YEAST

YEAST (SACCHAROMYCES CEREVISIAE) AS PROBIOTICS OF CHOICE
FOR LAYING CHICKENS

I.P. Ogbuewu and C.A. Mbajiorgu
Department of Agriculture and Animal Health, University of South Africa,
Florida Science Campus, Johannesburg, South Africa
Corresponding author’s e-mail: [email protected]

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Abstract
Antibiotics is included in minute level in chicken ration to promote productivity and physiological well-being. But studies have revealed that incorporation of antibiotics in feed to increase chicken performance causes the emergence of resistant bacteria. Their use in poultry feed lead to accumulation of significant amount of residues in animal products. These normally have led to the stoppage on the use of antibiotics in animal feed by the European Union (EU) in several parts of the world. This stoppage has elicited interest on the use of Yeast (Saccharomyces cerevisiae) as a replacement for antibiotics in chicken nutrition. Yeast is abundant in protein (44%) and moderate in other essential nutrients. Information exist that yeast supplementation enhance gut health and feed efficiency in chickens. This paper is an attempt to document all the information on the effect of yeast supplementation on health status, egg production and egg quality in laying chickens as to identify knowledge gap for future research.

Keywords: Probiotics, yeast supplementation, chickens, laying performance, egg quality

Introduction
The prolonged use of a small dose of antibiotics in livestock and poultry feed has implicated in the host and cross drug resistance (Jones and Ricke 2003). In view of the public health implication of using sub-dose of therapeutic antibiotics in feed calls the search for alternative natural growth stimulants such as yeast (Patterson and Burkholder 2003; Khan and Naz 2013). Studies by Reed and Naodawithana (1999) and McDonald et al. (1988) have shown that yeast is rich in protein and moderate in B-vitamins and trace mineral elements (Table 1). In addition, studies (Haiman and Frank 1994; Yalcin et al. 2014) showed that yeast contains all the essential amino acids needed by chickens for growth and egg production (Table 2). Furthermore, Samanta and Mondal (1988) revealed that dried yeast cell is very high in methionine (2.46%), threonine (3.98%) and tryptophan (0.77%). Results of proximate analysis of yeast showed dried yeast had 95.7% dry matter (DM), 10.7% ash, 48.7% protein, 0.55% crude fat, 0.5% fibre, 35.5% carbohydrates, 5.50% phosphorus, 2.0% potassium and 0.03% chloride (Hamad, 1986). Studies have revealed that S. cerevisiae stimulates appetite (Nahashon et al. 1992) and improve immunity (Toms and Powrie, 2001; Cotter et al., 2002) on layers. In the gut, yeast has been established to reduce the population of pathogenic micro-organisms and decrease pH (Fuller, 1989). Several investigators reported that feeding yeast mannan oligosaccharide (MOS) results to improve immune response in chickens (Raju and Devegowda, 2002; Cotter et al., 2002; Shashidhara and Devegowda 2003) while, yeast culture (YC) inclusion at 0.5 – 1.5 g/kg diet increases shell thickness, yolk weight and reduced egg yolk cholesterol content chickens (Yousefi and Karkoodi 2007). Similar results were obtained by other scientists who reported that YC supplementation increases egg production and weight (Thayer et al. 1975; Liu and Yoon 2002; Tangendjaja and Yoon 2002Yalc?n et al., 2008a; Yalcin et al. 2010), improve feed efficiency (Liu and Yoon, 2002; Tangendjaja and Yoon 2002; Dizaji and Pirmohammadi 2009) and reduced egg yolk cholesterol (Yalcin et al. 2008a) and serum cholesterol cum triglycerides concentration (Jin et al. 1998; Yalcin et al. 2010). Dizaji and Pirmohammadi (2009) noticed reduced egg weights on layers on YC supplementation contrary to the results of other authors (Thayer et al. 1975; Liu and Yoon 2002; Tangendjaja and Yoon 2002; Yalc?n et al. 2008a; Yalcin et al. 2010), while Nursoy et al. (2004) observed no statistical effect of yeast supplementation on egg production, egg weight, and feed efficiency in laying chickens. The growing benefits of S. cerevisiae on egg production in chickens are linked to either its direct nutritional effect or its potential to reduce the population of pathogenic microbes in the gut and strengthen the host’s natural body defense (Fuller 1977; Fuller 2001).
The objective of this review was to aggregate all the available information on egg production performance of laying hens fed yeast diets in a single document for easy access by researchers and research end-users as well as to identify knowledge gap for future research.