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Influence of Different Fat Sources on the Performance, Egg Quality, and Lipid Profile of Egg Yolks of Commercial Layers in the Second Laying Cycle1

Posted on: Sunday, 3 July 2005, 03:00 CDT

Primary Audience: Egg Producers, Nutritionists, Poultry Extension Personnel, Researchers

SUMMARY

This study was designed to evaluate the effects of different fat sources on the performance, egg quality, and lipid profile of the egg yolks of layers in their second production cycle. The fat sources were cottonseed oil, soybean oil, lard, sunflower oil, or canola oil. Experimental diets were fed to postmolt ISA Brown layers at 70 wk of age and the experimental period was 74 to 86 wk of age. The different fat sources did not influence performance or eggshell quality, but lipid profile of the egg yolk changed as a function of dietary fat sources. In general, the best changes, such as lower level of saturated fatty acids, higher levels of α-linolenic acid and DHA, and lower linoleic acid levels, were promoted by the addition of canola oil, but it did not promote enrichment of the eggs with polyunsaturated fatty acids.

Key words: fatty acids, forced molt, lipid profile, semi-heavy layers

2005 J. Appl. Poult. Res. 14:258-264

DESCRIPTION OF PROBLEM

There is presently great interest in n-3 polyunsaturated fatty acids (PUFA n-3) in human health. The PUFA of the n-3 series, as well as those of the n-6 series, are recognized as essential in the human diet. The α-linolenic acid (α-LNA), representative of the n-3 family, is found in considerable quantities in oil seeds, such as canola, soybeans, and linseed. Linoleic acid is the most important fatty acid of the n-6 series, and it is abundant in vegetable oils, such as sunflower, corn, soybeans, cottonseed oils [1]. However, both marine plants (algae, microalgae, phytoplankton) and animals (fishes, crustaceans) have other fatty acids with higher carbon numbers and a larger amount of double links, which also belong to the n-3 series. These are called the very long carbon chain fatty acids (higher than 18 carbon atoms), and include the eicosapentaenoic acid (EPA, C20:5n-3) and the docosahexaenoic acid (DHA, C22:6n-3).

TABLE 1. Fatty acid composition of fat sources (% of total fatty acids)1

The α-LNA can be metabolically converted into DHA and EPA, but the enzymes involved in this conversion are common in the desaturation pathway of linoleic acid into arachidonic acid. As the enzyme Δ-6 desaturase is the same that promotes the desaturation of linolenic acid into arachidonic acid and of α- LNA into DHA and α-linolenic EPA, there is competition for the formation of these products, i.e., an excess of linoleic acid will prevent the transformation of α-LNA into its derivates EPA and DHA, and the opposite is also true, i.e., if there is low intake of linoleic acid, there will be less arachidonic acid formation. Therefore, in linolcic-rich and α-LNA-deficient diets, there is higher formation of arachidonic acid and its eicosanoid derivates, which will increase cardiovascular problems and type-2 diabetes [2].

The damaging effects of excessive arachidonic acid in the diet or produced by the conversion of linolenic by the action of the Δ- 6 desaturase enzyme can be diminished by reducing the ingestion of n- 6-rich foods and increasing the ingestion of n-3-rich foods, that is, reducing the n-6:n-3 ratio. According to Schreiner et al. [3], the optimal n-6:n-3 ratio in human nutrition is 3:1, but as mentioned by Simopoulos [2], this ratio is actually between 10:1 to 15:1 in industrialized countries.

In this context, eggs enriched with PUFA, particularly n-3 acids, are of interest to both researchers and the food industry, as these acids are essential for the normal development and growth of the human organism, and in addition, these acids have an important role in the prevention and treatment of cardiovascular diseases, hypertension, diabetes, arthritis, and inflammatory and self-immune diseases, as well as cancer [2].

According to Van Elswyk [4], PUFA-enriched eggs can be obtained by enriching layer feeds with marine or oilseed oils, such as linseed, sunflower, and canola, as these easily promote the incorporation of n-3 acids in the egg yolk. The addition of these PUFA-rich fat sources in layer feeds aims at changing the lipid profile of the eggs, which represents an excellent marketing strategy to provide for a segment of consumers interested in foods that benefit human health.

