The anaerobic reduction of 1 mole of nitrate to ammonia consumes 8 moles of hydrogen and is thermodynamically more favourable than methanogenesis, which also consumes 8 moles of H2. Nitrate may therefore function as an alternative hydrogen sink to enteric methanogenesis when fed to ruminants. The ammonia generated can be utilized for microbial growth in diets low in crude protein. The aim of this experiment was to evaluate the methane mitigating effect of a dietary nitrate source and the persistency of this effect when this nitrate source is fed to dairy cows. Besides effects on methane production, the effects on animal performance and health were also monitored. Twenty lactating Holstein-Friesian dairy cows (milk production 33.2 + 6.0 kg/day; 104 + 58 DIM) were paired according to parity, milk production and lactation stage. Within a pair, cows were randomly allotted to one of two maize silage based diets containing either urea or nitrate (1.2 and 2.2% of diet DM, respectively) as non-protein nitrogen sources. Diets were formulated to be iso-nitrogenous. Cows were adapted to the diets for a period of 4 wks. During this adaptation period the concentrates containing the non-protein nitrogen sources gradually replaced a soybean meal based concentrate (25% per wk). After the adaptation period, cows were housed in indirect calorimetry respiration chambers for a period of 5 d to monitor methane production and animal performance. During the period in the chambers, animals were fed restrictedly (95% of ad libitum DMI) to avoid treatment effects on DMI and hence indirect effects on methane production. The measurement periods were repeated 3 times with 23-d intervals. Cows were kept on the same diets during the entire experiment. Nitrate intake averaged 398 g/day for the cows on the nitrate treatment. Methane production was reduced by 16% (P =0.009) in the nitrate-fed cows and this reduction was not affected by time (treatment*time interaction P=0.961), indicating that the methane reducing effect was persistent over a 4-month period. Milk production was unaffected by treatment (P= 0.452), but milk protein content was lower (P=0.041) for the nitrate-fed animals. Methemoglobin concentrations in blood were elevated (4.0% of Hb) in the nitrate-fed animals relative to the control (0.4% of Hb), but animals displayed no clinical signs of methemoglobinemia. Dietary inclusion of nitrate may be a useful tool to persistently lower enteric methane emissions from dairy cows.
|Title of host publication||Proceedings of the 4th international conference on greenhouse gases and animal agriculture, Banff, Canada, 3-8 October, 2010|
|Place of Publication||Banff|
|Publisher||Greenhouse Gases and Animal Agriculture|
|Publication status||Published - 2010|
|Event||4th international conference on greenhouse gases and animal agriculture, Banff, Canada - |
Duration: 3 Oct 2010 → 8 Oct 2010
|Conference||4th international conference on greenhouse gases and animal agriculture, Banff, Canada|
|Period||3/10/10 → 8/10/10|
van Zijderveld, S. M., Dijkstra, J., Gerrits, W. J. J., Newbold, J. R., & Perdok, H. B. (2010). Dietary nitrate persistently reduces enteric methane production in lactating dairy cows. In Proceedings of the 4th international conference on greenhouse gases and animal agriculture, Banff, Canada, 3-8 October, 2010 (pp. 127-127). Greenhouse Gases and Animal Agriculture.