Physical characteristics and chemical composition

British Poultry Science Volume 44, Number 4 (September 2003), pp. 586–590

Physical characteristics and chemical composition of Lesser Rhea (Pterocnemia pennata) eggs from farmed populations J.L. NAVARRO, F.R. BARRI, D.M. MAESTRI1, D.O. LABUCKAS1

AND

M.B. MARTELLA

ńica—Facultad de Ciencias Exactas Fı´sicas y Centro de Zoologıá Aplicada and 1Ca´tedra de Quı´mica Orga Naturales, Universidad Nacional de Co´rdoba, Argentina

Abstract 1. Eggs from 4 farmed populations of Lesser Rhea (Pterocnemia pennata) were studied to determine their physical and chemical characteristics. 2. None of the physical variables (weight of whole egg, yolk, albumen and shell; proportion of yolk based on egg content; proportion of shell based on entire egg weight; volume; density) showed significant differences between populations. 3. Among chemical variables, moisture, both saturated fatty acids (palmitic 16 : 0 and stearic 18 : 0), one monounsaturated fatty acid (palmitoleic 16:1), and one polyunsaturated fatty acid (arachidonic 20 : 4), did not differ between populations, whereas other variables (protein, lipid and ash contents; fatty acids: oleic 18 : 1, linoleic 18 : 2, linolenic 18 : 3; PUFA; PUFA/SFA; cholesterol) differed significantly.

INTRODUCTION In South America the commercial production of the Lesser Rhea (Pterocnemia pennata pennata) on farms is a comparatively recent agricultural activity. It started in the north of the Argentine Patagonia in 1994/95, and although farms and breeding stocks have been steadily increasing, few scientific publications related to production of this ratite species are available (Robles and Navarro, 2000; Navarro and Martella, 2002). High variability in hatching success (19 to 80%) and chick survival (5 to 89%) observed at Lesser Rhea farms (Navarro and Martella, 2002) emphasises the need for scientific information to help establish efficient farming systems. One aspect that may be relevant to improving hatchability at rhea farms is egg composition (see Navarro et al., 2001). In addition to the performance of Lesser Rheas in farming environments, the conservation status of their wild populations is a cause for concern. Any improvement in reproductivity will benefit not only commercial farms, but also management programmes for the conservation of this nearthreatened species. Captive breeding programmes are particularly important for the Andean subspecies, the Puna Rhea (Pterocnemia pennata garleppi/tarapacensis), which is considered endangered (del Hoyo et al., 1992). This study was set up to provide the first data on physical and chemical characteristics of Lesser Rhea eggs

from farmed populations, and to investigate possible differences in egg variables that might affect hatchability.

MATERIALS AND METHODS Fresh eggs of Lesser Rhea were collected from captive populations at farms located in the Argentine Patagonia (three in Rıó Negro Province and one in Santa Cruz Province). Sample sizes are a reflection of the difficulties in obtaining eggs of this ratite because of their high conservation and economic value: two eggs were collected at Choique Malal (40 320 S, 68 380 W; c.11 adult rheas in 3200 m2; hatchability of all eggs under artificial incubation in that breeding season: 73%), three at Choique Ruca (32 440 S, 61 550 W; c.23 adult rheas in 2300 m2; hatchability: 55%), and 5 eggs each at Choique Hue (40 80 S, 69 130 W, c.4 adult rheas in 2400 m2; hatchability: 23%) and La Carolina (51 040 S, 70 100 W, c.78 adult rheas in 19 200 m2; hatchability: 20%). At the farms, Lesser Rheas had access to minor amounts of vegetation, seeds, insects and small vertebrates, but their nutrition was mainly based on approximately 600 to 650 g/d of rations with different protein and lipid contents and fatty acid composition (Table 1). At Choique Hue, alfalfa (Medicago sativa) hay was provided occasionally to the rheas.

´rdoba, C.C. 122, Co ´rdoba (5000), Argentina. Correspondence to: Dr Joaquıń L. Navarro, Centro de Zoologıá Aplicada, Universidad Nacional de Co Fax: þ54-351-4332054 int. 101. E-mail: [email protected] Accepted for publication 26th March 2003.

ISSN 0007–1668(print)/ISSN 1466–1799(online) ß 2003 British Poultry Science Ltd DOI: 10.1080/00071660310001616237

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Eggs were collected within less than 48 h of laying and then stored at 4 C until they were processed using the same procedures as Navarro et al. (2001). After storage, the eggs were weighed, their volume determined gravimetrically and density calculated. Later, each egg was broken out and the yolk, albumen and shell were weighed and separately processed. Each liquid component was dehydrated at 38 to 42 C until a constant weight was obtained. Protein and ash contents were determined (AOAC, 1980). Protein values were based on a conversion factor of 6.25 times total nitrogen. Mineral composition was determined by atomic absorption spectroscopy from ash content of a sample composed of a mixture of equal aliquots taken from all the eggs of each population. Lipids were extracted from 10 g of dry matter using 2 chloroform:1 methanol (v/v) during 12 hs in a Soxhlet apparatus. Lipid content was quantified by weight difference (AOAC, 1980).

