N-fertilization of tropical pastures improves performance but not methane emission of Nellore growing bulls

Author(s)

Lima, Lais de Oliveira ; Ongaratto, Fernando ; Dallantonia, Erick Escobar ; Leite, Rhaony Goncalves ; Argentini, Gabriella Patricio ; Fernandes, Marcia Helena Machado da Rocha ; Reis, Ricardo Andrade ; Vyas, Diwakar ; Malheiros, Euclides Braga

• Document type: Journal article
• Source: JOURNAL OF ANIMAL SCIENCE; v. 101, p. 8-pg., 2023-01-03.

Abstract

Grazing management and N-fertilizer have been reported to improve tropical forage productivity and quality, however, their effect on methane emission of grazing animals remains uncertain. Therefore, this study aimed to assess the effects of increasing application rates of nitrogen (N) fertilization of Marandu palisadegrass under continuous stocking on intake, digestibility, nitrogen balance, and enteric methane emissions of Nellore growing bulls. We hypothesized that changes in the forage nutritive value caused by N fertilization of pastures combined with adequate grazing management (e.g., greater crude protein [CP] and digestibility) would lead to an increase in animal productivity (e.g., greater average daily gain [ADG] and gain per area), and then, to a decrease in methane emission intensity. Treatments consisted of different annual application rates of nitrogen fertilization: 0, 75, and 150 kg N/ha using ammonium nitrate (32% N) as the nitrogen source. The experimental design was completely randomized, with three treatments and four replications (12 paddocks). Intake, digestibility, N balance, and methane emissions were measured in eight animals per treatment. CP intake, digestibility and N balance increased linearly with the increase in N fertilization (P < 0.05). In addition, stocking rate (SR) and ADG linearly increased from 1.75 animal unit (AU = 450 kg)/ha and 0.62 kg/d (0 kg N/ha) to 3.75 AU/ha and 0.82 kg/d (150 kg N/ha), respectively. Individual methane emissions nor methane emission intensity were affected by treatment with an average of 164.7 g/d and 199.7 g/kg ADG (P > 0.05). Annual N fertilization with ammonium nitrate between 75 and 150 kg N/ha in palisadegrass pastures under continuous stocking enhances animal performance per unit area yet not affecting neither methane production nor intensity. Lay Summary The availability of nitrogen in the soil is one of the main factors that can affect plant growth and characteristics. Nitrogen fertilization is a tool to increase the efficiency in the productive responses of grazing beef cattle, reconciling the greater production per area, reduction of the production cycle, maximization of the use of nutrients, with the maintenance of the system sustainability by enhancing animal production indexes. The present study evaluated performance and methane production of Nellore growing bulls grazing continuously stocked Marandu palisadegrass fertilized with three rates of ammonium nitrate (0, 75, and 150 kg N/ha). Although nitrogen fertilization did not affect individual methane production, both stocking rate and average daily gain linearly increased as fertilization rate increased, thus increasing the beef productivity. Nitogen fertilization of marandu pastures improves grazing beef cattle performance but not affects individual methane emissions. (AU)

• FAPESP's process: 18/26492-0 - Environmental and productive impact of the process of intensification of the of growth and finishing phase of beef cattle managed in marandu grass
• Grantee: Laís de Oliveira Lima
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 17/18750-7 - Impact of sustainable intensification of beef production in tropical areas on climate change mitigation
• Grantee: Márcia Helena Machado da Rocha Fernandes
• Support Opportunities: Regular Research Grants