Comparative study of egg quality parameters of different breeds of peacock

ABSTRACT

The current research work was conducted to compare the external and internal egg quality parameters of different breeds of peacock. For this purpose, 130 freshly laid eggs of 2 species and 11 breeds (n = 10 per breed) were obtained from captive breeding facilities. In Pavo muticus muticus, higher egg weight (106.57 ± 0.69), egg length (7.21 ± 0.01), egg width (5.31 ± 0.01), egg breadth (28.18 ± 0.01), and egg volume (100.84 ± 0.48) were recorded. However, higher egg shape index (80.16 ± 0.27) was noted in black shoulder, while higher egg surface area (263.8 ± 0.01) was found in Spalding purple. Significantly higher albumen diameter (11.02 ± 0.05), albumen weight (47.06 ± 0.24), albumen height (0.946 ± 0.02), albumen ratio (49.83 ± 0.13), yolk height (1.66 ± 0.01), yolk index (35.75 ± 0.13), and shell thickness (0.67 ± 0.00) were found in Pavo cristatus. Albumen pH (6.43 ± 0.01), yolk diameter (6.93 ± 0.04), yolk ratio (61.80 ± 0.87), and yolk weight (51.66 ± 0.34) were noted to be higher in Indian white. Higher shell weight (16.38 ± 0.42), shell ratio (17.004 ± 0.38), and Haugh unit (88.57 ± 0.84) were observed in Buford bronze pied. The study suggested that P.m. muticus and Pavo cristatus showed best external and internal egg quality traits as compared to other breeds. It further provided a reference and theoretical basis for artificial breeding, ecological protection, raising, and management of different breeds of peacocks.

KEYWORDS:

• Peafowl
• Breed
• Egg quality
• Egg weight
• pH

Introduction

Peacock is the most admirable and adorable bird known as the “king of birds.” Its looks has raised it among one of the most beautiful animals in the world. It belongs to Phasianidae family, order Galliformes within class Aves that has 38 genera and about 138 species. Peafowls are represented by three species in the world including Indian blue peafowl (Pavo cristatus), Java green peafowl (Pavo muticus), and Congo peafowl (Afropavo congensis).^[1] Peacock are domineering fowls as they enjoy aesthetic, economical, and medicinal worth. Indian blue peacock is an inborn breed of Pakistan, India, Sri Lanka, and Bangladesh.^[2] Blue Peafowl is the provincial, ornamental bird of Punjab in Pakistan and is famous as a national bird of India.^[3,4] Pavo muticus (Green Peafowl) is resident of Burma in the east of Java that is why they are also called the Burmese or Java green. Green Peafowl has a massive body compared to blue Peafowl. Green Peafowl, Pavo muticus, is listed as vulnerable.^[5] Over the past two centuries, under artificial conditions, many color mutations of ordinary Indian Peafowl have been reared. The initial mutation in Indian Peafowl is black shoulder, then cameo and white. There are various colored mutants like black shoulder, cameo, buffered bronze, Pied, white Peafowl, etc.

The bird is under severe threats nowadays due to the consumption of its meat, habitat degradation, poaching, crop rotation, and contamination of its food and water resources through extensive use of fertilizers and pesticides.^[6] These are the reasons that peafowl has almost vanished from Bangladesh and from many other countries like Pakistan.^[7] In past few years, various natural and anthropogenic threats have been responsible for the decline of peafowl population in Thar, Pakistan. Malnutrition and bacterial and viral infections are other common threats. In recent years, many deaths of peafowl have been reported due to Newcastle disease.^[7]

Peacock breed during rainy season in the month of April to August.^[8] However, they usually reach puberty at the age of 2–3 years.^[9] In artificial environment, nutrition of birds is an important point, particularly in juvenile, molting, growing, and breeding period. Indian Peafowl is omnivorous and consumes grains, insects, and little creatures.^[10] The blue peacock eggs are preferred as food as they contain significantly higher amount of carbohydrates, protein, essential amino acids, total amino acids, calcium, and zinc, with low amount of water and fats.^[11] It is noticed that feed and housing conditions^[12] influence egg composition and its quality. Hatchability of birds depends on different factors like bird age and ratio of mating sex in reproductive groups. For hatching eggs, size of an egg and interior quality parameters are very essential. Egg parameters such as internal and external are affected by storing them for a long time, and as a result, changes occur in the physical and chemical nature of eggs. Breed and feed both affect the egg traits, especially egg yolk and albumin quality.^[13;14]

