Nitrate supplementation at two forage levels in dairy cows feeding: milk production and composition, fatty acid profiles, blood metabolites, ruminal fermentation, and hydrogen sink

Abstract

Nitrate may reduce the ruminal methane emission by competing methanogenesis to achieve more hydrogen. For this purpose, twenty Holstein lactating cows were examined using a 2×2 factorial design in 4 groups for 60 days with two forage levels (40% and 60%) and supplemental nitrate 0% (F40 and F60) and 3.5% (F40N and F60N) of diet dry matter (DM). Then, the effect of nitrate and forage levels on cow performance, ruminal fermentation, methane emission, and metabolic hydrogen sink were evaluated. The nitrate supplementation did not significantly affect milk yield and ECM/DMI while, milk urea nitrogen was increased. Lowest quantity of milk vitamins (A and E) was observed in nitrate groups. The nitrate supplementation increased c9-C18:1, unsaturated fatty acids, and n-6/n-3 contents of the milk. Blood parameters were affected by nitrate supplementation. Blood met-Hb concentration was increased, while blood glucose was decreased in nitrate groups. High forage and nitrate fed animals (F60N) had higher ruminal acetate and lower propionate concentration, and higher acetate+butyrate to propionate ratio than other groups. Nitrite and NH3-N concentrations were higher in the rumen of nitrate fed animals. Nitrate supplementation inhibited gas volume and methane emission without affecting volatile fatty acids at 12 and 24 h of incubation. The H2 balance, H2 production and consumption, and recovery percentage were significantly lower in F60N group. In conclusion, nitrate supplementation can be employed as an alternative strategy for improving ruminal fermentation, milk quality and methane inhibition.

Influence of nitrate supplementation on in-vitro methane emission, milk production, ruminal fermentation, and microbial methanotrophs in dairy cows fed at two forage levels

“…In addition to ammonium, changing the VFA profile can indicate changes in rumen fermentation and microbial activity. Similar to our results, an increase in acetate and a decrease in propionate by the nitrate supplementation have been preivusly reported by Hulshof et al (2012), Veneman et al (2015), Zhao et al (2015) and Sharifi et al (2021). Nonetheless, increasing the acetate and reducing the propionate may only illustrate the increase in accumulated hydrogen, not the change in methane production.…”

“…A disruption in NADH oxidation and subsequent reduction in NAD + concentrations have been shown to inhibit microbial fermentation (Hegarty and Gerdes, 1999). Conversely, the reduction in methane production could reduce energy lost through methanogenesis (Latham et al, 2016;Chen et al, 2019;Sharifi et al, 2021). Various studies have investigated the potential of unsaturated fatty acids, nitrate, sulphate, and fumarate as electron acceptors for the methane production reduction in livestock (Zeitz et al, 2013;Latham et al, 2016;Li et al, 2018).…”

“…From a thermodynamic perspective, nitrate has shown to be more effectual among the others (Veneman et al, 2015). On the one hand, converting nitrate to ammonia, is energetically more favorable than converting carbon dioxide to methane (Sharifi et al, 2021). On the other hand, due to the presence of other electron acceptors in the rumen, utilization of nitrate is facing to performance limitation (Hulshof et al, 2012;Clough et al, 2020).…”

Effects of calcium ammonium nitrate fed to dairy cows on nutrient intake and digestibility, milk quality, microbial protein synthesis, and ruminal fermentation parameters

“…Nitrates and NO 2 − are alternative [H] sinks that divert H 2 away from methanogenesis and biohydrogenation, which would explain lower SFA in the present study; however, we are still lacking enough studies validating this hypothesis because of low H 2 dissipation at the expense of ruminal biohydrogenation (Yang et al, 2019). Indeed, similar to our results, Sharifi et al (2021) observed no effects of NO 3 − supplementation to dairy cows on 18:0 proportion, as indicative of biohydrogenation in the rumen. According to Lourenço et al (2010), biohydrogenation could be affected indirectly when other ruminal activities are changed (i.e., CH 4 inhibition), because FA metabolism is strictly dependent on the microbial species that are involved in multiple metabolic processes along with H 2 metabolism.…”

Utilisation of slow-release non-protein nitrogen produced from agro-industrial by-products: feed digestibility and ruminal parameters

“…The agricultural sector contributes to this problem by adding nitrogen to surface waters and the atmosphere (Pavlidis and Tsihrintzis, 2018;Sharifi et al, 2022). A ruminant production system should be ABSTRACT.…”