The Encyclopedia of Farm Animal Nutrition
http://www.amazon.co.uk/Encyclopedia-Farm-Animal-Nutrition-Publishing/dp/0851993699/ref=sr_1_1?s=books&ie=UTF8&qid=1340007470&sr=1-1
Nutrient Digestion and Utilization in Farm Animals: Modelling Approaches
http://www.amazon.co.uk/Nutrient-Digestion-Utilization-Farm-Animals/dp/1845930053/ref=sr_1_1?s=books&ie=UTF8&qid=1340007706&sr=1-1