Fatty acid analyses were carried out from yolk lipids extracted with 2 chloroform:1 methanol (v/v) at room temperature. Lipids were subjected to alkaline saponification (1 N potassium hydroxide in methanol), and the unsaponifiable matter extracted with n-hexane. The fatty acid methyl esters (FAMEs) were obtained using 1 N sulphuric acid in methanol and analysed by gas chromatography (GC) according to Maestri and Guzmań (1993). From unsaponifiable matter, free cholesterol was converted to trimethylsilyl derivatives and quantified by GC (Bitman and Wood, 1980). All chemical determinations for each egg (except mineral composition) were conducted in duplicate. Differences between populations for each variable were determined by means of ANOVA or non-parametric Kruskal—Wallis tests. A posteriori least significant difference (LSD) or Dunn tests (Zar, 1984) were applied, depending on the distribution of the variable.

RESULTS AND DISCUSSION Table 1. Lipid and protein content (g/kg dry matter), fatty acid composition, concentrations of unsaturated (US) and polyunsaturated (PUFA) fatty acids (g/kg of total fatty acids), and PUFA/SFA ratio of the three rations fed at 4 Lesser Rhea farms in Patagonia, Argentina1

Protein Lipids 16 : 0 16 : 1 18 : 0 18 : 1 18 : 2 18 : 3 US PUFA PUFA/SFA

Choique Malal and Choique Ruca

Choique Hue

La Carolina

205.0 112.1 191.7 21.0 41.3 289.7 403.0 53.3 767.0 456.3 1.96

175.0 107.7 306.5 28.3 112.6 388.5 164.0 5.0 585.8 169.0 0.40

160.4 110.2 202.5 19.3 42.2 393.0 326.4 16.6 755.0 343.0 0.52

1

The ration at Choique Malal and Choique Ruca was one specifically formulated for ratites, whereas two different chicken rations were used at La Carolina and Choique Hue.

None of the physical variables of eggs differed significantly between the 4 populations (Table 2). Proportions of yolk and shell, and density, of Lesser Rhea eggs were very close to those of other ratite species either in captive or wild populations (see Romanoff and Romanoff, 1949; Hoyt et al., 1978; Keffen and Jarvis, 1984; Du Preez, 1991; Angel, 1993; Reiner et al., 1995; Noble et al. 1996; Navarro et al., 2001). The average weight of Lesser Rhea eggs is almost 5% lower than eggs of farmed Greater Rheas (Navarro et al., 2001). This small difference is almost exclusively due to the slightly lower density exhibited by eggs of Lesser Rheas, as egg volume in both species is nearly the same. Also, the proportion of yolk in Lesser Rhea eggs seems lower than in Greater Rheas (Navarro et al., 2001). Of the chemical variables, moisture, both saturated fatty acids (palmitic 16:0 and stearic

Table 2. Weight (whole, yolk, albumen and shell), proportion of yolk based on egg content, proportion of shell based on entire egg weight, volume and density of Lesser Rhea eggs from 4 farms in Patagonia, Argentina. Mean SE

Weight3 (g) Yolk4 (g) Yolk4 (g/kg) Albumen3 (g) Shell2 (g) Shell3 (g/kg) Volume3 (ml) Density4 (g/ml) 1

Choique Malal (n ¼ 2 eggs)

Choique Hue (n ¼ 5 eggs1)

La Carolina (n ¼ 5 eggs1,2)

Choique Ruca (n ¼ 3 eggs)

Overall mean

646.5 ± 24.50 171.0 ± 4.00 303.5 ± 1.52 392.5 ± 12.00 83.0 ± 8.50 128.1 ± 8.29 612.5 ± 12.50 1.06 ± 0.019

592.5 ± 36.49 152.0 ± 14.88 295.9 ± 14.76 361.9 ± 32.15 74.4 ± 2.98 126.4 ± 3.98 534.0 ± 35.30 1.11 ± 0.038

563.2 ± 15.93 134.6 ± 6.12 286.4 ± 15.97 337.0 ± 16.51 78.9 ± 4.14 141.8 ± 4.41 540.0 ± 16.96 1.04 ± 0.007

595.0 ± 18.92 168.8 ± 5.42 342.1 ± 2.70 324.8 ± 12.48 82.3 ± 3.44 138.3 ± 2.04 541.7 ± 22.05 1.10 ± 0.012

590.4 ± 14.66 153.5 ± 6.24 304.8 ± 8.61 350.4 ± 12.31 78.6 ± 2.05 133.6 ± 2.74 548.0 ± 14.42 1.08 ± 0.015