The effects of the addition of PUFA sources on the. performance and egg quality are mentioned in several studies [5, 6, 7, 8, 9, 10, 11], which evaluated the effect of different PUFA sources, different genetic lines, and age on the lipid profile of the yolk. The studies of Scheideler et al. [5], Grobas et al. [7], and Bean and Leeson [8] observed egg enrichment by means of PUFA addition in layer diets and differences as a function of age and breed.

TABLE 2. Diets composition (%)

The effects of egg enrichment by the feed manipulation are well- known in first-cycle layers. However, these effects are not mentioned in literature regarding second-cycle layers. Therefore, the aim of this study was to evaluate the effect of different fat sources on the performance, egg quality, and lipid profile of the egg yolks of layers in their second production cycle.

MATERIAL AND METHODS

One hundred and sixty postmolt, 70-wk-old ISA Brown layers [12] were distributed to 4 replicates of 8 birds per treatment. The treatments consisted of the addition of 5 different fat sources to diets: cottonseed oil, soybean oil, lard, sunflower oil, and canola oil. The dietary fats were included in the diets to standardize the energy level of 2,950 kcal ME/kg. The lipid profiles of the fat sources were determined by capillary gas chromatography (Table 1).

Feeds were formulated according to the recommendations of Rostagno et al. [13], and are presented in Table 2. Experimental feeds were supplied to the birds after the molt period, but the experimental cycles started 30 d later (74 wk of age), when the laying hens reached 60% egg production.

The second production cycle consisted of 4, 21-d periods, with the following performance parameters evaluated: feed intake (g/bird- day), egg production (% hen-day), egg weight (g), egg mass (g), and feed conversion per kilogram of eggs (kg/kg) and per dozen eggs (kg/ dozen), and during the last 2 d of each experimental period, average egg weight (g), eggshell thickness (mm), and egg specific gravity (g/ mL) were also evaluated. The analysis of the yolk fatty acid profile considered only the last experimental period, with the collection of yolks of 3 eggs to compose a pool for each replicate.

Yolk lipid extraction was carried out according to the AOAC [14] methodology. Yolk samples were transmethylated according to the method of Hartman and Lago [15], which consists of the saponification of fatty acids in methyl-esters . For fatty acid determination, a gas chromatograph [16], equipped with detector by flame ionization, split-type injector, capillary column of melted silica (50-m length 0.22-mm internal diameter) was used. Chromatography conditions were column temperature, 180C (isothermal), dragging gas, hydrogen at a 1.05 mL/min flow, and detector and injector temperature, 250C.

TABLE 3. Performance characteristics of hens fed different fat sources during the second cycle of production

Data were analyzed using general linear model of the SAS software [17]. Treatment means were compared by Tukey test, and significance was based on a 0.05 probability level.

RESULTS AND DISCUSSION

Performance Parameters

The addition of different fat sources to the feed of commercial layers in the second production cycle did not cause significant effects (P > 0.05) on performance parameters (Table 3). Baucellsetal. [6] and Mazalli et al. [ 1OJ, evaluating the incorporation of different PUFA sources, such as fish oil, linseed oil, sunflower oil, canola oil, and tallow, in commercial layer diets did not find differences in performance as well. On the other hand, Grobas et al. [7], also studying different PUFA sources in layer feeds, observed that although fat source did not influence feed intake, egg production, or feed efficiency, diets containing soybean oil produced heavier eggs as compared with tallow, olive oil, or linseed oil as PUFA sources.

Egg External Quality Parameters

As occurred with performance parameters, none of the egg external quality parameters were influenced (P > 0.05) by the addition of different fat sources to the feed (Table 4).

Although the present study did not show an effect of fat sources on eggshell quality parameters (P > 0.05), Grobas et al. [7] observed better eggshell quality in eggs derived from layers fed diets containing soybean oil. On the other hand, Mazalli et al. [10] found an effect of fat sources on eggshell percentage but only when vitamin E level was increased from 12 IU to 100 IU, with the lowest eggshell percentage determined by the addition of a mixture of fish oil and linseed oil (1:1) and by the addition of sunflower oil.

Fatty Acid Profile of Egg Yolks

Table 5 shows the fatty acid profiles of egg yolks of layers fed different dietary feed sources. The analyses showed that fat sources influenced the fatty acid profiles, except for (P > 0.05) the concentrations of the PUFA C20:3n-3 and C20:3n-6.

