The Metabolizable Energy of Sunflower Seed Kernel in Goffin's Cockatoo (Cacatua goffini) and a Review of the Amino Acid and Fatty Acid Composition of Oil Seeds Eaten by Parrots


Mark Hagen, M. Ag..
Research Performed at:
Department of Animal and Poultry Science
University of Guelph
Guelph, Ontario, Canada
N1G 2W1



Summary

The proximate analysis of the seed kernels of sunflower, safflower and peanut, common food for captive parrots, indicated that they contain very high fat and moderate protein levels with comparably high gross energies. The metabolizable energy value of sunflower seed kernel in caged Goffin's Cockatoos was 6,207 282 kcal/kg when determined in an ad libitum total collection trial and 6,094 86 kcal/kg when determined by force feeding with total collection. The mean daily existence metabolism for the Goffin's under caged maintenance conditions was 48 kcal/day/bird or 186 kcal/day/kg. This is about 2.2 times the basal metabolic rate predicted for these birds.

When comparing the essential amino acid profile for growth requirements in poultry to the levels found in oilseed kernel protein it appears that lysine and methionine are limiting in all three seeds examined plus threonine is also limiting in safflower and peanut protein. The comparative whole carcass amino acid composition of the chicken to a small parrot, the bugerigar shows a similarity which may allow the use of broiler requirements as estimates of parrot amino acid requirements.



INTRODUCTION

A recent nationwide survey of pet owners determined that 71 to 77% of bird owners purchased boxed or bagged seed with only 10% purchasing pellets.1 Yet few scientific studies have been performed on the nutritional value of these seeds. The guaranteed analysis on a seed package does not provide much information as to the nutritional value of the mix as it includes the high fiber hulls which parrots do not eat.

Additionally most birds will select their favorite seeds out of a mix before eating the other ingredients, if they eat them at all. Thus each mixture of seeds may provide different nutrient levels depending on the final ratio of seeds and other ingredients eaten by the bird. The oilseeds sunflower and safflower represent the major portion of most parrots' diets fed seed mixes as they are common ingredients and preferred by the birds over other seeds. Several varieties of sunflower are commercially grown. Oil-type seeds are grown to yield edible oil and high fiber protein meal. Whole confectionery seeds have loose kernels within the hull and are lower in oil because they have a higher fraction of hull.2 Both forms are included in seed mixes with the confectionery seed being more common.

The dietary energy which the bird can utilize is referred to as metabolizable energy (ME).3 Caloric need is the main factor controlling feed intake. Therefore knowing the daily energy requirements, and the ME value of a diet is helpful when formulating for a proper balance of vitamins, minerals and protein as the levels of these nutrients are based on the feed intake.

Gross energy (GE) represents the release of heat when a substance is completely oxidized and does not provide direct prediction of utilization of energy by a given animal.4 Apparent digestible energy (DE) is the GE of the feed consumed minus fecal energy.4 Fecal and urinary waste mix in the cloaca of birds before being voided thus DE is difficult to study in birds. The apparent metabolizable energy (AME), the most widely used measure of food energy available to birds, can be determined by subtracting by the energy of the excreta (fecal + urinary) from the GE of the feed eaten and dividing by the weight of the feed eaten.3 True ME (TME) determination requires the separation of the GE of the excreta of food origin from that of nonfood origin and correcting for this.5 TMEn is TME corrected for protein tissue growth or loss by adding to the excreta energy the energy equivalent of the nitrogen retained or subtracting from it the energy equivilant of the nitrogen lost. However this is relatively small for birds under maintenance conditions.5

The common method to determine ME is by assays in which the test feed is substituted for part of a reference diet or for some ingredient of known ME value.4 An inert, unabsorbed marker such as chromic oxide can simplify the assay by making total quantitative collections of excreta unnecessary. As in digestion studies, the relative concentration of the marker in feed and excreta is used to calculate the amount of excreta derived from a unit of feed consumed.5

The accurate addition and uniform consumption of an index material on a whole seed is not possible thus total feed intake and excreta output must be determined in order to calculate ME. In an ad libitum trial actual feed intake measurement and uncontaminated excreta collection is complicated by feed spillage. Goffin's Cockatoos are very active birds and beak out their feed from feeders. If wasted feed is mixed with the excreta it will increase experimental error because feed intake and excreta weight are both overestimated.

