Cheese production waste contains carbon source, one of which is lactose as an energy source in the development of fermentation, especially in the manufacture of probiotics for poultry. The research method used 3% fermented cheese whey in 17-week-old laying hen drinking water to analyze the productivity of laying hens and microbiology. The purpose of the research is to determine the effective concentration of fermented whey cheese to improve productivity, physical and chemical composition of eggs, and evaluate fat metabolism in laying hens. The present study used 120 laying hens aged 17 weeks. The experimental method was designed using the T-test method of control (P0), fermented whey cheese (P1). The observed variables were productivity (feed consumption, water consumption, daily egg production, feed conversion ration), and microbiology of small intestine and excreta (lactate acid bacteria, salmonella, Escherichia coli.). The effect of adding fermented whey cheese into drinking water decreased feed consumption and FCR in contrast to the control group (P0) but increased egg production, egg weight, and egg mass weight. The effect of adding fermented whey cheese into drinking water decreased the number of Escherichia coli bacteria and increases lactic acid bacteria in the digestive tract of broiler chickens, especially in the ileum, caeca, so also with those in the stool. The number of Salmonella Bacteria was significantly decreased and very significantly increased lactic acid bacteria in the feces during the fermentation of whey cheese. The decrease in ammonia in the stool was very significant compared to the control group. In conclusion, adding fermented whey cheese into drinking water can reduce feed consumption, feed conversion ratio (FCR), Escherichia coli, salmonella, ammonia (NH 3), and increase egg production, egg weight, egg mass weight, final body weight, and lactate acid bacteria. The use of fermented whey cheese can be used as a nutraceutical feed additive to inhibit pathogenic bacteria in the intestine and increase lactic acid bacteria.