EVALUATION OF TWO GLUCOPYRANOSYLAMINES AS NONPROTEIN NITROGEN SOURCES FOR CATTLE: DIGESTIBILITY AND EFFECT ON GROWTH AND FEED CONVERSION

Abstract

N-[carbamoyl]-β-D( + )-glucopyranosylamine (NCG) and N-[N′-hydroxymethyl-carbamoyl]-β-D ( + )-glucopyranosylamine (HNCG), manufactured from glucose and urea with molasses or barley as the source of glucose, were evaluated as slow release nonprotein nitrogen (NPN) supplements in two feeding trials with steers and a digestibility trial with wethers. In exp. 1, 50 steers (initial weight of 263 kg) were assigned to five treatments providing no source of supplemental N, urea, soybean meal, NCG, or HNCG in diets consisting of 1.8 kg/day of concentrate, 0.93-1.13 kg/day of liquid supplement and ad libitum chopped timothy hay (10.1% crude protein). Daily gain was reduced (P < 0.05) by 22% and dry matter per unit of gain was increased (P < 0.05) by 24% when HNCG was added to the control diet. No differences were observed between daily gain and feed conversion of steers on the other four treatments.In exp. 2, 16 steers were assigned to each of three treatments entailing individual feeding of diets containing no supplemental N, soybean meal, or NCG during a growth (67% straw in diet) and a finishing (15% straw in the diet) period. In the first period steers fed soybean meal grew faster (P < 0.05) than those fed no supplemental N while those given NCG grew at an intermediate rate. In the finishing period steers fed NCG grew more rapidly (P < 0.05) than those fed soybean meal, but not faster (P > 0.05) than steers fed the control diet. Dietary treatment had no significant influence on overall performance or carcass characteristics in this experiment. The digestible energy contents of NCG and HNCG supplements were estimated to be 14.6 and 12.6 MJ/kg dry matter respectively (SEM = 0.9) in exp. 3. Nitrogen balance of wethers was increased (P < 0.05) from − 4.9 to + 4.9 and 6.4 g N/day when NCG and HNCG, respectively, replaced 20% of a pelleted sun-cured alfalfa ration. It was concluded that NCG is a potential commercial slow-release NPN supplement for cattle whereas further research with HNCG would be necessary before it could be recommended as a slow-release NPN source for ruminants. Key words: Glucopyranosylamines, NPN, cattle, digestibility, growth efficiency