An alternative experiment which would eliminate these possible errors involves force feeding (FF) the birds a precisely measured amount of liquified feed. No other food would be available to the birds and pure excreta is collected. Parrots exhibit diurnal behaviour and have crops which can store enough food, to be slowly released, until the next feeding. With FF the bird no longer has control over the quantity of food ingested and the level given may not be that promoting energy equilibrium. An increase or decrease in the quantity of food FF may alter digestibility. This will be minimized by FF a quantity of seed kernel approximately equal to the amount ingested by the bird during the ad lib. trial.

Existence metabolism is defined as the energy expenditure of caged birds that maintained a constant body mass over a period of days when they are not undergoing reproduction, molting, migratory unrest, growth, or fat deposition.6 It measures the basal metabolic rate, plus energy for thermoregulation, for specific dynamic action, and for the limited amount of activity permitted by the confines of the cage.6 Existence metabolism for the caged Goffin's Cockatoos in this study can be calculated from the net amount of food eaten during the ad libitum trial and the determined ME of that feed.



EXPERIMENTAL PROCEDURES

The ME of sunflower seed kernel in adult Goffin's Cockatoo under maintenance conditions was determined by two different experimental methods, ad libitum and force feeding.

The ad lib. feeding trial lasted five days. To minimize error in this trial feeders were designed to minimize scattering of the feed, wasted feed was collected from under the bird and already hulled seed (kernels only) was fed. To reach the kernels, birds had to stick their heads into the small opening of a gravity feeder and could not easily toss the kernels out. Twice daily, wasted kernel was carefully brushed away from excreta and into a container marked for each bird and filled during the length of the trial. Feed intake over the five days was calculated from feeder weight loss and corrected for spillage of kernels. Daily energy expenditure for each bird can be calculated from the net feed intake and its ME.

The force feeding trial was performed with a syringe and steel feeding tube that was passed down the esophagus directly into the crop. To precisely measure the amount of liquified kernel fed, a syringe loaded with food was tared on a balance before feeding and then weighed after. The kernels were ground up in a coffee grinder and mixed with water to produce 37.5% solids. The birds were tube fed two times a day over three and a half days for a total of seven feedings.

The birds were starved for 36 hours before and after each trial in order to collect only and all excreta produced from feed ingested during the trial. Collection began just before the first feeding and ended 24 hours after the last. The collected excreta were homogenized, dried, finely ground and weighed on a dry matter basis. The birds were individually housed in cages 50cm x 50 cm x 66cm in a climate controlled room maintained at 18C and 50% relative humidity. The birds were kept under 12 hours light:12 hours dark lighting regime.

The two trials were run at different times on the same thirty birds. The ME's resulting from the two methods will be compared and possible areas of error identified. To eliminate bird to bird variation, only paired data from the same bird was used. A paired t test was used to compare ME means of the two groups and the F' statistic to compare the variances of the two treatments. Although the trials are confounded with time, it is assumed that this has no effect on ME with the adult birds used.

The assay to determine the GE of the feed and excreta is the bomb calorimeter technique. It consists of igniting a weighed sample in an oxygen atmosphere and measuring the amount of heat transmitted to a measured quantity of water. The GE's are used in the calculation of ME in each bird. The GE of excreta from each bird was determined in duplicate for mean excreta GE. Feed GE was based on the mean of four bombings of sunflower, and for comparison, safflower and peanut kernels.

Many ingredients used in the agriculture feed industry can not be fed in the pure form as the test animal would stop eating. Parrots will eat sunflower exclusively for many years. This simplifies calculations and increases the precision of the estimate as interactions with other ingredients in a basal test diet will not have to be considered.

Proximate analysis and the GE of three common oilseeds fed to parrots, sunflower, safflower and peanut were determined. A literature review of the amino acid and fatty acid composition of the three oilseeds was done and compared to the estimated requirements (based on broiler requirements) and whole budgie and chicken carcass composition.



