Abstract: An experiment was carried out to evaluate the effects of replacing corn with extruded Bakery Waste (BWP) in the diet of laying hens on the performance (feed intake, egg production, egg weight, egg mass and feed efficiency) and egg components (albumen, yolk and eggshell) and characteristics of eggshell (thickness and strength) and albumen (height and Haugh unit) and yolk (height and color (YH and YC)) and feed costs of egg production. Six isocaloric and isonitrogenous diets were formulated using 0, 20, 40, 60, 80 and 100% of BWP. The level of corn in the basal diet (0% BWP) was 60.16%. The replacement of corn for up to 100% with BWP reduced feed costs with no impairment on the performance, egg components, characteristics of eggshell and albumen and YH. Replacing dietary ≥40% of corn with BWP reduced YC. It is concluded that BWP can completely replace corn in laying hen diets without affecting the performance, egg components, egg characteristics of albumen and eggshell and YH. Yolk pigment should be added to the diet to improve YC when ≥40% of corn replaced with BWP.

P>INTRODUCTION

Over the past two decades, the egg industry in Saudi Arabia has expanded considerably, fueled by the increased demand of a growing population for highly nutritious and affordable poultry eggs. However, the continued sustainability and growth of Saudi’s egg sector will depend upon the cost of egg production. Feed is the largest component, representing approximately 60-80% of the economic inputs in the commercial poultry industry. Consequently, feed prices can have a dramatic impact. Corn is the main source of energy in formulating poultry rations. Higher corn prices driven by ethanol production are changing the cost of egg production. Small changes in feed ingredient selection and diet formulation can have large effects on the cost of production and prices sustainability at a profitable level. Poultry nutritionists are under pressure to keep feed costs under control while maintaining top production performance. Many local ingredients and leftover foods are available for consideration in the inclusion of dietary formulation. Al-Ruqaie (2007) used extruded leftover food as a source in fish diet. Recently, Al-Ruqaie et al. (2011) found that extruded Bakery Waste Products (BWP) could replace corn in broiler diets without any impairment on performance. The substitution of corn with BWP in broiler diet reduced costs of the diets and consequently production of chickens (Radwan, 1995; El-Yamny et al., 2003; Al-Ruqaie et al., 2011). The increase in available BWP and the need for poultry producers to enhance profitability make the use of BWP more important than in the past. The objective of this study was to evaluate the effect of replacing corn with BWP in laying hen diet on the performance, egg characteristics and feed cost of egg production.

MATERIALS AND METHODS

BWP was collected from local commercial bakeries (mainly Arabic bread) in Riyadh area and treated as previously mentioned (Al-Ruqaie et al., 2011). Samples of the BWP were analyzed in triplicate for moisture, protein, crude fiber, ether extract and ash according to the American Association of Cereal Chemists (AACC, 1994). Chemical composition of the BWP is shown in Table 1. Results from the chemical analysis of BWP samples in this study and earlier study (Al-Ruqaie et al., 2011) indicate that BWP is uniform in composition. It contains more protein and energy and lower fiber when compared to corn (Table 1). A total of 48 Hi-sex laying hens, 44 weeks of age kept individually in battery cages were used in the trial. Each bird was treated as an experimental unit. Eight replicates were randomly assigned to either one of six experimental diets. The experimental diets included a control corn based diet with 0% BWP and five different diets using 20, 40, 60, 80 and 100% BWP to replace corn in the basal diet. The level of corn in the basal diet (0% BWP) was 60.61%, respectively. The composition of the basal and experimental diets is shown in Table 2. The experiment lasted 10 weeks. Egg production and feed intake were recorded for each replicate. Feed and water were available ad libitum. A photoperiod of 16 h was maintained throughout the trial. Calculations of feed consumption were based on a 2nd week period and characteristics of eggs were based on a complete egg collection for one day each week.

Table 1:	Comparison of approximate analysis of Bakery Waste Products (BWP) and corn
1True Metabolizable Energy (TME) was calculated according the following equation: TME (kcal kg-1) = 4,340-100xCF-40xAsh-30xCP+10xEE (Dale et al., 1990)

Characteristics of eggs include egg weight, egg components (albumen, yolk and eggshell) and eggshell (thickness and strength), albumen (height and Haugh units) and yolk (height and color).

Measurements of characteristics of eggs: Each egg was initially weighed using an egg analyzer^TM(Sanovo Engineering, Odense NV, Denmark) and shell breaking strength was determined and recorded by eggshell force reader (Sanovo Engineering, Odense NV, Denmark) then the egg was broken and egg contents (albumin and yolk) were placed on the measuring tray of the egg analyzer^TM (Sanovo Engineering, Odense NV, Denmark) for the determination of albumen height, Haugh units (Haugh, 1937) and yolk color. Haugh units were automatically calculated within the system on the input of egg weight and albumen height. Yolk height was measured on the tray using an Ames tripod micrometer (Ames, Waltham, MA, USA).

The yolks were separated from the egg analyzer tray (albumen and yolk) using a Teflon spoon. Before the yolk weight was determined, the chalaza was removed with a spatula. Eggshells washed with water, dried with paper towels and then weighed. Albumen weight was calculated by subtracting the weights of yolk and eggshell from the weight of the egg. Three measurements of shell thickness including eggshell membranes were taken from the large end, equator and small end of each eggshell with a micrometer (Ames, Waltham, MA).

