Nutrient Metabolism—Research Communication Isomers of Conjugated Linoleic Acid (CLA) Are Incorporated into Egg Yolk Lipids by CLA-Fed Laying Hens 1 (Manuscript received 10 June 1999. Initial review completed 23 September 1999. Revision accepted 10 March 2000.) Sean Jones,* † David W. L. Ma,*** Frank E. Robinson, † Catherine J. Field* † ** and M. Thomas Clandinin* † ** 2 *Nutrition and Metabolism Research Group, † Department of Agricultural, Food and Nutritional Science, **Department of Medicine, University of Alberta, Edmonton, AB, Canada T6G 2P5 ABSTRACT This study was designed to determine the amount of conjugated linoleic acid (CLA) incorporated into egg lipids after dietary CLA supplementation. Single Comb White Leghorn laying hens (n  40; 28 wk old) were ran- domly assigned to four treatments of varying CLA levels (0, 0.01, 0.5 and 1 g CLA/kg diet). Eggs were collected daily for 36 d. Feed consumption and body weight were monitored. CLA content of egg yolk lipid was analyzed by gas-liquid chromatography. Birds fed 0.5 and 1.0 g CLA/kg feed had significantly more CLA in the egg yolk lipid vs. control and 0.01 g CLA/kg diet groups after 7 d (P < 0.0004). Incorpo- ration of CLA into egg lipid was highest on d 24 and 36. CLA enrichment in egg lipid in the 1.0 g CLA/kg diet group was similar to that in ruminant animal food products, 3 mg CLA/g fat. J. Nutr. 130: 2002–2005, 2000. KEY WORDS: ● conjugated linoleic acid ● fatty acid ● laying hens ● lipid ● egg Isomers of conjugated linoleic acid (CLA) have anticancer activity (Belury 1995, reviewed by Ip 1994, Scimeca et al. 1994), immune-enhancing qualities (Cook et al. 1993, Miller et al. 1994), weight-reducing effects (Belury and Kempa-steczko 1997, Scimeca et al. 1994) and possible antiatherogenic properties (Lee et al. 1994, Nicolosi et al. 1997) in animals at levels below 1% of the total energy in the diet (Ip et al. 1994). The c9, t11–18:2 isomer has been implicated as the biologically active form. CLA is found predominantly in food items produced from ruminant animals. The c9, t11–18:2 isomer is the predominant form found in foods, comprising 75% of all of the CLA isomers (Chin et al. 1992). Daily intake of CLA is not well documented but has been estimated to be under several hun- dred mg/d (Ens et al., unpublished data, Fritsche and Steinhart 1998, Ip et al. 1994). Animal data indicate that 3.0 g/d of CLA may be necessary for beneficial effects in humans (Ip et al. 1994). Reevaluation of these data on the basis of total dietary energy consumption suggests that 600 mg CLA/d may have anticancer effects (Ens et al., unpublished data). It is possible to change the lipid composition of food prod- ucts, such as eggs, by modifying the diet of the laying hens (Cruickshank 1934). The development of CLA-enriched foods could have implications in the poultry industry by im- proving immunity and health, increasing growth and improv- ing feed efficiency (Chin et al. 1994, Miller et al. 1994, Park et al. 1997). CLA fortification could contribute to diet-based cancer prevention in human populations (Hargis et al. 1991, Jiang et al. 1993). Thus, the objective of this study was to develop a feeding regimen to produce CLA-rich eggs. The short- and long-term effect of CLA supplementation for 36 d on the CLA content in eggs, the CLA content in the body fat of Shaver 2000 laying hens and on the weight of the hens were determined. MATERIALS AND METHODS Diets. Shaver 2000 Single Comb White Leghorn pullets (n = 40) were reared in floor pens to 18 wk of age. The rations were provided as follows: chick starter from 0 to 6 wk; grower ration 1 from 6 to 16 wk; and layer ration from 16 to 29 wk. At 18 wk, hens were moved to individual laying cages. At 29 wk, hens were fed a modified layer ration until the end of lay. The four diets consisted of a control diet (layer ration containing no CLA), a low CLA diet containing 0.01 g CLA/kg diet (0.001% wt/wt, 0.04% total added fat), a medium diet with 0.5 g CLA/kg feed (0.05% wt/wt, 1.8% total added fat), and a high CLA diet having 1.0 g CLA/kg feed (0.1% wt/wt, 3.7% added fat). Feed and water were consumed ad libitum from individual containers inaccessible to neighboring birds. Ten birds completed each diet treatment. Experimental design. Pullets were reared in light-tight floor pens with a bird density of 15.24 cm 2 /bird until 10 wk, then 60.96 cm 2 /bird until 18 wk. Chicks were subjected to a photoschedule of 23 h light (L) to 1 h dark (D) (23L:1D), which was reduced to 8L:16D at 4 d and maintained until 18 wk of age. Beak trimming was performed between 5 and 8 d of age. At 18 wk of age, pullets were moved to individual laying cages and fed a standard layer diet. Once in laying cages, the photoschedule was increased to 11L:13D, and was in- creased by 0.5 h of light/wk until it reached 14L:10D. At 29 wk, 40 pullets were weighed and assigned to one of the following four treatment groups: a control group (standard layer diet), CLA-en- riched diets of 0.01, 0.5 or 1.0 g CLA/kg diet. Pullets were fed these diets for 36 d and eggs were collected on d 1–12, 24 and 36. Individual feed intakes were calculated weekly. Intakes were calcu- lated by feed weigh-back, through recording the feed given, and subtracting the initial starting weight and the end weight to give the feed consumed. Body weight was measured biweekly. After 36 d, six hens from each group of ten were returned to the general laying population, and the remaining hens from each group were fed their respective diets until they reached the age of 68 wk. Feed intakes and body weight measures were taken every 4 wk until end of the lay. All birds survived until 68 wk of age. On the afternoon before being killed, the birds were deprived of food overnight (12–20 h) to permit gut content clearance. All experimental procedures performed on live birds were approved by the University of Alberta Faculty of Agricul- ture, Forestry and Home Economics Animal Policy and Welfare Committee. 1 Supported by grants from the Natural Sciences and Engineering Research Council of Canada and the Alberta Egg Producers Board. 2 To whom correspondence should be addressed. 0022-3166/00 $3.00 © 2000 American Society for Nutritional Sciences. 2002 by guest on May 19, 2014 jn.nutrition.org Downloaded from