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Fatty Acid Composition of Chick Embryo and Egg Yolk at Various Stages of Incubation1
FATTY ACID COMPOSITION OF CHICK EMBRYO AND EGG YOLK AT VARIOUS STAGES OF INCUBATION 1 W. E. DONALDSON Poultry Science Department, North Carolina Slate of the University of North Carolina, Raleigh, North Carolina (Received for publication January 14, 1964)
1
Contribution from the Poultry Science Department, North Carolina Agricultural Experiment Station, Raleigh, North Carolina. Published with the approval of the Director of Research as Paper No. 1722 of the Journal Series. This investigation was supported in part by PHS Research Grant AM 07833-01 from the National Institute of Arthritis and Metabolic Diseases, Public Health Service.
pie was extracted. Extraction of all samples was carried out without drying using a water-ethanol-diethyl ether-HCl solvent (30:20:20:1 by volume). Methyl esters of the extracted fatty acids were prepared using boron-trifluoride-methanol reagent.2 The methyl esters were separated using a Wilkens Aerograph model A-90-P2 gas chromatograph with thermal conductivity detector. A 0.6X152 cm. stainless steel column packed with 60-80 mesh firebrick coated with 20% diethylene glycol succinate was used. Column temperature was 200°C, and helium flow 100 ml./min. The fatty acid composition data in Table 1 show that yolk composition was not appreciably affected by incubation. The composition of the 8- and 12-day embryo varied from the composition of yolk. The most striking differences were the smaller proportions in the embryo of 16:1, 18:1, and 18:2 acids3 and the larger porportion of 20:4, 22:4, 24:1, or 2 acids and an unidentified acid.4 The differences between embryo and yolk composition became progressively less after 16 and 20 days incubation and were accompanied by an increase in percent ether extract of 2
Applied Science Laboratories, University Park, Pennsylvania. 3 The first number denotes carbon chain length and the second number denotes the number of double bonds. The numbers are used instead of names since the method employed does not distinguish among all the possible positional and cis-trans isomers of unsaturated fatty acids. 4 The retention volume of this peak was comparable to the expected volume for 24:4.
784
Downloaded from http://ps.oxfordjournals.org/ at NERL on May 13, 2015
Adipose tissue fatty acid composition of the chick embryo is similar to egg fatty acids but does not resemble the composition of non-adipose or structural lipids (Feldman et al., 1962; and Baker, 1961). This suggests that the fatty acid composition of chick embryo may be at maximal variance with egg fat during the early stages of incubation when adipose tissue formation is minimal and that the variance may decrease during the latter stages of incubation when adipose tissue formation is maximal. To test this hypothesis, the fatty acid composition of chick embryos and yolk contents at various ages was determined and compared to that of a six-day-old chick brain! Eggs from White Leghorn hens fed a corn-soya diet were incubated. Random samples of four eggs each were withdrawn from the incubator for analysis after 0, 8, 12, 16, and 20 days of incubation. Each egg was analyzed separately. The yolk material was thoroughly mixed and a 2 gm. sample was withdrawn for extraction. Embryos were homogenized in a Servall blendor for one minute and a 2 gm. sample was withdrawn for extraction except that the entire embryo was used at 8 days. The entire brain of a six-day-old chick was homogenized and a 2 gm. sam-
785
RESEARCH NOTES TABLE 1.-
-Fatty acid composition of yolk, embryo and chick brain, and embryo weight and ether extract at various incubation intervals
Fatty Acid1 0
Yolk
Embryo
Days incubated
Days incubated
8
1 2
16
20
8
percent 0.9 23.6 4.9 7.3 40.3 17.3 0.6 2.0 Trace 0.4 0.3
0.8 25.1 5.5 6.8 41.6 16.1 0.7 1.5 Trace 0.2 0.2
0.6 26.5 5.3 8.3 38.5 16.1 0.4 1.4 Trace 0.4 0.4
0.8 27.1 2.6 14.7 20.0 6.6 0.0 11.7 1.2 1.4 0.0
0.8 1.5
0.2 1.3
0.4 1.4
9.1 4.8 1.01 1.2
12
percent 0.5 0.8 23.4 27.0 2.7 3.4 14.2 9.6 19.9 29.6 8.3 15.1 0.0 0.7 11.5 6.3 0.5 1.9 1.3 0.6 2.4 0.3 6.5 6.6 9.56 0.9
20
16
3.6 2.3 18.66 3.4
0.8 26.9 4.7 9.2 33.8 15.9 0.3 4.8 0.0 0.4 0.4 1.8 0.7 35.34 S.9
percent 0.0 16.5 3.1 14.8 20.0 2.2 0.1 9.7 2.1 2.4 2.1 12.2 12.9
First number denotes chain length and second denotes number of double bonds. The retention volume of this peak was comparable to the expected volume for 24:4.