Laying period has an effect on egg quality. A study on pheasant eggs shows that the thickness of shell decreases as time passes. At the beginning of a laying period, yolk content was higher, whereas at the end, higher albumin quality shows the increase in Haugh unit. Results illustrate that eggs gathered at the beginning of a laying period are more fertile as compared to those gathered at the end of a laying period.^[15] Egg shell thickness inclined by many aspects like genetic, size and color of an egg, female condition, stress, and diet.^[16] Proper attention was required while capturing and limiting the peafowl to avoid any harm or much stress to the bird.^[17] Storage time and temperature influence the egg quality.^[18]

The aim of this study was to investigate the external and internal parameters of peacock eggs, which helped to improve the fertility rate in peacock. Current knowledge on the ecology, social behavior, and biology of pheasants is minimal, and there are opportunities for research and studies for biologists and avian scientists. The data reported here could open the opportunity to search for a suitable conservation strategy to improve richness of peafowl biodiversity, and the present study here served as a useful report that might have a significant impact on the breeding and conservation program of Indian blue and green peafowl gene pool. The current research can provide reference and theoretical basis for artificial breeding, ecological protection, raising, and management of different breeds of peacocks.

Materials and methods

This study was conducted at Zoology Laboratory, Department of Zoology, University of Lahore. The present study was planned to determine the various external and internal egg quality parameters of different breeds of peacock. The study period comprised 1 year. Ten peacocks of each breed were kept under appropriate conditions in well-ventilated rooms of Pak Peacock farm Bhalwal, Sargodha.

Animal management and housing

Peacocks of 13 breeds (male and female) were kept in separate cages. The size of the cage was 25 m³ × 8 m³ × 5 m^3.[19] The birds were fed a standard breeder diet containing 180 g crude protein, 11.3 MJ of metabolizable energy, and 30 g calcium per kg diet.^[20] The diet was offered to the birds daily at 09:00, whereas water was given ad libitum to all the birds. The cages were cleaned daily to prevent any disease outbreak. Vaccination and medication were done as and when required during the experimental period.^[21] The eggs of peacocks were collected from separate cages. Freshly laid eggs of 13 different breeds of peacocks were obtained from captive breeding facilities in Peacock farm Bhalwal, Sargodha. A total of 130 eggs, 10 eggs per breed, were used to calculate the external and internal egg quality parameters.

External egg quality parameters

Different external egg parameters were studied. Egg weight (g) was measured using a digital weighing balance (TH-500) measuring up to 0.001 g. Egg length and breadth (cm) were measured using a vernier caliper up to 0.01 cm. Egg volume, egg shape index, and egg surface area (cm³) were calculated by the following formulas (1, 2, 3).^[22–24] The equations show the formula of different external egg quality parameters:

(1) $\mathrm{V}={\mathrm{K}}_{\mathrm{V}}\times \mathrm{L}\times {\mathrm{B}}^2$(1)

where L is the egg length (cm), B is the egg breadth (cm), and Kv is the coefficient for volume (Kv = 0.496).

(2) $EggShapeIndex(\%)=\text{B/L}\times \text{100}$(2)

(3) $\mathbf{E}\mathbf{g}\mathbf{g}\mathbf{S}\mathbf{u}\mathbf{r}\mathbf{f}\mathbf{a}\mathbf{c}\mathbf{e}\mathrm{a}\mathrm{r}\mathrm{e}\mathrm{a}\mathbf{(}\mathbf{c}{\mathbf{m}}^{\mathbf{3}})=\mathrm{K}(\pi \mathrm{L}{\mathrm{B}}^2/6)$(3)

where is K is constant.

Internal egg quality parameters

For the study of internal quality parameters, eggs were broken in petri dish and quality parameters were measured after 5 min. The following internal egg parameters were studied. Albumen diameter (cm) was measured using a vernier caliper measuring up to 0.01 cm. Albumen height (cm) was measured using a vernier caliper measuring up to 0.01 cm. Albumen weight (g) was measured using a digital weighing balance up to 0.001 g. Albumen pH was measured using a digital pH meter.^[22] Albumen index, ratio (%), and Haugh unit were calculated by the following formulas (4, 5, 6):

(4) $AlbumenIndex(\%)=\text{Albumen}\text{height/Albumen}\text{Diameter}\times \text{100}$(4)

(5) $Albumenratio(\%)=\text{Albumen}\text{weight/Total}\text{egg}\text{weight}\times \text{100}$(5)

