Physical characteristics and nutritional composition of meat and eggs of five poultry species in Kenya

M Chepkemoi, J W Macharia¹, D Sila, P Oyier², P Malaki³, E Ndiema⁴, B Agwanda³, V Obanda⁵, K J Ngeiywa⁶, J Lichoti⁶ and S C Ommeh¹

Department of Food Science and Technology, Jomo Kenyatta University of Agriculture and Technology, Kenya. P O Box 62000- 00200, Nairobi, Kenya
¹ Institute for Biotechnology Research, Jomo Kenyatta University of Agriculture and Technology. P O Box 62000- 00200, Nairobi, Kenya
sommeh@jkuat.ac.ke
² Department of Information Technology, Jomo Kenyatta University of Agriculture and Technology, Kenya. P O Box 62000- 00200, Nairobi, Kenya
³ Department of Zoology, National Museums of Kenya. P O Box 40658-00100, Nairobi, Kenya
⁴ Department of Earth Sciences, National Museums of Kenya. P O Box 40658-00100, Nairobi, Kenya
⁵ Forensic and Genetics Laboratory, Kenya Wildlife Service. P O Box 40241–00100, Nairobi, Kenya
⁶ Directorate of Veterinary Services, State Department of Livestock, Ministry of Agriculture Livestock and Fisheries. Private Bag, Kangemi, 00625 Nairobi, Kenya

Abstract

The physical characteristics and nutritional composition of eggs and meat vary among different poultry species. Some poultry species are known to have better meat and egg quality compared to others. Furthermore, consumer needs and preferences have encouraged and further influenced the demand for meat and eggs that meet both nutritional and health standards while still maintaining great taste. In this study, we sought to determine the physical characteristics and nutritional composition of meat and eggs from different poultry species in Kenya: live indigenous and commercial chicken, domestic guinea fowl, and wild and commercial quail. The study areas were Kiambu, Busia, Bungoma and Siaya Counties. The live birds were weighed, slaughtered and their meat used for further analysis. Eggs were collected, cleaned, weighed and subjected to proximate analysis among others. Analysis of Variance (ANOVA) was done using GenStat (14.1) whereas separation of significant mean differences was done using Duncan’s Multiple Range Test.

Commercial chicken eggs were found to contain the highest percentage of edible parts with the egg shell accounting for a percentage of only 10.1 of the total weight. Commercial chicken eggs also had the highest york and albumen percentage at 24.9 and 64.9 respectively. Fat, moisture, protein and zinc content in the eggs showed no significant difference at p≤0.05. For meat samples, moisture, fat, ash, carbohydrates, calcium and zinc varied among the poultry species significantly at p≤0.05. Wild quail meat had the least saturated fatty acids (24.86%) and the highest polyunsaturated fatty acids (74.85%). Our findings indicate that poultry meat and eggs from different species, when included in a diet, provide a diverse array of nutrients that are essential for good health. Increased consumption of these poultry products could help combat malnutrition and ensure food security in Kenya.

Key words: diversity, fatty acids, health, minerals, proteins, proximate

Introduction

Poultry plays an important role both economically and socially in many communities as a source of food and income to Kenyan farmers (MOLD 2010). In rural areas, poultry, especially chicken, are a major source of dietary protein (Aswani et al 2017). Kenya has an estimate of 32 million birds comprising of 76% free range indigenous chicken, 22% commercial chicken (broilers and layers) and the remaining 2% is made up of the other species: ducks, turkey, pigeons, ostrich, guinea fowls and quails (MOLD 2010). These other species are increasingly becoming popular, important and common among small-scale farmers. They provide extra income and food to households thus contributing towards poverty alleviation, nutritional value and food security (MOLD 2010). Guinea fowl are kept as a source of meat, eggs and feathers (Adeola et al 2015) whereas quails are mainly kept for meat and eggs. Commercial (exotic) chickens are kept in the urban and peri-urban areas where there is the availability of ready market (Omiti and Okuthe 2010).

Poultry meat and eggs provide cheap protein that is important especially to children, the elderly and pregnant women, therefore, making a significant contribution in areas with malnutrition particularly in developing countries such as Kenya (Martin et al 2012).There is high demand for indigenous chicken, guinea fowl and quail meat and eggs which are deemed healthier and more nutritious. They are also preferred due to their advantageous traits such as heat tolerance, disease resistance and low input requirements (Ogada et al 2016). Moraa et al (2015) found indigenous chicken to possess phenotypic adaptations for dealing with heat stress in arid and semi-arid climates whereas Panyako et al (2016) suggested an adaptation of guinea fowl to their local climatic conditions due to their presence in many different parts of the country. Ommeh et al (2010), on the other hand, linked reduced susceptibility to avian influenza in vitro to a SNP in the Mx gene of indigenous chicken making this poultry adaptation an attractive venture for rural farmers.

