Production and reproduction responses by dairy cows fed varying undegradable protein coated with rumen bypass fat. 
Calcium soaps of fatty acids were used to coat proteins, thus reducing rumen degradability.  This material was used to determine the effects of either increasing undegradable intake protein with constant CP or varying degradable protein with constant undegradable protein intake.  Increased undegradable intake protein and Ca soaps fed for 120 DIM enhanced milk fat and FCM production during 140 and 305 DIM.  Reproductive performance also was improved.  Feed efficiency and partial efficiency of milk production were enhanced.  Varying degradable protein intake at constant undegradable protein intake using proteins coated with Ca soap resulted in decreased production when degradable protein intake was .4 kg/d lower than NRC recommendations, but no differences were significant when intakes were close to or .5 kg/d above NRC recommendations.  Use of Ca soaps to coat proteins appears to be useful to optimize protein supply to dairy cows while increasing ration energy density.