Abstract
This experiment aimed at evaluating the effects of the supplementation of different vegetable oils at different levels to the diet of commercial layers on egg cholesterol levels and nutritional composition (proteins, total solids, lipids, and ashes) for 112 days. Birds were distributed according to a completely randomized experimental design with 10 treatments (T1 - control; T2 - inclusion of 2.5% rapeseed oil; T3 - inclusion of 2.5% canola oil; T4 - inclusion of 2.5% soybean oil; T5 - inclusion of 5% rapeseed oil; T6 - inclusion of 5% canola oil; T7 - inclusion of 5% soybean oil; T8 - inclusion of 2.5% rapeseed oil + 2.5% soybean oil; T9 - inclusion 2.5% canola oil + 2.5% soybean oil; T10 - inclusion of 2.5% rapeseed oil + 2.5% canola oil) of six replicates of eight birds each, totaling 480 birds. Yolk cholesterol levels and nutritional composition were determined on days 20, 60 and 112 days of the experimental period. Data obtained during the experimental period were submitted to analysis of variance. Egg yolks produced by layer fed oils presented lower cholesterol levels after 20 days of inclusion in the experimental diets. On days 60 and 112, cholesterol levels were higher. It was concluded that supplementing layer diets with vegetable oils rich in polyunsaturated fatty acids does not change the nutritional composition of egg yolks. The supply of diets containing oils rich in polyunsaturated fatty acids does not reduce yolk cholesterol content.
Highlights
The enrichment of eggs with polyunsaturated fatty acids (PUFA), with omega-3 fatty acids has attracted the attention of both researchers and the food industry, because these fatty acids are essential for normal body development and play an important role in the prevention of heart diseases, diabetes, arthritis, inflammatory and auto-immune conditions, and cancer (Simopoulos, 2000).Most egg lipids are concentrated in the yolk, and consist of lipoproteins, phospholipids, triacylglycerols, and cholesterol
Cholesterol deposition in the egg yolk can be affected by nutrition (Hargis et al, 1991).The inclusion of specific feedstuffs in commercial layer diets, such as vegetable oils rich in unsaturated fatty acids used to change egg lipid profile and to reduce egg cholesterol content
This study aimed at evaluating the effects of the supplementation of rapeseed, soybean, and canola oil in commercial layer diets on yolk cholesterol levels and composition in terms of total solids, protein, lipids, and minerals
Summary
The enrichment of eggs with polyunsaturated fatty acids (PUFA), with omega-3 fatty acids has attracted the attention of both researchers and the food industry, because these fatty acids are essential for normal body development and play an important role in the prevention of heart diseases, diabetes, arthritis, inflammatory and auto-immune conditions, and cancer (Simopoulos, 2000).Most egg lipids are concentrated in the yolk, and consist of lipoproteins, phospholipids, triacylglycerols, and cholesterol. The lipid fraction of the yolk is composed of 8.7g saturated fatty acids, 13.2g monounsaturated fatty acids, 3.4 g polyunsaturated fatty acids and 1.120 mg cholesterol per 100 g of fresh yolk (Holland et al, 1997). Some researchers (Baucells et al, 2000; Grobas et al, 2001; Gómez, 2003; Mazalli et al, 2004) demonstrated the possibility of changing the fatty acid profile of the lipid fraction of eggs by reducing the dietary concentration of some fatty acids (lauric acid and short-chain saturated fatty acids) in exchange of long-chain fatty acids, such as eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C22:6n-3), which present more than 18 carbons in their chemical structure. According to Holland et al (1980) and Mori (2001), the addition of PUFA-rich oils in in the diet reduces blood and egg cholesterol concentrations. Other studies showed that yolk cholesterol content cannot be changed because it seems to be constant, independently of dietary factors (Bertechini, 2003)
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