RESULTS

The proximate analysis of confectionery sunflower kernel listed in Table 1 indicates its high fat and moderate protein composition. Another oilseed and a legume commonly fed to parrots, safflower and peanut, have a similar composition (Table 1). The GE's for the three kernels are high as would be expected from their proximate analysis (Table 1).

The metabolizable energy value of sunflower seed kernel in caged Goffin's Cockatoos was 6.207 0.282 kcal/g when determined in an ad libitum total collection trial and 6.094 0.086 kcal/g when determined by force feeding with total collection (Appendix 1 and 2).



Table 1. Proximate analysis of seed kernels or nut meat expressed as per cent (a) and their gross energy value.
=======================================================================
Kerne                  Crude    Crude  Crude           N.F.E   GE (e)
or Nut Meat   Moisture Protein  Fat    Fiber    Ash     (d)    kcal/kg
_________________________________________________________________________
Sunflower (b)	4.9	22.4	53.8	3.6	3.0	12.3    7,097
Safflower (c)	3.0	23.6	59.3	2.6	3.2	 8.3	7,429
Raw Peanut	3.6	29.4	53.0	2.4	2.3	 9.3	6,829
_________________________________________________________________________

(a) 	Mean values of two samples send to separate labs.
(b) 	Hulled confectionery sunflower as used in the ME trial.
(c) 	Hulled by hand from seeds found in Topper Bird Ranch Diet, Lexington, N.C.
(d) 	N.F.E. or nitrogen-free extract, is the difference between 100% and the sum  
        of the percentages of moisture, protein, fat, fiber, and ash.  It is considered 
        to represent the carbohydrate other than fiber.
(e) 	Mean values based on four bomb calorimeteries for each feed.



These mean values for each trial were not significantly different, however, there was significantly greater variation within the ad lib. trial than when the birds were force fed (Table 2).



Table 2. Comparison of ME value of sunflower determined by ad libitum and force fed methods.
======================================================================
Trial          Mean ME     Std.Dev.   Std.err     Min.       Max.
               kcal/kg                           kcal/kg   kcal/kg
______________________________________________________________________
Ad libitum    	6207 (a)     282 (b)     65       5,498     6,624
Force fed     	6094          86         20       5,899     6,208
______________________________________________________________________
	
(a) 	t statistic is insignificant and the means
	are thus equal; T = 1.53, d.f.= 36,  prob > [t] = 0.1337.
(b) 	The F' statistic is highly significant and the variances
	are thus different; F'= 10.76, d.f.= 18,18 , prob > F'=0.0001.



The mean daily existence metabolism for the Goffin's under maintenance conditions was 48 kcal/day/bird or 186 Kcal/day/kg (Appendix 1).

Wasted kernel during the ad lib. trial ranged from 14 g to 201 g with a mean of 58 g per bird.



DISCUSSION

REVIEW OF OILSEED AMINO ACID AND FATTY ACID COMPOSITION

Amino acid requirements are often listed in percentages of the diet however this way of expressing them makes it difficult to compare the amino acid profiles of diets with different energy and protein levels. Expressing amino acid levels as percentages of the protein rather than the whole diet or feed makes comparisons more meaningful.

The amino acid compositions of the oilseed proteins (Table 3) is based on kernel protein rather than oilseed meal protein which is more commonly found in the literature.7,8,9 Meals are the residue of the seed after extraction of the oil and their amino acid profiles may differ due to the inclusion of hull protein.

Although serine, cystine and tyrosine are not essential amino acids, they are included with the essential amino acids because they can spare a portion of the requirement for glycine, methionine and phenylalanine, respectively.



