Department of Animal Science


Date of this Version

January 1996


Published in 1996 Nebraska Beef Cattle Report; published by Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln.


Blood meal, meat and bone meal. and feather meal are high in escape protein, relative to oil meals and forages. and increase performance when included in forage-based diets sufficient in rumen degradable protein. Two factors that influence the nutritive value of animal byproduct meals are processing conditions and raw materials.

Renderers apply heat to drive off moisture. extract fat. and eliminate bacterial contamination from animal tissues. This cooking also denatures proteins. creating cross links and insoluble bonds within and between protein chains: enhancing resistance to microbial degradation in the rumen. However. processing at very high temperatures can limit the extent of enzymatic breakdown of proteins, reducing digestibility and absorption in the small intestine.

Variable inputs (deadstock, tankage, meat trimmings and bones) contribute to the great diversity encountered in commercial meat and bone meals. Concentration of meat and bone meal components. specifically bone. hair, and lean tissues. influence protein quantity and quality. Bone content, exhibited through ash, is negatively correlated with crude protein, whereas hair is high in protein but poorly digested. Animal performance with meat and bone meal supplementation has been inconsistent, and may result from inadequate escape protein and(or) poor protein digestibility arising from raw materials or processing conditions.

The objectives of this study were to determine how processing temperature and composition of animal byproduct meals influence in vivo true protein digestibility and escape protein concentrations. and to compare in situ and in vitro ammonia release techniques for measuring escape protein.