VITAMIN E AND HIGH OR LOW ERUCIC ACID RAPESEED OILS IN BROILER DIETS

Abstract

Regular rapeseed oil (RSO) from rapeseed containing approximately 25% erucic acid (C22:1) and low erucic acid rapeseed oils (LEAR) containing approximately 2.5% C22:1 prepared from the Oro (ORO and hydrogenated Oro oil, HORO) and Span (SPO) varieties of rapeseed were compared against soybean oil (SBO) or lard (LA) in diets for broilers. Two diets were formulated from each oil or fat, one containing no supplementary vitamin E, the other containing 30 mg/kg of supplementary vitamin E. Each ration was fed to two groups of 10 broiler-type chicks from day-old to 8 wk of age. Growth, lipid content and fatty acid composition of heart, liver and spleen tissues and plasma cholesterol levels were studied. Average body weight was highest in the chickens fed the SBO-, LA-, ORO- or HORO-containing diets, intermediate for SPO and lowest for the RSO-containing diet. Inclusion of supplementary vitamin E in the oil or fat-containing diets improved the growth rate in all cases. However, vitamin E status did not appear to be related to the deleterious effects reported with feeding high levels of rapeseed oil. No treatment effects were noted on the total lipid concentrations in heart and liver tissue. The total lipid concentration in the spleen was somewhat higher in chickens fed RSO than in those fed the other oils. RSO led to a relatively high, while LEAR oils led to minimal, tissue incorporation of C22: 1. Erucic acid concentration was highest in adipose tissue (9.2%), followed by breast muscle (6.8%), spleen (5.9%), cardiac tissue (4.8%) and liver (2.6%). Plasma cholesterol concentrations (PC) were highest in the chickens fed the RSO- and SPO-containing diets (122 mg % and 134 mg %, respectively); the other oils led to lower PC levels (approximately 100 mg %). It appears that the liver tissue can metabolize C22: 1 better than the other body tissues studied, perhaps by increased oxidation or by increased transport as cholesterol esters.