Though these advantageous traits present in poultry have been widely studied, the nutritional characteristics of meat and eggs from the game and domesticated poultry remain largely unfamiliar in Kenya. Our study, therefore, aimed to compare the physical characteristics and nutritional composition of meat and eggs from indigenous chicken, commercial chicken, domestic guinea fowl, commercial and wild quails consumed in Kenya. The findings could be used to improve nutrition in Kenyan households by encouraging the consumption of poultry products from a wider variety of poultry species while reducing the current overreliance on chicken as a source of poultry products.

Materials and methods

Permits

Permit of “no objection” No. RES/POL/VOL.XXVII/162 was obtained from the Ministry of Agriculture, Livestock and Fisheries, Directorate of Veterinary Services to allow sample collection from the domestic poultry while clearance for wild quails and guinea fowls was given by the Kenya Wildlife Services under Permit No. KWS/BRM/5001.

Experimental design

We used a cross-sectional study design. Three mature live birds and a tray of egg samples per poultry species were selected at random for analysis. The live commercial chicken and commercial quail birds and eggs were bought from Kiambu County in Central Kenya. The live birds and eggs samples of indigenous chicken, domesticated guinea fowl and wild quail were collected from Busia, Bungoma and Siaya counties respectively in Western Kenya. Due to their rarity, only five wild quail eggs were collected. The two study blocks were selected based on the high density of each poultry type (Okello et al 2010; Nyaga 2007). Only mature birds already in the market were sampled and age was not considered as a factor since the sellers are only interested in weights and healthy birds.

Evaluation of physical characteristics of poultry eggs

The eggs samples were first wiped using a damp cloth followed by a dry towel to remove contaminants from the shells, then weighed. The yolk was separated from the albumen manually and the respective weights determined using a Shimadzu weighing scale. The shells were weighed after drying overnight in an oven at 70⁰C and shell percentage proportion was calculated.

Determination of physical carcass characteristics

The live birds were weighed, slaughtered, bled for three minutes, de-feathered, eviscerated, dissected, intestines and legs removed and then weighed. The carcass was then deboned manually. The meat and bones were weighed separately and meat to bone ratios calculated. The meat with skin was minced and mixed thoroughly for homogeneity, put in plastic bags and frozen immediately at ˗18ºC until further analysis. Prior to chemical analysis, the frozen meat samples were thawed overnight in a refrigerator (+4ºC).

Chemical analysis

Proximate composition and mineral analysis were determined according to A.O.A.C methods (1995).The fatty acid profile was determined by reconstituting the oil extract with methanol/chloroform/ water (2:1:0.8 v/v) followed by methylation by refluxing the oil in 2 ml of 95:5 methanolic hydrochloric acid (HCl) for 1 hour. Identification of fatty acids was done by comparing the results with those of known methyl ester standards from Supelco Fatty Acids and Methyl Esters (FAME) Analytical Standards Mix C4-C24 (Sigma-Aldrich USA) according to Dyer and Blair (1959) method. This was under the following conditions: 15 DEGs column, nitrogen gas as mobile phase, hydrogen and oxygen gas as flame gas, initial and final column temperature was 170⁰ C , injection temperature was 220⁰ C , the detection temperature was 240⁰ C and an attenuation range of 2.

Data management and analysis

Data collected was subjected to Analysis of Variance (ANOVA) using GenStat (14^th edition-release 14.1). The difference at p˂0.05 was considered significant and the means separated using Duncan’s Multiple Range Test among the poultry types. All data was reported as mean (± standard error) of three replicates.

Results and discussion

Physical characteristics of poultry eggs

The results of the proportionate composition of poultry eggs in Kenya are presented in Table 1 below. Proportionately, the albumen makes the highest component of an egg in all the poultry species (>50%). The commercial chicken had the highest percentage albumen content at 64.9% while the least was observed in guinea fowls at 50.4%. The egg shell accounted for the second largest component of the egg accounting for over 30% in all the eggs except the commercial chicken eggs where it accounted for only 10.1% of the total weight. Commercial chicken eggs also had the highest yolk content.

We observed that commercial chicken eggs had more edible parts than indigenous chicken, guinea fowl or quail due to selection for maximum productivity (Haunshi et al 2010). Commercial quail egg weight was slightly higher than the 10.67g reported by Tunsaringkarn et al (2013) but was consistent with the findings of Song et al (2001) and Santos et al (2011). Guinea fowl egg weight in this study was lower than that reported by Song et al (2001) of 46.65g. Physical characteristics of eggs have been shown to be influenced by genetics, age, feeding management and environmental factors (Haunshi et al 2010; Song et al 2001) which could explain the difference in the results.

