Authors: HATİCE BASMACIOĞLU, MUSTAFA ERGÜL
Abstract: The effects of the age of the hen, genotype, rearing system and dietary structure on egg and serum cholesterol content and some other characteristics of eggs were investigated in laying hens. However, only the findings related to genotype and rearing system are given. A total of 840 hens, 21weeks of age and consisting of 400 white layers (Babcock-300) and 440 brown layers (IsaBrown) were used. The 2 genotypes had been housed in different rearing systems, floor pens and cages. Ten different feed groups consisting of controls (I and II), 2% and 4% fiber increment (III, IV, V and VI), 2% and 4% fiber increment + 250 mg/kg vitamin C (VII, VIII, IX and X) formed the feed material of the trial. Energy shortfalls in the diets were made good by soybean oil in one half, and by animal fat (beef tallow) in the other. Genotype and rearing system significantly affected egg and serum cholesterol content. The serum and egg yolk cholesterol contents of white layers were lower than those of brown layers. The effect of genotype on shell ratio and thickness was not significant. Differences between rearing systems were nonsignificant for egg weight, and shell weight and thickness. White layers were better than browns layers, and cage rearing was better than floor pen rearing for egg production, feed consumption and feed conversion. There were positive and significant correlations (P < 0.05) among egg cholesterol content and egg weight, and yolk weight, and also between serum cholesterol and egg production for each genotype. The correlations between serum and egg yolk cholesterol (mg/g and mg/egg) were negative for both genotypes, but were significant for white layers.
Keywords: Laying hen, cholesterol, genotype and rearing system
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