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Effect of time and diet on carcass fatty acid composition of bobwhites, Colinus virginianus
Camp. Biochem. Phvsiol. Vol. IlA, No. 4, pp. 623-626, 1984 Printed in Great Biitain
EFFECT
0300-9629184$3.00 + 0.00 ,c 1984 Pergamon Press Ltd
OF TIME AND DIET ON CARCASS FATTY ACID COMPOSITION OF BOBWHITES, COLINUS
VIRGINIANUS
SUZANNE M. ARRUDA Division
of Biology,
Kansas
State University.
and ROBERT J. ROBEL
Manhattan,
(Received
KS 66506, USA. Telephone:
913-532-6615
11 July 1983)
Abstract-l. Fatty acid composition of starved bobwhites returned to prestarved profiles within X-30 days as bobwhites on a recovery diet regained lost weight. 2. Percent composition of at least 50% of carcass fatty acids was significantly different from that of fatty acids in the bobwhite’s diet. 3. Nutritionally deprived bobwhites had a higher percent composition of arachidonic acid (20:4) than did birds on a nutritious diet. 4. Bobwhites altered the fatty acids of most diets in a consistent manner. 5. Discriminant analysis of carcass fatty acid composition correctly categorized 81% of the birds into their actual 20-day dietary treatment.
INTRODUCTION
Avian depot fats exhibit fatty acid profiles characteristic of season, diet, species, sex, and individual. Studies of the influence of diet on avian fatty acid profiles have produced conflicting results. Seasonal differences in the fatty acid composition of wild birds have been ascribed, at least in part, to seasonal differences in diet (Moss and Lough, 1968; West and Meng, 1968b; Barnett, 1970; Ijas et al., 1978). YomTov and Tietz (1978) concluded that diet affected the fatty acid composition of depot fat of rock partridge, Alectoris chucar, feeding on either sorghum seeds or olives in the same season. In contrast, dietary fatty acids were not found to influence the fat composition of the red poll, Acanthis,flrrmmea (West and Meng, 1968a), crossbills, Loxia curvirostra and L. leucoptera (Tanhuanpaa and Pullianen, 1975), and domestic fowl (Hazelwood, 1972). Most of the preceding studies involved direct statistical comparisons of the fatty acid content of the birds to that of their diets. However, the absence of statistical equality between the two fatty acid profiles does not mean that diet does not influence the fatty acid profile of an organism. Even if birds alter dietary fats, there may be a relationship between bird and diet fatty acids. Discriminant analysis may be a more appropriate statistical indicator of dietary influences on depot fatty acid composition than is analysis of variance. Discriminant analysis differentiates among groups and places individuals into specific categories (e.g. dietary) by simultaneously analyzing two or more variables (Snedecor and Cochran, 1967; Sokal and Rohlf, 1969). The purpose of this paper is to report the effect of time and diet on the fatty acid compositions of bobwhites, Colinus virginianus, under controlled laboratory conditions using both analysis of variance and discriminant analysis.
MATERIALS AND METHODS Weight stabilization Bobwhites used in this study were adult males obtained during winter from the Kansas Fish and Game Commission Quail Farm at Pittsburg, Kansas. Bobwhites were individually confined in 48 x 25 x 13 cm polypropylene cages with 1.3cm hardware cloth tops, and were housed in an environmental chamber with 9L: 15D photoperiod, 5°C temperature, and 85% relative humidity. Birds were provided a balanced mash (P-18) and water ad /ibitum for at least 30 days until their individual weights varied by less than k 2% of their individual mean weights during the previous 15 days. Experimental treatments For each of two experiments, 30 weight-stable birds were randomly divided into six 5-bird weight stratified groups. At the beginning of each experiment, one 5-bird group was selected at random and killed for fatty acid analysis. The other 5-bird groups were then starved to 757; of their initial stable weight. The first experiment studied the effects of time on fatty acid composition. One of the starved groups was killed and the remaining 4 groups were refed the P- 18mash ad libitum and killed at the end of 10, 20, 30, or 40 days. The second experiment studied the effect of diet on fatty acid composition. One starved group was killed and the remaining four groups were provided seeds of mile, Sorghunl culgare, sunflower, Helianthus maximiliani, soybean, SC@ max, false sunflower, Heliopsis helianthoides, or sumac, Rhus glabra, ad libitum for 20 days then killed for fatty acid analysis. Carcasses of all killed birds were stored frozen until analyzed for fatty acid composition.
