Dietary nitrate and presence of protozoa increase nitrate and nitrite reduction in the rumen of sheep.

Autor: Villar, María Laura, Hegarty, Roger Stephen, Clay, Jonathon William, Smith, Katherine Anne, Godwin, Ian Robert, Nolan, John Vivian
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Zdroj: Journal of Animal Physiology & Animal Nutrition; Sep2020, Vol. 104 Issue 5, p1242-1255, 14p
Abstrakt: Nitrate (NO3-) supplementation is an effective methane (CH4) mitigation strategy for ruminants but may produce nitrite (NO2-) toxicity. It has been reported that rumen protozoa have greater ability for NO3- and NO2- reduction than bacteria. It was hypothesised that the absence of ruminal protozoa in sheep may lead to higher NO2- 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% NO3- in DM. The effects of rumen protozoa on concentrations of plasma and ruminal NO3- and NO2-, 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 NO3- and NO2- 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 NO3- or with the addition of NO2-. 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 NO3-, NO2- and plasma NO2- concentrations tended to increase (p <.10) 1.5 hr after feeding in FAU relative to DEF sheep. In vitro results showed that NO3- reduction to NH3 was stimulated (p <.01) by incoming NO3- in both DEF and FAU relative to CON digesta. However, adding NO3- increased (p <.05) the rate of NO2- accumulation in the SOL fraction of DEF relative to both fractions of FAU digesta. Results observed in vivo and in vitro suggest that NO3- and NO2- are more rapidly metabolised in the presence of rumen protozoa. Defaunated sheep may have an increased risk of NO2- poisoning due to NO2- accumulation in the rumen. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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