Citation of this paper

Impact of layer egg storage conditions on eggs and embryo quality indices prior to incubation

J A Hamidu, K Adomako, S Adamu, A M Ajaottor, G J Amankwah, K M Gyasi, E M Shiburah, J O Darko and L A Konadu

Department of Animal Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
jahamidu.canr@knust.edu.gh

Abstract

Studies have shown that when hatching eggs are stored for long durations, egg quality is affected. An experiment was conducted to investigate the effect of storage duration (1, 4, 7, 10, 14 days) under different temperature conditions (cold room at 18^oC and ambient temperature, average 25^oC) to assess egg quality, blastoderm growth or shrinkage in Lohmann parent eggs. Four hundred (400) eggs were collected from 80 weeks old Lohmann parent flocks and subjected to different treatments as shown above. Eggs were broken and yolk, albumen and blastoderm quality determined. Data were analyzed using the SAS Proc Mixed model procedure and means separated using the PDIFF at 5% significance level. The egg weights before and after storage were not affected by storage duration and temperature conditions. However, egg weight loss increased significantly as storage duration increased and was higher in ambient temperature condition. With regards to all the intrinsic egg quality characteristics, albumen height, yolk diameter and blastoderm diameter measured were significantly affected by the length of storage. Albumen height declined heavily as storage duration increased especially by 14 days at ambient temperature but very slight decrease was recorded at cold room temperature. Yolk index also decreased with increasing duration at ambient temperature compared to the level of decline at cold room storage treatment. The blastoderm development at cold room temperature stayed statistically the same with increasing duration of egg storage. However, the blastoderm diameter increased with increasing storage duration in ambient temperature with an excessive increase in yolk mottling. There was clear evidence that Lohmann layer eggs stored in ambient temperature for longer durations were impacted negatively by the morphological and physiological indices which affected the blastoderm and may reduce their ability to incubate or produce viable embryos and saleable chicks at high quality.

Keywords: ambient temperature, blastoderm quality, cold room temperature, egg quality, storage duration

Introduction

The main goal of every poultry enterprise is to improve the performance of birds. These enterprises include egg production – both fertile and table eggs, meat production, and hatchery. However, many factors including nutrition, environmental influence, and genetic makeup influence the performance of birds (Tona et al 2004). On genetics, breeders have worked hard on improvement of farm birds to meet the demands of production but until recently little had been accomplished in selecting traits relating to reproduction (Decuypere et al 2001). Nutrition on the other hand, amongst the factors above, can easily be controlled by the farmer. There are many environmental factors that have an influence on poultry performance and these start immediately after oviposition until the eggs or meat enters the human food chain.

It is well known that day-old chicks are from fertile eggs and also, these day-old chicks are the fundamental assets of every poultry farmer. Studies have shown that the quality and integrity of day-old chicks is one of the most important determinants of the performances of the production flocks and it all depends on the quality of eggs used for incubation (Decuypere et al 2001; Fasenko et al 2009). Hatching eggs are stored for various reasons. These include inadequate incubator capacity, market demand for day-old chicks, incubator unavailability, and transportation cost of eggs to hatcheries. Though egg storage results in some consequences, the importance of storage cannot downplay its undesirable effect on the value of eggs, especially in this era where consumers are quick to raise concerns over the quality of products (Akter et al 2014). For many years the most important external and inner egg quality traits had been proven to be egg weight, egg form, breaking power, shell thickness, albumen height and weight, specific gravity, and yolk index. Samli et al (2014) reported that the most important parameters cited above in laying hens are influenced by way of the duration and temperature of storage.

A remarkable number of researchers have demonstrated that, storing fertile eggs for longer periods before incubation adversely affected the blastoderm, blastoderm numbers, blastodermal gene expression, yolk and albumen quality, embryonic development and metabolism, mortality, hatchability and ultimately the chick quality (Scott and Silversides 2000; Heiber and Jarp 2001; Tona et al 2004; Fesenko et al 2001, Hamidu et al 2010, 2011, Hamidu 2013; Uddin and Hamidu 2014; Addo et al 2018). Fasenko (2007) showed that egg storage had negative effects on embryo development. Mishra et al (2007) reported that, storing hatching eggs at ambient temperature for more than four days caused a decline in the hatchability of eggs by 3.3% daily. Day-old chicks from eggs cold stored for 14 days showed a remarkable decrease in the rate of growth and reduced chick quality compared with eggs saved for 4 days (Fasenko et al 2001).