Poultry carcass quality

We observed that wild quail meat had the highest meat/bone ratio of 2.3%. Indigenous chickens were found to weigh more than commercial chicken at 1426.67g and 1118.67g respectively. This is contrary to Lokman et al (2011) who found that even under same feeding, environment and management conditions, the commercial chicken had a higher weight in terms of the carcass, meat, bone, fat as well as whole carcass quality and meat content compared to indigenous chicken and red jungle fowl. The carcass quality results are shown in table 2 below.

Kokoszyński et al (2013) reported higher average live and carcass weight of commercial chicken as compared to the results of our study. The live weight of wild quails is consistent with results by Chang et al (2009) while El-Dengawa and Nassar (2001) reported the weight to be between 65-71g. Carcass characteristics including the dressing weights are influenced by the stage of maturity, the degree of finish, breed and intestinal contents including offals (Mareko et al 2006; Nobo et al 2012) which may explain the differences observed. Meat quality has been reported to be a function of the interaction between genotype and environmental factors (Lokman et al 2011).

Proximate composition of poultry eggs

We report no significant difference in moisture, fat and protein content between the eggs from the different poultry species. However, commercial quail eggs were found to contain a significantly higher ash content of 1.09±0.05% compared to commercial chicken eggs which had an ash content of 0.86±0.12%. The proximate composition of poultry eggs in Kenya are shown in table 3 below.

Domesticated guinea fowl egg had the highest carbohydrate content at 12.6% while commercial chicken had the least at 5.81%. Indigenous and commercial chicken eggs results are consistent with those of Haunshi et al (2010) on moisture and ash content, lower in fat but higher in relation to protein content. Tunsaringkarn et al (2013) reported similar results on quail egg ash and moisture content but higher carbohydrate and protein content. With the exception of ash content, all other categories differed with Song et al (2001) study on quail and guinea fowl eggs.

Proximate composition of poultry meat

We report that the moisture content in commercial chicken, domestic guinea fowl and commercial quail were the highest and did not differ significantly. Indigenous chicken and wild quail had the lowest levels at 69.6% and 65.1%. The differences observed could be attributed to age at slaughter as moisture content decreases with age (Seman and McKenzie-Parnell 1989; Boni et al 2010). Ash content indicates the number of minerals found in a food. The ash content in food determines the extent to which dietary minerals would be available in food and the rate at which energy in food can be made available (Ogunmola et al 2013). The ash content was highest in wild quail meat (1.03%) and domestic guinea fowl (1.00%) and lowest in commercial chicken meat (0.68%). The results on proximate composition of poultry meat varied with the poultry species as shown in table 4. Commercial chickens are fed on commercial feed which could be low in minerals and high in anti-nutrients (Gilani 2005; Sidhu et al 2004). Wild quail, indigenous chicken and guinea fowls are usually left to scavenge and thus consume a wider range of foodstuffs resulting in higher mineral content (Nyaga 2007). El-Dengawy and Nassar (2001) found wild quail meat to contain 2.4-36g/100g ash content which is higher than the results from this study. Ogunmola et al (2013) reported higher ash contents in indigenous chicken meat (2%) and exotic (commercial) chicken (4%). Mareko et al (2008) showed that in guinea fowl, the ash content is influenced by dietary treatment, increase with age and environmental factors like floor type.

We observed that the fat content did not differ significantly between the different poultry species. The fat content of muscles depends on the energy value of feeds given to the birds (Atteh 2002) and dietary fat contents of feeds (Moreki et al 2012).

Wild quail meat had the highest protein content (25.50%) while indigenous chicken meat had the least (18.15%). Indigenous chicken meat in this study had lower protein content than those reported by Tougan et al (2013), both under confinement and free range systems.

TheThe carbohydrate content was highest in indigenous chicken (8.25%). Domestic guinea fowl meat, quail meat and commercial chicken recorded lower amounts with commercial chicken meat containing the least carbohydrate content (2.57%).The nutritional content of poultry meat varies from one study to another and this can be attributed to variation in the breed, feed, age at slaughter, the system of production, sex, processing, and the part of the cut as suggested by Haunshi et al (2010).

Mineral composition of poultry meat

Calcium, iron and zinc are minerals that are vital for normal body function and are amongst the most lacking in the diet of many citizens of developing countries (White 2009). Calcium is necessary for teeth and bone development. Severe deficiency of iron causes iron deficiency anaemia which affects many people globally especially pregnant women in developing countries (Soetan et al 2010). Zinc is a trace element involved in many body reactions such as the construction and maintenance of DNA, formation, growth and repair of body tissues, hair, skin, bones, nails and teeth (Yakoob et al 2011). Mineral compositions of poultry meat are presented in Table 5.