Fatty acid analysis Head, wings, feet, skin and crop contents were removed from each frozen carcass, leaving subcutaneous fat deposits on the carcass. Carcasses were weighed to + 0.1 g and processed through a food chopper (Beardmore and Robel, 1976). Individual processed carcasses were blended in 300 ml of chloroform-methanol (2: 1 v/v). vacuum filtered, and reblended with another 200 ml of the debris chloroform-methanol (modified from Folch et al., 1957). Each combined chloroforn-methanol solution was washed
624
SUZANNE M. AKKUDA and ROBERT J. ROBEL
FATTY :
70
m 2
40
ACID
COMPOSITIONS
&12:0
Ej14:o
pl6:O
E_16:1
s14:1 F 16:2
g1e:o
lj1e:1
L16:2
J2O:O
K20.4
C20:5
; F u,
30
0 k 0 0
20
D 0 4
10
> : 4 u.
0 STABLE
1 STARVED TIME
Fig. 1. Percentage
1 lo AFTER
DAys
I20
BEGINNING
DAYS OF
130
DAYS
1
40
composition of carcass fatty acids and body weights of bobwhites (stable), starved. and IO-day recovery phases of this experiment.
twice, each time with 250 ml of deionized distilled water. Dietary lipids were extracted from ground seed using the method, with no modifications, from Folch et ul. (1957). Methyl esters were formed from the concentrated extracted lipids by adding 5 ml of boron trichloride in methanol, shaking the mixture and allowing it to set for I hr at room temperature, then adding hexane. Methyl esters collected from the upper layer were analyzed by gas-liquid chromatography on columns of diethylene glycol succinate at 170-180°C. The percent fatty acid composition of the mixture was calculated using peak-height times the width at one-half height (Heftman, 1967). Fatty acids not identified by comparison with standards were identified on a plot of the log retention times of known fatty acids against their carbon numbers and compared to Table II of Hofstetter and Holman (1965: 539).
DAYS
EXPERIMENT
during
prestarved
16: 1. 18: 1, and 18 :2 fatty acids than the prestarved group. The relative amounts of five of these fatty acids returned to the prestarved normal within 20-30 days and 16: I returned by 40 days. Their fatty acid composition at 40 days was not significantly different from that of the weight-stable bobwhites (Fig. 1). The percentages of fatty acids 18 : 0 and 20: 4 increased in starved bobwhites, but also returned to normal after l&20 days as the birds regained their prestarvation weight. A dramatic percentage increase of arachidonic acid 20:4 might be diagnostic of starved bobwhites. The consistency of the new fatty acid profile with the original profile suggests a causal relationship between dietary fats and their alteration into body fats.
Statistical analysis Analysis of variance (ANOVA) and least squares separation of means were used for direct comparison of bird and dietary fatty acids. Not all fatty acid data could be used in the ANOVA due to differences in their variances. Discriminant analysis was used for assigning bobwhites into diet categories based on carcass fatty acids only. The statistical computer package SAS (Helwig and Council, 1979) was used. Statistical significance was P = 0.05.
RESULTS
AND DISCUSSION
Effect of time Bobwhites starved to 75’j, of their pretrial body weights regained their lost weight after 20 days on an ad libitum recovery diet of P-18 (Fig. I). Starved bobwhites had lower percentages of 12:O. 14:0, 16:O.
