India has 23.5% of world sheep and goat population, ranking first in goat and fifth in sheep. Sheep and goat seem to be the best choice of the component to provide food security to growing population and well-being of the society. Complete ration / total mixed ration is a accepted concept for feeding the small ruminants throughout the year and search of alternative to animal trial for rumen studies are not yet completed. This book explores the nutrients availability and anti-nutritional factors and its alleviation process in agro-industrial by-products and possibilities of rumen studies by rumen simulation Techniques (RUSITEC) in formulating complete ration for small ruminant production by agro-industrial by products. The results obtained in this work hopefully are of great importance in using rumen simulation techniques that offers a convenient means of comparing the extent of microbial degradation and the fermentation pattern of agro-industrial by-product for formulating complete ration for small ruminants.