Effects of barley grain processing on productivity of cattle

Abstract

Barley grain is one of the most common feed grains used in diets for dairy and beef cattle. Because the endosperm of the barley kernel is surrounded by the pericarp, which is extremely resistant to microbial degradation in the rumen, dry barley grain needs to be processed to improve its utilization by beef and dairy cattle. Dry rolling is a common processing method, and increases ruminal digestibility of grain and productivity of animals, but the grain kernels often shatter during processing, producing many fine particles, which has been associated with inconsistent animal performance. Steam rolling and temper rolling can reduce production of fine particles during rolling, allowing more uniform particle size distribution. Steam flaking uses moisture, heat and pressure to gelatinize starch granules, but positive effects of starch gelatinization on animal performance may be less for barley grain versus corn or sorghum because barley starch, once exposed to microbial organisms in the rumen, is readily degradable even without being gelatinized. Treatment of grains with NaOH may increase its ruminal starch digestibility without increasing ruminal rate of starch release. Roasting and aldehyde treatment decrease the rate of crude protein degradation and optimize organic matter degradation in the rumen, while application of ammonia or fibrolytic enzymes can increase degradation of the hull. Consistency in processed grain quality (e.g., particle size) and predictability in animal performance should be considered as an important quality parameter of processing. In addition, initial grain quality, extent of processing, processing method, and their interactions, determine the feeding value of barley grain and affect the productivity of cattle. Further research is warranted to develop a common quality parameter accounting for variations in physical, chemical and biochemical properties for processed barley grain.