Abstract
In trial 1,16 wether lambs were utilized in a N depletion-repletion experiment and were randomly allotted to four diets: (1) chopped smooth bromegrass-alfalfa hay, 50% of diet as fed; (2) chopped untreated wheat straw, 41.6% (WS); (3) water plus NH3-treated wheat straw, 57.8% (ENS-S), and (4) stacked NH3-treated wheat straw, 43.6% (S-S). Water (50%) and anhydrous NH3 (3%) were added to the ENS-S and the product was stored in a silo-press bag. The S-S product was stacked under plastic and 3.8% anhydrous NH3 was added. The rest of each diet consisted of steam-rolled barley and supplement. Nitrogen retention for the final 3 wk of repletion averaged 15.5, 7.4, 25.7 and 44.0 g/wk and dry matter digestibilities were 75.4, 66.8, 70.9 and 75.0% for the four diets, respectively. In trial 2 these diets were fed to four ruminally fistulated wethers in a Latin square, split-plot experiment. Ruminal samples were taken on d 10 and 15 of each period. Mean ruminal NH3-N values were 13.1, 8.0, 5.3 and 6.4 mg/dl with the four diets, respectively. Total VFA concentrations were 87.3, 73.5, 75.8 and 73.2 µmol/ml, respectively. Propionate concentration was higher (P<.01) in sheep fed NH3 straw diets than in sheep fed WS. Similar diets were fed to calves in trial 3. Hay, WS and ENS-S were fed for 133 d and S-S for 105 d. Average daily gains for the 39 bulls and steers were 1.10, 1.04 and .91 kg with hay, ENS-S and S-S, respectively. Heifer gains were .98, .70, .84 and .65 kg/d with the four diets, respectively. Ammonia treatment of straw resulted in higher N retention, dry matter disappearance and dry matter intake. Copyright © 1982. American Society of Animal Science . Copyright 1982 by American Society of Animal Science.

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