EFFECTS OF FIBROLYTIC ENZYMES IN CORN OR BARLEY DIETS ON PERFORMANCE AND CARCASS CHARACTERISTICS OF FEEDLOT CATTLE

A study was conducted to establish whether fibrolytic enzyme feed addi tives influence performance of feedlot cattle fed high grain diets, an d to compare the effects of feeding diets of barley or corn on perform ance and carcass characteristics. Crossbred beef steers (408 kg) were offered high concentrate diets (95.1%, dry matter basis), consisting m ainly of barley and barley silage or corn and corn silage. Concentrate s were treated with either no enzyme or one of two enzyme mixtures. Ca lves were slaughtered after a 103- to 145-d feeding period at an avera ge weight of 570 kg and 10.8 mm of backfat. Barley-fed calves grew fas ter (1.45 vs. 1.29 kg d(-1)), ate more dry matter (DM; 9.79 vs. 9.31 k g d(-1)), and converted DM to gain (6.85 vs. 7.35 kg DM kg(-1) gain) m ore efficiently compared with corn-fed calves (P < 0.001). Meat from b arley-fed calves tended to be more highly marbled and was brighter in colour than meat from corn-fed calves, but diet had no effect on muscl e score, rib eye area, or carcass leanness. Effect of enzymes differed for corn and barley diets; Enzyme 1, a preparation with higher xylana se activity than Enzyme 2, improved (P < 0.05) feed conversion ratio o f barley diets by 11% over the finishing period, but enzyme treatments had no such effect for corn diets. Fibrolytic enzymes can be used to improve the digestibility of barley-based diets, but are not advantage ous for corn diets. Further work is necessary to determine optimum for mulation and level of application of enzyme preparations for use in ba rley diets. Further study of the differences in carcass characteristic s of cattle fed barley or corn diets is warranted to substantiate the trends observed on this limited group of animals.