Domestic guinea fowl meat had the highest calcium content (233.3mg/100g) though not significantly different from commercial and wild quails. Wild quail meat had the highest iron content (5.04mg/100g) while the indigenous chicken was the best source of zinc (1.10mg/100g). The results on commercial chicken meat calcium content in this study are higher compared to Scholtz et al (2001) while zinc and iron content showed consistency. On the other hand, the results reported by Ogunmola et al (2013) on iron, calcium and zinc content of indigenous and commercial chicken meat were higher.

Mineral composition of poultry eggs

Domestic guinea fowl eggs were found to have the highest calcium content (194.30mg/100g). Iron content was significantly higher in commercial quail eggs compared to indigenous chicken, commercial chicken eggs and domestic guinea fowl eggs which showed no significant difference. Zinc content in commercial chicken eggs was the lowest (0.51mg/100g) which could be attributed to a large proportion of commercial feeds constituting grains which contain anti-nutrients that interfere with mineral absorption (Sidhu et al 2004). Domestic guinea fowl egg results on zinc and iron content were lower than those reported by (Adeyeye 2010) but calcium content was higher. The mineral composition of poultry eggs in Kenya are presented in Table 6.

Fatty acid profile of meat

We report that wild quail meat contained the highest levels (74.8%) of polyunsaturated fatty acids (PUFA) and the lowest levels of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) at 24.86% and 0.21% respectively. This is similar to the results reported by El-Dengawy and Nassar (2001) and Boni et al (2010). Commercial chicken and domestic guinea fowl had the highest amounts of MUFA. Fatty acid profiles of poultry meat in Kenya are represented in Table 7 below.

Palmitic acid, oleic acid and linoleic acid were found to be the most abundant SFA, MUFA and PUFA respectively in all the poultry species. Relative amounts of saturated (SFA) and unsaturated fatty acids in lipids are important to nutrition and health and their ratios determine their effects on a diet (Adeyeye 2012). Higher ratios of PUFA/SFA in lipids are considered nutritionally advantageous and have been found to discourage the development of atherosclerosis.

Fatty acid profile of eggs

We observed that the percentages of SFA, MUFA and PUFA showed a similar trend as seen with the poultry meat results (Table 7). Fatty acid profiles of poultry egg in Kenya are represented in table 8 beneath. Commercial quail eggs contained the most unsaturated fatty acids and the least saturated fatty acids. The percentage levels of MUFA, PUFA and saturated fatty acids were 36.6%, 21.94% and 41.4% respectively. Similarly, we found palmitic acid, oleic acid and linoleic acid to be the most abundant SFA, MUFA and PUFA respectively in all the poultry species. This is in agreement with the results of Genchev (2012) who studied the quality and composition of Japanese quail eggs. These results were also similar to those reported by (Olik et al 2014) for commercial chicken eggs. Commercial quail egg PUFA content is consistent with those reported by Polat et al (2013). Differences in fatty acid composition of eggs can be attributed to the variation in diets used on the bird which has a direct influence on egg composition and also the difference in breeds kept.

PUFA, especially n-3 fatty acids such as linoleic acid, have been proven to have a positive influence on the blood vessels and the heart, reduce inflammation while others have shown to be anti-carcinogenic according Mennicken et al (2005). These fatty acids are therefore vital and need to be included in our diet.

Conclusions

• Our results indicate that poultry meat and eggs from indigenous chicken, commercial chicken, domestic guinea fowl, commercial quail and wild quail are nutritionally diverse. Diet diversification to include poultry products from the different species is necessary to ensure good health and prevent malnutrition.
  
  
• Wild quails have the highest meat/bone ratio, high protein, ash, minerals and PUFA content and low SFA content making it the healthiest. There is a need for consumer and farmer awareness on the sustainable use and the conservation of wild quail so as to benefit from their nutritional resources without threatening their numbers in the wild.

Recommendations

• Encouraging farmers to include domestic guinea fowl and quail in their poultry flocks would not only improve nutrition at a family level but also boost the farmer’s income from the sale of the poultry birds. This will help contribute towards poverty alleviation.
  
  
• There is a need for further research work to determine the amino acid profile of poultry meat and eggs.

Competing interests

The authors declare that they have no competing interest.

Acknowledgements

The authors express their gratitude to Jomo Kenyatta University of Agriculture and Technology, Ministry of Agriculture Livestock and Fisheries, National Museums of Kenya and Kenya Wildlife Service. This work was made possible by research grants awarded to Dr. Sheila Ommeh by the Research Production and Extension Division of Jomo Kenyatta University of Agriculture and Technology (JKU/2/4/RP/181) and International Foundation of Science (B/5364-1) in partnership with Syngenta Foundation.

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Received 28 January 2017; Accepted 1 May 2017; Published 1 August 2017

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