Fatty acid profiles of bobwhites recovering their weight were significantly different in 2-5 of the six diet/carcass fatty acid comparisons, but there was no consistent pattern in the fatty acids that differed (Table 1). Fatty acid composition also differed between bobwhites provided different recovery diets for 20 days (Table 2). Most of these differences occurred in the level of fatty acids 18: 1, 18:2 and 20:4. These fatty acids constitute from 55.7 to 70.9”$ of the overall fatty acid profile. Carcasses of starved bobwhites and those birds provided a diet of sumac or false sunflower had very high levels of arachidonic acid (20:4). Bobwhites on false sunflower or sumac were not able to regain weight and survived no longer than 6 days into the
Fatty
625
acids of bobwhites
Table I. Mean percent fatty acid compositions of dietary items and of carcasses of bobwhites ihat were on those diets during a 20-day weight recovery period N
Percent fatty acid (carbon:unsaturated) 16:0 18:0 18:l 18:2* Saturated*
P-18 Carcass
2 5
16.5t 15.7t
2.4t 7.51
31.7t 17.2f
54.3t 22.6r
18.6t 40.0$
81.4t
Milo Carcass
2 5
16.7t 11.4t
2.7t 12.3f
39.0t 18.9f
51.2t 23.4f
17.at 29.0$
82.7t 68.6f
Sunflower Carcass
2 4
10.6t 10.9t
4.4t IS.01
13.0t
73.9t
9.3t
45.51
14.2t 29.31
85.8t 71.31
Soybean Carcass
2 3
24.1t 14.9:
14.4t 12.lt
28.lt 19.lt
44.5t
34.7t
25.1t
32.0t
68.2t 68.0t
False sunflower Carcass
2 7
1o.ot 14.7t
5.5t 11.6t
35.0t 12.91
56.8t 18.51
14.8t 26.3f
85.2t 73.61
Sumac Carcass
2 6
23.5t 12.1$
16.9t 11.8t
36.0t IO.32
25.6t II.8$
44.6t 26.81
55.4t 73.21
Dietary treatment
Unsaturated’ 60.0f
‘Statistical analysis performed on raw data. All other data arcsine transformed. t$ = Least square mean values with common superscripts within a column in a section are not significantly different (P = 0.05).
20-day weight recovery period. The high percentage of arachidonic acid in these food-stressed birds may have reflected preferential retention of this essential fatty acid while other fatty acids were being utilized. This preferential retention supports observations of Suttie (1972: 57) and Hilditch (1956: 478) who pointed out the necessity of arachidonic acid for proper growth and cell maintenance. Arachidonic acid is not a major component of the triglycerides, which are the major lipids used for energy reserve (Gunstone, 1958: 19). Unsaturated fatty acids constituted the majority of the fatty acids of bobwhites throughout this study (Table 1). While Bower and Helms (1968) showed the absolute energetic gain of selectively storing unsaturated fats to be of minor adaptive significance, Johnson and West (1973) proposed that the increased mobility of unsaturated fats might be of adaptive significance during the metabolic demands of migration. The increased mobility of unsaturated fatty acids may also be important for non-migratory birds during periods of food deprivation and/or extreme environmental conditions, when energy reserves need
to be mobilized quickly to maintain homeostasis in ambient temperatures below the thermoneutral zone (Geers and Decuypere, 1978). Perhaps all that may be concluded from these comparisons is the degree to which the bird’s fatty acid composition resembles that of the diet. The question of whether or not diet influences the fatty acid composition of birds is not answerable by such analyses. It is known that dietary lipids are broken down in the small intestine and also are synthesized from nonlipid compounds (Hazelwood, 1972). Idehfication
of diet using discriminant analysis
Discriminant analysis of carcass fatty acid composition correctly categorized all (23) of the bobwhites provided diets of P-18, mile, false sunflower, or sumac. The analysis was also able to correctly categorize two of four birds on the sunflower diet, and one of three birds on the soybean diet (Table 3). Thus, use of discriminant analysis on carcass fatty acid compositions allowed the correct classification of 26 of 32 (81.25%) bobwhites into their dietary groups. This successful determination of specific diets
Table 2. Mean percent fatty acid compositions of prestarved (stable) and starved bobwhites, and of bobwhites at the end of 20 davs on soecific weight recovery diets Experimental group Recovery diet Fatty acid (carbon:unsaturated) .~ _______ 12:o 14:o 14:l 16:O 16:l 16:2 18:O 18:l 18:2* 20:o 20:4*
Weight stable lO.Of 9.4t 5.5t 15.7t
@It%
o.ot 7.5t
17.2tt 22.6tf o.ot 15.9t!:
Starved
Mile
Sunflower
Soybean
I.61 I .4f I .4f 15.2t 0.1t: o.ot 14.5tf 14.ltfB 14.7G o.ot 39&O
2.11 2.3t 1.4f 11.4t 5.6f o.ot 12.3t: 1s.9t 23.4tt 0.2t 25.6t
I .6f
2.4% 1.91 2.4)f 14.9t o.ot 0.1t 12.lif 19.ltf 25.1t 0.4t 21.7tz
2.21 2.4f 10.9t 0.1t1 0 5t lS.O$ 9.35 45.511 O.lf
13.8f
False sunflower 2.3$
1.4$ 2.9t$ 14.7t o.ot 0.1t I1.6t$ 12.915 18.5tt o.ot 39.34
Sumac 2.l$ 1.4i 2.4f 12.1t o.ot o.ot ll.st$ IO.35 ll.S$ o.ot 48.811
N 5 5 4 3 7 6 *Statistical analysis performed on raw data. All other data were arcsine transformed. t$§11= Least square mean values with common superscripts within a row are not significantly different (P = 0.05)
626
SUZANNE
M. ARRUUA and ROBEKT J. RO~EL
Table 3. Discriminant analysis asstgnment of bobwhites into dietary categories using czarcabs fatty acid composition of starved birds on specific recovery diets for 20 days Dietary treatment P-18 Mile False sunflower Sumac Sunflower Soybean
Number of birds 5 5 I h 2 ?
