Optimizing Flaxseed Oilcake Yield and Nutritional Quality Through Sowing Density and Fertilization Management

Flaxseed oilcake, the by-product of oil extraction, has potential as a feed ingredient. The effect of agronomical practices on the oilcake remains limited. This study evaluated the effect of sowing density and type of fertilizer on oilcake yield and nutritional value. A two-year field experiment was conducted in a split-plot design with two sowing densities (500 and 300 plants m−2) and four fertilization treatments: control, urea, urea with urease and nitrification inhibitors, and an organic fertilizer (compost and tomato pomace). Oilcake was obtained by cold pressing and analyzed for dry matter, ash, crude protein, fat, crude fiber, neutral detergent fiber (NDF), and acid detergent fiber (ADF), while feeding indices were estimated using predictive equations. Year did not affect any trait, whereas the interaction between sowing density and fertilizer type affected most traits. Urea with inhibitors produced the highest oilcake yield at the low density (42% higher than the control), whereas at the high density it did not differ from the control. Fertilization increased protein content by 5–12%, while urea with inhibitors increased ash and, under high density, produced the highest protein and fat contents, but also increased NDF. Crop management thus affected both the quantity and composition of flaxseed oilcake, with trade-offs between yield and compositional traits.