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

• Published in: Annals of animal science Vol. 22; no. 3; pp. 1015 - 1026
• Main Authors: Sharifi, Majid, Taghizadeh, Akbar, Hosseinkhani, Ali, Palangi, Valiollah, Macit, Muhlis, Salem, Abdelfattah Z. M., Elghndour, Mona M.M.Y., Abachi, Soheila
• Format: Journal Article
• Language: English
• Published: Kraków Sciendo 01.07.2022; De Gruyter Poland
• Subjects: Acetic acid; Ammonia; Animal fat; Cattle; Chemical composition; Dairy cattle; dairy cows; Diet; Dry matter; Emission analysis; Emissions control; Factorial design; Fatty acids; Feed additives; Fermentation; Flora; Forage; Lactose; Metabolites; Methane; Methanotrophic bacteria; methanotrophs; microbiota; Microorganisms; Milk; Milk production; milk yield; nitrate; Nitrates; Oxidation; Propionic acid; Rumen; ruminal fermentation; Urea; Volatile fatty acids
• ISSN: 2300-8733; 1642-3402; 2300-8733
• DOI: 10.2478/aoas-2021-0087

Modifying the chemical composition of a diet can be a good strategy for reducing methane emission in the rumen. However, this strategy can have adverse effects on the ruminal microbial flora. The aim of our study was to reduce methane without disturbing ruminal function by stimulating the growth and propagation of methanotrophs. In this study, we randomly divided twenty multiparous Holstein dairy cows into 4 groups in a 2×2 factorial design with two forage levels (40% and 60%) and two nitrate supplementation levels (3.5% and zero). We examined the effect of experimental diets on cow performance, ruminal fermentation, blood metabolites and changes of ruminal microbial flora throughout the experimental period (45-day). Additionally, methane emission was evaluated. Animals fed diet with 60% forage had greater dry matter intake (DMI) and milk fat content, but lower lactose and milk urea content compared with those fed 40% forage diet. Moreover, nitrate supplementation had no significant effect on DMI and milk yield. Furthermore, the interactions showed that nitrate reduces DMI and milk fat independently of forage levels. Our findings showed that nitrate can increase ammonia concentration, pH, nitrite, and acetate while reducing the total volatile fatty acids concentration, propionate, and butyrate in the rumen. With increasing nitrate, methane emission was considerably decreased possibly due to the stimulated growth of , , type II Methanotrophs, and , especially with high forage level. Overall, nitrate supplementation could potentially increase methane oxidizing microorganisms without adversely affecting cattle performance.