(6) $Haughunit=100\text{Log}(\text{h-1}.\text{7w+7}.\text{6})$(6)

where h is the albumen height (mm) and w = egg weight (g). Furthermore, yolk diameter and yolk height (cm) were measured using a vernier caliper measuring up to 0.01 cm. Yolk weight (g) was measured using a digital weighing balance measuring up to 0.001 g.^[22,25] Yolk index and ratio (%) were calculated by the following formulas (7, 8):

(7) $YolkIndex(\%)=\text{Yolk height}\text{/}\text{Yolk}\text{Diameter}\times \text{100}$(7)

(8) $\mathbf{Y}\mathbf{o}\mathbf{l}\mathbf{k}\mathbf{r}\mathbf{a}\mathbf{t}\mathbf{i}\mathbf{o}\mathbf{(}\mathbf{\%}\mathbf{)}\mathbf{=}\mathrm{Y}\mathrm{o}\mathrm{l}\mathrm{k}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}/\mathrm{Y}\mathrm{o}\mathrm{l}\mathrm{k}\mathrm{e}\mathrm{g}\mathrm{g}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\times 100$(8)

Moreover, yolk pH was measured using a digital pH meter. Shell weight (g) was measured using a digital weighing balance measuring up to 0.001 g.^[22] The shell membrane thickness, shell thickness, and shell ratio were measured by the following formulas (9, 10, 11):

(9) $\mathbf{S}\mathbf{h}\mathbf{e}\mathbf{l}\mathbf{l}\mathbf{m}\mathbf{e}\mathbf{m}\mathbf{b}\mathbf{r}\mathbf{a}\mathbf{c}\mathbf{e}\mathbf{t}\mathbf{h}\mathbf{i}\mathbf{c}\mathbf{k}\mathbf{n}\mathbf{e}\mathbf{s}\mathbf{s}\mathbf{(}\mathbf{m}\mathbf{m}\mathbf{)}(\mathrm{S}\mathrm{h}\mathrm{a}\mathrm{r}\mathrm{p}\mathrm{p}\mathrm{o}\mathrm{i}\mathrm{n}\mathrm{t}+\mathrm{E}\mathrm{q}\mathrm{u}\mathrm{a}\mathrm{t}\mathrm{o}\mathrm{r}+\mathrm{S}\mathrm{t}\mathrm{u}\mathrm{b}\mathrm{b}\mathrm{y})/3$(9)

(10) $\mathbf{S}\mathbf{h}\mathbf{e}\mathbf{l}\mathbf{l}\mathbf{t}\mathbf{h}\mathbf{i}\mathbf{c}\mathbf{k}\mathbf{n}\mathbf{e}\mathbf{s}\mathbf{s}\mathbf{(}\mathbf{m}\mathbf{m}\mathbf{)}(\mathrm{S}\mathrm{h}\mathrm{a}\mathrm{r}\mathrm{p}\mathrm{p}\mathrm{o}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{t}\mathrm{h}\mathrm{i}\mathrm{c}\mathrm{k}\mathrm{n}\mathrm{e}\mathrm{s}\mathrm{s}+\mathrm{E}\mathrm{q}\mathrm{u}\mathrm{a}\mathrm{t}\mathrm{o}\mathrm{r}\mathrm{t}\mathrm{h}\mathrm{i}\mathrm{c}\mathrm{k}\mathrm{n}\mathrm{e}\mathrm{s}\mathrm{s}+\mathrm{S}\mathrm{t}\mathrm{u}\mathrm{b}\mathrm{b}\mathrm{y}\mathrm{t}\mathrm{h}\mathrm{i}\mathrm{c}\mathrm{k}\mathrm{n}\mathrm{e}\mathrm{s}\mathrm{s})/3$(10)

(11) $\mathbf{S}\mathbf{h}\mathbf{e}\mathbf{l}\mathbf{l}\mathbf{r}\mathbf{a}\mathbf{t}\mathbf{i}\mathbf{o}\mathbf{(}\mathbf{\%}\mathbf{)}\mathbf{=}\mathrm{S}\mathrm{h}\mathrm{e}\mathrm{l}\mathrm{l}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}/\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{e}\mathrm{g}\mathrm{g}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\times 100$(11)

Statistical analysis

Data were analyzed using analysis of variance (ANOVA), and means were compared by least significant difference. All statistical computations were executed with R studio (statistical software for Windows).