Also, Tona et al (2004) concluded that storing eggs extra than 7 days and at regular storage conditions (10°C - 20°C and 50% - 80% Relative Humidity) caused an interruption in the time of hatching. In addition, Schmidt et al (2009) concluded that prolonging the duration of egg storage from 2 to 14 days caused embryo death or mortality to increase from 7.05% to 26.4%. These authors further emphasized that total embryonic mortality for eggs stored up to 7 days (2, 4 and 6 days) was 9.52%, and for eggs stored for more than 7 days (8, 10, 12 and 14 days), it turned out to reach as high as 22.0%. Also, storing eggs for 4 versus 14 days reduced live embryonic cells numbers 81% to 68% (Hamidu et al 2011). Hristakieva et al (2011) reported that egg and embryo quality rests on the period and environment of storage. This experiment is focused on assessing the impact of especially ambient storage conditions (temperature and duration) on the inherent and external components of laying eggs that decide embryo quality at the blastodermal level in hot environments.

Materials and methods

Experimental sites

The research was conducted at the Department of Animal Science, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi-Ghana. Kumasi lies on 06^o 41‟N and longitude 01^o 33‟W with an elevation of 261m above ocean level with an ambient temperature between 23° to 31°C (Adomako 2009; Meteorological Services Department, Kumasi 2015).

Egg sampling and storage

A total of 400 eggs were selected at random from Lohmann layer breeding stock. Half of the total eggs (200) were stored in cold room temperature of 18^oC, whiles the other half was stored at ambient temperature (21^oC- 35^oC). Both groups were sub-divided and stored for five different durations (1, 4, 7, 10, 14 days) at a constant relative humidity (RH) of 75% showing a 2×5 factorial design. Thus, 2 levels of temperature treatment (cold room storage and ambient temperature) and 5 levels of egg storage durations (1, 4, 7, 10, and 14 days). A total of 50 eggs were selected randomly from each temperature treatment and 10 eggs per storage duration for evaluation of intrinsic and extrinsic parameters. For testing, each egg was weighed and broken, and data was recorded on the thick egg white (albumen), egg yolk, and blastoderm.

Data collection

The external characteristics of eggs were egg weight (g), whereas internal quality parameters included albumen height (mm), yolk diameter (cm) and yolk height (cm). The weight of egg was determined by weighing eggs individually on an electric balance. Albumen height was determined by the use of tripod spherometer, and yolk height and diameter with the Vernier callipers.

Weight loss measurement

Total weight loss in an egg (g) was computed as; Initial egg weight (g) – Final egg weight (g). Percentage weight loss was computed relative to the initial egg weight. Percentage weight loss= (weight loss (g)/ initial weight (g)) × 100.

Yolk index measurement

Yolk index = Yolk height (cm) /Yolk diameter (cm) was used in computing for the yolk indices.

Statistical analysis

Data collected were subjected to SAS Proc Mixed Model Procedure (SAS 2003). The statistical model includes the fixed effects of storage temperature and storage duration, together with interaction between the two factors. The random error term was declared from the interactions of storage temperature and storage duration and nested in egg weight before storage. Significant differences between the Lsmeans of treatments were separated using PDIFF of SAS at a probability level of P<0.05.

Results and discussions

Table 1. The effect of egg storage temperature and storage duration on external egg quality characteristics in Lohmann layers
Source	Egg weight before storage (%)	Egg weight after storage (%)	Egg weight loss(%)

Storage temperature
Ambient (23- 31^oC)	54.7	53.3	2.38^a
Cold room (18^oC)	53.7	53.1	0.84^b
SEM¹	0.55	0.69	0.17
Days of Storage
1day	54.4	54.5	0.00^d
4days	53.5	53.0	0.69^cd
7days	54.5	53.3	1.45^c
10days	54.3	52.9	2.30^b
14days	54.3	52.3	3.60^a
SEM	0.86	1.08	0.27
Interaction
Ambient x 1day	55.3	55.5	0.00^d
Ambient x 4days	52.5	51.8	1.12^c
Ambient x 7days	55.7	54.4	2.51^b
Ambient x 10days	55.8	53.3	3.46^b
Ambient x 14days	54.3	51.8	4.80^a
Cold room x 1day	53.5	53.5	0.00^d
Cold room x 4days	54.5	54.2	0.25^cd
Cold room x 7days	53.3	52.3	0.38^cd
Cold room x 10days	52.8	52.6	1.15^c
Cold room x 14days	54.2	52.9	0.39^b
SEM	1.22	1.46	0.39
p – values
Storage temperature	0.178	0.789	<0.0001
Storage duration	0.936	0.701	<0.0001
Interaction	0.242	0.496	0.0069
Superscript^a-d different letters indicate differences at p<0.05.

