Effects of dietary conjugated linoleic acid on fatty acid composition and cholesterol content of hen egg yolks

Abstract

The main objectives of the present study were to determine the effect of dietary conjugated linoleic acid (CLA) isomers on the fatty acid composition and cholesterol content of egg-yolk lipids. Forty-five 25-week-old laying hens were randomly distributed into five groups of nine hens each and maintained in individual laying cages, throughout 12 weeks of the experiment. They were assigned to the five treatments that consisted of commercial layer diets containing 0, 5, 10, 15 or 20 g pure CLA/kg. Feed intake of hens varied little and insignificantly. Egg mass was uniformly lower (P, 0·05) in the hens fed the CLA-enriched diets. Feed conversion efficiency, when expressed per kg eggs, was impaired (P, 0·05), although without obvious relation to the dietary CLA concentration. Feeding the CLA-enriched diets resulted in gradually increasing deposition of CLA isomers (P, 0·01) in egg-yolk lipids. Saturated fatty acids were increased (P, 0·01) and monounsaturated fatty acids decreased (P, 0·01). Polyunsaturated fatty acids (PUFA), when expressed as non-CLA PUFA, were also significantly decreased (P,0·01). The most striking effects (P, 0·01) were observed for palmitic (16 : 0) and stearic (18 : 0) acids, which increased from 23·6 to 34 % and from 7·8 to 18 %, respectively. On the other hand, oleic acid (18 : 1n-9) decreased from 45·8 to 24·3 %. Among non-CLA PUFA, linoleic (18 : 2n-6) and a-linolenic (18 : 3n-3) acids were strongly (P, 0·01) decreased, from 14·2 to 7·7 % and from 1·3 to 0·3 %, respectively. The same was true for arachidonic (20:4n-6) and docosahexaenoic (22 : 6n-3) acids. The cholesterol content of egg yolks, when expressed in mg/g yolk, was not affected by the dietary CLA concentrations. In conclusion, unless the adverse effects of CLA feeding to laying hens on the fatty acid profile of egg yolks are eliminated, the CLA-enriched eggs cannot be considered functional food products.

Effect of dietary conjugated linoleic acid on laying hen performance, egg yolk fatty acid composition and egg quality during refrigerated storage

“…SFA and PUFA was increased (P<0.01) by dietary CLA compared with the control group (0% CLA), whereas the concentration of MUFA decreased (P<0.01). These results are in accordance with the findings of Chamruspollert and Sell (1999) and Szymczyk et al (2003). …”

The effect of dietary fat on the fatty acid composition and cholesterol content of Hy-line and Warren hen eggs

“…Garg et al (1988) demonstrated that both linseed oil and fish oil diets inhibited delta-9 desaturase activity in rat liver microsomes. investigators (Yang et al 2002;Szymczyk & Pisulewski, 2003). Increased levels of linoleic and α-linolenic acids in the fat added to the diet significantly increased the concentration of linoleic, α-linolenic, and docosahexaenoic (DHA) in white and brown eggs, although the levels of arachidonic and docosapentaenoic acids decreased during the AF-SO dietary period.…”

The effect of feeding regular or low α-linolenic acid linseed on laying performance and total cholesterol content in eggs

“…In recent years linseed cultivars containing oil low in α-linolenic acid and rich in linoleic acid have been introduced (Borowiec et al, 2001). Enrichment of laying hen diets with conjugated linoleic acid has been reported to decrease the yolk weight and cholesterol content of eggs (Szymczyk and Pisulewski, 2003). The aim of this study was to compare the effects of feeding laying hens with seeds of regular or modified low-α-linolenic acid cultivars of linseed on laying performance and cholesterol content in eggs.…”

“…The egg is considered an ideal target for dietary modification leading to the development of functional food (Szymczyk and Pisulewski, 2003). Enrichment of laying hen diets with regular full-fat linseeds beneficially affected the functional value of eggs due to an increased content of n-3 polyunsaturated fatty acids (PUFA) (Scheideler and Froning, 1996;Van Elswyk, 1997).…”