| Livestock Research for Rural Development 30 (10) 2018 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
In Kenya, the demand for poultry and poultry products has been on the increase and the trend is expected to continue. Consumers are demanding for poultry products that adhere to recognized quality criteria, while farmers are looking for ways of identifying eggs with high hatchability so as to increase their chicken flocks. Indigenous chicken (IC) production has been surpassed by the demand resulting to the utilization of exotic breeds. An IC genetic performance improvement program using Barred Plymouth Rock (BPR) and Rhode Island Red (RIR) was initiated to supply cross breeds that can produce in low input production system. However, the program has not been evaluated in terms of the egg quality characteristics from the resulting chicken generations. The objective of this study was therefore to evaluate the potential impact on the IC genetic diversity and the subsequent effects on egg characteristics of using exotic breeds in the genetic improvement program in Kenya. A total of 240 eggs from three genetic groupings; purebred Barred Plymouth Rock (BPR), crossbred between BPR and RIR (F1) progeny and IC were randomly selected and evaluated. Descriptive statistics were used to describe the internal and external egg characteristics. F1 progeny eggs were heaviest with 70.1 g, BPR had eggs 67.8 g, and IC had 46.3 g. The IC had the thickest shell of 0.58 mm. Although all the chicken had a high Haugh Unit (HU), the IC trailed with 73.4. Generally, there was improvement on the egg quality analysed following use of exotic breeds. However, this needs to be considered in light of the potential loss of genetic diversity.
Key words: Barred Plymouth Rock, egg quality traits
Increase in urbanization and per capita income in developing countries have resulted in an increase in demand for animal protein (Ayieko et al 2014). This increase has occurred in times when there has been more emphasis on sustainable protein production. The implication of considering the environmental effects resulting from animal protein prouction has tended to favour rearing of species whose production results in minimal damage to the environment. Additionally, the products should be affordable to the majority of the population (Hussain et al 2013). The indigenous chicken, which are commonly reared extensively, have been identified as having potential in plugging the protein gap while ensuring that the production environment is maintained. Furthermore, chicken eggs have been a traditional source of high biological value protein and are affordable to the resource poor due to their packaging into low value units (Hussain et al 2013; King'ori et al 2010). Besides protein, IC provide many other tangible and intangible benefits to poor rural households in developing countries. Despite playing such important socio-economic roles, the production of eggs and meat from the IC is characterised by low productivity (King'ori et al 2010) underlining the need to consider intervention strategies that can result in increased production and profitability per hen. The increase should be accompanied by an increase in products quality as demanded by the consumers.
The preference for large eggs has been indicated as the consumer’s value for money (Liu and Winston 2010), while the preference for egg shell colour varies according to consumer’s culture and creates confidence and preference for the product (Grobbelaar et al 2010; Hussain et al 2013). Conversely, shell quality is one of the major contributors of product losses during laying, collection, packaging and transportation of eggs (Rayan et al 2010), leading to 13% to 20% loss (Sultana et al 2007). To the developing embryo, the shell colour affects hatchability since it offers protection against thermal and harmful solar radiation (Liu and Winston 2010). Genetic improvement through selection and mating offers an opportunity for increases in productivity and quality. Selection for egg and meat production has been going on globally and currently there are various specialised breeds for eggs and meat production.
The external and internal qualities of an egg are mainly affected by the age and genotype of the birds (Monira et al 2003). Additionally, the quality is determined by the value of the internal and external characteristics based on certain set standards that include; shape index, yolk index, shell thickness and Haugh Unit (HU) (Ihsan 2012). Egg quality is also an important factor in embryonic development (Niraj et al 2014). Egg qualities are influenced by the environment (production) system (Travel et al 2010).
There is scanty information regarding egg quality characteristics of the IC and other breeds used in their improvement in Kenyan production circumstances. The objective of this study was to quantify the external and internal egg characteristics of the BPR, the F1 progeny, and IC. This study evaluated the quality of commercial eggs from BPR, F1 progeny and IC reared in an intensive production system. The results of this study will inform future breed improvement programs through crossbreeding in Kenya.
A total of 240 eggs from BPR (90), F1 progeny (90), IC (60) were randomly selected for the study from flocks reared under an intensive production system in KALRO Naivasha poultry section. The eggs were collected on the same day and evaluated within a period of 72 hours. Soiled eggs were wiped with a wet cloth to avoid extra weight on the eggs and shells were wiped after breaking and air dried before weighing.
