Improving nutrient utilization in ruminants through extruded pelleted feeds

Abstract

This study examined whether extrusion process can be optimized to produce pellets with tailored density and rumen fluid stability for improved nutrient utilization in ruminants. High-density pellets bypass the rumen to deliver nutrients directly to the intestine, while floating pellets enhance the synchronization of nutrient release and digestion. Barley, maize, and soybean meal (SBM) were extruded both individually and as 50:50 mixtures (barley + SBM and maize + SBM) under different conditions. Specific density (SD), specific density in rumen fluid (SDrf), sinking velocity (SV) and fluid stability index (FSI) of pellets were evaluated using in vitro methods. Pellets exhibited a broad range of SD values: those with an SD below 0.78 g/mL floated in rumen fluid, whereas pellets with an SD above 1.05 g/mL were deemed optimal for rumen escape. Cereal grain pellets spanned floating (SD < 0.78 g/mL), slow-sinking (SD 0.85–0.90 g/mL), and fast-sinking (SD > 0.96 g/mL) categories and showed high FSI (averaged 893 ± 67 g/kg DM), while SBM and mixtures produced high-density (SD 0.89–1.18 g/mL), fast-sinking pellets with lower FSI (averaged 173 ± 113 g/kg DM). For cereal grains, cooling the extruder’s last section at a screw speed of 210 rpm yielded pellets with optimal SD and FSI for rumen escape, whereas adjusting the screw speed (minimum 210 rpm for maize and 300 rpm for barley) produced floating pellets. Pellets from SBM and mixtures did not meet the desired criteria and require alternative processing conditions. Indeed, these in vitro evaluations require in vivo validation.