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Forage Sources for Growing Cattle¹

Washington State University, Pullman 99164-6320

Abstract

In an initial experiment, 229 mixed breed steer calves were allotted randomly to 18 pens. The pens of cattle were allotted to the following dietary treatments: 1) bromegrass-alfalfa hay; 2) barley silage; 3) wet NH₃-treated wheat straw + formaldehyde-treated soybean meal; 4) wet NH₃-treated wheat straw + soybean meal; 5) dry NH₃-treated wheat straw and 6) chopped wheat straw. Roughage consisted of 50%, supplement 15% and steam rolled barley 35% of diet dry matter. Gains were .96, .78, .76, .69, .61 and .58 kg·steer^–1·d^–1 for the six diets, respectively. The higher (P<.01) gain obtained with the hay diet was due to higher (P<,01) dry matter intake (dry matter intakes were 7.3, 6.2, 6.6, 6.2, 5.5 and 5.4 kg·steer^–1 · d^–1, respectively). All diets except for formaldehyde soybean meal were evaluated in a Latin square digestion trial. Dry matter and gross energy digestibility were 56.15, 56.39; 60.19, 60.17; 49.60, 49.27; 45.26, 44.94 and 44.85, 45.28% for the five diets, respectively. Digestibility of the barley silage diet was higher (P<.01) than all other treatments. The wet NH₃-treated straw diet resulted in higher but nonsignificant dry matter digestibility compared with the other straw diets. In another experiment, 131 steer calves were allotted to 14 pens. The dietary treatments were: 1) brome-grass-alfalfa hay; 2) barley silage; 3) NH₃-barley silage; 4) dry NH₃-wheat straw; 5) wet 3% NH₃-wheat straw; 6) wet 1.5% NH₃-wheat straw. Gains were 1.27, 1.14, 1.02, .59, .93 and .78 kg · steer^–1·d^–1, respectively. The higher (P <.01) gains with the hay diet were associated with higher (P<.01) dry matter intake. Ammonia treatment of barley silage did not affect gains. The wet NH₃ treatment of straw was superior to dry NH₃ treatment in both experiments. In a final experiment, supplementation of the wet 1.5% NH₃ straw with dehydrated alfalfa (24.2% crude protein) or soybean meal (31.31% crude protein) supplements resulted in a numerical improvement in gains compared with the unsupplemented control diet. Dry matter intake of barley silage diets limited performance compared with cattle fed hay as a roughage source. Protein supplementation of NH₃-treated straw diets resulted in improved performance.

¹ Scientific Paper No. 6434. College of Agriculture and Home Economics Research Center, Washington State Univ. Research conducted under Project 0539.

² Dept. of Anim. Sci.

³ The authors wish to acknowledge the assistance of Dan Caldwell (forage preparation), Milt Russell and Dan Coonrad (animal care) and Loyd Falen (laboratory analysis).