Abstract: An experiment was conducted to improve the nutrient content of tapioca by product to produce β carotene rich feed as alternative poultry feed through fermentation by using carotenogenic fungi (Neurospora crassa) as inoculums. The experiment was determination of substrate composition (carbon source and nitrogen source) based on nutrient quality and quantity of these fermented products. The study was conducted in experimental methods, using the completely randomize design in factorial with 2 treatment were : 1. A factor, ( tapioca by product as carbon source with nitrogen sources: A 1 = tapioca by product+tofu waste, A 2 = tapioca by product + palm kernel cake and A 3 = tapioca by product + rice bran. 2. B factor (Percentage of composition of carbon source with nitrogen source), B 1 = 90% : 10%, B 2 = 80% : 20%, B 3 = 70% : 30% and 60% : 40%). Results of study showed that optimum substrate composition of the fermentation by Neurospora crassa was the mixture 60% tapioca by product with 40% tofu waste. This conditions can increase β carotene and crude protein and also decrease crude fiber which made the nutritional value of the product based on dry-substance was 295.16 μg/g, β carotene 20.44% crude protein, 2.75% crude fat, 11.96% crude fiber, 0.24% calcium, 0.17% phosphor, metabolic energy 2677 Kcal/kg, 67.05% nitrogen retention and 35.44% fiber digestion.