Table 2:	Composition of the experimental diets (g kg-1)
1The composition of vitamins and minerals in the premix (per kg of diet): vitamin A, 6000 IU; vitamin E, 10 IU; menadione, 2.5 mg; Vitamin. D, 2000 ICU; riboflavin, 2.5 mg; Ca pantothenate, 10 mg; nicotinic acid, 12 mg; choline chloride, 500 mg; vitamin B12, 4 μg; vitamin B6, 5 mg; thiamine, 3 mg; folic acid, 0.50 mg; biotin, 0.2 mg; Zn, 40 mg; Fe, 40 mg; Cu, 4 mg; Se, mg 0.10; carrier (pollard) made up to 2g; 2calculated values from NRC (1994); 3ME = Metabolizable Energy; 4CP = Crude Protein; 5AP = Available Phosphorus was calculated on the basis of 30% availability of phosphorus in plant products. 6Met+Cys = Methionine+Cysteine

Data collected were subjected to analysis of variance using GLM procedures (SAS, 1988). Where significant variance ratios were detected, differences between treatment means were tested using the Least Significant Difference (LSD) procedures.

RESULTS AND DISCUSSION

The basic ingredient of bakery products in Saudi Arabia is wheat flour (Mousa et al., 1992). The effects of replacing corn with BWP in the diet of laying hens on the performance (feed intake, rate of egg production, egg weight, egg mass, feed conversion (g feed/g egg)) and egg components and characteristics of eggshell (thickness and strength), albumen (height and Haugh unit) and yolk (height and color) and costs of diets and feed for egg production are shown in Table 3 and 4 and Fig. 1, respectively.

The substitution of corn with BWP in the diet of laying hens did not influence the performance, egg components, characteristics of eggshell and albumen and yolk height. However, increasing dietary level of BWP significantly (p<0.01) reduced egg yolk color (0%BWP = 20%, BWP>40% = 60%, BWP>80%, BWP>100% BWP). These results were in agreement with Lazaro et al. (2003), Ciftci et al. (2003) and Cufadar et al. (2010) who concluded that wheat can be used instead of corn as an energy feedstuff in laying hen diets without affecting performance or egg quality except for egg yolk egg yolk color. Egg yolk color was lower with wheat-based diets when compared with those of corn-based diets (Saha et al., 1998; Ciftci et al., 2003; Cufadar et al., 2010).

In the present study, the egg yolk color decreased with increasing replacement level of corn with BWP (40% and above) when compared to the control diet (0% BWP). Yolk pigmentation results primarily from carotenoid pigments especially xanthophylls, provided in the diet of laying hens. Since, birds do not synthesize pigments in their physiological system (Marusich and Bauernfeind, 1981). The lower egg yolk pigmentation of BWP diets is due to the low xanthophylls content of the BWP when compared with corn.

Fig. 1:	Relaitive costs of diets and feed for egg production of laying hens fed graded levels of Bakery Waste Products (BWP) as a replacement of corn. The feed cost of experimental diets and egg production were compared to the basal control diet (0% BWP) on the basis of 100%; a-ccolumns with different superscripts are significantly different (p<0.05)

Table 3:	Performance and egg components of laying hens fed graded dietary levels of Bakery Waste Products (BWP) as a replacement for corn in their diets1
1The level of corn in the basal diet (0% BWP) was 60.16%

Table 4:	Characteristics of egg components of laying hens fed graded dietary levels of Bakery Waste Products (BWP) as a replacement for corn in their diets1
1The level of corn in the basal diet (0% BWP) was 60.16%; a, bmeans within column followed by different superscripts are significantly different (p<0.05)

The lower xanthophylls content of the BWP can be easily balanced in the rations with other sources of egg yolk pigments such as marigold oil, yeast products, synthetic compounds and even corn-based distillers dried grains with soluble (Dufosse, 2006). These yolk pigments are widely available and often can be included in rations on a least cost basis. Consumers prefer yolk color ranging from yellow to orange (Vuilleumier, 1969).

The BWP price is approximately 60% of corn price. The replacement of corn with BWP in the diets of laying hens reduced the cost of the diet by approximately 6.1, 12.9, 18.3, 24.7 and 30.2% for 20, 40, 60, 80 and 100% BWP diets, respectively. Whilst the cost of feed for egg production was significantly reduced by 13.2, 24.6, 28.8, 32.7 and 41.2% for 20, 40, 60, 80 and 100% BWP diets, respectively when compared with those fed the corn basal diet (0% BWP, Fig. 1). Replacing 100% of corn with BWP significantly (p<0.01) reduced feed cost of egg production when compared with those of 0, 20 and 40% BWP. There was no significant difference in feed cost for egg production among 60, 80 and 100% BWP diets. The replacement of corn with BWP in laying hens diets reduced costs and consequently increased profits. Similar findings were reported when BWP replaced corn in diets of growing chickens (Radwan, 1995; El-Yamny et al., 2003; Al-Ruqaie et al., 2011). While current industrial processes of grains will continue to influence prices and availability of grains as feed ingredients, poultry nutritionists will keep looking for alternate ingredients that are very much dependent on supply of ingredients from various industrious wastes and processes.

CONCLUSION

It is concluded that BWP can completely replace corn in laying hen diets without affecting the performance, egg components and characteristics of albumen and eggshell. The substitution of 40% and above of dietary corn content (601.6 g kg^-1 diet) with BWP reduced egg yolk color and yolk pigment supplements should be added to the diet to improve yolk color that meet consumer preferences.

ACKNOWLEDGEMENTS

The researchers would like to express their sincere appreciation to the King Abdulaziz City for Science and Technology (KACST) for the generous financial support provided for this research project through grant number 28-126. Special thanks are extended to the Deanship of Scientific Research and Agriculture Research Center of King Saud University for support in conducting this study. Researchers gratefully acknowledge the excellent technical assistance of Mr. S.A. Swillam.