Paper II: Effect of Non conventional egg storage methods on the external and internal egg qualities East African Journal of Sciences (2018) Volume 12 (2) 137-144 ______________________________________________________________ Licensed under a Creative Commons *Corresponding Author. E-mail: mohamedkrt7@gmail.com Attribution-NonCommercial 4.0 International License. ©Haramaya University, 2018 ISSN 1993-8195 (Online), ISSN 1992-0407(Print) Effect of Non-Conventional Storage Methods on External and Internal Egg Qualities Mohammed Y. Kurtu 1*, Dereje Duressa¹, and Alemu Yami ² 1 Haramaya University, P. O. Box 138 Dire Dawa, Ethiopia ² US AID Addis Ababa, Ethiopia Abstract: To know and identify the traditional practices and generate relevant information on egg storage methods, a survey work was conducted in the East Wollega Zone of Ethiopia. The survey was carried out with a stratified sampling technique and a structured questionnaire using a total of 315 households (225 from rural and 90 from urban owning chickens) were purposefully selected. Two experiments, of similar experimental materials, procedures and designs were conducted at different time of the year (May and August) to evaluate these traditional storage methods at Haramaya University poultry farm. A factorial experiment of 2 by 5 with completely randomized design using storage containers and storage time as treatment was used. The storage times were 4, 6, 8, 12 and 20 days. Five most common egg storage containers were identified in the rural and urban areas of East Wollega. These storage methods include cartons, polyethen bags, baskets, clay pots and teff grain. The result further indicated that depending on the availability of the storage materials in the locality, 87 percent of the urban households (n = 90) store eggs in cartons and polyethene bags in order of availability. Seventy nine percent of the rural households (n = 225) ranked teff as the most common storage materials used followed by the basket and clay pots. Among the quality parameters considered, weight loss (%) and daily weight loss (%) of eggs were highly affected (P < 0.001) by storage containers, durations and their interactions during both experiments. The maximum weight loss was observed after storage period of 16 days for all containers. Polythene bags storage maintained minimum weight loss Vs the baskets at all stages of storage duration. Only storage durations had significant effects (P < 0.05) on the egg shell thickness during experiment I. Inconsistent but significant effect of storage durations was observed on the shell weight during experiment I, and weights of yolk and albumen during experiment II. Storage containers during experiment I, and storage durations during experiment II showed significant effects on albumen height and haugh unit values. Except polythene bags which had higher albumen height and haugh unit values, the other containers did not show significant variations for both parameters. The effect of storage duration on these parameters was linear with increasing storage duration; and higher beyond the 16 days of storage. Thus, it was concluded that using polyethylene bags and 16 days of storage could give the best result to store eggs among the traditional methods compared in this experiment. Keywords: Traditional Egg Storage; Changes in Egg Quality; Optimum Egg Storage Duration 1. Introduction The majority of poultry in Ethiopia are raised under traditional system of production. These birds contribute eggs for hatching and consumption (market). Alemu (1995) stated that collecting agents gather together larger numbers of eggs stored in various methods before marking them. The marketing places are usually larger towns and cities where distances to these marketing points are long hence, there is marked deterioration of egg quality. This may create problems on quality and hatchability of eggs from the traditional system of production. Thus, eggs decline in quality and hatchability very easily from the time of laying the different storage methods coupled with storage time practiced by farmers can aggravate the loss