Results and discussion

The present study was conducted to compare the external and internal parameters of eggs of different breeds of peacock and to compare the characteristics among them. Heavier birds have eggs with high values as compared to the birds with lower weight. Table 1 shows the egg weight, length, breadth, volume, shape index, and surface area of different birds. During the present study, 130 eggs of different breeds of peacock were taken and the effect of egg weight on egg quality, characteristics, and growth traits was determined.

Table 1. Comparison of external egg quality parameters of peacock breeds (n = 10/breed).

Sr. No.	Species	Egg weight (g)	Egg length (cm)	Egg width (cm)	Egg breadth (cm^2)	Egg volume (cm^3)	Egg shape index (%)	Egg surface area (cm^2)
	Breeds
1	Pavo muticus	85.44 ± 0.59^g	6.32 ± 0.02^g	4.94 ± 0.01^c^d	24.94 ± 0.10^cd	78.22 ± 0.57^g	79.08 ± 0.11^ab	87.61 ± 0.5^f
2	P.m. muticus	106.57 ± 0.69^a	7.21 ± 0.01^a	5.308 ± 0.01^a	28.18 ± 0.01^a	100.84 ± 0.48^a	73.61 ± 0.09^ef	103.92 ± 0.02^a
3	Spalding Emerald	87.87 ± 1.39^efg	6.65 ± 0.03^def	5.04 ± 0.02^cd	25.43 ± 0.20^cd	84.24 ± 0.06^cdefg	75.74 ± 0.01^cde	91.95 ± 0.09^cdef
4	Pavocristatus	94.44 ± 0.4^2cde	6.98 ± 0.02^b	4.95 ± 0.01^d	24.55 ± 0.12^d	85.02 ± 0.44^cdefg	71.01 ± 0.31^g	92.74 ± 0.55^cdef
5	Indian blue pied	93.67 ± 0.87^cdef	6.64 ± 0.04^def	5.12 ± 0.01^bc	26.25 ± 0.10^bc	86.63 ± 0.81^cdef	77.30 ± 0.30^bcd	93.77 ± 0.07^cde
6	Spalding Cameo	94.41 ± 0.34^cde	6.98 ± 0.01^b	5.09 ± 0.01^cd	25.91 ± 0.05^cd	89.73 ± 0.10^bcd	72.91 ± 0.19^fg	96.15 ± 0.02^bc
7	Cameo Pied	95.73 ± 0.47^bcd	6.94 ± 0.01^bc	5.13 ± 0.01^bc	26.27 ± 0.07^bc	90.41 ± 0.11^bc	73.87 ± 0.24^ef	96.64 ± 0.28^bc
8	Bronze	102.29 ± 0.53^ab	6.95 ± 0.02^bc	5.25 ± 0.00^ab	27.58 ± 0.04^ab	95.13 ± 0.40^ab	75.60 ± 0.14^de	99.94 ± 0.02^ab
9	Black Shoulder	86.18 ± 0.16^fg	6.29 ± 0.02^g	5.05 ± 0.03^cd	25.58 ± 0.29^cd	80.12 ± 1.12^fg	80.16 ± 0.27^a	88.93 ± 0.09^ef
10	Indian White	85.49 ± 1.55^g	6.47 ± 0.04^fg	5.05 ± 0.04^cd	25.65 ± 0.41^cd	82.98 ± 1.80^defg	78.00±.28^abc	90.73 ± 0.19^def
11	Spalding Purple	88.51 ± 0.5^defg	6.55 ± 0.04^ef	5.018 ± 0.01^cd	25.19 ± 0.11^bc	81.68 ± 0.13^efg	76.89 ± 0.58^bcd	263.8 ± 0.01^def
12	Buford Bronze Pied	96.33 ± 0.62^bc	6.76 ± 0.01^cde	5.09 ± 0.01^cd	25.97 ± 0.14^cd	87.12 ± 0.55^cdef	75.33 ± 0.18^de	94.21 ± 0.40^cd
13	Buford Bronze White eyed	97.44 ± 0.74^bc	6.81 ± 0.01^bcd	5.12 ± 0.01^bc	26.22 ± 0.17^bc	88.66 ± 0.71^bcde	75.17 ± 0.95^de	95.2823 ± 0.18^bcd