1 :!
Starved
I 1
Categorized into P-18 Milo False sunflower Sumac Sunflower SUllldf Soybean Mile Milo
Sumac
from fatty acid compositions of carcasses reflects a relationship between the fatty acid profile of the diet and the carcass. As noted in Table 1, the fatty acids of the diet are not simply absorbed and stored unaltered in the bobwhite carcass. Variations did exist between bobwhites in different treatments, and the only factor that differed in these treatments was their diet. Therefore, diet must have influenced the fatty acid profile of the bobwhites. Discriminant analysis results indicate that bobwhites produce a specific fatty acid nrofile when metabolizing certain dietarv items. In this study, fatty acid profiles were unique-for diets of P-18. milo. false sunflower. and sumac. but not unique for diets of sunflower and soybean, or for the starved birds. Half of the latter were misclassified as sumac. Both starved birds and sumac-fed birds were malnourished, based on weight loss and survival. Additional use of discriminant analysis in the study of fatty acid compositions may provide insights into the biological significance of different diets in the survival of food-stressed wild birds. Ackno~ledgetttents-We are grateful to A. D. Dayton for statistical consultation, and W. Klopfenstein for use of the gas-liquid chromatograph and interpretation of data. The study was financed by the Kansas Agricultural Experiment Station and the National Science Foundation (Grant No. BSR-8022568). Contribution No. 83-252-J. Division of Biology, Kansas Agricultural Experiment Station, Kansas State University. Manhattan, KS 66506.
REFERENCES Barn&t L. B. (1970) Seasonal changes in temperature acclimatization of the House Sparrow, Pussc~r domesticus. Camp. Biorhem. Physioi. 33, 559-578. Beardmore C. J. and Robe1 R. J. (1976) Weight and body fat recovery by dieldrin-dosed, underweight bobwhites. I. Wifdl. Mgmt 40, 118-121. Bower E. and Helms C. (1968) Seasonal variation in fatty acids of the Slate-colored junco (Bunco h,renzcrlis). fhysio(. Zool. 41, 157-168. Folch J., Lees M. and Sloane-Stanley G. II. (IY57) A simple method for the isolation and purification of total lipids from animal tissues. J. hiol. Chem. 226, 497-509.