In terms of PUFA composition, the concen\trations of linoleic acid, α-LNA, and DHA must be highlighted due to their importance to human metabolism. In the present study, it was observed that the addition of canola oil to the feed decreased (P < 0.01) the concentration of linoleic acid in the yolk. The highest concentration of α-LNA and DHA were verified in the eggs of layers fed canola oil, although these values were not different as compared with the addition of soybean oil.

According to Simoupolos [2], the linoleic and α-LNA fatty acids are critical because they are precursors of the longer n-6 and n-3 PUFA; therefore, its adequate consumption is required. However, once ingested, these linoleic and α-LNA can be elongated to chains with at least 20 or 22 carbon atoms. Linoleic acid can be metabolized into other n-6 acids, including α-linolenic and arachidonic acid. The α-LNA is metabolized into other n-3 fatty acids as EPA or DHA. Thus, an excess of linoleic acid will prevent the transformation of α-LNA into its derivates EPA and DHA, and the opposite is also true, i.e., if there is low intake of linoleic acid, there will be less arachidonic acid formation, which will then reduce the formation of thromboxane A2, lowering the risk of coronary diseases.

TABLE 4. Egg external quality of hens fed different fat sources during the second cycle of production

The concentrations of saturated, monounsaturated, and PUFA in the egg yolks were signilicanlly (P < 0.01) influenced by the addition of different fat sources to the diets (Table 6). The lowest concentration (P < 0.05) of saturated fatty acids was obtained with the addition of canola oil, although it was not different from that obtained with the addition of soybean oil. On the other hand, the feed containing canola oil increased the concentration of monounsaturated fatty acids and decreased the content of polyunsaturated fatty acids as compared with diets containing other fat sources. In the study of Mazalli et al. [11], among the different fat sources evaluated, canola oil also caused the highest concentration of monounsaturated fatty acid and the lowest concentration of PUFA in the egg yolks.

TABLE 5. Yolk egg fatty acid profile (%) of hens fed different fat sources during second cycle of production

In the present study, as well as 1 study of Mazalli et al. [11], the inclusion of canola oil resulted in an increase in the concentration of monounsaturated fatty acid in egg yolks, because of the largest content of monounsaturated fatty acid of this source. Although from the viewpoint of human nutrition, the increase in the ingestion of monounsaturated fatty acids in substitution to the saturated fatty acid is desirable, the inclusion of canola oil in the laying hen diets still resulted in a decrease of the concentration of PUFA. This effect could not indicate the use of the canola oil to enrichment of eggs with PUFA. Consistent with the results found by Mazalli et al. [11], the present study indicates that canola seems to result in a more adequate n-6:n-3 ratio in terms of human nutrition.

TABLE 6. Fatty acid characteristcs of yolk eggs of the hens fed different fat sources during the second cycle of production

As to polyunsaturated to saturated fatty acids ratio (P:S) in the yolk (Table 6), the production of yolks with the lowest (P < 0.05) P:S ratio was promoted by the addition of canola oil to the feed; however, the value was not different from those observed with the addition of cotton-seed or sunflower oil. Mazalli et al. [11], evaluating several fat sources in layer feeds, verified a trend for canola oil to present the lowest P:S ratio as compared with the other sources.

There was no effect of the fat sources (P > 0.05) on the concentration of n-3 fatty acids in the yolk (Table 6), but a significant effect was observed on the level of n-6 fatty acids (P < 0.01), with the lowest concentration determined by the addition of canola oil in the feed as compared with the other sources. The n- 6:n-3 ratio in the yolks resulting from the addition of sunflower oil to the diet was twice as high as the ratio obtained with the canola oil. According to Briz [18], the n-6:n-3 ratios recommended in the European Union and the US are between 4 and 10:1.

CONCLUSIONS AND APPLICATIONS

1. The evaluated fat sources did not cause differences in the performance or the egg quality.

2. The different fat sources resulted in changes in the profile of fatty acids of the yolk.

3. The addition of canola oil decreased the concentration of saturated fatty acids, increased the concentrations of monounsaturated fatty acid, α-linolenic and DHA, and lowered n- 6:n-3 ratio, but it did not promote enrichment of the eggs with PUFA.

4. The use of canola oil in layer feeds is favorable as, from the human nutrition perspective, it causes desirable changes in the lipid profile of yolks, but its use depends on its price as compared with other fat sources.

