Improving Egg Quality in Tropical Environments: Assessing the Maize Meal Replacement by Wheat Bran and Soybean Oil in Laying Hen Diets

Abstract

ABSTRACT

Background

The use of wheat bran (WB) in the monogastric animal feed is limited due to its high fibre content and low energy contents.

Objectives

The current study evaluated the effect of replacing maize meal with WB, in the absence or presence of soybean oil, on egg quality and economic performance indicators.

Methods

In a completely randomized design, 36 ISA Brown laying hens (age: 40 weeks) were used. The hens were distributed in individual cages (4 individuals/cage; n = 4) and subjected to three treatments: T1 (basal diet), T2 (basal diet with 20% maize meal replaced by WB) and T3 (basal diet with 20% maize meal replaced by 17.5% WB and 2.5% soybean oil). To assess egg quality over an 8‐week period, the following parameters were calculated: egg weight, length and width, shell resistance and thickness, shell, yolk and albumen percentage, Haugh unit and yolk colour. For the economic assessment, feeding costs, production cost per egg, production cost per dozen eggs, gross revenue, gross added value, profitability index, contribution margins and break‐even point were calculated. The data were subjected to two‐way analysis of variance (ANOVA) and the Tukey test.

Results

The partial replacement of maize meal with WB, in the absence or presence of soybean oil, showed no differences (p > 0.05) for all evaluated egg quality parameters; however, a significant reduction in gross revenue along with a notable increase in gross added value, profitability index and contribution margin was observed (p < 0.05). Regarding the break‐even point, no significant effect was observed (p > 0.05).

Conclusion

It was concluded that the addition of soybean oil to diets containing 20% WB was as efficient as the basal diet regarding egg quality, together with an improvement of the economic performance.

Introduction

Egg production is one of the most significant economic activities worldwide. It plays a vital role in nutrition, health, economic stability and food security (FAO 2019). Chicken meat is recognized for its high protein and low fat content, contributing to the prevention of various diseases such as obesity, diabetes and cardiovascular problems.

Despite the crucial role it plays in the economic development of nations, the poultry industry faces significant challenges, mainly due to high feed production costs driven by escalating electricity and raw material costs (Afodu et al. 2024). To mitigate the effects of soaring raw material prices, there is a growing interest in alternative and cheaper ingredients, such as food waste and agricultural by-products, including wheat bran (WB) (Katileviciute et al. 2019; Chuang et al. 2021).

WB is a by-product of the wheat flour industry obtained during the milling process. It essentially consists of the fraction that remains after separating the flour, including the outer layers (cuticle, pericarp and seed coat), mixed with varying amounts of endosperm (Delcour and Poutanen 2013). On average, WB contains approximately 12%–14% protein, 1%–2% fat, 10%–14% fibre and around 60%–65% starch (Sztupecki et al. 2023). Additionally, it is rich in B vitamins, such as thiamine and niacin, as well as minerals like iron and zinc (Katileviciute et al. 2019).

Despite being inexpensive, widely available and having high nutritional value, the use of WB is limited due to its high fibre content and low energy composition (Katileviciute et al. 2019; Novela et al. 2023). Therefore, to reduce the negative effects of this high fibre content, it is essential to explore strategies that enhance the utilization of WB in poultry feed.

Soybean oil is a vegetable oil extracted from soybean seeds, mainly produced for human consumption. The soybean oil used in feed production is typically crude or degummed crude. Crude soybean oil contains gums rich in choline, phospholipids, antioxidants and vitamin E, which improve the oil's digestibility and storage stability (Clemente and Cahoon 2009; Medic et al. 2014). It consists of substantial amounts of oleic acid and linoleic acid, along with smaller quantities of palmitic, linolenic and stearic acids, as well as traces of palmitoleic and myristic acids (Block et al. 2022). This composition determines the ratio between saturated and unsaturated fatty acids. Soybean oil serves as an energy source, and its energy value basically depends on the total fat content (saponifiable fraction), as moisture, impurities and unsaponifiable fractions do not have any energy value (considering the non-elutable fraction and oxidation products) (Wanzenböck et al. 2018; Gao et al. 2021).

The oil and fat inclusion in poultry diets has shown beneficial effects on poultry performance, often exceeding expected biological value, reflected in improved growth rates, feed ingredient utilization and metabolizable energy content (Ferreira et al. 2005; Wanzenböck et al. 2018; Gao et al. 2021). Recently, Novela et al. (2023), adding soybean oil to a diet containing WB for laying hens, observed a positive effect on feed conversion.