Comparison of external egg quality parameters of breeds of peacock

In the present study, higher egg weight (106.57 ± 0.69), egg length (7.21 ± 0.01), egg width (5.308 ± 0.01), egg breadth (28.18 ± 0.01), and egg volume (100.84 ± 0.48) were observed in Pavo muticus muticus (P.m. muticus) and lower egg weight (85.44 + 0.59), egg length (6.32 ± 0.02), egg width (4.94 ± 0.01), and least egg volume (78.22 ± 0.57) were found in Pavo muticus. Least egg breadth was found in Pavo cristatus (24.55 ± 0.12). The egg weight of P.m. muticus was much higher as compared to other breeds, perhaps, due to the massive size of the bird. Dudusola^[26] noticed the same difference in guinea fowl and quail eggs. Egg shape index was observed to be higher in black shoulder (80.16 ± 0.27) and least in Pavo cristatus (71.01 ± 0.31). These results were close to the findings of Dudusola^[26] as the shape indices of quail (79.93) and guinea fowl (79.57) eggs were with no statistical difference.^[26] Higher egg surface area was found in Spalding purple (263.8 ± 0.01), whereas a lower value (87.61 ± 0.5) was found in Pavo muticus (Table 1).

Fumin et al.^[11] compared the quality and nutritional components of eggs from blue peafowl and jingbai hens. They found that the average egg weight, egg yolk relative weight, and egg shell thickness of blue peafowl were significantly higher than the eggs of hens. The egg weight in P. colchicus varied from minimum of 20 g to maximum of 40 g, with an average of 26.94 ± 5.37 g. Average egg length was 4.19 ± 0.20 cm, average width was 3.36 ± 0.18 cm, egg volume was 23.10 ± 3.639 cm³, egg surface area was 80.80 ± 12.728 cm², and shape index was 80.11 ± 2.93%.^[22] In our study, it was found that peacocks with heavier eggs have more egg length, breadth, volume, yolk diameter, and yolk pH. It was also observed that egg weight, its quality, and its composition are affected by many factors such as breed, feed, housing conditions, and age of the bird that is in close conformity with the findings of Champati et al.^[27]

Comparison of internal eggs quality parameters of breeds of peacock

During the present study, it was found that internal egg quality traits of Pavo cristatus were the best among all breeds of peacock as they showed significantly higher albumen diameter (11.02 ± 0.05), albumen weight (47.06 ± 0.24), albumen height (0.946 ± 0.02), albumen ratio (49.83 ± 0.13), yolk height (1.66 ± 0.01), yolk index (35.75 ± 0.13), and shell thickness (0.67 ± 0.00). On the contrary, least albumen diameter (9.366 ± 0.07) and albumen weight (27.92 + 0.65) were measured in Buford bronze pied. However, least albumen height was noticed in Spalding emerald (0.69 ± 0.01). Buford bronze pied showed higher albumen index (10.12 ± 0.16), whereas Indian white expressed the least value of albumin index (6.02 ± 0.12). In the current study, significantly higher albumen (12.66 ± 0.28 g) and yolk weight (10.08 ± 0.31 g) were observed in heavy-egg-weight category as compared to medium- and lightweight categories in accordance with the previous study conducted by Ashraf et al.^[22]

In our study, a higher value of albumen index was observed in Buford bronze pied (10.12 ± 0.16), followed by Buford bronze white eyed (9.65 ± 0.17), P.m. muticus (7.68 ± 0.14), Spalding purple (7.02 ± 0.09), and Pavo muticus (7.01 ± 0.15), and the least albumen index was observed in Pavo cristatus (6.60 ± 0.04), Spalding emerald (6.38 ± 0.10), and Indian white (6.02 ± 0.12). Average albumen index value measured during the present study was greater than average albumen index value of 2.82 ± 0.33% calculated by Ashraf et al.^[22] and was greater than albumen index value of 1.47–0.37% observed by Kirikci et al.^[28]