Probability of correct categorization 0.9999 0.9534 I .oooo 0.9999 I .oooo OX!%4 0.Y984 0 992X 0.9950 0.9330
Geers R. and Decuypere M. H. (1978) Critical analysis of fasting metabolism data in Rhode Island Red Hens (Gullus gallus). Ann. Biol. An. 18, 1363-l 369. Gunstone F. D. (1958) An Introduction to the Chemistry of‘ Fats nnd Fatty Acids. Wiley, New York. Hazeiwood R. L. (1972) The intermediary metabolism of birds. In Aviun Bia1og.v (Edited by Farner D. S. and King J. R.), pp. 471526. Academic Press, New York. Heftmdn E. ( 1967) C~r~~~?~~t(~gr~~ph~, 2nd edn. Reinhold. New York. Helwig J. T. and Council K. A. (1979) SAS ~~ser‘.s Guide. SAS Institute. Raleigh, North Carolina. Hilditch T. P. (I 956) 7%~ Chemical Constitution of N~tlirul Fats. 3rd edn. Wilev. New York. Hofstetter H. and Holman R. (1965) Characterization of unsaturated fatty acids. J. Am. Oil Chem. Sec. 42, 537-540. Ijas L., Nuiya I., Sormajar J. and Valkeaja P. (1978) Body lipid-composition in winter fed and control populations of wild male Black grouse (L,wurus-Tetrir-L) in autumn and spring. Comp. Biochrm. Physiol. 6OA, 313-3 17. Johnson S. R. and West G. C. (1973) Fat content, fatty acid composition, and estimates of energy metabolism of Adelie penguins during the early breeding season fast. Comp. Biochem. Ph~sio~. 458, 709-719. Moss R. and Lough A. K. (1968) Fatty acid composition of depot fat in some game birds (Tf,tru~~njdu~,). romp. B&hem. Physiof. 25, 559-562. Snedecor G. W. and Cochran W. C. (1967) Stuti.sticaf Methods, 6th edn. Iowa State University Press, Iowa Sokal R. R. and Rohlf F. J. (1969) Biometry,. Freeman & Comp. San Francisco, CA. Suttie J. W. (1972) introduction to Biochemktry. Holt, Rinehart & Winston, New York. Tanhtuinpaa E. and Pulhainen E. (1975)Effect of diet on the fatty acid composition of some organ fats in crossbills: (Loxia currkstra & L. leucoptera). Ann. 2001. Fenn. 12, 156-t59. West G. C. and Meng M. S. (i968a) The effect of diet and captivity on the fatty acid composition of redpoll (Acurlthis ,~anzrneu ) depot fats. C‘onrl). ~i~c~zt,f?z. ~i~.~.si~I. 25, 535-540. West G. C. and Meng M. S. (1968b) Seasonal changes in body weight and fat and the relation of fatty- acid composition to diet in Willow ptarmigan. Wilsnn Bull. 80, . 426-441. Yom-Tov Y. and Tietz A. (1978) The effect of diet, ambient temperature, and day length on fatty acid composition in the depot fat of the european starling (Sturnus wlgoris) and the rock partridge (Alec/ori.v chucur). Camp. Biochem. Physiol. 6OA, 16 I - 164.
EFFECT
0300-9629184$3.00 + 0.00 ,c 1984 Pergamon Press Ltd
OF TIME AND DIET ON CARCASS FATTY ACID COMPOSITION OF BOBWHITES, COLINUS
VIRGINIANUS
SUZANNE M. ARRUDA Division
of Biology,
Kansas
State University.
and ROBERT J. ROBEL
Manhattan,
(Received
KS 66506, USA. Telephone:
913-532-6615
11 July 1983)
Abstract-l. Fatty acid composition of starved bobwhites returned to prestarved profiles within X-30 days as bobwhites on a recovery diet regained lost weight. 2. Percent composition of at least 50% of carcass fatty acids was significantly different from that of fatty acids in the bobwhite’s diet. 3. Nutritionally deprived bobwhites had a higher percent composition of arachidonic acid (20:4) than did birds on a nutritious diet. 4. Bobwhites altered the fatty acids of most diets in a consistent manner. 5. Discriminant analysis of carcass fatty acid composition correctly categorized 81% of the birds into their actual 20-day dietary treatment.
INTRODUCTION
Avian depot fats exhibit fatty acid profiles characteristic of season, diet, species, sex, and individual. Studies of the influence of diet on avian fatty acid profiles have produced conflicting results. Seasonal differences in the fatty acid composition of wild birds have been ascribed, at least in part, to seasonal differences in diet (Moss and Lough, 1968; West and Meng, 1968b; Barnett, 1970; Ijas et al., 1978). YomTov and Tietz (1978) concluded that diet affected the fatty acid composition of depot fat of rock partridge, Alectoris chucar, feeding on either sorghum seeds or olives in the same season. In contrast, dietary fatty acids were not found to influence the fat composition of the red poll, Acanthis,flrrmmea (West and Meng, 1968a), crossbills, Loxia curvirostra and L. leucoptera (Tanhuanpaa and Pullianen, 1975), and domestic fowl (Hazelwood, 1972). Most of the preceding studies involved direct statistical comparisons of the fatty acid content of the birds to that of their diets. However, the absence of statistical equality between the two fatty acid profiles does not mean that diet does not influence the fatty acid profile of an organism. Even if birds alter dietary fats, there may be a relationship between bird and diet fatty acids. Discriminant analysis may be a more appropriate statistical indicator of dietary influences on depot fatty acid composition than is analysis of variance. Discriminant analysis differentiates among groups and places individuals into specific categories (e.g. dietary) by simultaneously analyzing two or more variables (Snedecor and Cochran, 1967; Sokal and Rohlf, 1969). The purpose of this paper is to report the effect of time and diet on the fatty acid compositions of bobwhites, Colinus virginianus, under controlled laboratory conditions using both analysis of variance and discriminant analysis.
