Long-Term Encapsulated Nitrate Supplementation Modulates Rumen Microbial Diversity and Rumen Fermentation to Reduce Methane Emission in Grazing Steers

Author(s)

Granja-Salcedo, Yury Tatiana ^[1] ; Fernandes, Rodolfo Maciel ^{[1, 2]} ; de Araujo, Rafael Canonenco ^[3] ; Kishi, Luciano Takeshi ^[4] ; Berchielli, Telma Teresinha ^{[1, 5]} ; de Resende, Flavio Dutra ^{[1, 2]} ; Berndt, Alexandre ^[6] ; Siqueira, Gustavo Rezende ^{[1, 2]}

Affiliation

^[1] Univ Estadual Paulista, UNESP, Fac Ciencias Agr & Vet, Dept Anim Sci, Jaboticabal - Brazil

^[2] Agencia Paulista Tecnol Agronegocios, Dept Anim Sci, Colin - Brazil

^[3] GRASP Ind & Com LTDA, Curitiba, Parana - Brazil

^[4] Univ Estadual Paulista, UNESP, Fac Ciencias Agr & Vet, Dept Technol, Jaboticabal - Brazil

^[5] INCT CA UFV, Dept Anim Sci, Vicosa, MG - Brazil

^[6] Embrapa Southeast Livestock, Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: FRONTIERS IN MICROBIOLOGY; v. 10, MAR 29 2019.
• Web of Science Citations: 1

Abstract

This study investigated the long-term effects (13 months) of encapsulated nitrate supplementation (ENS) on enteric methane emissions, rumen fermentation parameters, ruminal bacteria, and diversity of archaea in grazing beef cattle. We used a total of thirty-two Nellore steers (initial BW of 197 +/- 15.3 kg), 12 of which were fitted with rumen cannulas. For 13 months, the animals were maintained in 12 paddocks and fed a concentrate of ground corn, soybean meals, mineral supplements, and urea (URS) or encapsulated nitrate (EN) containing 70 g of EN/100 kg of BW (corresponding to 47 g NO3-/100 kg BW). Encapsulated nitrate supplementation resulted in similar forage, supplement and total DMI values as URS (P > 0.05), but ENS tended to increase (+48 g/d; P = 0.055) average daily weight gain. Daily reductions in methane emissions (-9.54 g or 18.5%) were observed with ENS when expressed as g of CH4/kg of forage dry matter intake (fDMI) (P = 0.037). Lower concentrations of NH3-N and a higher ruminal pH were observed in ENS groups 6 h after supplementation (P < 0.05). Total VFA rumen concentration 6 h (P = 0.009) and 12 h after supplementation with EN resulted in lower acetate concentrations in the rumen (P = 0.041). Steers supplemented with EN had a greater ruminal abundance of Bacteroides, Barnesiella, Lactobacillus, Selenomonas, Veillonella, Succinimonas, Succinivibrio, and Duganella sp. (P < 0.05), but a lower abundance of Methanobrevibacter sp. (P = 0.007). Strong negative correlations were found between daily methane emissions and Proteobacteria, Erysipelotrichaceae, Prevotellaceae, and Roseburia, Kandleria, Selenomonas, Veillonella, and Succinivibrio sp. (P < 0.05) in the rumen of ENS steers. Encapsulated nitrate is a feed additive that persistently affects enteric methane emission in grazing steers, thereby decreasing Methanobrevibacter abundance in the rumen. In addition, ENS can promote fumarate-reducer and lactate-producer bacteria, thereby reducing acetate production during rumen fermentation. (AU)

• FAPESP's process: 17/02034-0 - Degradation and in situ ruminal microbial dynamics of different sources of protein for beef cattle
• Grantee: Yury Tatiana Granja Salcedo
• Support Opportunities: Scholarships in Brazil - Post-Doctoral