Effect of storage duration and temperature on egg weight and egg weight loss

Table 1 shows the impact of storage temperature and duration on percentage weight loss in layer eggs. There were no differences in eggs weight before and after storage between the treatments. Similarly, the interaction between the treatments were not different. Percentage weight loss increased (p<0.05) with increasing length of duration for both temperatures. However, egg weight reductions at ambient storage especially at 7, 10 14 days were higher in contrast to the cold room temperature. Comparable outcomes were recorded in similar studies (Aktar et al 2014; Hassan et al 2005; Addo et al 2018) but in other breeds of chicks. These authors indicated that an increase in the time of storage results in the decrease of egg weight. Samli et al (2005) reported that, amid storage at 21°C, egg weight reduction was 0.65 g and 1.03 g at 5 days and 10 days of storage respectively.

Effect of storage duration and temperature on albumen height

The effect of egg storage duration and temperature is shown in Table 2. It was noticed that the albumen height was higher in cold room storage compared to ambient temperature. Similarly, as storage period increased the albumen height reduced significantly (p<0.05). These outcomes demonstrated an extraordinary deterioration of egg albumen height in eggs put away at room temperature when contrasted with eggs put away at cold room temperature. It was observed that the albumen height diminished from 7.87 mm to 2.71 mm and from 6.82 mm to 5.43 mm at ambient and cold room respectively from 1 to14 day of storage. The decline in albumen height is owed to ovomucin-lysozyme complex cessation, which assists to upsurge the pH of eggs and movement of water from the albumen to the yolk. These are also detriment to hatching eggs because as the yolk gets too big it becomes difficult for third trimester chicks (15 to 18 days of incubation) to adsorb the remaining yolk sac into its abdomen during hatching. This situation increases the risk of yolk sac infection and increased navel opening, which serve as disease routes to bacteria (Addo et al 2018). It was reported that high temperatures at storage stimulate the interruption of the ovomucin-lysozyme complex (Akter et al 2014). This finding is consistent with other studies (Hamidu et al 2011; Akter et al 2014). These researchers demonstrated that the albumen height and weight keep on diminishing with each extra day of storage. Also, these outcomes are in concurrence with those of Scott and Silversides (2000), who detailed that the albumen height diminished significantly (p<0.05) from 9.16 to 4.75 mm in eggs stored for 10 days.

Table 2. The effect of egg storage temperature and storage duration on internal egg quality characteristics in Lohmann layers
Source	Albumen height (mm)	Yolk index	Blastoderm diameter (mm)

Storage temperature
Ambient (23- 31^oC)	4.52^b	0.29^b	0.87^a
Cold room (18^oC)	5.94^a	0.40^a	0.49^b
SEM¹	0.19	0.35	0.68
Days of Storage
1day	7.35^a	0.43^a	0.48^c
4days	5.53^a	0.37^b	0.59^bc
7days	4.88^bc	0.32^c	0.67^bc
10days	4.31^c	0.31^c	0.74^ab
14days	4.07^c	0.27^d	0.93^a
SEM	0.30	0.34	0.68
Interaction
Ambient x 1day	7.87^a	0.44^a	0.50^c
Ambient x 4days	4.26^de	0.35^d	0.68^bc
Ambient x 7days	4.01^ef	0.24^e	0.82^b
Ambient x 10days	3.72^ef	0.24^e	0.97^b
Ambient x 14days	2.71^f	0.16^f	1.38^a
Cold room x 1day	6.82^a	0.43^ab	0.47^c
Cold room x 4days	6.81^ab	0.40^bc	0.49^c
Cold room x 7days	5.76^bc	0.40^bc	0.52^c
Cold room x 10days	4.89^cde	0.38^cd	0.51^c
Cold room x 14days	5.43^cd	0.38^cd	0.48^c
SEM	0.43	0.34	0.68
p – values
Storage temperature	<.0001	<0.0001	<0.0001
Storage duration	<.0001	<0.0001	0.0013
Interaction	0.0002	<0.0001	0.0021
Superscript^a-d different letters indicate differences at p<0.05.

