Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2007
Publication Date: 8/1/2007
Citation: Kostenbauder, M.J., Coleman, S.W., Chase, C.C., Kunkle, W.E., Hall, M.B., Martin, F.G. 2007. Intake and Digestibility of Bahiagrass Hay Supplemented with Molasses or Molasses-urea with or without Soybean Hulls when Fed to Cattle. Professional Animal Scientist. 23:373-380. Interpretive Summary: Most beef cattle operations in the southeastern United States rely on a forage-based diet. Unfortunately for many producers, the needed forage quality or quantity is limited at certain times of the year. If forage is the only feed source, cattle may not be able to consume enough net energy to meet the requirements for a preferred level of performance. Because of this, producers often turn to grain or liquid supplements such as molasses to make up for the nutritional shortfalls. However, while grains are high in available energy, they frequently depress forage digestion and molasses are marginal in crude protein content. Soybean hulls, a high fiber energy source, have become a commonly used supplement in forage-based diets. We conducted studies to determine the effect of supplemental soybean hulls, with or without added molasses or molasses-urea (21% crude protein equivalent) on intake, nutrient digestibility, and growth of cattle fed bahiagrass hay. Both soybean hulls and molasses-urea increased nitrogen retention and daily gains by increasing total digestible dry matter intake. Molasses alone depressed fiber and protein digestion. Concentration of urea nitrogen in blood plasma was increased with soybean hulls and with molasses-urea, but depressed with molasses alone. Soybean hulls may be an effective supplement in forage-based systems for increasing average daily gains. Molasses should to be fortified with a nitrogen source. An inexpensive and effective source of nitrogen is urea.
Technical Abstract: Two experiments were conducted to evaluate the effect of molasses or molasses-urea supplementation with or without soybean hulls on digestibility, intake and animal performance in cattle fed bahiagrass hay. In experiment 1, Holstein steers were fed one of six treatment diets: 1) hay only; 2) hay plus molasses; 3) hay plus molasses-urea; 4) hay plus soybean hulls; 5) hay plus soybean hulls-molasses; and 6) hay plus soybean hulls-molasses-urea. Molasses and soybean hulls were fed at .75% of body weight, and urea was fed at 3.5% of the weight of molasses. Digestibility of dietary dry matter, NDF, and ADF was increased with soybean hulls (P < .05) supplementation. Molasses supplementation decreased digestion of crude protein (P < .10), and fiber (P < .05). Addition of urea to molasses increased (P < .05) crude protein and NDF digestion when soybean hulls were absent, and increased crude protein digestion (P < .10) when soybean hulls were present. All supplements increased intake and fecal excretion of N, but nitrogen retained as a percent of intake or absorbed N was not affected by supplementation. Plasma urea nitrogen was increased (P < .05), non-esterified fatty acids were decreased ( P < .10), and blood-glucose was not affected by soybean hulls. Molasses supplementation increased non-esterified fatty acids (P < .05) both with and without soybean hulls.In experiment 2, the same treatment diets as in Exp. 1 were fed to 36 beef calves in Calan headgates for 43 d (6 calves/treatment). Overall hay intake was depressed (P < .10) with supplementation by soybean hulls, but diet effects changed over the 6-wk experiment. Average daily gain was improved (P < .01) with soybean hulls supplementation, and also by urea (P < .05). Plasma urea nitrogen was increased by soybean hulls (P < .01) and urea supplementation (P < .05). Molasses decreased plasma urea nitrogen concentrations when soybean hulls were included in the diet (P < .01). Non-esterified fatty acid concentration was not affected by treatments. Blood glucose was increased by soybean hulls (P < .01) and by molasses-urea (P < .01) when soybean hulls were included. Soybean hulls may be an effective supplement in forage-based systems for increasing average daily gains without decreasing hay intake. For molasses to be effective in growing cattle, it should be fortified with a nitrogen source. An inexpensive and effective source of nitrogen is urea. Keywords: Beef cattle, Bahiagrass hay, Soybean hulls, Molasses-urea, Intake, Digestion