J. King Saud Univ., Vol. 13, Agric. Sci. (2), pp. 125-135, Riyadh (1421/2001)
The Effect of Vegetarian Diet on the Production, Egg Component Yields and on Egg Yolk Cholesterol and Fatty Acid Content of Laying Hens
Department of Animal Production, College qf Agriculture, King Saud University, PO. Box 2460, Riyadh, Saudi Arabia
Abstract. The effects of all-vegetarian (low fat-high carbohydrate) diet on egg production, egg grade, egg component yields and on egg yolk lipid, cholesterol and fatty acid concentrations of hens were studied for 12 weeks. There was no significant difference between the control and all-vegetarian diets in weight gain, total feed intake, rate of lay, egg weight, egg mass of pullets nor of percentage of jumbo, extra large or small eggs produced nor of lipid, cholesterol, linolenic acid or arachidonic acid concentration of their yolks. Pullets fed the all-vegetarian diet produced higher palmitic, stearic and linoleic acid concentrations in their yolks, percentage of medium eggs, percentage of adjusted albumin, and lower oleic acid concentration and US/S [the proportion unsaturated (oleic plus linoleic plus linolenic plus arachidonic) to saturated (palmitic plus stearic)] fatty acid in yolk lipid and M/P [the proportion of monounsaturated (oleic) to polyunsaturated (linoleic plus linolenic plus arachidonic)] fatty acid ratios in their yolks, yolk weight, percentage of large eggs, percentage of eggshell, percentage of adjusted yolk, than those fed the control diet. Egg size did not significantly affect yolk lipid concentration. However, medium size eggs had a significantly higher yolk stearic acid concentration and percentage of eggshell than those found in large or extra large eggs. Younger hens had significantly higher rate of lay, percentage of large, medium and small eggs and percentage of eggshell and lower egg weight, yolk weight, egg mass, percentage of jumbo, extra large and unmarketable eggs and yolk linoleic acid concentration than those of older age. It was concluded that all-vegetarian (low fat-high carbohydrate) diet reduced US/S and M/P fatty acid ratios of egg yolks. The degree of saturation can be improved by increasing the percentage of energy from fat in the vegetarian diet.