the embryo. The fatty acid distribution of the earlier embryos was similar to the distribution of fatty acids from the whole brain of a six-day-old chick except that embryonic 16:0 and 18:2 acids were higher and 24:1 or 2 acid and the unidentified acid were lower. The results of this study suggest that the fatty acid deposition by the early embryo is in structural fats. In the older embryos, deposition of adipose tissue fatty acids dilutes the structural fats so that total composition approaches that of
yolk fatty acids. The variation between embryonic and yolk fatty acid distribution suggests that the embryo is selective in uptake and/or deposition and oxidation of yolk fatty acids. REFERENCES Feldman, G. L., H. T. Jonsson, T. W. Culp and R. H. Gowan, 1962. Fatty acid composition of embryonic fat organ lipids. Poultry Sci. 41: 18511857. Baker, R. W. R., 1961. Ester-linked long-chain fatty acids of nervous tissue. Biochem. J. 79: 642-648.
NEWS AND
NOTES
{Continued from page 775) Endocrine Society, Society for the Study of Fertility, and Sigma Xi. Dr. A. H. Smith, another member of the Poultry Science Association, is also a member of the Department. BACK ISSUES OF POULTRY SCIENCE The Department of Poultry Science, University
of Saskatchewan, Saskatoon, Saskatchewan, Canada, has the following back issues of Poultry Science, which they will send free of charge on request: Volume 3, No. 3 and 5; Volume 4, No. 4; Volume 6, No. 3 and 5; Volume 7, No. 2 and 5; Volume 8, No. 2 and 6; Volume 9, No. 1, 2, 3, 4, 5 and 6; Volume 10, No. 1, 2, 3, 4, 5, 6 and 7; Volume 11, No. 1, 2, 3, 4, 5 and 6; Volume 12, No. 1, 2, 5 and 6; Volon page 798)
Downloaded from http://ps.oxfordjournals.org/ at NERL on May 13, 2015
14:0 0.7 0.6 16:0 23.7 24.4 16:1 S.2 4.0 18:0 7.8 8.4 18:1 39.7 40.2 18:2 17.2 19.1 18:3 0.9 0.6 20:4 1.4 2.1 22:4 0.0 0.1 22:5 0.5 0.2 24:0 0.2 0.0 24:1 or 24:2 1.1 0.1 ?2 1.5 0.2 Embryo weight, gms Embryo ether extract, %
12
6-dayold chick brain
1
Contribution from the Poultry Science Department, North Carolina Agricultural Experiment Station, Raleigh, North Carolina. Published with the approval of the Director of Research as Paper No. 1722 of the Journal Series. This investigation was supported in part by PHS Research Grant AM 07833-01 from the National Institute of Arthritis and Metabolic Diseases, Public Health Service.
pie was extracted. Extraction of all samples was carried out without drying using a water-ethanol-diethyl ether-HCl solvent (30:20:20:1 by volume). Methyl esters of the extracted fatty acids were prepared using boron-trifluoride-methanol reagent.2 The methyl esters were separated using a Wilkens Aerograph model A-90-P2 gas chromatograph with thermal conductivity detector. A 0.6X152 cm. stainless steel column packed with 60-80 mesh firebrick coated with 20% diethylene glycol succinate was used. Column temperature was 200°C, and helium flow 100 ml./min. The fatty acid composition data in Table 1 show that yolk composition was not appreciably affected by incubation. The composition of the 8- and 12-day embryo varied from the composition of yolk. The most striking differences were the smaller proportions in the embryo of 16:1, 18:1, and 18:2 acids3 and the larger porportion of 20:4, 22:4, 24:1, or 2 acids and an unidentified acid.4 The differences between embryo and yolk composition became progressively less after 16 and 20 days incubation and were accompanied by an increase in percent ether extract of 2
Applied Science Laboratories, University Park, Pennsylvania. 3 The first number denotes carbon chain length and the second number denotes the number of double bonds. The numbers are used instead of names since the method employed does not distinguish among all the possible positional and cis-trans isomers of unsaturated fatty acids. 4 The retention volume of this peak was comparable to the expected volume for 24:4.
