Methane and carbon dioxide emissions from manure of dairy cows fed red clover- or corn silage-based diets supplemented with linseed oil

Abstract Text: The objective of this study was to examine the effects of forage source (red clover: RC vs. corn silage: CS) and linseed oil (LO) supplementation of dairy cow diets on CH₄ and CO₂ emissions from manure storage. The diets contained 57% of RC or CS, on dry matter (DM) basis while LO was supplemented at 4% of dietary DM. For this purpose, twelve lactating cows were used in a block design with a 2 × 2 factorial arrangement of treatments. Manure (feces and urine) was collected from each cow on 2 consecutive days, mixed (1:1) with an inoculum from a bioreactor, and stored (at 20°C) under anaerobic conditions in glass bottles (6 replicates/cow) for 17 weeks. Quantity of gas produced was measured daily and sampled to determine gas composition. The MIXED procedure of SAS was used to determine the effects of forage source, LO supplementation and their interaction, and statistical significance was declared at P ≤ 0.05. Interactions between forage source and LO supplementation were not significant (P ≥ 0.16) for the measured variables. Compared to manure from cows fed RC-based diets, manure of cows fed CS-based diets emitted more (P < 0.01) CH₄ (182 vs. 118 L/kg of organic matter, respectively) and CO₂ (134 vs. 91 L/kg of organic matter, respectively). Emissions of CH₄ and CO₂ from manure also increased (P ≤ 0.05) by 15% and 11% for CH₄ and CO₂, respectively, when cows were fed LO-supplemented diets compared to those fed non-supplemented diets. Organic matter losses were higher (P < 0.01) from manure of cows fed CS-based diets compared to manure of cows fed RC-based diets (30.6 vs. 22.5%, respectively). Organic matter losses of manure increased (+ 12%) with the addition of LO to the diets. Thus, it can be concluded that CH₄ and CO₂ emissions and organic matter losses from manure storage are higher if cow are fed CS-based diets compared to RC-based diets, and increase if LO is supplemented to the diet at 4% of dietary DM.

Keywords: Manure, CH₄ emissions, forage source, linseed oil