Evaluation of Greenhouse Gas Emissions from the Excreta of Steers Supplemented with Afiber®

Abstract

The study of dietary additives to mitigate enteric methane (CH₄) emissions has progressed in recent years; however, it is still necessary to evaluate their overall effects, including emissions derived from excreta. In this context, the traditional nutritional management of feedlot steers was compared with a high-energy, low-forage fiber corral diet for growing Holstein steers, and an alternative single-pellet diet with high non-forage fiber content (Afiber®), supplemented with tannins (0.15% DM) and ruminal buffers (1.0% DM). Afiber® has shown reductions in enteric CH₄ emissions of approximately 20%.

Emissions of CH₄, carbon dioxide (CO₂), and nitrous oxide (N₂O) from the feces of animals with or without Afiber® were evaluated. Fresh excreta were applied to the soil inside static chambers (n = 7; 1 control without feces and 3 per treatment), with 1 kg of fresh matter per chamber. Gas emissions were monitored throughout a 60-day period.

Although differences in temporal dynamics were observed (such as a second N₂O peak in the control treatment), no significant differences were found between treatments in emission rate, cumulative emission, or emission factors for CH₄, N₂O, or CO₂. The average emission factor for CH₄ was 1.37 ± 0.92 kg CH₄.kg⁻¹ VS, and for N2O it was 0.03 ± 0.01 kg N₂O-N.kg⁻¹ N applied, which are similar to the values reported by the IPCC for dry-lot systems.

In conclusion, the Afiber® additive influenced the dynamics of N₂O, although it did not significantly alter the total gas emissions from the excreta. These results highlight the importance of evaluating additives comprehensively, considering both enteric emissions and those generated by manure.