1 This research was supported by the Fundao de Amparo Pesquisa do Estado de So Paulo (FAPESP).

REFERENCES AND NOTES

1. Dziezak, J. 1989. Fats, oils, and fat substitutes. Food Technol. 43:66-74.

2. Simopoulos, A. P. 2000. Symposium: Role of poultry products in enriching the human diet with N-3 PUFA: Human requirement for N-3 polyunsaturated fatty acids. Poult. Sci. 79:961-970.

3. Schreiner, M., H. W. Hulan, E. Razzazi-Fazeli, J. Bhm, and C. Iben. 2004. Feeding laying hens seal blubber oil: Effects on egg yolk incorporation, stereospecific distribution of omega-3 fatty acids, and sensory aspects. Poult. Sci. 83:462-473.

4. Van Elswyk. M. E. 1997. Comparison of n-3 fatty acid sources in laying hen rations for improvement of whole egg nutritional quality: A review. Br. J. Nutr. 78(Suppl. 1):61-69.

5. Scheideler, S. E., D. Jaroni, and G. W. Froning. 1998. Strain and age effects on egg composition from hens fed diets rich in n-3 fatty acids. Poult. Sci. 77:192-196.

6. Baucells, M. D., N. Crespo, A. C. Barroeta, S. Lpez-Ferrer, and M. A. Grashorn. 2000. Incorporation of different polyunsaturated fatty acids into eggs. Poult. Sci. 79:51-59.

7. Grobas, S., J. Mndez, R. Lzaro, C. Blas, and G. C. Mateos. 2001. Influence of source and percentage of fat added to diet on performance and fatty acid composition of egg yolks of two strains of laying hens. Poult. Sci. 80:1 171-1179.

8. Bean, L. D., and S. Leeson. 2003. Long-term effects of feeding flaxseed on performance and egg fatty acid composition of brown and white hens. Poult. Sci. 82:388-394.

9. Gmez, M. E. D. B. 2003. Modulao da composio de cidos graxos poliinsaturados mega 3 de ovos e tecidos de galinhas poedeiras, atravs da dieta. I. Estabilidade oxidativa. So Paulo. Page 149 in Tese de Doutorado. USP, Pirassununga, SP, Brazil.

10. Mazalli, M. R., D. E. Faria, D. Salvador, and D. T. Ito. 2004. A comparison of the feeding value of different sources of fats for laying hens: 1, Performance characteristics. J. Appl. Poult. Res. 13:274-279.

1 1. Mazalli, M. R., D. E. Faria, D. Salvador, and D. T. Ito. 2004. A comparison of the feeding value of different sources of fats for laying hens: 2. Lipid, cholesterol and vitamin E profiles of egg yolk. J. Appl. Poult. Res. 13:280-290.

12. ISA S.A.S. Saint Brieno, France.

13. Rostagno, H. S., D. J. Silva, P. M. A. Costa, and C. Gomide. 2000. Composio de alimentos e exigncias nutricionais (Tabelas brasileiras para aves e sunos). Imprensa Universitria, Viosa, MG, Brazil.

14. Association of Official Analytical Chemists. 1995. Official Methods of Analysis. Vol. 1. 16th ed. Association of Official Analytical Chemists. Washington, DC.

15. Hartman, L., and B. C. A. Lago. 1973. Rapid preparation of fatty acid methyl esters from lipids. Lab. Pract. 22:475-477.

16 Shimadzu model GC-14B, Shimadzu-Hicap, Australia.

17. SAS Institute. 1996. SAS User's Guide: Statistics. Version 6 ed. SAS Institute Inc., Cary, NC.

18. Briz, R. C. 1997. Ovos com teores mais elevados de cidos graxos n-3. Pages 153-193 in Proc. 7th Simpsio Tcnico de Prodyo de Ovos- APA. Campinas, So Paulo, Brazil

R. da Silva Filardi,*,2 O. M. Junqueira,* A. C. de Laurentiz,* E. M. Casartelli,* E. Aparecida Rodrigues,* and L. Francelino Arajo[dagger]

* Departamento de Zootecnia, Faculdade de Cincias Agrrias e Veterinrias, Universidade Estadual Paulista, Jaboticabal, SP, 14884- 900, Brazil; and [dagger] Faculdade de Zootecnia e Engenharia de Alimentos, USP, Pirassununga, SP, Brazil

2 To whom correspondence should be addressed: rofilardi@ig.com.br.

Copyright Poultry Science Association Summer 2005

Source: Journal of Applied Poultry Research

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