Effect of storage temperature and duration on yolk index

A tabular presentation of the yolk index (yolk height/yolk width) showed that the yolk indices of the eggs reduced with additional days of storage (Table 2). The yolk indices were different between storage temperature, between storage durations and among the interactions of storage temperature and storage duration. Yolk index in cold room storage reduced marginally from 0.43 at day 1 of storage to 0.38 at 14 days of storage. A dramatic reduction of yolk index from 0.44 at day 1 of storage to 0.16 at 14 days of storage was recorded in eggs stored at ambient temperature. The trend is comparable to other outcomes demonstrated in previous research where the yolk index decreased from 0.49 to 0.3 following 10 days of room temperature storage but whiles at refrigerator storage, the yolk index reduced slightly from 0.49 to 0.48 (Gravena et al 2011). Also, Samli et al (2014) showed that the yolk index diminished from 44.1% to 39.0% and from 44.1% to 32.7% at 21°C and 29°C respectively after 10 days of storage. Akter et al (2014) recorded an increase in yolk width with increasing duration of storage. They further explained that at a higher temperature, there is an increase in water movement from the albumen into the yolk and this caused the yolk diameter to increase.

Effect of storage duration and temperature on blastoderm development

In this study, it was observed that significant differences existed between storage temperature treatments, storage duration treatments and interactions. The blastoderms in the ambient temperature were bigger than those in cold room temperature treatment by about a factor of 2. It was also noticed that as storage duration increased the diameter of the balstoderms increased (Table 2). Among the interactions, the blastoderm diameter was not different between those from the cold room storage at different storage durations. However, in ambient temperature storage treatment, blastoderm size appeared to increase linearly until 14 days of storage where it increased greatly. This is because the higher temperature in the room where eggs were stored was favorable enough to support embryonic development. Proof of effect of egg storage has been accounted for at temperatures of 25°C with doubled blastoderm size showing features of embryonic streak phase whereas in eggs stored at 15 or 20°C no observable increase in blastoderm size and growth were recorded after 2 weeks of storage (Malecki et al 2005). Mather and Laughlin (1979) showed that egg storage at 10°C induced blastodermal cell-shrinkage. The rate of blastodermal cell-shrinkage correlated negatively with layer age but increased with the period of storage. Arora and Kosin (1966); Mather and Laughlin (1979) have proven that eggs stored at 13°C tended to show deteriorating changes and cell death in the blastoderm.

Effect of storage duration and temperature on yolk mottling

Yolk mottling may refer to the colour of the yolk becoming uneven or patchy, or vary from the desired colour range (deep-yellow to orange-yellow) characteristic of eggs. Yolk mottling was recorded highest in eggs put away at room temperature from day 7 to 14 as shown in plate a and plate b (Figure 1). Additionally, it was distinguished in the examination that, the yolk of eggs put away for a longer period at ambient temperature (plate c) had a tendency to be very unstable and effectively breaks easily on egg breakout. These eggs appear “watery” and resulted in difficulty of recording majority of information to determine quality characteristics. Out of the 10 eggs available for the 14 days stored eggs at ambient temperature only 4 could be assessed due to high level of yolk membrane breaking. Kirunda and McKee (2000) mentioned that the strength of the egg vitelline-membrane declines in the course of storage making the yolk more vulnerable to rupturing. Consequently, water sluggishly moved into the yolk from the egg white, so this generated a blotchy form in yolk known as yolk mottling. Also yolk turns out to be flattened as shown in plate b. Comparative observations recorded quite recently indicate that for eggs stored at ambient temperatures for longer days, the integrity of vitelline-membrane of the yolk diminished causing the yolk to easily break and extend into the albumen (Akter et al 2014). This is an important economic factor for incubation because eggs exhibiting high numbers of yolk mottling may not develop past the first 7 days of incubation and would be classified as clear eggs after breakout.


Figure 1. Degrees of yolk molting during storage: Plate a. Egg at day 4 & 7 in ambient storage shows blastoderm development with blood rings; Plate b. Shows intense yolk mottling in an egg stored for 14 days at room temperature; Plate c. This shows a ruptured egg at day 14 of ambient room storage due to weakened vitelline membrane

Conclusions

This study has confirmed that the quality attributes of eggs were favorably influenced when eggs were put away in cold room, however room temperature influenced some egg quality qualities negatively by reducing egg weight, affecting the blastoderm and by decreasing yolk index and albumen height over the time of egg storage.
It is inferred that eggs set aside for incubation should be stored in cold room temperature up to 14 days.
At room temperature eggs could only be kept for up to 4 days as recommended from observations in the current research.

Acknowledgment

Our appreciation goes to the Department of Animal Science, KNUST and the Olympio hatchery for the fertile eggs used for the project.

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Received 14 September 2018; Accepted 1 October 2018; Published 1 November 2018

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