fatty acid (VFA) and ruminal ammonia (NH3 ) were investigated. Subsequently, two in vitro experiments were conducted to determine the contribution of protozoa to NO 3 - and NO 2 - reduction rates in DEF and FAU whole rumen digesta (WRD) and its liquid (LIQ) and solid (SOL) fractions, incubated alone (CON), with the addition of NO 3 - or with the addition of NO 2 - . The results from the in vivo experiment showed no differences in total VFA concentrations, although ruminal NH3 was greater (p < .01) in FAU sheep. Ruminal NO 3 - , NO 2 - and plasma NO 2 - concentrations tended to increase (p < .10) 1.5 hr after feeding in FAU relative to DEF sheep. In vitro results showed that NO 3 - reduction to NH3 was stimulated (p < .01) by incoming NO 3 - in both DEF and FAU relative to CON digesta. However, adding NO 3 - increased (p < .05) the rate of NO 2 - accumulation in the SOL fraction of DEF relative to both fractions of FAU digesta. Results observed in vivo and in vitro suggest that NO 3 - and NO 2 - are more rapidly metabolised in the presence of rumen protozoa. Defaunated sheep may have an increased risk of NO 2 - poisoning due to NO 2 - accumulation in the rumen.
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Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Rúmen
/
Ovinos
/
Dieta
/
Ração Animal
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Nitratos
/
Nitritos
Limite:
Animals
Idioma:
En
Revista:
J Anim Physiol Anim Nutr (Berl)
Assunto da revista:
CIENCIAS DA NUTRICAO
/
FISIOLOGIA
/
MEDICINA VETERINARIA
Ano de publicação:
2020
Tipo de documento:
Article
País de afiliação:
Austrália