Four eggs for yolk and albumen analyses. Four eggs for shell analyses. 3 LSD test; 4 Dunn test. (none of the variables showed significant differences among populations). 2

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Table 3. Proximate composition of yolk and albumen of Lesser Rhea eggs from 4 sources in Patagonia, Argentina. Mean SE Choique Malal (n ¼ 2 eggs) Yolk

Albumen

Choique Hue (n ¼ 5 eggs1) Yolk

La Carolina (n ¼ 4 eggs)

Albumen

Yolk

Albumen

Choique Ruca (n ¼ 3 eggs) Yolk

Albumen

Moisture 530.5 ± 3.50 890.5 ± 4.59 516.9 ± 18.35 889.5 ± 2.58 525.0 ± 5.76 882.8 ± 1.89 508.3 ± 3.18 891.0 ± 4.04 (g/kg) 721.8 ± 8.16 264.6a ± 5.18 701.0 ± 7.72 285.5bc ± 5.88 704.7 ± 3.50 Protein 266.6ab ± 8.45 698.2 ± 12.95 299.2c ± 5.71 (g/kg dry matter) Lipids 653.6a ± 3.85 0 677.1bc ± 7.66 0 683.2c ± 3.13 0 662.4ab ± 5.21 0 (g/kg dry matter) Ash 36.0 ± 2.20 55.8a ± 0.45 36.9 ± 0.45 58.0ab ± 1.00 36.0 ± 1.35 60.6bc ± 0.12 35.9 ± 1.10 63.1c ± 1.79 (g/kg dry matter) Means of the respective egg portion followed by a different superscript letter within each row are significantly different (LSD test except for moisture in yolk, in which a Dunn test was conducted) at P < 0.05 except for lipids, in which P ¼ 0.055. 1 Four eggs for moisture analysis.

Table 4. Fatty acid composition, concentrations of unsaturated (US) and polyunsaturated (PUFA) fatty acids (g/kg of total fatty acids), PUFA/SFA ratio, and cholesterol content (mg/g lipid) of Lesser Rhea eggs from 4 sources in Patagonia, Argentina. Mean SE

16:01 16:11 18:01 18:12 18:21 18:31 20:42 US1 PUFA1 PUFA / SFA1 Cholesterol1

Choique Malal (n ¼ 2 eggs)

Choique Hue (n ¼ 5 eggs)



181.0 ± 1.75 19.1 ± 2.70 89.6 ± 7.35 417.0a ± 8.10 256.4a ± 8.00 26.1a ± 2.00 10.9 ± 1.10 729.5 ± 9.10 293.4a ± 1.70 1.09a ± 0.03 33.90a ± 0.30

206.6 ± 10.67 26.8 ± 3.70 93.6 ± 3.48 415.1a ± 19.4 216.4b ± 8.12 25.4a ± 1.99 19.1 ± 3.71 702.8 ± 11.81 260.9a ± 10.48 0.87a ± 0.51 30.41b ± 0.61

223.2 ± 19.47 28.7 ± 4.56 94.1 ± 5.35 480.4b ± 10.62 148.8c ± 7.70 11.5b ± 2.75 14.6 ± 1.00 684.0 ± 15.43 174.9b ± 9.72 0.56b ± 0.06 39.91c ± 0.97

203.3 ± 9.44 22.1 ± 0.70 84.5 ± 1.53 408.9a ± 7.07 246.8a ± 11.52 23.6a ± 2.93 10.9 ± 0.38 712.2 ± 9.77 281.2a ± 14.27 0.98a ± 0.08 27.93d ± 0.39

Means followed by a different superscript letter within each row are significantly different at P < 0.05. 1 LSD test. 2 Dunn test.

18:0), one monounsaturated fatty acid (palmitoleic 16:1), and one polyunsaturated fatty acid (arachidonic 20:4) did not differ between populations, whereas the other variables of either yolk or albumen differed significantly (Tables 3 and 4). The highest protein contents in yolk were in eggs from Choique Hue and Choique Ruca, while the lowest lipid contents were in those from Choique Malal and Choique Ruca (Table 3). In albumen, the protein content did not differ between populations, while the ash content was significantly higher in eggs from Choique Ruca and La Carolina (Table 3). In contrast to chickens (Cook and Briggs, 1973) and ostrich (Reiner et al., 1995; Sales et al., 1996), the ash content of Lesser Rhea eggs was higher in albumen than in yolk (Table 3). The lipid concentration of the yolk is higher in Lesser Rheas than in Greater Rheas (Navarro et al., 2001). The fatty acid profile of the yolk of Lesser Rhea eggs (Table 4), showed high percentages of oleic (18 : 1) and linoleic (18 : 2) acids within the unsaturated acids, whereas palmitic (16 : 0) was the principal saturated acid. Eggs from La