Egg weight and shell weight were determined using a 0.001 g sensitive electronic weighing machine. Egg length and width were determined using a Vanier calliper and measurements used to calculate the shape index as described by Rayan et al (2010) as:
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A digital micrometre screw gauge was used to measure shell thickness (Dasari et al 2013; Reddy et al 1979; Sola-Ojo 2011). Egg surface area was determined using the formula:
 |
Where 3.9782 and 0.7056 are constants and W is the egg weight (Nasr et al 2012). Egg shell percentage and egg shell density were calculated by dividing shell weight by egg weight and egg surface area respectively. Other parameters observed were shell colour and shell appearance.
Albumen and yolk weight, height and width were measured separately (Dasari et al 2013; Shabbir et al 2013). The albumen and yolk height were measured according to the procedure by Alewi and Teklegiorgis (2012). The albumen and yolk height measurements were used to determine HU and other egg indices according to Yakubu et al (2008) and Thomas (1968).
The HU (Hussain et al 2013), was calculated as:
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Where H is the height of the albumen and W the egg weight.
The egg volume was calculated as follows:
 |
Where Lg is the longitudal length, Wd is the transverse width and 0.519 is a specific calculation coefficient (Teusan et al 2008).
As indicated in Table 1, the F1 progeny had the highest egg weight (70.1 g) which is greater than the weights of the parent stock BPR (67.9 g). This could have resulted from hybrid vigour since F1 was a crossbreed of RIR and BPR. The IC had the least observed means in all the characteristics except for shell thickness (0.58 mm). IC had the lowest egg weight of 46.3 g which compares to IC eggs which were evaluated by Hussain et al (2013) and Yakubu et al (2008). The low egg weights are perhaps due to the poor genetic potential of IC. In most of the developing countries IC has poor genetic potential due to lack of selective breeding and poor breeding strategies. BPR egg were heavier when compared to the weight of the same breed evaluated in Bangladesh which had 64.0 g (Monira et al 2003). The egg weight contrast with literature findings for RIR studied under intensive management system in Ethiopia of 55.6 g (Niraj et al 2014). This may be an effect of the different production system in which the chickens are raised on (Travel et al 2010). The egg shell thickness varied amongst breeds with the highest being recorded for the IC (0.58) and the lowest for BPR (0.43). Observed differences in shell thickness may be due to breed differences and age of the birds (Monira et al 2003). The egg shell quality has been reported to affect hatchability and recommendations made of between 0.33 mm to 0.35 mm to be the ideal minimum thickness for incubation eggs (Niraj et al 2014), all the eggs would thus be considered for incubation based on shell thickness.
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Table 1. External egg physical characteristics |
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Egg Parameter |
F1 progeny |
BPR |
IC |
SEM |
|
Egg Weight (g) |
70.1a |
67.9b |
46.3 c |
7.59 |
|
Egg Length (cm) |
6.20a |
6.01b |
5.33c |
0.26 |
|
Egg Width (cm) |
4.52b |
4.48b |
4.01a |
0.16 |
|
Shell thickness (mm) |
0.49a |
0.43b |
0.58c |
0.04 |
|
Shell weight (g) |
6.06a |
5.62b |
4.94c |
0.33 |
|
abc Means in the same row without common letter are different at P<0.05 |
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Seventy-eight percent of the eggs laid by FI birds were brown with 84% having plain shell appearance. Three egg shell colourations (white, brown and cream) were observed in eggs laid by the IC unlike the F1, and BPR which had two as shown in Table 2. Of the sampled IC egg shells 53% were cream, 30% were white and 17% brown. This is an indication of the available genetic diversity in the IC. In all cases, the brown eggs were heavier than the cream and white eggs. For instance, brown eggs in F1 progeny weighed 71.1g compared to the cream coloured eggs which weighed 67.5 g. Similar results were obtained in a study by Rayan et al (2010) with brown egg strains having heavier eggs (56.8 g) compared to light coloured egg strains (55.3 g). In this study, plain eggs were more than tinted eggs but their difference in weights was not significant (p<0.05).
