EFFECT OF THE ORIGIN OF QUAILS ON THEIR UTILITY TYPE AND SELECTED EGG QUALITY TRAITS

Zofia Tarasewicz, Danuta Szczerbińska, Marek Ligocki, Alicja Dańczak, Danuta Majewska, Justyna Kurzawa

ABSTRACT

The study was aimed at determining the effect of quail origin on their utility and egg quality traits. Young quails were reared at own farm under most favorable microclimate conditions using the standard feeding adapted to particular rearing stages. In the fifth week of life, the quails were weighted and three groups were formed for Pharaoh breed and White and Golden varieties, 24 birds each. Adult birds were kept in cages as before using standard microclimate parameters and 17 hours long light day. The feeding was based on whole-meal feed mix with nutritive value consistent with recommended poultry feeding standards. In the 18th week of life of the laying quails, 20 eggs of each group were collected to evaluate their quality traits. The effect of quail origin on laying rate and feed consumption converted to one egg was found. Relationship between the weight of egg and its morphological composition was stated, as well as that between the content of triglycerides in egg yolk and quail origin

Key words: cholesterol, egg quality, fatty acids, origin, performance, quail..

INTRODUCTION

In the recent years egg consumption has been on the down-grade in many developed countries due to not fully justified fear of cholesterol, the yolk content of which amounts to 240-280 mg in hen eggs [4] and 55-57 mg in quail eggs [19]. The shaping of consumer attitudes is influenced by current bad opinions. Despite the fact that nutritive value of eggs is enormous considering their model amino acid composition, vitamin content, fat-soluble ones in particular, as well as the contents of choline and biotin and of mineral compounds, mostly deficit ones such as iodine, selenium and manganese, the egg and the fat comprised in it will be still the target of continuous attacks from different circles, including also scientific ones [17]. Egg nutritive values depend unquestionably on the yolk level of essential polyunsaturated fatty acids, including linolenic acid, total cholesterol, including also low-molecular lipid (LDL) and high-molecular lipid (HDL) fractions. Basing on daily consumption it has been determined that egg introduces less than a half and more than one third of 85 g cholesterol comprised in the kidneys and liver. One of the characteristic values of egg is its larger suppleness to qualitative manipulations than other products of animal origin, thus their quality traits are improvable and laying-hens can lay in result the so-called “designed eggs” containing in their yolks better available n-3 fatty acids with long chains. Nevertheless the quantity of fat to total weight of egg and its main nutritive components is fixed and dependable on avian species. Quail eggs are considered to have lower cholesterol content compared to hen eggs. Stępińska et al. [18] showed lower cholesterol content in the eggs of green-legged hens when compared to those of Rhode Island Red and Leghorn hens. Niemiec and Świerczewska [10] and Melluzi et al. [9] found the effect of hen genotype on the content of yolk lipid compounds. According to Stadelman [17] the importance of eggs in human diet history not only can no t be omitted but should be simply stressed.

The aim of the undertaken study was to determine the effect of the origin of quails on their utility type as well as the quality traits of their eggs and the content of lipid compounds in egg yolk.

MATERIALS AND METHODS

Studies were carried out at an experimental farm belonging to the Agricultural University in Szczecin and located on the premises of the Faculty of Biotechnology and Animal Husbandry on basic flocks of table quails representing Pharaoh breed and two varieties: White and Golden (lighter).

Young quails were reared in cages at the own farm. Rearing parameters (temperature, humidity, stocking, and light conditions) were adapted to standards for particular rearing stages. Feeding was based on whole-meal feed mixes with nutritive value consistent with common recommendations [11].Birds were weighted in their 5th week of life and female quails with body weight approximating the average weight for a given genetic group were singled out (24 individuals of each group) for the experiment. Adult quails were kept in cages as before in optimal microclimate conditions with 17 hours long light day (17L:7D). All genetic groups were given a whole-meal feed mix – by rationing – with energy value of 11.72 MJ of metabolic energy and total protein content of 20.7% (Table 1).

In the 18th week of life of the laying quails, 20 eggs of each group were collected twice to evaluate quality traits including the egg weight and egg shape index, egg shell thickness and weight, egg yolk and egg white indices, and the egg density which was determined in sodium chloride solutions with a density ranging from 1.058 to 1.082 g·cm^-3, raising successively by 0.005. Participation of egg particular parts was also determined in the eggs as well as the content of ether extract and ash in egg yolk with conventional methods. Moreover, cholesterol content in egg yolk was established, with regard to its free and esterificated forms, using the method described by Krause et al. [7] with cholesterol extraction done with Bitman and Wood’s method [3]. Triglycerides quantitative analyses were made with thin-layer chromatography method. Fatty acids content was determined with HPLC liquid chromatography method according to Osterroht [12], whereas that of mineral components by t he method of emission spectrometry with induction in ICP-OES argon plasma compressed inductively. Also pH of egg yolk and egg white were determined in eggs of each group. The results were analyzed statistically with one-factor analysis of variance and Duncan’s test.