Maize meal and soybean meal are excellent raw materials for poultry feeding due to their high nutrient quality and high inclusion rates (Aguirre et al. 2022). However, the demand for maize meal and soybeans for human consumption and biofuel production, coupled with limited production in certain years and high prices in the international market, has made these raw materials increasingly scarce for animal feed (Selle et al. 2020). In this context, the aim of this study was to evaluate the effect of partially replacing maize meal with WB, with or without the inclusion of soybean oil, on egg quality and economic performance indicators.

Materials and Methods

Study Duration and Experiment Location

The research took place between April and August 2022 at the animal farm of the Faculty of Veterinary Medicine at Eduardo Mondlane University, located in Maputo City, Mozambique. The city of Maputo is located at a latitude of 25.9653°S and sits approximately 85 m.a.s.l. The city experiences a tropical savanna climate, significantly affected by its coastal location. Average temperatures remain warm, consistently exceeding 20°C, and the annual temperature fluctuation is typically less than 10°C. Relative humidity ranges between 55% and 75%, whereas the region receives moderate rainfall, with annual totals varying from 500 mm inland to 1000 mm along the coast. The rainy season spans from October to April, during which 60%–80% of the annual precipitation occurs, predominantly between December and February.

Experimental Setup

In an 8-week study, 36 ISA Brown laying hens were used. All hens were 30 weeks old prior to the commencement of the experiment. The hens were housed in a battery cage system within a deep pit that benefitted from natural ventilation and illumination from both artificial and natural light sources. Using a completely randomized design, the hens were categorized into three groups of 12 individuals, each further divided into 3 replications of 4 birds. They were assigned to one of three dietary treatments: T1 (basal diet), T2 (basal diet with 20% maize meal replaced by WB) and T3 (basal diet with 20% maize meal replaced by 17.5% WB and 2.5% soybean oil). The dietary composition and the calculated nutrient levels are illustrated in Table 1. WB and soybeans were obtained from the local industrial market.

TABLE 1 Composition of experimental diets in the present research.

	Calculated composition
	(Kg)
	T1	T2	T3
Ingredients
Yellow maize meal	60.00	40.00	40.00
Soya bean meal	36.65	36.65	36.65
Wheat bran	0	20.00	17.50
Soya bean oil	0	0	2.50
Bacillus amyloliquefaciens CECT 5940	0.00	0.00	0.80
Trace mineral premixa	3.00	3.00	3.00
Vitamin premixb	0.10	0.10	0.10
Dicalcium phosphate	0.25	0.25	0.25
Total	100	100	100
Calculated composition
Energy (kcal/kg)	3298.28	3076.00	3250.48
Protein	14.60	14.50	14.50
Fibre	3.19	2.95	2.89
Ether extract	3.32	3.26	3.23
Lysine	2.59	2.62	2.61
Methionine	1.86	1.81	1.81
Calcium	4.00	4.04	3.947
Phosphorus	0.40	0.702	0.684

The hens were maintained under consistent management practices throughout the study. They had ad libitum access to water, and each bird was fed 120 g of feed per day. Any remaining feed was weighed to determine daily feed intake. All groups were treated identically for the duration of the experiment. All the research staff were previously trained for adequate animal care and handling.

Initial body weights and egg production ratios for all experimental laying hens were recorded at the beginning of the study and subsequently monitored on a weekly basis. Daily records were kept for egg production, the occurrence of soft eggshells, egg weights and mortality rates. Additionally, weekly feed consumption was recorded. Calculations were made weekly for feed intake, egg yield ratio, soft eggshell yield ratio, feed conversion per egg mass, feed conversion per dozen eggs and mortality ratios.

Egg Quality Parameters

At the end of the experiment, two eggs were randomly selected from each replication. Quality measurements included egg specific gravity, weight, length and width, shell resistance and thickness, shell, yolk and albumen percentage, Haugh unit and yolk colour.

Egg specific gravity was measured using the egg floating method in a salt water solution (Nowaczewski et al. 2010). Eggshell resistance was assessed using a compression test for eggshell fracture force, conducted with a texture analyser (WAZAU, Berlin, Germany), as outlined by Carvalho et al. (2018). The eggshell thickness, egg length and width were measured using a digital micrometre (Mitutoyo, Kawasaki, Japan), which provides readings accurate to 0.001 mm. The yolk, eggshell and albumen percentages were determined according to the methodology outlined by Wu et al. (2005).

