Estimating enteric methane emissions from smallholder dairy cows under seasonal and agro-ecological variations in feed digestibility in Kenya

Abstract

In Sub-Saharan Africa, national greenhouse gas (GHG) inventories are computed with non-country specific Emission Factors (EF) of the Intergovernmental Panel on Climate Change (IPCC) Tier I approach. An alternative is Tier II or Tier III approach, which is country-specific using detailed animal performance and feed characteristics data and more accurate EF for developing Nationally Appropriate Mitigation Actions (NAMAs) and Low Emission Development Strategies (LEDS).This study sought to provide improved EF with data from a typical African livestock system sampled in Nandi County in Kenya. The EF were computed from methane production based on animal performance measurements using a sample of 487cows in 127 households across 36 villages spread over three major agro-ecological zones (AEZs). The cows were monitored for a period of one years. The mean EF estimate was50.6kg CH4/head/year for dairy cows (>2yrs), and was 23.4% higher than the IPCC Tier I estimates for unspecified African adult cattle. The dry matter digestibility (DMD) of feeds across the AEZs and seasons (60.0 – 68.4%) were not different and but the daily methane production (DMP) across the AEZs and seasons were significantly different (p<0.001 and p<0.001 respectively), which suggest that AEZs and seasons have influence on enteric methane emissions. The study showed that an increase in DMD caused a decrease in DMP (r=-0.06) implying that DMD across AEZs and seasons affected DMP. Daily methane production increased with increase in milk yield. This influence was because of energy required for high milk production associated with dry matter intake (DMI) where an increase in DMI caused an increase in DMP. The use of IPCC Tier IEFs to develop Kenya’s national inventory for enteric methane emissions from livestock sector can lead to high uncertainties hence similar research is needed to develop emission factors for other livestock systems in other AEZs. Feeding management that includes high digestible feeds will lead to reduced enteric methane emissions and improved production with lower emission intensities associated with dairy farming.