Table 3. Estimated Essential Amino Acid Requirements of Parrots and Composition of three common seed kernel/nut meats (g amino acid/16 g nitrogen).
=========================================================================
Essential     Estimated  Sunflower Safflower Peanut  Budgie     Chicken
Amino Acid(a) Require(b) Kernel(c) kernel(d) meat(e) Carcass(f) Carcass(g)
_________________________________________________________________________
Arginine         6.0      10.0       9.4      11.2       5.9      6.8
Glycine          5.0       9.3       9.3      10.4      10.8       -
   + Serine
 Histidine       1.5       2.8       2.6       2.4       2.2      4.1
 Isoleucine      3.5       4.5       3.7       3.3 h 94% 3.9      3.9
Leucine	         5.9       7.0       6.0       6.6       6.2      6.5
Lysine	         5.0       3.9 h 78% 3.2 h 64% 3.2 h 64% 7.1      9.9
Methionine       3.6       3.7       3.2 (h)   2.5 (h)    -       4.3
   + Cystine
Methionine       1.9       1.8 h 95% 1.5 h 79% 1.2 h 63% 2.2      1.9
Phenylalanine    5.9       7.4       7.2       8.9       6.8      6.7
   + Tyrosine
Phenylalanine    3.2       4.7       4.3       5.0       3.9      3.6
Threonine        3.7       3.8       3.2 h 86% 3.1 h 84% 4.0      3.4
Valine           3.6       5.2       5.3       4.2       4.8      4.4

Number of Limiting Amino Acids        2         3         4
__________________________________________________________________________

(a) 	Essential for growing poultry.(4)
(b) 	Based on NRC requirement (4) for Broilers receiving a diet of 20%
        protein and 3200 kcal ME/kg.
(c) 	From Robinson RG.(11) and Sastry, MCS, Murray, DR. (17)
(d)	From Vanetten et al.(12) and Food and Agriculture. (13)
(e) 	From Food and Agriculture Organization(13) and Pancholy et al. (14)
(f) 	From Massey DM, Sellwood EHB, Waterhouse CE.(15)
(g) 	From Scott ML.(16)
(h) 	Limiting amino acids and % of requirement supplied when compared
        to estimated requirements.


However under certain conditions the requirement for cystine may not be met by synthesis from methionine, especially if the diet is low in both these amino acids. Feather protein contains a higher amount of cystine than other body proteins.10 Thus, during maximum feather growth in a nestling or molting in an adult, the relative requirement for cystine may increase.

Cystine also serves as the precursor of taurine which in chickens and probably parrots as well, is conjugated with cholic acid during the formation of bile.5 Bile formation is induced by fat which is high in oilseed kernels. Thus, these kernels may induce more conversion of methionine to cystine to taurine for formation of taurocholic acid.

Along with incomplete absorbtion, methionine is probably a limiting amino acid in sunflower kernel and isoleucine in peanut meat, during growth or reproduction although their levels are similar to the estimated requirement.

Another factor which may alter specific amino acid requirements in birds being fed oilseed kernel exclusively is that peroxidizing polyunsaturated fats produce aldehydes which may bind lysine.5 The major portion of fat in sunflower and safflower is in the form of the polyunsaturated fatty acid, linoleic (Table 4) and this factor may further exacerbate the already limiting status of lysine within these proteins.

The comparative whole carcass amino acid composition of the chicken to a small parrot, the budgerigar shows a similarity which may allow the use of broiler requirements as estimates of parrot amino acid requirements for growth. Research at UC Davis found the lysine requirement of Cockatiels to be 0.8% and total protein requirement 20% of the diet on a dry matter basis.21,22 This is very similar to the broiler requirements used here as estimates for parrot growth requirements.



Table 4. Fatty Acid Composition of Sunflower, Safflower and Peanut Oils.
=======================================================================

Fatty Acids         Sunflower(a)    Safflower(b)   Peanut(c)

Saturated               
Palmitic (16:0)        5 - 7          5 - 7         8 - 12
Stearic (18:0)         2 - 6          1 - 3         2 - 5
Arachidic (20:0)      tr.- .5         trace         1 - 2
Behenic (22:0)        .7 - 1          trace         2 - 3
Unsaturated
Oleic (18:1)          16 - 35 (d)     9 - 20 (d)   42 - 54
Linoelic (18:2) {e}   57 - 71        66 - 80       20 - 37
Linolenic (18:3)      trace-2        trace-3        trace
_______________________________________________________________________

