Majority of the primary studies reviewed showed that addition of yeast probiotic in laying hen diets improved feed utilization efficiency

Majority of the primary studies reviewed showed that addition of yeast probiotic in laying hen diets improved feed utilization efficiency, egg number/weight, egg (external and internal) quality traits and health status, thus an indication that yeast probiotic can serve as an alternative to in-feed antibiotics. Yeast may have achieved via one or combinations of the following modes of action: (i) increasing the number of good microbes in gut through selective exclusion and antagonism (Kabir et al. 2005; Schneitz 2005), (ii) inhibiting the production of toxins by pathogenic microbes (Musa et al. 2009), (iii) Alteration of gut metabolic processes in favour of production and release of endogenous digestive enzymes as against the production bacterial enzyme activity and ammonia (Han et al. 1999; Yoon et al. 2004), (iv) direct nutritional effects or improving feed intake, digestion and nutrient utilization (Kabir, 2004; Ezema 2007), (v) Activation of gut defense system (Haghighi et al. 2006; Apata 2008), and (vi) Decreasing gut pH via increased volatile fatty acids production (Chichlowski et al. 2007; Choudhari et al. 2008). Furthermore, there were no consensus results on the duration of feeding and optimum inclusion level with the best production response. Therefore, it is suggested that future research should be directed at determining the dose-related response on egg production and quality to dietary supplementation be modeled in laying chicken using quadratic equation quadratic.