Higher albumen pH (6.43 ± 0.01) and yolk diameter (6.93 ± 0.04) were observed in Indian white, whereas lower albumen pH (6.15 ± 0.00) and yolk diameter (4.63 ± 0.03) were observed in Pavo cristatus. Lower yolk height (1.03 ± 0.02) and yolk index (14.99 ± 0.31) were found in Indian white. Higher yolk pH was observed in P.m. muticus (6.35 ± 0.016), whereas it was lower in Pavo cristatus (6.15 ± 0.01). Higher yolk ratio (61.80 ± 0.87) and yolk weight (51.66 ± 0.34) were observed in Indian white, lower yolk ratio (33.52 ± 0.57) and yolk weight (31.6 ± 0.06) were observed in Pavo cristatus, and lower shell thickness was noticed in Pavo muticus (0.33 + 0.01). In the present study, higher yolk diameter was observed in Indian white (6.93 ± 0.04), and statistically same yolk diameter was followed by Spalding cameo, cameo pied, and P.m. muticus as 6.76 ± 0.04. A little bit of variation was found in Spalding emerald, Buford bronze white eyed, and Buford bronze pied as 6.2 ± 0.05, followed by Pavo muticus (5.90 ± 0.04) and Pavo cristatus (4.63 ± 0.03). The eggs of Pavo cristatus (35.75 ± 0.13) showed greater yolk index, followed by Spalding purple (20.93 ± 0.82), Indian blue pied (20.52 ± 0.50), Pavo muticus (20.22 ± 0.96), and Indian white (14.99 ± 0.31). The values of yolk index measured during the present study were mostly less, while yolk percentage recorded was higher than the values mentioned in research.^[22]

The most important international index used to study internal egg quality traits is Haugh unit. In the present research, elevated values of Haugh unit were significantly observed in the eggs of Buford bronze pied (88.57 ± 0.84), followed by Buford bronze white eyed (85.65 ± 0.95), Indian blue pied (84.33 ± 0.65), Spalding cameo (81.85 ± 1.03), bronze (81.68 ± 0.52), cameo pied (80.53 ± 1.08), and black shoulder (78.97 ± 1.35). A normal value of Haugh unit was measured in P.m. muticus (78.27 ± 0.68), Spalding purple (77.00 ± 0.75), Spalding emerald (76.14 ± 0.94), Pavo cristatus (75.45 ± 0.30), and Indian white (74.11 ± 0.56), while the least was found in Pavo muticus (73.48 ± 1.08). The higher the value of Haugh unit and yolk index, the more desirable is the internal quality of the egg.^[29] Da Silva et al.^[30] investigated that Haugh unit decreases due to the breakdown of proteins inside the albumin and loss of moisture, which is similar to the findings of Malfatti et al.,^[31] who found that the higher the Haugh unit, the higher is the albumin quality of the egg. Furthermore, Dong et al.^[32] and Alig et al.^[33] also supported the close relation of Haugh unit to albumin pH and albumin height. Higher shell weight (16.38 ± 0.42) and shell ratio (17.01 ± 0.38) were observed in Buford bronze pied, whereas they were lower in Pavo muticus as 10.03 ± 0.27 and 11.74 ± 0.58, respectively (Table 2).

Table 2. Comparison of internal egg quality parameters of breeds of peacocks (n = 10/breed).

