Simple SummaryPelleting or extrusion have been used in the feed industry to improve nutrient utilization and reduce the load of pathogenic microorganisms. High temperature and high pressure during this process cause loss of heat-sensitive vitamins, such as vitamin K3 (VK3). Encapsulation techniques have been gradually applied to feed additives, which may improve the stability of vitamins. Our previous work has shown that VK3 was the most unstable vitamin during heat processing. Therefore, the aims of this study were to determine the effects of sources, formulations of VK3, extrusion temperature and pelleting parameters on its stability. The results indicate that menadione nicotinamide bisulfite (MNB) is more stable than menadione sodium bisulfite (MSB) during high temperature and high-pressure processing. The micro-capsule/micro-sphere formulation VK3, manufactured through the encapsulation technique, had a higher recovery during pelleting but not during extrusion. Therefore, a reasonable decrease in the intensity of feed processing and choosing a more suitable formulation of VK3 could be a solution for accurate VK3 nutrition, according to current research results.Two studies were conducted to determine the stability of vitamin K3 (VK3) in swine diets during extrusion or pelleting. The two sources were menadione sodium bisulfite (MSB) and menadione nicotinamide bisulfite (MNB), and the three formulations were crystal micro-capsule formulation and micro-sphere formulation. The recovery of six types of VK3 in swine diets was investigated after extrusion at 100 °C or 135 °C in Experiment 1. The recovery of six types of VK3 was investigated when the diets were pelleted at 60 °C (low temperature; LT) or 80 °C (high temperature; HT) and the length to diameter ratios were 5.2:1 (low length to diameter ratio; LR) or 7.2:1 (high length to diameter ratio; HR) in Experiment 2. In Experiment 1, MNB recovery (72.74%) was higher than MSB recovery (64.67%) after extrusion, while recovery of VK3 of crystal (74.16%) was higher than the recovery of micro-capsule (65.25%) and micro-sphere (66.72%). The recovery of VK3 (70.88%) was higher when extruded at 100 °C than that at 135 °C (66.54%). In Experiment 2, MNB recovery (86.21%) was higher than MSB recovery (75.49%) after pelleting, while the recovery of VK3 of micro-capsule (85.06%) was higher than the recovery of crystal (81.40%) and micro-sphere (76.09%). The recovery of VK3 (75.50%) was lower after HTHR pelleting than LTLR (83.62%), LTHR (81.52%) or HTLR (82.76%) treatment. Our results show that MNB has greater stability than MSB. VK3 of crystal or VK3 of micro-capsule were recommended for extrusion or pelleting, respectively.