MATERIALS AND METHODS Weight stabilization Bobwhites used in this study were adult males obtained during winter from the Kansas Fish and Game Commission Quail Farm at Pittsburg, Kansas. Bobwhites were individually confined in 48 x 25 x 13 cm polypropylene cages with 1.3cm hardware cloth tops, and were housed in an environmental chamber with 9L: 15D photoperiod, 5°C temperature, and 85% relative humidity. Birds were provided a balanced mash (P-18) and water ad /ibitum for at least 30 days until their individual weights varied by less than k 2% of their individual mean weights during the previous 15 days. Experimental treatments For each of two experiments, 30 weight-stable birds were randomly divided into six 5-bird weight stratified groups. At the beginning of each experiment, one 5-bird group was selected at random and killed for fatty acid analysis. The other 5-bird groups were then starved to 757; of their initial stable weight. The first experiment studied the effects of time on fatty acid composition. One of the starved groups was killed and the remaining 4 groups were refed the P- 18mash ad libitum and killed at the end of 10, 20, 30, or 40 days. The second experiment studied the effect of diet on fatty acid composition. One starved group was killed and the remaining four groups were provided seeds of mile, Sorghunl culgare, sunflower, Helianthus maximiliani, soybean, SC@ max, false sunflower, Heliopsis helianthoides, or sumac, Rhus glabra, ad libitum for 20 days then killed for fatty acid analysis. Carcasses of all killed birds were stored frozen until analyzed for fatty acid composition.
Fatty acid analysis Head, wings, feet, skin and crop contents were removed from each frozen carcass, leaving subcutaneous fat deposits on the carcass. Carcasses were weighed to + 0.1 g and processed through a food chopper (Beardmore and Robel, 1976). Individual processed carcasses were blended in 300 ml of chloroform-methanol (2: 1 v/v). vacuum filtered, and reblended with another 200 ml of the debris chloroform-methanol (modified from Folch et al., 1957). Each combined chloroforn-methanol solution was washed
624
SUZANNE M. AKKUDA and ROBERT J. ROBEL
FATTY :
70
m 2
40
ACID
COMPOSITIONS
&12:0
Ej14:o
pl6:O
E_16:1
s14:1 F 16:2
g1e:o
lj1e:1
L16:2
J2O:O
K20.4
C20:5
; F u,
30
0 k 0 0
20
D 0 4
10
> : 4 u.
0 STABLE
1 STARVED TIME
Fig. 1. Percentage
1 lo AFTER
DAys
I20
BEGINNING
DAYS OF
130
DAYS
1
40
composition of carcass fatty acids and body weights of bobwhites (stable), starved. and IO-day recovery phases of this experiment.
twice, each time with 250 ml of deionized distilled water. Dietary lipids were extracted from ground seed using the method, with no modifications, from Folch et ul. (1957). Methyl esters were formed from the concentrated extracted lipids by adding 5 ml of boron trichloride in methanol, shaking the mixture and allowing it to set for I hr at room temperature, then adding hexane. Methyl esters collected from the upper layer were analyzed by gas-liquid chromatography on columns of diethylene glycol succinate at 170-180°C. The percent fatty acid composition of the mixture was calculated using peak-height times the width at one-half height (Heftman, 1967). Fatty acids not identified by comparison with standards were identified on a plot of the log retention times of known fatty acids against their carbon numbers and compared to Table II of Hofstetter and Holman (1965: 539).
DAYS
EXPERIMENT
during
prestarved
16: 1. 18: 1, and 18 :2 fatty acids than the prestarved group. The relative amounts of five of these fatty acids returned to the prestarved normal within 20-30 days and 16: I returned by 40 days. Their fatty acid composition at 40 days was not significantly different from that of the weight-stable bobwhites (Fig. 1). The percentages of fatty acids 18 : 0 and 20: 4 increased in starved bobwhites, but also returned to normal after l&20 days as the birds regained their prestarvation weight. A dramatic percentage increase of arachidonic acid 20:4 might be diagnostic of starved bobwhites. The consistency of the new fatty acid profile with the original profile suggests a causal relationship between dietary fats and their alteration into body fats.
