Effects of fibrolytic enzymes in corn or barley diets on performance and carcass characteristics of feedlot cattle

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Abstract
A study was conducted to establish whether fibrolytic enzyme feed additives influence performance of feedlot cattle fed high grain diets, and to compare the effects of feeding diets of barley or corn on performance and carcass characteristics. Crossbred beef steers (408 kg) were offered high concentrate diets (95.1%, dry matter basis), consisting mainly of barley and barley silage or corn and corn silage. Concentrates were treated with either no enzyme or one of two enzyme mixtures. Calves were slaughtered after a 103- to 145-d feeding period at an average weight of 570 kg and 10.8 mm of backfat. Barley-fed calves grew faster (1.45 vs. 1.29 kg d−1), ate more dry matter (DM; 9.79 vs. 9.31 kg d−1), and converted DM to gain (6.85 vs. 7.35 kg DM kg−1gain) more efficiently compared with corn-fed calves (P < 0.001). Meat from barley-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 muscle score, rib eye area, or carcass leanness. Effect of enzymes differed for corn and barley diets; Enzyme 1, a preparation with higher xylanase activity than Enzyme 2, improved (P < 0.05) feed conversion ratio of 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 advantageous for corn diets. Further work is necessary to determine optimum formulation and level of application of enzyme preparations for use in barley diets. Further study of the differences in carcass characteristics of cattle fed barley or corn diets is warranted to substantiate the trends observed on this limited group of animals. Key words: Feedlot cattle, barley, corn, enzymes, cellulase, xylanase

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