Haugh units were determined using the formula: HU = 100 × log (H + 7.57 − 1.7W^0.37). In this equation, H represents the albumen height (AH), and W signifies the egg weight (Eisen et al. 1962). AH was measured using a gauge micrometre (Mitutoyo, Kawasaki, Japan), and the average was considered AH; the albumen weight was measured using a sensitive balance (Mettler Toledo, Greifensee, Switzerland). Yolk colour was assessed using a colour fan (DSM, Porto Alegre, Brazil).

Economic Parameters

The economic parameters assessed in this study included feed expenditure, cost of egg production per unit, cost per dozen eggs, gross revenue, profitability index, gross added value and the break-even point. This evaluation adhered to a modified methodology based on the approaches suggested by Andriani et al. (2020) and Egbetokun and Obisesan (2023).

To determine feed costs, the prices of each ingredient in the feed formulation were taken into account, in addition to the overall ingredients’ cost for each experimental group. The production cost per egg was calculated by dividing the total production costs by the number of eggs produced. The cost associated with producing a dozen eggs was ascertained by considering the amount of feed needed to produce that quantity in relation to the feed price.

Gross revenue was calculated by multiplying the total number of eggs produced by the selling price per egg. Gross added value was calculated by subtracting feed costs from the overall sales revenue generated from egg sales. The profitability index represents the rate of available income, whereas the break-even point indicates the quantity of eggs required to be produced in order to cover feed costs.

Statistical Analysis

The data collected were subjected to a two-way analysis of variance (ANOVA) using SPSS software version 25 (IBM Corp., NY, USA). The Tukey test was employed to compare treatment means, with a significance level set at 5%. The statistical model was used according to the equation below, where the treatment effect (fixed effect) was considered the unique factor of variation.

• Statistical model: Y_ij = μ + T_i + e_ij

where Y_ij is value observed in the experimental unit that received the treatment. μ is overall mean (mean of all experimental units for the variable under study). T_i is the effect of treatment (fixed effect). e_ij is random error associated with each observation.

Results

Effect of Adding Soybean Oil to WB Diets on Egg Quality

Table 2 shows the egg quality results of laying hens that were fed different types of feed: a control feed (T1), a feed in which 20% of the maize meal in the control feed was replaced by WB (T2), and a diet in which 20% of the maize meal was replaced by WB and soybean oil (T3).

TABLE 2 Effect of the partial replacement of maize meal with wheat bran (WB), with or without the addition of soybean oil, on egg quality.

	T1	T2	T3	p value
Egg external quality parameters
Egg weight (kg)	58.65 ± 1.27	60.08 ± 1.99	60.60 ± 1.61	0.397
Egg length (mm)	55.21 ± 1.60	55.71 ± 0.66	57.72 ± 1.15	0.160
Egg width (mm)	43.03 ± 0.52	43.58 ± 1.05	43.36 ± 0.50	0.428
Shell resistance (kgf)	0.02 ± 0.00	0.04 ± 0.00	0.02 ± 0.01	0.055
Shell thickness (um)	400 ± 20	390 ± 40	370 ± 20	0.305
Egg internal quality parameters
Shell (%)	9.62 ± 0.37	9.95 ± 0.16	9.39 ± 0.08	0.371
Yolk (%)	26.61 ± 0.39	27.58 ± 0.93	27.68 ± 0.72	0.125
Albumen (%)	63.15 ± 0.87	62.47 ± 1.08	62.76 ± 1.04	0.477
Haugh unit	75.66 ± 1.26	77.56 ± 1.77	77.69 ± 1.24	0.412
Yolk colour	12.00 ± 0.00	12.00 ± 0.00	11.00 ± 0.00	1.000

As it can be seen in Table 2, the partial replacement of maize meal with WB showed no statistically significant differences in relation to all evaluated variables, namely, egg weight, length and width, shell resistance and thickness, shell, yolk and albumen percentage, Haugh unit and yolk colour (p > 0.05). Similarly, when adding soybean oil to the diet in which maize meal was replaced by WB, no statistically significant differences were found in the analysed egg quality variables (p > 0.05).

Influence of Adding Soybean Oil to WB Diets on the Economic Efficiency of Laying Hens

Table 3 presents the results of the effect of partially replacing maize meal with WB, with or without the addition of soybean oil, on the following variables: feed production cost, total feed consumption, feed cost, egg production and egg production cost, relative to layers fed with feed containing 20% WB instead of maize meal, with or without soybean oil.