Sr. No	Species	Albumen diameter (cm)	Albumen height (cm)	Albumen index (%)	Albumen pH	Albumen ratio (%)	Albumen weight (g)	Yolk diameter (cm)	Yolk height (cm)	Yolk index (%)	Yolk pH
	Breeds
1	Pavo muticus	9.79 ± 0.06^de	0.68 ± 0.01^ef	7.01 ± 0.15^cdef	6.34 ± 0.01^b	33.35 ± 0.68^ef	28.71 ± 0.73^e	5.90 ± 0.04^bcd	1.2 ± 0.06^b	20.22 ± 0.96^b	6.18 ± 0.00^cd
2	P.m. muticus	10.67 ± 0.07^abc	0.81 ± 0.01^bcd	7.68 ± 0.14^dcde	6.28 ± 0.01^bcd	48.39 ± 0.56^cd	42.06 ± 0.35^b	6.73 ± 0.08^a	1.17 ± 0.39^b	18.35 ± 0.86^bc	6.35 ± 0.016^a
3	Spalding Emerald	10.76 ± 0.05^ab	0.69 ± 0.01^ef	6.38 ± 0.10^f	6.24 ± 0.01^cde	39.13 ± 0.36^cd	34.8 ± 0.88^b	6.03 ± 0.01^bc	1.10 ± 0.02^b	18.28 ± 0.40^bc	6.24 ± 0.01^bc
4	Pavo cristatus	11.02 ± 0.05^a	0.73 ± 0.00^def	6.60 ± 0.04^ef	6.15 ± 0.00^f	49.83 ± 0.13^a	47.06 ± 0.24^a	4.63 ± 0.03^f	1.66 ± 0.01^a	35.75 ± 0.13^a	6.15 ± 0.01^d
5	Indian blue pied	10.92 ± 0.05^ab	0.86 ± 0.00^abc	7.85 ± 0.04^bc	6.27 ± 0.00^bcd	43.24 + 0.45^bc	40.61 + 0.66^b	5.59 ± 0.03^de	1.14 ± 0.03^b	20.52 ± 0.50^b	6.25 ± 0.00^b
6	Spalding Cameo	10.73 ± 0.65^ab	0.84 ± 0.02^abcd	7.83 ± .17^bcd	6.26 ± 0.00^cd	31.83 ± 0.66^ef	30.1 ± 0.63^de	6.76 ± 0.04^a	1.21 ± 0.02^b	17.96 ± 0.36^bc	6.22 ± 0.53^bc
7	Cameo Pied	10.73 ± 0.05^abc	0.82 ± 0.02^bcd	7.68 ± 0.18^bcde	6.246 ± 0.01^cde	33.04 ± 0.68^ef	31.47 ± 0.58^de	6.69 ± 0.03^a	1.18 ± 0.02^b	17.63 ± 0.25^bc	6.21 ± 0.01^b
8	Bronze	10.36 ± 0.09^bcd	0.85 ± 0.01^abcd	8.27 ± 0.15^b	6.20 ± 0.01^def	39.24 ± 0.30^b	40.17 ± 0.39^b	5.75 ± 0.04^cde	1.16 ± 0.01^b	20.31 ± 0.17^b	6.213 ± 0.00^bcd
9	Black Shoulder	9.81 ± 0.14^de	0.77 ± 0.02^cde	8.21 ± 0.34^bc	6.29 ± 0.01^bc	39.92 ± 0.41^cd	34.1 ± 0.33^cd	5.70 ± 0.03^cde	1.11 ± 0.02^b	19.47 ± 0.36^bc	6.24 ± 0.01^bc
10	Indian White	10.13 ± 0.04^cd	0.61 ± 0.01^f	6.02 ± 0.12^def	6.43 ± 0.01^a	35.84 ± 0.32^de	30.21 ± 0.31^de	6.93 ± 0.04^a	1.03 ± 0.02^b	14.99 ± 0.31^c	6.34 ±0.01^a
11	Spalding Purple	10.42 ± 0.02^bc	0.73 ± 0.01^def	7.02 ± 0.09^cdef	6.27 ± 0.01^bcd	43.02 ± 0.62^bc	38.26 ± 0.70^bc	5.45 ± 0.06^e	1.1 ± 0.03^b	20.93 ± 0.82^b	6.21 ± 0.01^bcd
12	Buford Bronze Pied	9.366 ± 0.07^e	0.946 ± 0.02^a	10.12 ± 0.16^a	6.158 ± 0.06^ef	48.05 ± 0.51^f	27.92 ± 0.65^e	6.2 ± 0.05^b	1.22 ± 0.01^b	20.26 ± 0.35^b	6.194 ± 0.01^bcd
13	Buford Bronze white eyed	9.37 ± 0.07^e	0.90 ± 0.02^ab	9.65 ± 0.17^a	6.17 ± .06^ef	30.68 ± 0.67^f	29.76 ± 0.63^de	6.24 ± 0.05^b	1.19 ± 0.02^b	19.29 ± 0.36^bc	6.19 ± 0.01^bcd
Sr. No	Species	Yolk ratio (%)	Yolk weight (g)	Shell thickness (mm)		Shell membrane thickness(mm)	Shell weight (g	Shell ratio (%)		Haugh Unit
	Breeds
1	Pavo muticus	48.57 ± 0.33^bc	41.46 ± 0.34^de	0.33 ± 0.01^f		0.07 ± 0.00^b	10.03 ± 0.27^e	11.74 ± 0.58^e		73.48 ± 1.08^f
2	P.m. muticus	48.39 ± 0.56^bc	51.27 ± 0.34^ab	0.54 ± 0.00^bc		0.07 ± 0.00^b	15.19 ± 0.09^ab	14.26 ± 13.56^cd		78.27 ± 0.68^bcdef
3	Spalding Emerald	44.91 ± 0.19^cd	39.3 ± 0.51^ef	0.54 ± 0.00^bc		0.09 ± 0.00^a	12.71 ± 0.15^d	14.46 ± 10.76^c		76.14 ± 0.94^def
4	Pavo cristatus	33.52 ± 0.57^f	31.6 ± 0.06^g	0.67 ± 0.00^a		0.08 ± 0.00^ab	13.7 ± 0.17^bcd	14.51 ± 41.10^c		75.45 ± 0.30^def
5	Indian blue pied	39.08 ± 0.28^e	36.5 ± 0.33^f	0.54 ± 0.01^bc		0.08 ± 0.00^ab	13.19 ± 0.22^cd	14.08 ± 24.53^cd		84.33 ± 0.65^abc
6	Spalding Cameo	51.19 ± 0.54^b	48.19 ± 0.37^abc	0.41 ± 0.01^e		0.07 ± 0.00^b	12.13 ± 0.06^d	12.85 ± 16.98^de		81.85 ± 1.03^abcd
7	Cameo Pied	49.49 ± 0.40^b	47.36 ± 0.44^bc	0.44 ± 0.12^de		0.07 ± 0.00^b	12.31 ± 0.09^d	12.86 ± 18.84^de		80.53 ± 1.08^bcdef
8	Bronze	44.14 ± 0.30^cd	45.2 ± 0.45^cd	0.57 ± 0.01^bc		0.08 ± 0.00^ab	14.67 ± 0.03^abc	14.34 ± 5.88^c		81.68 ± 0.52^abcde
9	Black Shoulder	48.35 ± 0.74^bc	41.18 ± 0.49^e	0.34 ± 0.01^f		0.07 ± 0.00^b	12.98 ± 0.20^cd	15.06 ± 16.83^bc		78.97 ± 1.35^bcdef
10	Indian White	61.80 ± 0.87^a	51.66 ± 0.34^a	0.51 ± 0.00^cd		0.08 ± 0.00^ab	12.44 ± 0.16^d	14.55 ± 10.42^bc		74.11 ± 0.56^ef
11	Spalding Purple	41.79 ± 0.73^de	36.7 ± 0.47^f	0.54 ± 0.01^bc		0.08 ± 0.00^ab	12.6 ± 0.05^d	14.24 ± 10.21^cd		77.00 ± 0.75^cdef
12	Buford Bronze Pied	47.00 ± 0.51^bc	46.4 ± 0.65^c	0.588 ± 0.01^b		0.09 ± 0.002^a	16.38 ± 0.42^a	17.004 ± 0.38^a		88.57 ± 0.84^a
13	Buford Bronze white eyed	47.681 ± 0.53^bc	46.524 ± 0.65^c	0.58 ± 0.01^b		0.09 ± 0.002^a	15.77 ± 0.39^a	16.18 ± 52.16^ab		85.65 ± 0.95^ab