in egg quality. The quality deteriorations are mainly associated to the external and internal quality of eggs (Romanoff and Romanoff, 1949; Stadelman and Cotterril, 1977; Mountney, 1989). Consequently a lot of eggs could be lost and hatchability would dramatically affected. Little work has been done in this regard especially under Ethiopian condition, hence there is a knowledge gap in understanding the traditional egg storage methods used in Ethiopia particularly in Wollega Zone despite the prevailing of various traditional methods being used by farmers. This study is, therefore, designed to investigate and assess the effect of different storage methods on internal and external qualities of eggs. 2. Materials and Methods 2.1. Study Design A formal survey with stratified sampling technique was applied for survey data collection. Five PAs and two towns were randomly selected from each of the agro- ecologies. Then, 15 households who currently own poultry were randomly selected from each of the selected peasant associations and towns and subjected to Mohammed et al. East African Journal of Sciences Volume 12 (2) 137-144 138 the structured questionnaires. A total of 315 households (225 from rural and 90 from urban) were included in the survey. Information on egg storage practices were collected and described using descriptive statistics. Two experiments of similar materials and procedures were conducted as factorial experiment 2 by 5 in a completely randomized design using different storage containers and storage time as treatment. The storage containers were bamboo basket, cartons, clay pots, polythene bags and mixing with Teff grains and the storage times used were 4, 6, 8, 12 and 20 days. The experiments were conducted at different times of the year (May and August) at Haramya University (HU) poultry farm in year 2000. All eggs used in the experiment were obtained from white leghorn layers having equal age, in similar laying stage and kept under the same standard management of the HU poultry farm. Eggs were collected twice per day (following the usual procedure of the farm) at 11: am and 5: pm using plastic trays. Eggs from four consecutive collections were used for each of the storage durations. Storage periods were calculated from the time the eggs were allocated to the storage containers. After collection, eggs were candled and eggs with visible cracks were removed. Eggs were then weighed using a sensitive balance and their initial weights were recorded and marked on the blunt end of each egg. Codes referring to the storage container and duration were randomly given and marked on each egg. At the end of each collection period, all eggs were allocated to the respective containers at random. Except the polythene bags whose open side were folded once, the containers were not covered during the storage period. The temperature of the room was recorded four times daily during the entire period of the storage using a thermo-hygrometer. 2.2. Measurements All eggs stored in each container (bamboo baskets, cartons, clay pots polyethylene bags, and teff grains) and for each specific storage period i.e. 2, 6, 8, 12 and 20 days (treatments) were taken out for measurement. The parameters used to measure the effect of storage methods on internal and external egg quality were according to Haugh (1937); Egg weight loss Percentage weight loss Daily weight loss of eggs (%) Eggshell thickness Albumen height (AH) Haugh unit (HU) 2.3. Data Analysis Data analysis of the experiment was performed using the computer software (MSTAT, 1989). Whenever the ANOVA revealed significant differences among the treatment means, Duncan’s Multiple Range Test (DMRT) was used to separate the means. All statements of significance are based on the 5 % level of probability. 