Mulberry (Morus alba) leaf meal as partial replacement for soybean meal in indigenous chicken layer diets

Mwai Lilian Muthoni, Anthony Macharia King’ori and Mary Kivali Ambula

Department of Animal Sciences, Egerton University P.O. Box 536-20115 Egerton, Kenya
mulimwa@gmail.com

Abstract

This study aimed to determine the effects of inclusion of mulberry leaf meal as a protein source in the diet of indigenous layer chicken. Sixty, 29-week old indigenous chicken were allocated to diets with 0, 5, 10 and 15% mulberry leaf meal partially substituting soybean meal.

Feed intake was increased by 27%, with a curvilinear trend 15% of mulberry leaf meal replaced 9% of soybean meal in the diet. The increase in feed intake was reflected in better feed conversion up to the 10% level of mulberry leaf meal in the diet beyond which the feed conversion deteriorated. Egg production followed the same trend as feed conversion with maximum production being reached at 10% mulberry leaf meal in the diet.

Keywords: β-glucan, ethnomedicine, phenols, prebiotics

Introduction

Indigenous chicken in Kenya, with an estimated population of 23 million (Behnke and Muthami 2011), are kept by most rural households. Annual egg production is 60 small eggs (Mengesha 2012), the low rates being attributed to low genetic potential, poor nutrition and disease. Nutrition is the major influence and well managed indigenous hens can produce about150 eggs per year (Okitoi et al 2008). However, improved nutrition usually means increased dependence on imported feed ingredients such as soybean meal.

Mulberry leaf meal is a protein source which is available in rural areas in Kenya. The fruits are consumed by people, the leaves are used for feeding silkworms (Tuigong et al 2015), while the tree branches are used for wood fuel and timber. Mulberry leaves contain β-carotene, which can be converted by poultry to vitamin A and xanthophylls, which can be a source of pigmentation of egg yolk (Srivastava et al 2006).

This research evaluated the use of mulberry leaf meal as a partial replacement of soybean in layer diets for indigenous chicken.

Materials and methods

Sixty, 29-week old indigenous chickens were offered diets with 0, 5, 10 and 15% mulberry leaf meal (MLM) as partial substitute for soybean meal (Table 1). The diets were formulated to meet nutritional requirements of layers (NRC 1994).

Measurements of bird performance

Daily feed intake = feed intake per cage/number of birds in the cage for each day.

FCR = feed consumed/mass of eggs produced.

Hen day production = Total number of eggs produced in a day/ Total number of hens present on that day) *100.

Laboratory analysis of feeds and mulberry leaves was according to AOAC (2006) methods.

The design was completely randomized (CRD). Data were analyzed using the GLM option in the ANOVA software of SAS (2009).

Proximate analysis

Feed samples were analysed (Tables 2 and 3) for proximate composition following the procedures of AOAC (2006).

Feed intake increased by 27%, with a curvilinear trend, as mulberry leaf meal partially replaced soybean meal in the diet (Table 4; Figure 1). This increase in feed intake was reflected in better feed conversion up to the 10% level of mulberry leaf meal in the diet (Figure 2) beyond which the feed conversion deteriorated. Egg production followed the same trend as feed conversion with peak production being reached at 10% mulberry leaf meal in the diet (Figure 3).

Figure 1. Increasing the proportion of mulberry leaf meal in the diets lead to curvilinear increases in feed intake	Figure 2. Increasing the proportion of mulberry leaf meal in the diets lead to a curvilinear improvement in feed conversion

Figure 3. Increasing the proportion of mulberry leaf meal in the diets lead to curvilinear increases in egg production

Discussion

Increasing the percentage of mulberry leaf meal in the diet as replacement for soybean meal led to an increase in the proportion of crude fiber in the diet which, on the basis of most nutritional studies with poultry (eg: De Vries 2015), would be expected to lead to depressed egg production. The fact that egg production increased in the early stage of mulberry leaf meal substitution for soybean implies that, despite the increase in percentage of fiber in the diet, as mulberry leaf meal replaced soybean meal, the birds produced more eggs and with improved efficiency.

The corollary to this result is that the mulberry leaf meal is conferring benefits to the birds not explained by conventional nutritional theory. The fact that these benefits decreased as the substitution rate of soybean by mulberry leaf meal was increased implies that the benefits from mulberry leaf meal are partially linked to non-nutritional factors and are not explained in terms of protein and fiber levels in the diet.

Mulberry leaves have long been known to have medicinal properties (Lim et al 2013; Chan et al 2016; Simin et al 2016; Thanchanit et al 2918; Photo 1).

Photo 1. Fresh leaves of mulberry and a typical extract marketed on the Internet

Recent research suggests they may even play a role in modulating the effects of pathogens such as the Covid-19 virus (Martín-Prieto et al 2020).

Lin et al (2017) supplemented chicken layer diets with 0, 0.1, 0.2 and 0.3% mulberry leaf meal. The egg mass and feed conversion rate were improved by the mulberry leaf supplementation with the best results being obtained at the 0.5% level. The egg yolk weight, shell weight, shell strength, shell thickness, yolk color, and Haugh unit were all increased among the mulberry leaf levels. The authors concluded that “0.5% mulberry leaf level could be used as a new feed additive to potentially modulate the antioxidative status of laying hens and improve their production performance and egg quality”. These benefits were ascribed to the presence of phenolic compounds in the mulberry leaves modulating the anti-oxidant status and hence the health of the birds.

The other feature of mulberry leaves is that they are rich in β-glucan, a polysaccharide of D-glucose monomers linked by β-glycosidic bonds, that is found in the cell walls of plants and yeasts. An extract from mulberry leaves rich in beta-glucan has been shown to have beneficial effects on growth and health of piglets (Lee et al 2017). It has been shown that β-glucan can activate the immune system and stimulate a cascade of pathways that enhance both innate and adaptive immune responses (Vannucci et al. 2013). The fact that levels as low as 0.5% of the diet were effective in stimulating hen layer performance (Lin et al 2017) implies that the role of mulberry leaf meal in stimulating animal response may be related equally to the presence of phenolic compounds, and/or β-glucan, enhancing the immune system, as well as being a source of protein.

Conclusions

• Feed intake was increased by 27%, with a curvilinear trend, as 15% of mulberry leaf meal replaced 9% of soybean meal in the diet of indigenous chicken layers.
  
  
• The increase in feed intake was reflected in better feed conversion up to the 10% level of mulberry leaf meal in the diet beyond which the feed conversion declined.
  
  
• Egg production followed the same trend as feed conversion with peak production being reached at 10% mulberry leaf meal in the diet.
  
  
• It is proposed that the role of mulberry leaf meal, in stimulating animal response may be related equally to the presence of phenolic compounds, and/or β-glucan, enhancing the immune system, as well as being a source of protein.

Acknowledgments

The authors thank the Centre of Excellence in Sustainable Agriculture and Agribusiness Management (CESAAM), Egerton University for financial support that made this study possible.

References

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Received 16 April 2020; Accepted 8 May 2020; Published 1 June 2020

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