RESULTS AND DISCUSSION

The chemical composition of feed mix fed to quails in groups of different origin is presented in Table 1. Out of determined nutritive components only feed mix fiber content was slightly higher compared to standards given for that poultry species. The content of other components approximated the feeding needs of adult quails [11].

The body weight of white variety quails and Pharaoh quails in the 5th week of life was similar both in males and females. Golden variety quails were significantly lighter compared to Pharaoh quails and white variety quails. Golden variety quails reached sexual maturity by 7 days later, which was one of the reasons for significantly lower egg laying compared to white variety and Pharaoh quails in particular. Despite the lack of differences in body weight and time taken to reach sexual maturity between white variety quails and Pharaoh quails, significant differences were observed in egg production until 18th week of life. Significantly larger egg laying was characteristic for Pharaoh quails (80.0%). The least laying ratio was found in Golden variety quails – 58.0% (Table 2).

Table 2. Quail utility indicators (±SD)

Largest amounts of feed needed for producing an egg were consumed by Golden variety quails (43.2 g), and the least by Pharaoh quails (35.5 g). These differences proved to be statistically significant. No significant differences were found between groups of White variety and Pharaoh quails, though Pharaoh quails consumed by about 2 g less feed (in absolute numbers) for producing an egg. The evaluation of the health state of quails based on loss rates showed similar condition in birds of particular genetic groups (Table 2).

It results from the carried out studies that there are significant differences concerning morphological traits of eggs from quails of different origin. It was found that largest eggs were laid by White variety quails (12.69 g), and the least by Golden variety quails (9.90 g). The weight of yolk from eggs of White variety quails differed significantly compared to that of two other genetic groups. The largest egg yolk proportion (36.68%) was found in eggs of Golden variety quails and it was higher by about 4.5% when compared to eggs of Pharaoh quails (Table 3).

The amount of egg white in the analyzed eggs did not differ significantly ranging from 5.56 (Golden variety quails) to 7.40 g (White variety quails), which constituted 57.7 and 58.0%, respectively. The largest proportion of egg white was found in eggs of Pharaoh quails. Slightly higher percentage of egg white in eggs of quails of that breed was found by Tarasewicz [19]. As Yannakopoulos and Tserveni-Gousi [21] state the egg yolk and egg white contents are age-dependent. The proportion of egg yolk in the egg increases with the age of laying quail and that of egg white decreases. However, such relations take place to a certain age. According to the authors mentioned above the increase of egg yolk proportion takes place until the 100th day of life, and about the 150th day the egg yolk percentage in the egg is comparable to that obtained in eggs from the initial period of egg laying.

The broadest ratio of egg white to egg yolk was found in eggs of Pharaoh quails (1.92), whereas the narrowest in eggs of Golden variety quails (1.61). Singh and Panda [14] are of the opinion that these correlations in quail eggs are formed at similar level as in hen eggs, thus the most favorable egg white:egg yolk ratio has been determined in eggs of White variety quails (1.81). The increase of egg white proportion in eggs is not favorable, both from the point of view of the consumer and the hatchability.

The lowest shell weight (0.89 g), as well as its lowest proportion in egg weight (8.93%), was characteristic for eggs of Golden variety quails (Table 3). It was significantly lower compared to quails of other two genetic groups, with the value obtained in the own study being by 0.5% higher from the highest value given for Japanese quails by Yannakopoulos and Tserveni-Gousi [21] but by about 1% lower than that given by Panda and Singh [13] also for eggs of Japanese quails. Egg shell proportion obtained in the own study in eggs of Pharaoh quails approximated literature reference data the most. The thickest egg shells were also found in eggs of Pharaoh quails (0.25 mm) and they were significantly thicker compared to egg shells of Golden variety quails and by 0.05 mm thicker from the value obtained by Yannakopoulos and Tserveni-Gousi [21] for eggs from the initial stage of laying of Japanese quails.

Specific weight is an indirect index of egg shell thickness, thus its lowest value was found for eggs of Golden variety quails.

The eggs originating from quails of different genetic groups had uniformed shape and it can be admitted to be normal, with eggs of Pharaoh quails approximated spherical shape the most (Table 3).

No significant differences were found in egg yolk index, which amounted to 0.46-0.48, being contained within the range for fresh eggs. The lowest value of egg white index was found in eggs of Golden variety quails (0.11), and the largest in those of Pharaoh quails (0.16). The differences between compared groups of quails proved to be significant. The value of egg white and egg yolk indices obtained in eggs from all quails, irrespective of their origin, were within higher ranges for hen eggs (Table 3).