3. Results and Discussion Five most common egg storage containers were identified in the rural and urban areas of East Wollega (Table 1). These storage methods include cartons, polyethen bags, baskets, clay pots and teff grain. The result further indicated that depending on the availability of the storage materials in the locality, 87 percent of the urban households (n = 90) store eggs in cartons and polyethene bags in order of availability. Seventy nine percent of the rural households (n = 225) ranked teff as the most common storage materials used followed by the basket and clay pots. A similar results has been obtained from the previous work done by Tadele (1990). Table 1. Some most common egg storage containers identified by the surveyed urban and rural households of East Wollega (number and percent). Container Rank Urban Rural No. % No % 1 5 5.6 74 32.9 2 14 15.6 94 41.8 Baskets 3 20 22.2 66 29.3 4 33 36.7 54 24 5 39 43.3 60 26.7 1 5 5.6 43 19.1 2 10 11.1 52 23.1 Clay pots 3 15 16.7 77 34.2 4 17 18.9 50 22.2 5 21 23.3 57 25.3 1 3 3.3 108 48 2 11 12.2 70 31.1 Mixing with Teff grain 3 12 13.3 64 20.4 4 18 20.0 40 17.8 5 13 14.4 40 17.8 1 42 46.7 - - 2 32 35.6 9 4 Cartons 3 23 25.6 21 9.3 4 11 12.2 45 20 5 10 11.1 44 19.6 1 37 41.1 - - 2 23 25.6 - - Polythene 3 20 22.2 15 6.7 4 11 12.2 36 16 5 7 7.8 24 10.7 Storage containers, durations and their interactions had highly significant effects (P < 0.001) on the percent weight loss of eggs during both experiments. The mean percent loss of egg weights due to the interaction effects of storage containers and durations during experiments I and II are shown in Tables 1 and 2, respectively. In experiment one, the mean percent weight loss of eggs during the first 4 days of storage was not significant for all containers. But eggs stored in all containers lost about 1 percent of their original weights during the first 4 days of holding in both experiments. In both experiments, the rate of weight loss was increasing when the storage duration was extended Mohammed et al Effect of Non-Conventional egg Storage Methods on Egg Qualities 139 beyond 16 days (Tables 1 and 2) with the exception of polyethylene which was lowest 2.2 and 0.03 for experiment 1 and 2 respectively. As indicated in Table 3, for experiment I, the percent loss of weight from eggs kept in all containers except polythene bag increased linearly; the rate of increment being highest beyond the 16th day of holding for all containers. Similar trend was also observed during experiment II (Table 4). At the end of the 20 days of storage, the maximum weight loss was recorded from eggs kept in basket, carton, clay pot and mixing with teff grain during both experiments. During experiment I, the mean weight loss from eggs kept in these containers was more than 5 percent during the longest (20 days) storage. Table 2. Total weight loss (percent) of eggs stored using different containers each at different length of storage period (Experiment I). Storage Durations (days) Containers 4 8 12 16 20 Control 0.78q 1.49n 1.90lm 2.26j 4.73d Baskets 1.2o 2.03kl 2.64hi 3.78e 6.30a Cartons 1.07op 1.98kl 2.48i 3.60e 5.76b Clay pots 0.88pq 0.75q 1.75m 2.80gh 5.57c Polythene 0.88pq 0.36r 0.35r 0.50r 2.16jk Mixing with teff grain 1.02op 2.89g 2.50i 3.28f 5.50c Containers X durations interaction *** Note: *Means followed by the same letters within rows and columns are not significantly different; *** = significant at 0.1% level of probability; DMRT. Table 3. Total weight loss (percent) of eggs stored using different containers each at different length of storage period (experiment II). Storage Durations (days) Containers 4 8 12 16 20 Control 1.31k 1.36jk 1.58ij 1.61ij 2.61d Baskets 1.28k 1.68hi 2.01fg 2.37de 3.48a Cartons 1.21k 1.67hi 1.83jhi 1.90gh 2.95c Clay pots 1.14k 1.66hi 1.80ghi 1.6ij 2.51d Polythene 0.64l 0.48lm 0.42lm 0.25m 0.34m Mixing with teff grain 1.26k 1.71hi 2.18ef 2.44d 3.23b Containers X durations interaction ** Note: Means followed by the same letters within rows and columns are not significantly different, ** = significant at 1% level of probability, DMRT. Table 4. Average daily weight loss (percent) of eggs stored using different containers each at different length of storage period (Experiment I). Storage durations (days) Containers 4 8 12 16 20 Control 0.20hijk 0.19ijkl 0.16kl 0.14lm 0.24efgh Baskets 0.30bc 0.25cdefg 0.22fghij 0.24efgh 0.32b Cartons 0.27bcdef 0.25def 0.21ghij 