Statistical analysis Analysis of variance (ANOVA) and least squares separation of means were used for direct comparison of bird and dietary fatty acids. Not all fatty acid data could be used in the ANOVA due to differences in their variances. Discriminant analysis was used for assigning bobwhites into diet categories based on carcass fatty acids only. The statistical computer package SAS (Helwig and Council, 1979) was used. Statistical significance was P = 0.05.
RESULTS
AND DISCUSSION
Effect of time Bobwhites starved to 75’j, of their pretrial body weights regained their lost weight after 20 days on an ad libitum recovery diet of P-18 (Fig. I). Starved bobwhites had lower percentages of 12:O. 14:0, 16:O.
Fatty acid profiles of bobwhites recovering their weight were significantly different in 2-5 of the six diet/carcass fatty acid comparisons, but there was no consistent pattern in the fatty acids that differed (Table 1). Fatty acid composition also differed between bobwhites provided different recovery diets for 20 days (Table 2). Most of these differences occurred in the level of fatty acids 18: 1, 18:2 and 20:4. These fatty acids constitute from 55.7 to 70.9”$ of the overall fatty acid profile. Carcasses of starved bobwhites and those birds provided a diet of sumac or false sunflower had very high levels of arachidonic acid (20:4). Bobwhites on false sunflower or sumac were not able to regain weight and survived no longer than 6 days into the
Fatty
625
acids of bobwhites
Table I. Mean percent fatty acid compositions of dietary items and of carcasses of bobwhites ihat were on those diets during a 20-day weight recovery period N
Percent fatty acid (carbon:unsaturated) 16:0 18:0 18:l 18:2* Saturated*
P-18 Carcass
2 5
16.5t 15.7t
2.4t 7.51
31.7t 17.2f
54.3t 22.6r
18.6t 40.0$
81.4t
Milo Carcass
2 5
16.7t 11.4t
2.7t 12.3f
39.0t 18.9f
51.2t 23.4f
17.at 29.0$
82.7t 68.6f
Sunflower Carcass
2 4
10.6t 10.9t
4.4t IS.01
13.0t
73.9t
9.3t
45.51
14.2t 29.31
85.8t 71.31
Soybean Carcass
2 3
24.1t 14.9:
14.4t 12.lt
28.lt 19.lt
44.5t
34.7t
25.1t
32.0t
68.2t 68.0t
False sunflower Carcass
2 7
1o.ot 14.7t
5.5t 11.6t
35.0t 12.91
56.8t 18.51
14.8t 26.3f
85.2t 73.61
Sumac Carcass
2 6
23.5t 12.1$
16.9t 11.8t
36.0t IO.32
25.6t II.8$
44.6t 26.81
55.4t 73.21
Dietary treatment
Unsaturated’ 60.0f
‘Statistical analysis performed on raw data. All other data arcsine transformed. t$ = Least square mean values with common superscripts within a column in a section are not significantly different (P = 0.05).
