Dietary fat effects on egg yolk lipid composition and hepatic lipogenic enzymes

Menhaden oil, corn oil, olive oil or animal fat (1, 3, 5 or 8% of diet) effects on egg yolk fatty acids and hepatic lipogenic enzymes were studied in 35 week-old laying hens. Except for significantly lowered egg weights by menhaden oil, performance was unaffected. Yolk saturated fat remained constant (33-38% of yolk fat) regardless of fat source. Maximum o-3 fatty acid incorporation (.31 g/yolk) was reached with a deposition efficiency of 36.3% by feeding 5% menhaden oil. Yolk lipid contained.3% linolenic (C18:3o3), 1.0% eicosapentaenoic (C20:5o3), and 3.8% docosapentaenoic (C22: 5o3) acids. Maximum o-6 fatty acid incorporation (1.65 g/yolk) occurred with 17% efficiency when 8% corn oil was fed, primarily by increasing linoleic acid to 25.5%. Yolk oleate was inversely related to dietary linoleate. Only the highest menhaden oil levels significantly affected lipogenic enzymes: fatty acid synthetase and ATP citrate lyase (EC 4.1.3.8) activities were inhibited, while glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity was 2-3 times that of hens fed the basal diet. Malic enzyme (EC 1.1.1.40) activity was not significantly influence by dietary fat