TABLE 3 Effect of partial replacement of maize meal with wheat bran (WB), with or without the addition of soybean oil, on feed production cost, total feed consumption, feed cost, egg production and egg production cost.

Parameters	T1	T2	T3
Feed production cost ($/kg)	0.58a	0.34b	0.36b
Total feed consumption ($/kg)	0.01a	0.10b	0.10b
Feed cost ($/kg)	3.59a	2.22b	2.31b
Egg production (units)	53.16	52.52	52.96
Egg production cost ($/unit)	0.07a	0.04b	0.04b

According to Table 3, the partial replacement of maize meal with WB, whether without (T2) or with the addition of soybean oil (T3), revealed a statistically significant increase in feed consumption and a statistically significant reduction in the unit cost of feed production, feed costs and egg production costs (p < 0.05).

Economic Evaluation of Incorporating Soya Oil Into WB-Based Diets for Laying Hens

The economic benefits stemming from the partial substitution of maize meal with WB, both without (T2) and with the addition of soya oil (T3), were evaluated in terms of gross revenue, gross added value, profitability index, contribution margins and break-even point, as detailed in Table 4.

TABLE 4 Effect of the partial replacement of maize meal with wheat bran (WB), with or without the addition of soybean oil, on different economic variables.

Parameters	T1	T2	T3
Gross revenue ($)	12.48a	12.33b	12.43ab
Gross added value ($)	8.88a	10.11b	10.12b
Profitability index (%)	71.00a	82.00b	81.00b
Contribution margin ($)	0.71a	0.82b	0.81b
Break-even point	0.17	0.17	0.17

The partial replacement of maize meal with WB, either without (T2) or with the addition of soybean oil (T3), led to a significant reduction in gross revenue (p < 0.05) and a notable increase in gross added value, profitability index and contribution margin (p < 0.05). Regarding the break-even point, no significant effect was observed (p > 0.05).

Discussion

In the quest to lower the costs of egg production, agricultural by-products such as WB surged as alternative dietary ingredients that can replace maize meal without harming egg quality or health (Huang et al. 2021; Wei et al. 2021).

In this study, the partial replacement of maize meal with WB, both supplemented and unsupplemented with soybean oil, did not reveal a statistically significant effect (p > 0.05) on the following egg quality parameters: egg weight, length and width, shell strength and thickness, shell, yolk and albumen percentage, Haugh unit and yolk colour. These findings indicate that the incorporation of WB, regardless of the addition of soybean oil, did not compromise egg quality. This could be attributed to nutritional benefits, such as increased fibre content, enhanced digestion and potential improvements in egg quality. WB is rich in insoluble fibre, which can promote digestive health in laying hens (Röhe and Zentek 2021). Effective digestion leads to better nutrient absorption, which is essential for egg production and quality (Wei et al. 2024). Moreno et al. (2006) states that an adequate dietary fibre can improve calcium metabolism and absorption, which is critical for eggshell formation. However, the long-term effects of high levels of WB on the health of laying hens warrant careful consideration, as high levels of dietary fibre can exert pressure on the liver due to increased metabolic demands and may lead to digestive challenges, such as reduced nutrient absorption and altered gut microbiota composition (El-Katcha et al. 2021). Regarding the egg weight parameter, the absence of statistically significant differences when substituting maize with WB, with or without soybean oil, may indicate that the nutritional content available in the eggs was unaffected. This result aligns with the observation by Araujo et al. (2008), who reported that including WB in proportions ranging from 0% to 9% in laying hens diets did not significantly impact productive performance or egg quality. Wei et al. (2021) also described similar results when evaluating dietary soybean oil supplementation on production performance, egg quality and keel bone health in laying hens. Wanzenböck et al. (2020), investigating the effect of adding different quantities of WB and vegetable oils to laying hens feed, concluded that even with an increased fibre content in the feed, up to a level of 15% incorporation, there were no significant changes in egg quality. In the present study, 20% (T2) and 17.5% (T3) of WB were incorporated; however, it was not enough to cause a significant effect on egg quality. Wei et al. (2021) reported that oil-based diets were often applied in the poultry industry to provide more energy and facilitate the absorption of nutrients. Many factors can influence the effect of oils on layer hens’ performance, such as the type of oil, the quantity added and the nutritional level (Gao et al. 2022). Thus, the addition of oils to feed could result in several effects on egg quality and production performance. Therefore, it is particularly important to add adequate types and amounts of oil to the diets (Alagawany et al. 2019). A previous study by Dänicke et al. (2000) reported that dietary soybean oil supplementation at 3.5% or more increased egg weight and daily egg production in laying hens. Furthermore, Küçükersan et al. (2010) also found that egg weight and production were improved in hens fed a diet based on 3% soybean oil. In contrast to the present study, the addition of soybean oil did not show any significant effects on egg quality or egg production. However, it should be considered that in the present study, only 2.5% of soybean oil was added. Moreover, for the basal diet, maize meal had already been partly replaced by 17.5% WB.