20-day weight recovery period. The high percentage of arachidonic acid in these food-stressed birds may have reflected preferential retention of this essential fatty acid while other fatty acids were being utilized. This preferential retention supports observations of Suttie (1972: 57) and Hilditch (1956: 478) who pointed out the necessity of arachidonic acid for proper growth and cell maintenance. Arachidonic acid is not a major component of the triglycerides, which are the major lipids used for energy reserve (Gunstone, 1958: 19). Unsaturated fatty acids constituted the majority of the fatty acids of bobwhites throughout this study (Table 1). While Bower and Helms (1968) showed the absolute energetic gain of selectively storing unsaturated fats to be of minor adaptive significance, Johnson and West (1973) proposed that the increased mobility of unsaturated fats might be of adaptive significance during the metabolic demands of migration. The increased mobility of unsaturated fatty acids may also be important for non-migratory birds during periods of food deprivation and/or extreme environmental conditions, when energy reserves need
to be mobilized quickly to maintain homeostasis in ambient temperatures below the thermoneutral zone (Geers and Decuypere, 1978). Perhaps all that may be concluded from these comparisons is the degree to which the bird’s fatty acid composition resembles that of the diet. The question of whether or not diet influences the fatty acid composition of birds is not answerable by such analyses. It is known that dietary lipids are broken down in the small intestine and also are synthesized from nonlipid compounds (Hazelwood, 1972). Idehfication
of diet using discriminant analysis
Discriminant analysis of carcass fatty acid composition correctly categorized all (23) of the bobwhites provided diets of P-18, mile, false sunflower, or sumac. The analysis was also able to correctly categorize two of four birds on the sunflower diet, and one of three birds on the soybean diet (Table 3). Thus, use of discriminant analysis on carcass fatty acid compositions allowed the correct classification of 26 of 32 (81.25%) bobwhites into their dietary groups. This successful determination of specific diets
Table 2. Mean percent fatty acid compositions of prestarved (stable) and starved bobwhites, and of bobwhites at the end of 20 davs on soecific weight recovery diets Experimental group Recovery diet Fatty acid (carbon:unsaturated) .~ _______ 12:o 14:o 14:l 16:O 16:l 16:2 18:O 18:l 18:2* 20:o 20:4*
Weight stable lO.Of 9.4t 5.5t 15.7t
@It%
o.ot 7.5t
17.2tt 22.6tf o.ot 15.9t!:
Starved
Mile
Sunflower
Soybean
I.61 I .4f I .4f 15.2t 0.1t: o.ot 14.5tf 14.ltfB 14.7G o.ot 39&O
2.11 2.3t 1.4f 11.4t 5.6f o.ot 12.3t: 1s.9t 23.4tt 0.2t 25.6t
I .6f
2.4% 1.91 2.4)f 14.9t o.ot 0.1t 12.lif 19.ltf 25.1t 0.4t 21.7tz
2.21 2.4f 10.9t 0.1t1 0 5t lS.O$ 9.35 45.511 O.lf
13.8f
False sunflower 2.3$
1.4$ 2.9t$ 14.7t o.ot 0.1t I1.6t$ 12.915 18.5tt o.ot 39.34
Sumac 2.l$ 1.4i 2.4f 12.1t o.ot o.ot ll.st$ IO.35 ll.S$ o.ot 48.811
N 5 5 4 3 7 6 *Statistical analysis performed on raw data. All other data were arcsine transformed. t$§11= Least square mean values with common superscripts within a row are not significantly different (P = 0.05)
626
SUZANNE
M. ARRUUA and ROBEKT J. RO~EL
Table 3. Discriminant analysis asstgnment of bobwhites into dietary categories using czarcabs fatty acid composition of starved birds on specific recovery diets for 20 days Dietary treatment P-18 Mile False sunflower Sumac Sunflower Soybean
Number of birds 5 5 I h 2 ?
1 :!
Starved
I 1
Categorized into P-18 Milo False sunflower Sumac Sunflower SUllldf Soybean Mile Milo
Sumac
from fatty acid compositions of carcasses reflects a relationship between the fatty acid profile of the diet and the carcass. As noted in Table 1, the fatty acids of the diet are not simply absorbed and stored unaltered in the bobwhite carcass. Variations did exist between bobwhites in different treatments, and the only factor that differed in these treatments was their diet. Therefore, diet must have influenced the fatty acid profile of the bobwhites. Discriminant analysis results indicate that bobwhites produce a specific fatty acid nrofile when metabolizing certain dietarv items. In this study, fatty acid profiles were unique-for diets of P-18. milo. false sunflower. and sumac. but not unique for diets of sunflower and soybean, or for the starved birds. Half of the latter were misclassified as sumac. Both starved birds and sumac-fed birds were malnourished, based on weight loss and survival. Additional use of discriminant analysis in the study of fatty acid compositions may provide insights into the biological significance of different diets in the survival of food-stressed wild birds. Ackno~ledgetttents-We are grateful to A. D. Dayton for statistical consultation, and W. Klopfenstein for use of the gas-liquid chromatograph and interpretation of data. The study was financed by the Kansas Agricultural Experiment Station and the National Science Foundation (Grant No. BSR-8022568). Contribution No. 83-252-J. Division of Biology, Kansas Agricultural Experiment Station, Kansas State University. Manhattan, KS 66506.
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Probability of correct categorization 0.9999 0.9534 I .oooo 0.9999 I .oooo OX!%4 0.Y984 0 992X 0.9950 0.9330
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