Abstract
The effects of different dietary lipids on the fatty acid profiles of eggs produced by 20 and 54 wk old Dekalb laying hens were investigated. Laying hens were subjected to three defined treatments according to the source of lipid added to their diets: soybean oil, beef tallow, and a control diet (without the addition of oil). The experimental design was in a 3x2 factorial arrangement (three treatments and two different ages). The fatty acid composition of the yolks in the eggs produced by the laying hens was analyzed. The eggs produced by laying hens on the soybean oil diet had a large amount of polyunsaturated fatty acids (PUFA) omega-6 (n-6) and omega-3 (n-3) in their yolks (23.55, 2.30% respectively), whereas egg yolks from hens who were given beef tallow had higher percentages of monounsaturated fatty acids (47.53%) compared to soybean oil (47.53%) and the control diet (38.72%). The percentages of trans fats present in the egg yolks in all treatments were considered very low (0.91; 0,11; 0.05%). Young layers are more efficient at depositing n-3 fatty acids (1.40%), specially C22:6 (0.76%) with the best ratio n6:n-3 (13.97) compared to old layers (1.35; 0.72; 14.81% respectively). Based on these results, it was concluded that the amount of fatty acids present in the egg yolks can be modified by the sources of lipids included in the diet and that independent of the sources of lipid in the diet and the age of the chicken, egg yolks have insignificant amounts of trans fatty acids.
Highlights
Oils and fats are concentrated sources of energy, essential to the composition of diets of high nutritional density and for maintenance of the calorie/protein equilibrium
Among all the saturated fatty acids (SAT), C16:0 and C18:0 had the highest percentage in the egg yolk composition, while very low levels of trans fatty acids were detected in the egg yolks of soybean (0.91%), beef tallow (0.11%) and control diet (0.05%), independent of the diets given to the laying hens and and independent of the laying hen age (0.85%)
The diet fed to the hens had a significant effect (p
Summary
Oils and fats are concentrated sources of energy, essential to the composition of diets of high nutritional density and for maintenance of the calorie/protein equilibrium. About 45% oleic acid and only 1 to 3% linoleic acid Soybean oil is another energy source often added to chicken diets; obtained by the processing of raw soybeans, it is composed mainly of oleic (C18:1), linoleic (C18:2), linolenic (C18:3) and palmitic (C16:0) fatty acids. Many unsaturated fatty acids can be formed from saturated fatty acids (SAT) by the additional reactions of elongation and or desaturation. Saturated (SAT) and monounsaturated fatty acids (MUFA) can be synthesized by animals; animals cannot synthesize linoleic acid (C18:2) and linolenic acid (C18:3) (LESKANICH; NOBLE, 1997; LEHNINGER et al, 2002). The FA belonging to the n-6 series are important precursors of eicosanoids of the paracrine system, such as prostaglandins, leukotrienes, prostacyclins, tromboxanes, and hydroxyacids, whereas the n-3 series fatty acids participate in functions of the nervous and visual system tissues, are responsible for regulatory activities of cardiovascular homeostasis, and play important regulatory functions in the immune system (LEVINSON et al, 1990; LESKANICH; NOBLE, 1997; NEURINGER et al, 1998)
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