EFFECTS OF LACTATIONAL STATUS ON FORAGE INTAKE, DIGESTIBILITY, AND PARTICULATE PASSAGE RATE OF BEEF-COWS SUPPLEMENTED WITH SOYBEAN-MEAL, WHEAT MIDDLINGS, AND CORN AND SOYBEAN-MEAL

Sixteen mature, lactating (453 kg) and 16 nonlactating (487 kg) Hereford and Angus x Hereford cows were used to determine effects of different dietary supplements and lactational status on forage intake, digestibility, and particulate passage rate. Supplement treatments and amounts fed (kg/d) were as follows: control, 0; and equal daily amounts of CP from soybean meal (SBM), 1.36; wheat middlings (WM), 3.41; or a blend of corn and soybean meal (corn-SBM; 22% corn and 76% SBM), 3.41. Cows were fed supplements at 0800 and had ad libitum access to prairie hay (4.9% CP) in stalls from 0800 to 1100 and from 1300 to 1600 for three 17-d periods. Lactational status and supplement type did not interact (P > .50) for hay DMI, DM digestibility, or particulate passage rate. Cows fed SBM ate more hay DM (P < .01) and had greater hay DM digestibility (P < .01) than did cows in other treatment groups. Average hay DMI (kg/100 kg of BW) was 1.95, 2.16, 1.94, and 1.89, and hay DM digestibility was 52, 61, 55, and 53% for control, SBM, WM, and corn-SBM supplements, respectively. Total diet DM digestibility was increased by supplementation (P < .01), but no differences (P > .18) were observed among supplements. Lactating cows ate more (P = .13) hay DM (2.11 vs 1.87 kg/100 kg of BW) and had greater (P < .05) fecal output (4.6 vs 4.3 kg/d) than did nonlactating cows. Dry matter digestibility and particulate passage rate were not affected (P > .35) by lactational status. Total ME intake did not differ (P > .50) for cows supplemented with WM or corn-SBM. Lactating beef cows did not seem to differ in usage of protein or energy supplements compared to nonlactating cows in early gestation.