Effects of ground flaxseed in swine diets on pig performance and on physical and sensory characteristics and omega-3 fatty acid content of pork. II. Duration of 15% dietary flaxseed

Four barrows and four gilts were assigned to each of five dietary treatments: a control (CO) diet or a 15% flaxseed (FS) diet fed for 7, 14, 21, or 28 d prior to slaughter. Flaxseed treatments did not affect any production or carcass traits (P 0.10). No pork processing problems due to lack of firmness were encountered. Amounts (milligrams/gram of tissue) and percentages of alpha-linolenic acid (ALA [18: 3n-3]), arachidonic acid (AA [20:4n-6]), and eicosapentaenoic acid (EPA [20:5n-3]) increased (P 0.001) in both backfat layers and in kidney (leaf) fat and docosahexaenoic acid (DHA [22:6n-3]) increased (P 0.006) in the middle/inner backfat layer after FS. The effects of dietary FS on fatty acid profiles were maintained in lard and pastry. Alpha-linolenic acid, AA, and EPA increased (P 0.001) and DHA increased (P 0.021) in the raw belly in response to FS; the effect was maintained throughout processing to microwaved bacon. Percentage of oleic acid (OA [18: 1n-9]) decreased (P 0.016) in raw bellies after FS. Alpha-linolenic acid and EPA increased (P 0.001) with duration of FS in longissimus thoracis and liver neutral lipids, polar lipids, and combined lipid fractions, but DHA increased (P 0.004) only in longissimus thoracis polar and combined lipid fractions. Arachidonic acid decreased in the longissimus thoracis polar lipid fractions (P 0.037) and in liver neutral (P 0.01) and combined lipid fractions (P 0.006) with FS. All ALA:AA and EPA:AA ratios increased (P 0.001 to P 0.048) with increased duration of FS (except ALA:AA in pastry [P