Stoddard et al.^[34] reported that eggshells are most exposed to external factors and breeding success is largely dependent upon them. Rosenbeger et al.^[35] claimed that egg shell thickness varied due to physiological limitations, environmental conditions, and nutrition. In the current research, higher shell thickness was observed in Pavo cristatus (0.67 ± 0.00), whereas it was lower in Pavo muticus (0.33 ± 0.01). Shell membrane thickness of various breeds was found to be of comparable magnitudes. A higher value was observed in Spalding emerald, Buford bronze pied, and few others as 0.09 ± 0.00, and a lower value was observed in Spalding cameo and cameo pied as 0.07 ± 0.00. Khaliduzzaman et al.^[36] commented that eggs with thicker shells may produce healthier offsprings, as they are the major source of minerals and provide better protection to internal contents. Higher shell weight was noted in Buford bronze pied (16.38 ± 0.42), and lower shell weight was observed in Pavo muticus (10.03 ± 0.27). Higher shell ratio was observed in Buford bronze pied (17.004 ± 0.38), and lower shell ratio was of Pavo muticus (11.74 ± 0.58). The strength of the egg is dependent not only on the thickness of shell but also on its construction material and the egg breaking strength. Lack of minerals and vitamins in diet is responsible for poor egg production, decreased external and internal egg quality parameters, fertility, and hatchability.^[37]

Conclusion

The current study concluded that all the external and internal egg quality parameters were highly significant in different breeds of peacock, and the best quality of eggs were laid by Pavo cristatus and P.m. muticus. Nutritious diet, better care, and the best housing conditions improve egg quality traits. Better quality eggs are responsible for the healthy development of chicks, and better housing conditions can promote the further growth of chicks. Based on all the above observations, we can state that a strong correlation is present between feed, egg quality parameters, and morphological parameters. Furthermore, the main objective of this work was to highlight the large gap in our way of interpreting the species and to suggest some plans to conserve them. The reason for the perilous status of many species including peafowl is the consistent preference toward endangered species and conservation interferences that are based on limited resources.

Disclosure statement

No potential conflict of interest was reported by the author(s).