Assessment of the Impact of Coffee Waste as an Alternative Feed Supplementation on Rumen Fermentation and Methane Emissions in an In Vitro Study

Spent coffee waste is the most common by-product of coffee processing, and it has the potential to be used as a source of organic compounds for ruminant diets. The objective of this study was to evaluate the optimal inclusion level and method for using spent coffee waste (SCW) as a ruminant feed and investigate its effects on rumen fermentation characteristics and methane (CH₄) production. The present in vitro batch culture study was conducted using two different experimental designs. The first experimental design (TRIAL. 1) was performed using a control diet of 500 mg of fresh matter basal diet (60% hay/40% concentrate), with SCW being used as a feed additive at 1%, 10% and 20% of the substrate. The second experimental design was performed using the same control diet, with spent coffee waste replacing either part of the hay (TRIAL. 2) or some of the concentrate mixture (TRIAL. 3) at four different dosages (30:70, 50:50, 70:30 and 100). When SCW was supplemented as a feed additive, there were increases in the production of volatile fatty acids and gas; however, it did not show any suppressive effects on CH₄ production. In contrast, when SCW was included as a replacement for hay or concentrate, there were significant reductions in CH₄ production with increasing levels of SCW inclusion. These reductions in CH₄ production were accompanied by negative effects on nutrient digestibility and total volatile fatty acid production. These findings demonstrate that SCW could potentially be used as a prebiotic feed additive. Additionally, when SCW is used as a replacement for silage at 70:30 and 50:50 dosages appear to be feasible as a substitute for animal feed (hay and concentrate).