784
Downloaded from http://ps.oxfordjournals.org/ at NERL on May 13, 2015
Adipose tissue fatty acid composition of the chick embryo is similar to egg fatty acids but does not resemble the composition of non-adipose or structural lipids (Feldman et al., 1962; and Baker, 1961). This suggests that the fatty acid composition of chick embryo may be at maximal variance with egg fat during the early stages of incubation when adipose tissue formation is minimal and that the variance may decrease during the latter stages of incubation when adipose tissue formation is maximal. To test this hypothesis, the fatty acid composition of chick embryos and yolk contents at various ages was determined and compared to that of a six-day-old chick brain! Eggs from White Leghorn hens fed a corn-soya diet were incubated. Random samples of four eggs each were withdrawn from the incubator for analysis after 0, 8, 12, 16, and 20 days of incubation. Each egg was analyzed separately. The yolk material was thoroughly mixed and a 2 gm. sample was withdrawn for extraction. Embryos were homogenized in a Servall blendor for one minute and a 2 gm. sample was withdrawn for extraction except that the entire embryo was used at 8 days. The entire brain of a six-day-old chick was homogenized and a 2 gm. sam-
785
RESEARCH NOTES TABLE 1.-
-Fatty acid composition of yolk, embryo and chick brain, and embryo weight and ether extract at various incubation intervals
Fatty Acid1 0
Yolk
Embryo
Days incubated
Days incubated
8
1 2
16
20
8
percent 0.9 23.6 4.9 7.3 40.3 17.3 0.6 2.0 Trace 0.4 0.3
0.8 25.1 5.5 6.8 41.6 16.1 0.7 1.5 Trace 0.2 0.2
0.6 26.5 5.3 8.3 38.5 16.1 0.4 1.4 Trace 0.4 0.4
0.8 27.1 2.6 14.7 20.0 6.6 0.0 11.7 1.2 1.4 0.0
0.8 1.5
0.2 1.3
0.4 1.4
9.1 4.8 1.01 1.2
12
percent 0.5 0.8 23.4 27.0 2.7 3.4 14.2 9.6 19.9 29.6 8.3 15.1 0.0 0.7 11.5 6.3 0.5 1.9 1.3 0.6 2.4 0.3 6.5 6.6 9.56 0.9
20
16
3.6 2.3 18.66 3.4
0.8 26.9 4.7 9.2 33.8 15.9 0.3 4.8 0.0 0.4 0.4 1.8 0.7 35.34 S.9
percent 0.0 16.5 3.1 14.8 20.0 2.2 0.1 9.7 2.1 2.4 2.1 12.2 12.9
First number denotes chain length and second denotes number of double bonds. The retention volume of this peak was comparable to the expected volume for 24:4.
the embryo. The fatty acid distribution of the earlier embryos was similar to the distribution of fatty acids from the whole brain of a six-day-old chick except that embryonic 16:0 and 18:2 acids were higher and 24:1 or 2 acid and the unidentified acid were lower. The results of this study suggest that the fatty acid deposition by the early embryo is in structural fats. In the older embryos, deposition of adipose tissue fatty acids dilutes the structural fats so that total composition approaches that of
yolk fatty acids. The variation between embryonic and yolk fatty acid distribution suggests that the embryo is selective in uptake and/or deposition and oxidation of yolk fatty acids. REFERENCES Feldman, G. L., H. T. Jonsson, T. W. Culp and R. H. Gowan, 1962. Fatty acid composition of embryonic fat organ lipids. Poultry Sci. 41: 18511857. Baker, R. W. R., 1961. Ester-linked long-chain fatty acids of nervous tissue. Biochem. J. 79: 642-648.
NEWS AND
NOTES
{Continued from page 775) Endocrine Society, Society for the Study of Fertility, and Sigma Xi. Dr. A. H. Smith, another member of the Poultry Science Association, is also a member of the Department. BACK ISSUES OF POULTRY SCIENCE The Department of Poultry Science, University
of Saskatchewan, Saskatoon, Saskatchewan, Canada, has the following back issues of Poultry Science, which they will send free of charge on request: Volume 3, No. 3 and 5; Volume 4, No. 4; Volume 6, No. 3 and 5; Volume 7, No. 2 and 5; Volume 8, No. 2 and 6; Volume 9, No. 1, 2, 3, 4, 5 and 6; Volume 10, No. 1, 2, 3, 4, 5, 6 and 7; Volume 11, No. 1, 2, 3, 4, 5 and 6; Volume 12, No. 1, 2, 5 and 6; Volon page 798)
Downloaded from http://ps.oxfordjournals.org/ at NERL on May 13, 2015
14:0 0.7 0.6 16:0 23.7 24.4 16:1 S.2 4.0 18:0 7.8 8.4 18:1 39.7 40.2 18:2 17.2 19.1 18:3 0.9 0.6 20:4 1.4 2.1 22:4 0.0 0.1 22:5 0.5 0.2 24:0 0.2 0.0 24:1 or 24:2 1.1 0.1 ?2 1.5 0.2 Embryo weight, gms Embryo ether extract, %
12
6-dayold chick brain