Effect of dietary nitrate on enteric methane emissions, production performance and rumen fermentation of dairy cows grazing kikuyu-dominant pasture during summer

Abstract

Highlights• Dietary nitrate as methane mitigation strategy for grazing dairy cows • Concentrate DMI and milk yield decreased with nitrate addition • Total DMI was unaffected by treatment • Methane production and yield tended to decrease with nitrate addition • Ruminal pH fluid and total VFA concentration increased with nitrate addition AbstractDietary nitrate supplementation is an effective methane (CH4) mitigation strategy in total mixed ration based diets fed to ruminants. To date, limited information is available on the effect of dietary nitrate on CH4 production from grazing dairy cows. Fifty-four multiparous Jersey cows were subjected to a randomised complete block design (blocked according to milk yield, days in milk and parity) to evaluate the effect of three dietary nitrate levels on enteric CH4 emissions and cow production performance. Additionally, six rumen-cannulated cows in a replicated 3 x 3 Latin square design were used in a rumen study. Dietary treatments consisted of concentrate fed at 5.4 kg of DM/cow per day containing one of three levels of dietary nitrate: 0 g (control), 11 g (low nitrate), and 23 g of nitrate/kg of dry matter (DM; high nitrate). Cows grazed late-summer pasture containing approximately 3 g of nitrate/kg of DM. Concentrates were formulated to be isonitrogenous, by substituting urea, and isoenergetic. Cows were gradually adapted to concentrates over a 3-wk period before the onset of a 57-d experimental period. Enteric CH4 emissions and total dry matter intake (DMI) from 11 cows per treatment were measured during one 6-d measurement period using the sulphur hexafluoride tracer gas technique. Individual pasture DMI was determined using TiO2 and indigestible neutral detergent fibre (NDF). Milk yield decreased by approximately 12% when feeding the high nitrate diet compared with the control and low nitrate diets.Although total DMI was unaffected by treatment, concentrate DMI decreased linearly (5.5 to 3.7 kg/d) while pasture DMI increased linearly (9.1 to 11.4 kg/d) with increasing dietary nitrate addition. Methane production (313 to 280 g/d), CH4 yield (21.8 to 18.7 g/kg of DMI) and CH4 energy per gross energy intake (6.9 to 5.9%) tended to decrease linearly with increasing dietary nitrate addition. Diurnal ruminal pH of the high nitrate group was greater, for selective periods after concentrate feeding, than the control and low nitrate groups. Spot sample ruminal pH (6.2 to 6.3) tended to increase while total volatile fatty acid (VFA) 3 concentration (99.9 to 104 mM/L) increased quadratically with increasing dietary nitrate addition. Individual VFA concentrations were unaffected by treatment. Rate of NDF disappearance (2.4 to 2.8%/h) after 18 h of ruminal incubation tended to increase quadratically with increasing dietary nitrate addition. Dietary nitrate fed to grazing dairy cows tended to decrease CH4 emissions while improving the fibrolytic environment of the rumen. However, when feeding high levels of dietary nitrate a decrease in milk yield could be expected due to a decreas...

Risk assessment of nitrate and nitrite in feed

“…Multiparous Jersey cows (average bw 408 kg) were acclimated for 3 weeks to increased dietary nitrate levels (n = 20), followed by 8 weeks on 0, 11 and 23 g of NO 3 -/kg (DM) corresponding approximately to 0, 150 or 310 mg NO 3 -/kg bw per day, given in concentrate feed (DMI of concentrate 5.4 kg/day). Cows exposed to 314 mg NO 3 -/kg bw per day showed 12% lower milk yield and 13% lower fat milk than the control with no effects observed in the 150 mg/kg bw per day group for milk protein (van Wyngaard et al, 2018). Reduced protein content of milk by 9% was also observed in Jersey cows (default bw average 454 kgsee NRC, 2001) fed diet containing 15 g NO 3 -/kg feed DM (corresponding approximately to 570 mg/kg bw per day with a DMI of 17.2 kg DMI), compared with controls (Meller et al, 2019).…”

Research Progress on Greenhouse Gas Emissions From Livestock in Sub-Saharan Africa Falls Short of National Inventory Ambitions

“…A feeding trial in South Africa using the SF 6 tracer technique found that increasing dietary feed concentrate levels to a basal diet of pasture for exotic purebred (Jersey) cows reduced CH 4 yield by ~14% from the lowest (29.1 g CH 4 kg -1 DMI) to highest concentrate feeding level (25.1 g CH 4 kg -1 DMI) (59). Another study in South Africa found that increasing dietary nitrate levels decreased CH 4 emissions from Jersey cows on seeded pasture diets, with CH 4 yield declining from 21.8 g CH 4 kg -1 DMI in the control diet to 20.1 g CH 4 kg -1 DMI (-8%) for low and 18.7 g CH 4 kg -1 DMI (-14%) for high nitrate feeding levels (60).…”

Mitigation of Enteric Methane Emission through Feed Modification and Rumen Manipulation

“…Perbedaan suhu lingkungan dapat berdampak pada produksi gas metana di manur ternak, yakni secara umum produksi metana dari manure akan meningkat dengan semakin meningkatnya suhu lingkungan (IPCC 2006). Saat musim panas, emisi gas metana enterik pada sapi Jersey di awal laktasi yang digembalakan dan diberi pakan tambahan konsentrat adalah sebesar 280-313 g/ekor/hari (van Wyngaard et al 2018a). Sedangkan saat musim semi sebesar 400-405 g/ekor/hari (van Wyngaard et al 2019).…”