(a) 	Ranges found in the literature.(18,19)
(b) 	Ranges found in the literature.(18,19)
(c) 	Ranges found in the literature.(20)
(d) 	High Oleic (>80%) with low linoelic (<10%) varieties of sunflower
	and safflower are now available.
(e) 	Essential fatty acid for poultry.(4)


Based on these estimated requirements for growth in parrots it appears that all three oilseed proteins of sunflower, safflower and peanut are deficient in lysine and methionine/cystine, safflower is also deficient in threonine, and peanut is also deficient in threonine and isoleucine (Table 3). Thus it appears that safflower has a better amino acid profile than peanut and sunflower has a better profile than both safflower and peanut.



METABOLIZABLE ENERGY

Cockatiels fed only safflower seed had an adversion to it with three out of five losing weight and displaying shivering while those fed only sunflower gained 65% more weight in 60 days than those fed safflower.23

The greater variation in ME during the ad lib. trial was probably due to the large amount of feed wastage the birds did. The birds on average wasted 58.3 g which is much more than the 38.5 g that they ate over the same period. It appears that the natural hulling behaviour of the birds is strong as they were trying to hull the already hulled kernels.

The AME of sunflower kernel is high when compared to that of formulated diets commonly used in the poultry feed industry.4 This should be expected with the high fat composition of the kernel. High ME's should also be expected for safflower and peanut kernel whose nutrient composition is similar to that of sunflower seed.

The predicted basal metabolic rate (BMR) based on the formula for nonpasserine birds in kcal/day/kg body weight (BMR = 91.0 b.w.0.729)24 for a 0.261 kg bird is 83.8 kcal/day/kg. Comparing this to the existence metabolism of 186 kcal/day/kg calculated from the ad lib. trial data (Table 1) it appears that in these birds existence metabolism is about 2.2 times the predicted BMR. The thermal neutral zone (TNZ) of Green-cheeked Amazons (Amazona viridigenalis) was found to be from 26.5C to at least 35.0C.25 Both Green-cheeked Amazons and Goffin's Cockatoo come from similar tropical environments and probably have similar TNZ. The housing temperature in this study was 18C, below the lower critical temperature found for the amazon. Therefore the cockatoos in this study probably expended energy to maintain body temperature.

Bird number 15 had an existence metabolism below even the BMR predicted for its weight, 70 vs. 84 kcal/day/kg (Appendix 1). While it was not checked this bird must have lost weight over the period of the trial.

The ME value of sunflower kernel is high (and is expected to be high for safflower and peanut too) and cage bird owners whose birds are obese should be advised to limit the amount of oilseeds that they give to their birds.



THE NUTRITIONAL VALUE OF OILSEEDS IN THE POPULAR LITERATURE

The Department of Avian Sciences, University of California Davis, has published several papers on the nutritional value of sunflower seed kernel and its proximate composition compared to safflower seed kernel.23,26,27 However conflicting nutrient analysis is often found in the popular literature usually because it includes the fibrous hulls which Psittacines do not eat.28,29,30 One booklet does not differentiate the requirements for growth and maintenance, lists inaccurate sunflower seed amino acid levels and incorrectly concludes that sunflower seed contains low quality protein.31 Thus confusion, as to which seed is more nutritious, continues with many "experts" saying that safflower is more nutritious based on the falsely assumed lower fat content, or exaggerated unsaturated fatty acid differences.32,33 Birds may in fact be avoiding the safflower because of its bitter taste and cathartic effect and therefore eating a greater variety of food items.34,35

Authors of articles for popular magazines should use figures of nutrient levels derived from laboratory analysis or refereed journals and not quote from agriculture feed tables that may include the fiberous hull in the analysis. The oilseed nutrient values listed here should help those who are involved in advising pet bird owners and aviculturists on seed mixes and prepared pelleted diets.

Acknowledgments

Rolf C. Hagen, Inc. funded the research, provided the birds and their custom made cages and the University of Guelph provided the facilities to perform the bomb calorimeter and house the birds.



Part 2
Return to Table of Contents
Return to H.A.R.I. Home Page