THE INTAKE AND DIGESTIBILITY OF AMMONIATED CEREAL STRAWS BY CATTLE

The effects of treatment with 3.5% anhydrous ammonia on the nutritive value of straws from Neepawa wheat, Bonanza barley and Random oats were investigated with growing Hereford steers. Ambient temperatures during the 6-wk post-treatment period were 0.1 °C for wheat and barley straws and 15 °C for oat straw. The four treatments were untreated and ammoniated straw, fed with or without 4-kg supplements per day over four periods to four steers in a 4 × 4 latin square design. Crude protein was doubled in wheat and barley straws and trebled in oat straw following ammoniation. The consumption of all three straws without concentrates was increased significantly by ammoniation. Apparent digestibility of dry matter and crude fiber on straw rations were higher (P < 0.05) in ammoniated wheat and oat straw than in the corresponding untreated straws. Neither straw intake nor dry matter digestibility were improved (P > 0.05) by ammoniation when supplements were fed, though crude fiber digestibility was increased (P < 0.05) in wheat and oat straw rations. Straw treatment had no effect (P > 0.05) on ruminal pH, dehydrogenase activity, or total or molar proportions of volatile fatty acids. Ruminal ammonia concentrations were higher (P < 0.01) for ammoniated than for untreated straws fed alone and similar to those when concentrates were also fed. Plasma urea, measured 0, 0.5, 1, 2, 4 and 7 h post-prandial, was highest in steers fed ammoniated wheat and oat straw and lowest when untreated straw was fed alone.