Carolina showed the highest values of oleic acid and a significant decrease in the relative contents of linoleic and linolenic acids. The total polyunsaturated fatty acid (PUFA) percentage, and the PUFA/SFA ratio were lowest in eggs from La Carolina, whereas the total unsaturated fatty acid percentage did not differ between populations (Table 4). Oleic, linoleic and palmitic acids represented 85% of total fatty acids in Lesser Rhea eggs. Although this value is similar to that found in eggs of Greater Rheas (Navarro et al., 2001), percentages of palmitic and linoleic acids seem to be slightly lower in Lesser Rhea eggs. On the other hand, concentrations of unsaturated and polyunsaturated fatty acids of eggs from all populations other than La Carolina seem to be higher than those of farmed Greater Rheas (Navarro et al., 2001). The concentrations of oleic and linolenic (18:3) acids observed in eggs from the 4 Lesser Rhea farms are similar to those of farmed Greater Rheas, whereas eggs collected from wild populations of the latter species have a much higher proportion of linolenic acid

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LESSER RHEA EGGS

Table 5. Mineral content (mg/g dry matter) of yolk and albumen of Lesser Rhea eggs from 4 sources in Patagonia, Argentina. Values represent a single result from pooled samples of each farm Choique Malal (n ¼ 2 eggs)

Calcium Magnesium Sodium Potassium Iron Copper Zinc 1

Choique Hue (n ¼ 5 eggs)



Yolk

Albumen

Yolk

Albumen

Yolk

Albumen

Yolk

Albumen

1.61 0.20 0.55 1.43 0.10 0.02 0.055

n/a1 1.13 7.25 0.37 0 0.02 0.01

1.83 0.12 0.60 1.78 0.09 0.025 0.045

0.48 0.58 5.50 n/a1 0 0.02 0.01

1.72 0.20 0.62 1.64 0.08 0.02 0.05

0.69 0.75 8.50 0.65 0 0.015 0.01

1.83 0.24 0.55 1.40 0.07 0.015 0.045

0.56 1.00 6.75 0.10 0 0.03 0.01

Missing data.

(Navarro et al., 2001). This difference seems to be related to a low content of this component in the rations provided to the birds reared under captive conditions. Average concentrations of cholesterol varied from 28 to 40 mg/g lipid (Table 4). This is higher than all but one of the respective averages observed in wild and farmed Greater Rheas (18 to 35 mg/g lipid; Navarro et al., 2001). Total concentrations of magnesium and iron were higher in eggs from Choique Malal, whereas sodium and, to a lesser degree, calcium were higher in those from La Carolina, and potassium in those from Choique Hue (Table 5). On the other hand, copper and zinc were comparatively constant among populations. Lesser Rhea eggs had lower total concentrations of calcium and potassium, and higher concentrations of magnesium and copper than eggs of Greater Rheas (Navarro et al., 2001). Most chemical variables of Lesser Rhea eggs differed significantly between populations. These variations can be attributed to several factors such as the female’s dietary composition (see Cook and Briggs, 1973), genetic characteristics of the hens, environmental causes and the farming techniques. However, their individual contributions cannot yet be determined. On the other hand, physical variables were fairly constant among populations. This is similar to that observed in the Greater Rhea by Navarro et al. (2001). The farms whose eggs showed higher contents of polyunsaturated fatty acids, particularly linolenic acid (18 : 3), as well as higher PUFA/ SFA ratios, had better hatchability figures during that season. This is similar to that found by Noble et al. (1996) in the ostrich (Struthio camelus), and Noble et al. (1993) in alligators (Alligator mississippiensis). The relevance of PUFA and, among them, linolenic acid (an essential fatty acid) during embryo development has been emphasised by several authors (for review see Leskanich and Noble, 1997). The results of the present study support the idea that more attention should be given to the fatty acid profile of the diet offered to rheas in

order to improve egg viability and hatchability at farms. Further research, including larger sample sizes from more farms is clearly needed to understand the relative importance that each chemical component of the egg has in terms of its effect on hatchability.

ACKNOWLEDGEMENTS We are grateful to A. Garrido, O. Merlo, J. Bracchio, J. Taux and C. Fernańdez, for allowing us to use eggs from their farms, and for providing housing. Special thanks are due to A. Manero, L. Bellis, P. Vignolo, and workmen of the study areas who helped us with egg collection and transport. G. M. Giacone checked the English, and an anonymous referee made helpful suggestions. J.L.N., D.M.M. and M.B.M. were supported by the Universidad Nacional de ´ rdoba and the Consejo Nacional de InvestigaCo ciones Cientı´ficas y Tećnicas (CONICET). This work was partly supported by a grant to M.B.M. ń Of the Agencia Nacional de Promocio ´ gica of Argentina (PICT Cientı´fica y Tecnolo 01—00000—02225).

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