Linseed (Linum usitatissimum L.) is well known for containing functional compounds with health-related benefits. Assessed were the agronomic and seed-quality traits of 13 linseed advanced breeding lines (ABLs) varying in seed mucilage content (SMC) that could be better suited to Chilean environments and food and feed market needs. Analysis of variance revealed highly significant genotype and environment effects for most of the traits assessed. Seed mucilage content ranged from 0.89 to 5.45%, and various ABLs exhibited similar yield and yield-related traits to the controls, but some outperformed them for harvest index, plant height, and days to 5% flowering. The yellow-seeded ABLs showed the highest and lowest oil and hull content, respectively, as compared with the brown-seeded lines. The majority of the ABLs exhibited high linolenic acid content, similar to 60%. The four most promising ABLs were further characterized for the content of the cyanogenic glycosides (CGs) linustatin and neolinustatin, where LuCGNA11 and LuCGNA67 had the lowest values for both CGs. We evaluated the effects of two ABLs contrasting in SMC on laying hen weight (control = 1794 g), egg production (control = 117 eggs), and egg weight (control = 62.9 g) over a 4-wk period. Hens fed the low SMC diet had an increase of 78.6 g, 13 eggs, and 3.86 g, while the high SMC diet had a reduction of 36.8 g, 25 eggs, and 2.8 g for body weight, egg production, and egg weight, respectively. These new high and low SMC ABLs offer opportunities to the food and feed industry for the generation of new value-added products.