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Table 2. Shell characteristics and their respective mean weights |
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Breed |
Parameter |
Proportion |
(%) |
Mean |
|
F1 |
Shell Colour |
Brown |
78 |
71.1 |
|
Cream |
21 |
67.5 |
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|
Shell appearance |
Plain |
84 |
70.4 |
|
|
Tinted |
16 |
68.7 |
||
|
BPR |
Shell Colour |
Brown |
94 |
68.2 |
|
Cream |
6 |
64.2 |
||
|
Shell appearance |
Plain |
59 |
67.8 |
|
|
Tinted |
41 |
68.3 |
||
|
IC |
Shell Colour |
White |
30 |
44.7 |
|
Brown |
17 |
48.9 |
||
|
Cream |
53 |
46.4 |
||
|
Shell appearance |
Plain |
100 |
46.3 |
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Table 3 shows the internal egg physical characteristics. The albumen and yolk characteristics of IC were significantly lower than those of F1 progeny and BPR. Monira et al (2013) reported 8.92 mm of albumen height in BPR which is higher than the 6.53 mm recorded for the same breed in this study. Albumen weight of F1 progeny (40.6 g) and BPR (40.6 g) was higher than reported for Isa Brown (33.4 g), Bovan Brown (34.5 g) and Potchefstroom Koekoek (25.5 g) by Desalew et al (2015) in Ethiopia. However, the IC had a low albumen weight of 24.5 g which had a significant difference from the eggs from other breeds, but compares with indigenous eggs in other studies (Hussain et al 2013;Yakubu et al 2008). This may have been due to the difference in nutrition and age of the birds.
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Table 3. Means of internal egg physical characteristics |
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Egg Parameter |
Breed |
SEM |
||
|
F1 progeny |
BPR |
IC |
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|
Albumen Weight (g) |
40.6a |
40.6a |
24.5b |
5.37 |
|
Albumen Height (mm) |
7.18 a |
6.53b |
3.43c |
1.16 |
|
Albumen Width (mm) |
7.23b |
7.16b |
6.61a |
0.20 |
|
Yolk Weight (g) |
19.1b |
18.5b |
14.6a |
1.41 |
|
Yolk Height (mm) |
1.46b |
1.62a |
1.48b |
0.05 |
|
Yolk Width (mm) |
4.33a |
4.19b |
3.82c |
0.15 |
|
abc Means in the same row without common letter are different at P<0.05 |
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The HU of the F1 progeny, BPR, and IC was 83.0, 86.2, and 72.8 respectively (Table 4). Eggs with HU values >70 are considered to be of good quality (Desalew et al 2015; Momoh et al 2010; Niraj et al 2014; Rajaravindra et al 2015). Eggs can be graded according to the shape index; <72 sharp, 72-76 standard shape, and >76 rounded (Niraj et al 2014). All the eggs were of standard shape with their shape index falling within the 72 - 76 range. The RIR hens reared under intensive manangement system in Pakistan had a shape index of 73.1 (Ali and Anjum 2014). Shape index in this study contrasted with those reported by Rajaravindra et al (2015) in broiler chicken (0.77) and Niraj et al (2014) in RIR (77.3) and Bovans (78.4) under intensive manangement system. Shape index and egg weight can be used to predict the size of chicks to hatch (Khushid et al 2003).
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Table 4. Egg traits parameters Mean |
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Egg Parameter |
Breed |
SEM |
||
|
F1 progeny |
BPR |
IC |
||
|
HU |
83a |
86.2b |
72.8c |
4.04 |
|
Egg Surface Area (cm2) |
79.7a |
78b |
59.5c |
6.47 |
|
Shell density (g/cm3) |
0.04a |
0.01b |
0.01b |
0.01 |
|
Egg volume (cm3) |
65.8a |
62.8b |
44.8c |
6.56 |
|
Egg density (g/cm3) |
1.07a |
1.08b |
1.06ab |
0.01 |
|
Shape index |
73.1a |
74.7b |
75.3c |
0.66 |
|
Shell index |
7.60a |
7.2b |
8.15c |
0.28 |
|
abc Means in the same row without common letter are different at P<0.05 |
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The authors are grateful for the support from the Kenya Agricultural Productivity and Agribusiness Project (KAPAP) through the Indigenous Chicken Value Chain Project (ICVCP). More gratitude goes to the staff at KALRO Naivasha Poultry Research Unit for the assistance accorded during data collection.
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Received 6 June 2018; Accepted 9 September 2018; Published 1 October 2018