0.22fghi 0.29bcd Clay pots 0.22fghij 0.09n 0.15lm 0.18ijkl 0.28bcde Polythene 0.22fghij 0.04o 0.03o 0.03o 0.11mn Mixing with teff grain 0.25cdefg 0.36a 0.21ghij 0.20ghjk 0.27bcde Containers X durations interaction *** S.e.m. () = 0.015; C.V. (%) = 10.19 Note: Means followed by the same letters within rows and columns are not significantly different; ***= Significant at 0.1% level of probability; S.e.m. = Standard error of the mean; CV = Coefficient of Variation. Mohammed et al. East African Journal of Sciences Volume 12 (2) 137-144 140 Table 5. Average daily weight loss (percent) of eggs stored using different containers each at different length of storage period (Experiment II) Storage Durations (days) Containers 4 8 12 16 20 Control 0.33a 0.17efg 0.13hij 0.10k 0.13hij Baskets 0.32ab 0.21d 0.17efg 0.15ghi 0.17ef Cartons 0.30bc 0.21d 0.15fgh 0.12jk 0.15ghi Clay pots 0.28c 0.21d 0.15gh 0.10k 0.13ij Polythene 0.16efg 0.06l 0.03m 0.02m 0.02m Mixing with teff grain 0.31ab 0.21d 0.18e 0.15fgh 0.16efg Containers X durations interaction *** S.e.m. () =0.015; CV.(%) =10.19 Note: Means followed by the same letters within rows and columns are not significantly different; *** = Significant at 0.1% level of probability; S.e.m. = Standard error of the mean; CV = Coefficient of Variation. In both experiments, eggs stored in polythene bags were recorded the lowest weight loss for all storage durations. Accordingly, eggs stored in polythene bags lost only 2 and 0.34 percent of their initial weights at the end of 20 days during the first and second experiments, respectively. The low weight loss of eggs kept in polythene bags may be attributed to the ability of the material to prevent moisture loss from eggs by lowering the direct air blowing around the eggs. This is in agreement with the findings of several authors such as Romanoff and Romanoff (1949) and Smith (1930) who recommended the enclosure of eggs in plastic containers during storage for an extended period. Conversely, eggs stored in bamboo baskets with straw bedding lost the highest weight for all storage periods which could be due to the nature of the basket that allows free movement of air around the eggs. Smith (1930) and. Romanoff (1940) concluded that the rate at which the egg looses weight by evaporation tends to be greater if the air surrounding the egg is moving rapidly. The temperature of the basket was similar to that of the room. The effects of storage containers x duration interaction on the mean percent egg weight losses per day during the entire period of experiment I and II are presented in Tables 3 and 4, respectively. Similar pattern as the total egg weight loss was observed for the daily percent weight loss of eggs. Though the figures are inconsistent for experiment I, the daily percent weight loss of eggs kept in all containers showed a linearly declining trend up to the 16th day of storage during both experiments. In agreement with this point, Romanoff (1940, 1943b) concluded that in terms of the egg’s original weight, the daily loss diminishes through out the holding periods. However, in both experiments of the present study the daily percent weight loss of eggs kept in all containers showed a marked increase during the last 17 to 20 days of holding. Table 6. Effects of storage containers on some external and internal qualities of eggs during experiment I. Containers WL (%) WLPD (%) SHT(mm) SHW (%) YKW (%) ALBW (%) AH(mm) HU Control 2.33d 0.18b 0.339 9.9 31.7 58.6 4.3b 76b Baskets 3.19a 0.27a 0.326 9.7 31.1 59.2 4.0b 74b Cartons 2.98b 0.25a 0.322 9.7 31.9 58.4 4.4b 76b Clay pots 2.35c 0.18b 0.331 9.6 31.5 58.9 4.3b 76b Polythene 0.85e 0.09c 0.331 10.2 31.1 58.8 5.6a 86a Mixing with teff grain 3.04b 0.26a 0.334 10.2 31.2 58.6 4.3b 77b Prob.  *** *** NS NS NS NS ** * S.e.m. () 0.028 0.007 0.002 0.027 0.03 0.026 0.008 1.815 C.V. (%) 3.68 10.19 4.83 2.75 1.72 1.08 15.72 6.22 Note: Means within columns followed by common letters are not significantly different from each other; WL = Percentage weight loss; WLPD = Percentage weight loss per day; SHW = Percentage weights of shell; YKW = Yolk weight; ALBW = Albumen weight; SHT = Shell thickness; AH = Albumen height and HU = Haugh unit; * = significant at 5%; ** = Significant at 1%; *** = Significant at 0.1%; NS = Not significant at 5%; s.e.m. = Standard error of the mean; CV = Coefficient of Variation. Mohammed et al Effect of Non-Conventional egg Storage Methods on Egg Qualities 141 Table 7. Effects of storage durations on some external and internal qualities of eggs during experiment I. Storage Duration (days) s.e.m Parameter 4 8 12 16 20 Significance () WL (%) 0.97e 1.58d 1.94c 2.70b 5.00a *** 0.026 WLPD (%) 0.24a 0.20b 0.16c 0.17c 0.25a *** 0.006 SHT (mm) 0.322b 0.336ab 0.321b 0.342a 0.332ab * 0.002 SHW (%) 9.6b 9.8ab 9.6b 10.2a 10.0ab * 0.025 YKW (%) 30.8 31.7 31.6 31.4 31.5 NS 0.028 ALBW (%) 59.6 58.5 58.9 58.3 58.3 NS 0.024 AH (mm) 5.5a 4.6b 4.8ab 3.9c 3.5c *** 0.007 HU 84a 79a 80a 73b 70b *** 1.657 Note: Means within rows followed by common letters are not significantly different from each other; WL = Percentage weight loss; WLPD = Percentage weight loss per day; SHW = Percentage weights of shell; YKW = Yolk weight; ALBW = Albumen weight; SHT = Shell thickness; AH = Albumen height and HU = Haugh unit; *= Significant at 5%; **= Significant at 1%; ***= Significant at 0.1%; NS = Not significant at 5%; S.e.m. = Standard error of the mean. During the first experiment, eggs stored in polythene bags and clay pots lost small weights per day when storage period was extended from 8 to 16 days. After 20 days of storage (experiment I), the daily weight loss (%) of eggs from all containers except the polythene bag did not show significant variation. The mean daily weight losses of eggs kept in the polythene bag were 0.22, 0.04, 0.03, 0.03, and 0.11 percent during storage periods of 4, 8, 12, 16, and 20 days respectively. Except for the first 4 days of holding, the mean percent weight loss of eggs kept in polythene bags was significantly lower than eggs kept in cold room. During experiment II, on the other hand, the daily weight loss of eggs from polythene bags were significantly lower than the control for all storage periods. In experiment I, the daily percent weight loss of eggs stored in all containers at the end of 20 days was slightly higher than the corresponding values observed at 4 days of storage, where as the reverse was true during the second experiment. The relatively high environmental temperature that prevailed during the entire period of the first experiment might be one of the main reasons for the high weight losses of eggs during the first experiment than the second. It has been indicated by many investigators that temperature and relative humidity are the most important environmental variables to affect the loss of moisture from eggs during holding; other factors being kept constant. Romanoff (1940) stated that the rate of weight loss is accelerated at higher temperatures and retarded at higher relative humidity. Egg Shell thickness Only the storage durations had significant effects on shell thickness (P < 0.05) during the first experiment (Table 8). Statistically, no significant differences were observed (P > 0.05) among the means of egg shell thickness for storage containers (Table 7), durations (Table 8), and their interactions during experiment II. Table 8. Effects of storage containers on some external and internal qualities of eggs experiment II. Containers WL (%) WLPD (%) SHT(mm) SHW (%) YKW (%) ALBW (%) AH(mm) HU Control 1.70c 0.17c 0.341 9.0 31.5 59.5 5.6 88 Baskets 2.16a 0.20a 0.351 9.3 31.6 59.1 5.7 90 Cartons 1.91b 0.19b 0.336 9.1 32.2 58.7 5.4 86 Clay pots 1.74c 0.17c 0.328 8.7 32.1 59.2 5.1 86 Polythene 0.43d 0.06d 0.332 9.3 31.1 59.5 5.6 87 MWTG¶ 2.16a 0.20a 0.343 9.3 32.5 58.7 5.0 84 Significance *** *** NS NS NS NS NS NS S.e.m. () 0.038 0.003 0.006 0.196 0.304 0.358 0.024 1.648 CV (%) 7.22 6.14 5.41 6.81 3.03 1.92 14 6.02 Note: MWTG¶ = Mixing with teff grain; Means within columns followed by common letters are not significantly different from each other; WL = Percentage weight loss; WLPD = Percentage weight loss per day; SHW = Percentage weights of shell; YKW = Yolk weight; ALBW = Albumen weight; SHT = Shell thickness; AH = Albumen height and HU = Haugh unit; *** = Significant at 0.1%; NS = Not significant at 5%; S.e.m. = Standard error of the mean; CV= Coefficient of Variation. Mohammed et al. East African Journal of Sciences Volume 12 (2) 137-144 142 Table 9. Effects of storage durations on some external and internal qualities of eggs during experiment II. Storage Duration (days) S.e.m Parameter 4 8 12 16 20 Significance () WL (%) 1.14d 1.43c 1.64a 1.70b 2.52a *** 0.035 WLPD (%) 0.28a 0.18b 0.14c 0.11e 0.13d *** 0.003 SHT (mm) 0.331 0.347 0.341 0.337 0.337 NS 0.005 SHW (%) 9.1 9.4 9.0 9.2 9.0 NS 0.179 YKW (%) 31.0c 32.3a 31.9ab 31.4bc 32.2ab * 0.278 ALBW (%) 59.9a 58.3c 59.2abc 59.4ab 58.8bc * 0.327 AH (mm) 6.5a 5.5b 5.4b 4.9bc 4.6c *** 0.022 HU 94a 87b 88b 83bc 81c *** 1.504 Note: Means within rows followed by common letters are not significantly different from each other; WL = Percentage weight loss; WLPD = Percentage weight loss per day; SHW = Percentage weights of shell; YKW = Yolk weight; ALBW = Albumen weight; SHT = Shell thickness; AH = Albumen height and HU = Haugh unit; * = Significant at 5%; ** = Significant at 1%; *** = Significant at 0.1%; NS = Not significant at 5%; S.e.m. = Standard error of the mean; CV = Coefficient of Variation. Percentage Weights of the Major Egg Parts There were no significant effects of type of storage containers and container X duration interaction observed (P > 0.05) on the mean percentages of the shell, yolk and albumen during both experiments (Table 7). Storage durations had significant effects on the weight of egg shell (P < 0.05) during experiment I (Table 8). As indicated in table 10 during experiment II, the percent weights of yolk and albumen were significantly affected (P < 0.05) by storage duration. Though the trend seems inconsistent with days of holding, the percent weights (proportion) of yolk and albumen fluctuates with a negatively correlated manner. The significant weight loss of albumen was observed at day 8 of holding during which the yolk gained the maximum weight. The inconsistency of the proportion of the two components might be due to the fluctuating environmental temperature during the entire period of the experiment. It has been indicated that during the early holding period, the albumen looses water not only by evaporation through the shell, but also by diffusion to the yolk. This movement of water between the components is the result of osmotic gradient across the vitelline membrane. Romanoff (1949) reported that the direction of diffusion is initially from albumen to yolk, because the osmotic pressure of the yolk is greater. The movement of water reverses when albumen, becomes more concentrated as a result of diffusion. Smith (1990) also reported that the noticeable enlargement of the yolk in the aging egg is due to its increased content of water. Albumen Height (AH) and Haugh Units (HU) Both albumen height and haugh unit values were significantly affected by storage containers during experiment I, (Table 7) whereas the effect was non significant for both parameters during experiment II (Table 8). The interaction of storage containers and durations had no significant effects (P > 0.05) on the albumen height and HU values (Table 3) for both experiments. Except the polythene bag that had significantly higher AH and HU values (5.6 and 86 respectively), the other containers did not show significant difference for the mean values of both parameters. The highest albumen height observed for eggs stored in polythene bags might be attributed to the ability of the plastic material to minimize the rate of water loss mainly from the albumen. North (1984) indicated that water comprises about 84 percent of the albumen and whenever the rate of water loss is minimum the albumen retains its water content and the dense part will remain firm giving higher AH and HU values which is an indication of internal quality. During experiment II, (Table 7) the mean HU values were in descending order and the variation was not statistically significant (P > 0.05). Storage durations had