The highest percent content of fat in the yolk was obtained in eggs from White variety quails (34.32%), the lowest in the yolk of eggs from Golden variety quails (32.89%), with 33.98% in the yolk of eggs from Pharaoh quails (Table 4). According to Shanawany [16], fat content in the yolk of Japanese quail eggs amounts to 32.61%, as in the own study in the yolk of Golden variety eggs and being by about 2% lower than that in the yolk of White variety eggs. Both total cholesterol quantity and free cholesterol quantity, as well as cholesterol esters, in the yolk of eggs from quails of different origin was at similar level, ranging from 16.25 to 16.70 mg^.g^-1 yolk, not differing significantly. Reference literature data concerning total cholesterol content converted to 1 g quail egg yolk are quite divergent and range from 11.96 to 26.02 mg [1, 5, 8, 15]. While evaluating 9 quail lines, Baumgartner and Simeonova [2] found higher cholesterol co ntent in eggs coming from quails of heavier lines (20.46 mg^.g^-1 yolk). This quantity in light birds was within the range of 16.20 to 18.31 mg^.g^-1 yolk. The cited data are far higher compared to the results of own observations, both in relation of heavier quails (Pharaoh and White variety) and the lighter ones (Golden variety). Witkowski et al. [20] stated clear differences in cholesterol content in 1 g yolk between quail eggs from long and short laying cycles. These authors suggest also differences in cholesterol concentration in quail eggs depending on the size and the color of shell spots. The effect of quail origin on the content of triglycerides in 1 g yolk was found in the own study. Significantly more triglycerides were found in eggs of Golden variety quails.

The highest values of egg yolk and egg white pH (Table 4) was determined in eggs of White variety quails and it amounted to 6.03 and 9.13, respectively, differing significantly in case of the first parameter compared only to Pharaoh quails, and the second one compared both to Pharaoh and Golden variety quails. Lower value of egg white pH suggests that egg white is thinner in Pharaoh quail and Golden variety quail eggs, which contributes to more rapid aging of egg and weakening of immunological mechanisms.

Important nutritive component of egg yolk are fatty acids occurring in it mostly in the form of glycerides and phospholipids and less in free form, lipoproteides and chemically bounded in molecules of other compounds. In the yolk of eggs, including quail eggs, mono- and polyunsaturated fatty acids, very desired physiologically, are particularly abundant. Table 5 presents proportion of egg yolk fatty acids with regard to total content of fatty acids. As in the study of Panda and Singh [13], the highest but statistically non-significant proportion of oleinic acid was found in egg yolk of all examined quail groups – from 37.6% in Golden variety quails to 38.8% in White variety quails. From amongst the most important polyunsaturated fatty acids, statistically significant differences were found for linolenic acid – Pharaoh quails (2.97%) vs. Golden variety quails (3.55%), and arachidonic acid – White variety quails (0.37%) vs. Golden variety quails (0.56%). Significant diff erences were also stated in respect of myristolenic and palmitolenic acids, but no statistical differences were found in case of linoleic acid. Assuming the content of polyunsaturated fatty acids in the yolk of eggs from Pharaoh quails to be 100%, significantly higher content PUFA n-3 acids was found in the yolk of eggs of Golden and White quail varieties, respectively by 19.5 and 18.5%, and that of PUFA n-6 acids by 3.1 and 5.6%. The ratio of polyunsaturated fatty acids, PUFA n-6/n-3, was most favorable in the group of Pharaoh quails and amounted to 3:1. In other examined groups it had the value of 2.7:1 and 2.6:1, respectively for White and Golden quail varieties. Some researchers state that proportion between n-6 and n-3 acids should be as 3:1, 4-10:1 or 6:1 on the average. Koreleski et al. [6] are of the opinion that one may modify the ratio of acids of n-6 and n-3 families by supplementing feed mixes with fish or rape oils. In respect of saturated fatty acids, statistically significant differences were f ound only for acids with shorter carbon chains: capronic, lauric, myristic and palmitic aicds.

Table 5. Yolk fatty acids content (%) in eggs of quails of different origin (±SD)

The content of Na, Ca, Fe, Zn and Mn in the yolk of eggs was similar in all genetic groups (Table 6). Significantly larger quantities of K and Mg were found in the yolk of eggs of White variety quails compared to Pharaoh quails. Also the largest quantity of phosphorus (8.22 mg^.g^-1) was found in this group, significantly different from the content of that element in two other groups. In reference literature there are no data concerning the content of chemical elements in the yolk of eggs. Most often are given values converted to egg content, thus comparison of own study results with such ones obtained by other authors is impossible, mostly due to different concentration of chemical elements in particular egg parts.

Table 6. Yolk selected chemical elements content in eggs of quails of different origin (±SD)

CONCLUSIONS

1. Quail origin had an effect on body weight in the 5th week of life, laying rate, as well as on feed consumption converted to an egg.

2. Significant relationship between the weight of egg and its morphological composition and the quail origin was demonstrated.

3. The largest egg white index was found in eggs of Pharaoh quails, and the highest egg white pH was stated in White variety quails.

4. Quail origin affected egg yolk contents of total fat and triglycerides, as well as its pH.

5. Significantly higher content of PUFA n-3 acids was found in the yolk of eggs of Golden and White quail varieties compared to that of Pharaoh quails, whereas most favorable ratio of polyunsaturated fatty acids n-6/n-3 was stated in the group of Pharaoh quails.

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