Changes in methane release from organic matter passing through the digestive tract of horses

Abstract

Using the tests of methanogenic activity (TMA) changes in methane yield (Y_CH4) and anaerobic degradability (D_c) of organic matter of feeds and excrements were studied in an experimental group of six horses while complete analytical methods were applied (N-compound matters, proteins, non-protein N-compound matters, fat, nitrogen-free extract, ash, crude fibre, organic matter, NDF, ADF, hemicelluloses, cellulose, lignin and chemical oxygen demand COD) and the material balance was determined. The horses utilised 48.8% of organic matter of feeds in dry matter while the daily weight of droppings was 21 kg with 5.20% of dry matter and 4 kg of urine with 7% of organic matters. It is important that the theoretical methane yield per 24 hours corresponding to the organic matter of ingested feeds which was transferred to excrements is 1.771 m³ CH₄ at 0°C and 1 013.25 hPa while the actual daily methane yield of droppings is 1.739 m³ CH₄ at 0°C and 1 013.25 hPa, i.e. practically identical, because the yield from urine organic matters was not included in the actual daily methane yield. Because the anaerobic degradability of the used feed mixture and horse droppings is practically identical, it is obvious that besides the enteric fermentation according to the reaction CO₂ + 4 H₂ → CH₄ + 2 H₂O by hydrogenotrophic methanogens no classical anaerobic digestion takes place in the digestive tract of horses; it means that the horse breeding sector is not a factor contaminating the atmosphere by methane.