highly significant effects (P < 0.001) on the albumen height and HU values during both experiments (Tables 7 and Table 8). During experiment I, the mean AH values were moreover, higher rates of AH and HU losses observed from eggs held beyond 12 days. During experiment II the loss of albumen height (AH) and haugh unit (HU) values were linear with extended storage periods compared to experiment I (Table 7 and 8). The relatively lower environmental temperature and higher initial egg weights during the second experiment might be the reasons for the higher albumen height (AH) and Hough unit (HU) values observed in experiment II (Table 9) than the first. Mountney (1989) indicated that as the environmental temperature increases, the carbonic acid held in the albumen breaks yielding additional carbon dioxide and water which will escape to the environment through the eggshell. As a result the much in fibers lose their firmness and the proportion of the thick albumen decreases. 4. Conclusion In both experiments, eggs stored in polythene bags were found to have the lowest weight loss for all storage durations. The low weight loss may be attributed to the Mohammed et al Effect of Non-Conventional egg Storage Methods on Egg Qualities 143 ability of the material to prevent moisture loss from eggs by lowering the direct air blowing around the eggs. Conversely, eggs stored in bamboo baskets with straw bedding lost the highest weight for all storage periods which could be due to the nature of the basket that allows free movement of air around the eggs. Except the polythene bag that had significantly higher AH and HU values (5.6 and 86 respectively), the other containers did not show significant difference for the mean values of both parameters. The highest albumen height observed for eggs stored in polythene bags might be attributed to the ability of the plastic material to minimize the rate of water loss mainly from the albumen. The overall result of the present study show that egg kept for a period of more than 16 days could be stored in a polythene bag to maintain its quality. Moreover, egg should not be held for longer periods especially in hot season during which the environmental temperature is high. 5. Acknowledgement The authors fully appreciate Haramaya University for providing the main author with both material and financial support to undertake this work. All staff in the Department of Animal Sciences that have directly or indirectly made an important contribution to the success of this work are highly acknowledged. 6. References Alemu, Y. 1995. Poultry production in Ethiopia. World’s Poultry Science Journal, 51: 197-201. Haugh, R. R. 1937. The Haugh Unit for measuring eggs quality. US. Poultry magazine Mountney, G. J. 1989. Poultry products technology (2nd Edn.). Food products press, New York, London MSTATC. 1989. A micro-computer statistical program for experimental design, data management and data analysis. Michigan State University, crop and soil Sciences, Agricultural Economics and Institution of International Agriculture, USA. North, M. O. 1984. Commercial chicken production manual (3rd. Edn.). AVI publishing CO; Westport, Conn. Romanoff, A. L. and Romanoff, A. J. 1949. The Avian Egg. The Macmillan Company New York, Wiley. Romanoff, A. L. 1940. Physico chemical changes in unfertilized, incubated eggs of Gallus domestic us. F O Res., 5: 291 306 Romanoff, A. L. 1943b. Distribution of dry constituents and of yolk and albumin in the developing avian egg. A note Rec. 87: 303-306 Smith, A. J. 1930. Department of Animal Science. Ind .Research (Brit), Food investigation. Department, 1929. 74-80. Smith, A. J. 1990. Poultry-Tropical Agriculturalist series. CTA, Macmillan publishers, London, pp 179-189. Stadelman, W. J. and Cotterill, O. J. 1977. Egg Science and Technology (2nd Edn.). University of Missouri- Colombia. Tadelle, D. 1996. Studies on village poultry production systems in the central high lands of Ethiopia. MSc. Thesis. Swedish University of Agricultural Sciences, Uppsala, Sweden. Mohammed et al. East African Journal of Sciences Volume 12 (2) 137-144 144