Intake and Digestibility of Bahiagrass Hay by Cattle that are Supplemented with Molasses or Molasses-Urea with or without Soybean Hulls12

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 (Paspalum notatum Flugge) hay. In Experiment 1, 6 Holstein steers (average BW 256 ± 15 kg) were fed 1 of 6 treatment diets: 1) bahiagrass hay only; 2) hay plus molasses; 3) hay plus molasses-urea; 4) hay plus soybean hulls; 5) hay plus soybean hulls and molasses; and 6) hay plus soybean hulls and molasses-urea. Molasses were fed at 0.59% ofBW (DM basis), soybean hulls at 0.75%, and urea at 4.5% of the weight of the molasses. Dry matter intake and apparent digestibility were measured in an incomplete Latin square design with a 28-d recovery period between each period. Digestibility of dietary DM, OM, and ADF was increased with soybean hulls (P < 0.05) supplementation. Molasses supplementation tended to increase (P < 0.10) DM digestibility but decreased digestion of CP (P < 0.10) and fiber (P < 0.01). Addition of urea to molasses increased (P < 0.05) CP and NDF digestion when soybean hulls were absent, but only increased CP digestion (P < 0.05) when soybean hulls were present. Plasma urea nitrogen was increased (P < 0.05), but nonesterified fatty acids and blood glucose was not affected (P > 0.10) by soybean hulls. Urea added to molasses increased nonesterified fatty acids (P < 0.10) both with and without soybean hulls. In Exp. 2, the same treatment diets as in Exp. 1 were fed to 36 beefcalves (average BW 225 kg) in Calan headgates for 43 d (6 calves/treatment). Hay intake averaged over the trial was not affected by dietary treatment, but diet effects changed over the 6-wk experiment. Average daily gain and plasma urea nitrogen were increased with soybean hulls (P < 0.05) or urea (P < 0.10) supplementation. Molasses decreased plasma urea nitrogen concentrations when soybean hulls were included in the diet (P < 0.01). Nonesterified fatty acid concentration was not affected (P > 0.10) by treatments. Blood glucose was increased (P < 0.05) when molasses-urea were included along with soybean hulls. Soybean hulls may be an effective supplement for increasing average daily gains without decreasing hay intake for cattle fed mature bahiagrass hay, and for molasses to be effective in growing cattle, it should be fortified with a nitrogen source such as urea.