Effect of Oats Grain Inclusion as a Main Source of Crude Fibre in Wheat–Barley and Rye-Based Diets for Growing–Finishing Pigs

Dietary fibre is important for gastrointestinal health and feed efficiency in pigs, but alternative fibre sources, particularly in high-rye diets, require further evaluation. This study examined the effects of rye and oat inclusion on growth performance, carcass characteristics, and economic efficiency in growing–finishing pigs. A total of 920 DanBred fattening pigs were allocated to four dietary treatments: wheat− and barley-based control (CON), control + 10% oats (CON + O), rye-based diet with 30% rye in the grower diet and 60% in the finisher diet (RYE), and RYE + 10% oats (RYE + O). During the grower phase, rye significantly increased daily weight gain, whereas oat supplementation to the rye-based diet significantly reduced feed intake and weight gain. During the finisher phase, oat supplementation significantly increased daily weight gain in both dietary groups and improved feed conversion in pigs receiving the rye-based diet. Over the entire fattening period, oat-supplemented groups had significantly higher weight gain, while RYE + O had lower feed intake and feed conversion than RYE. Rye-containing diets produced significantly leaner carcasses, and oat supplementation in the rye-based diet reduced backfat thickness. RYE + O resulted in the lowest cost of weight gain and higher average simplified profit per pig. These findings indicate that the combination of rye inclusion and oat supplementation had phase-dependent effects and may have improved production efficiency and economic outcomes.