Feed intake and nutrient utilizationStudies abound that show the benefit of yeast supplementation on feed conversion ratio (kg feed/kg egg) in layers (Maziar et al. 2007; Songsak et al. 2009; Hassanein and Soliman 2010), weight gain (Sharmah et al. 2001; Yalcin et al.
2008a), energy utilization (Bradley and Savag 1995) and digestion coefficient of crude protein (Soliman 2003). In contrast, Yousefi and Karkoodi (2007) and Yalcin et al. (2014), respectively found that yeast supplementation (0.5 -1.5 g/kg feed) and 1.0 – 4.0 g/kg feed) had similar effect on feed intake, body weight and feed conversion ratio (FCR) in laying birds. Additionally, Swain et al.
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(2011) showed that of yeast (0.5 – 2.0%) did not affect feed intake in laying birds which also confirmed the earlier statement of Sehu et al. (1997) that up to 15% of inactivated brewer’s yeast can be added in laying hen diets without adverse effect on feed intake and FCR in quails. Contrary to these results, others have observed noticed that yeast supplementation at 0.
2% (Liu and Yoon (2002) and 0.3 -0.6% (Sanaa et al.
2013) reduced feed intake in quails. The disparity on the response of laying birds to varying levels of yeast diets may be linked to yeast type, supplementation rate, duration of feeding, genetic up and environmental differences (Mahdavi et al. 2005).