WB is the main raw ingredient used in laying hen nutrition to decrease energy levels, reduce egg production costs and increase dietary neutral detergent fibre (de Sousa et al. 2019). Our results corroborate these findings, as they were able to show the beneficial economic effects of using WB as a partial replacement for maize meal by significantly reducing egg production costs, feed production and feed costs. Furthermore, an increase in gross revenue, gross added value, contribution margin and profitability index, with or without the addition of soybean oil, was also observed. This agrees with Donkoh and Zanu (2010), who highlighted that agro-industrial by-products containing low energy, such as WB, maize bran, rice bran, spent distiller grains and cocoa pod husk, have been shown to be cost-effective feed sources that could greatly benefit the performance of laying hens, leading to increased net returns without sacrificing productivity.

Gross added value is the value that producers have added to goods, leading to increased income. In the present study, WB-based diets, with or without the addition of soybean oil, had a significant effect on gross added value. One of the benefits of adding soybean oil to the gross added value is the health benefits it brings to egg quality as it helps to regulate egg yolk cholesterol levels (Djoussé and Gaziano 2008). Moreover, WB, with its high level of crude fibre, lowers serum cholesterol concentration by inhibiting cholesterol absorption (Pantaya et al. 2020). Additionally, a study by Gao et al. (2022) stated that the addition of soybean oil to the diet increased the content of nutrients and antioxidant enzymes in eggs. These combined effects of WB and soybean oil contribute to adding more value to the final product, leading to increase gross added value, which in turn improves the contribution margin and profitability index. Another factor behind these findings may be the lower energy content of wheat-based diets compared to maize meal which can lead to more efficient feed conversion and improved egg production. The use of wheat-based diets can also reduce the risk of gut health problems associated with high-energy feeds. A healthy gut is essential for optimal egg production and immune function, so reducing the risk of gut health problems can help to improve overall flock performance and profits (Leeson and Summers 2001).

A previous study indicated that there was a relationship between the economic viability of egg production and the energy content of layer feed as hens can adjust their feed intake according to their energy requirements (Kim and Kang 2020). Our results, which agree with this statement, showed that hens can perform more profitably on a low-energy diet by adjusting their feed consumption to their needs and producing greater profit. To meet their dietary requirements without affecting egg production, our results demonstrated that layers significantly increased total feed consumption per kilogram when maize meal was partly replaced by WB, either with or without the addition of soybean oil (p > 0.05; Table 3). Although the incorporation of WB has led to increased feed consumption, the economic returns were not affected because egg production was not affected as well, and the gross added value of the eggs significantly increased.

In conclusion, the partial replacement of maize meal, with or without the addition of soybean oil, did not affect egg quality, reduced feed production costs and, consequently, increased the economic profitability indices in egg production.

Author Contributions

Mariana Novela, Abilio P. Changule, Igor I. S. Munguambe and Marcos Mabasso contributed to acquisition of data. Mariana Novela, Abilio P. Changule, Leonel A. Joaquim and Eunice J. Chivale played roles in analysis and/or interpretation of data. Igor I. S. Munguambe, Abilio P. Changule, Leonel A. Joaquim, Ramos J. Tseu, Otília H. T. Tomo, Manuel Garcia-Herreros and Custódio G. Bila contributed to drafting the manuscript. Manuel Garcia-Herreros and Custódio G. Bila performed critical review/revision. Custódio G. Bila created study conception and design. All authors have thoroughly read and approved the final manuscript.

Disclosure

The authors declare financial support was received for the research, authorship and/or publication of this article.

Ethics Statement

Ethical review and approval were not required for the study because only previous data records were used from the research database and none of the animals were handled or restricted at any time for this study.

Conflicts of Interest

The authors declare no conflicts of interest.

Publisher's Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

Data Availability Statement

Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.

Peer Review

The peer review history for this article is available at .

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