THE EFFECTS OF AMOUNT OF WHOLE BARLEY, BARLEY BULK-DENSITY, AND FORM OF ROUGHAGE ON FEEDLOT LAMB PERFORMANCE, CARCASS CHARACTERISTICS, AND DIGESTA KINETICS

We conducted two feedlot trials and one metabolism trial to evaluate t he effect of barley level, barley bulk density, and physical form of r oughage on lamb growth performance and digesta kinetics. Level of whol e barley (50, 70, 90%) and type of roughage (chopped or pelleted alfal fa) were evaluated in Trial 1 (50 d period). Trial 2 (50 d) evaluated barley bulk density (heavy = 671 and light = 607 kg/m(3),) form of rou ghage (pelleted or chopped alfalfa), and level of barley (80 or 40%). The influence of treatments used in Trial 2 on digesta kinetics was ev aluated in Trial 3. Gain:feed increased and DMI decreased (P < .10) Li nearly with increasing level of barley, and ADG and DMI were greater ( P < .10) for lambs fed pelleted vs chopped alfalfa in Trial 1. The 70% barley diet produced the highest yield grade and kidney-pelvic fat an d the lowest leg score among barley levels (P < .10). Lambs fed pellet ed alfalfa had heavier carcasses and a thicker body wall than lambs fe d chopped alfalfa(P < .02). In Trial 2, DMI was less and gain:feed gre ater (P < .01) for lambs fed the heavy barley than for lambs fed the l ight barley and for the 80% barley diet compared to the 40% barley die t. Lambs fed pelleted alfalfa had greater dressing percentages than la mbs fed chopped alfalfa. Backfat and body wall thickness were greater (P < .10) for lambs fed the 80% barley diet than for those fed the 40% barley diet. In Trial 3, retention time of barley was greater (P < .1 0) for lambs fed light rather than heavy barley, and retention time of alfalfa was greater (P < .10) for lambs fed chopped compared with pel leted alfalfa. Acetate:propionate ratio was greater (P < .10) for lamb s fed light vs heavy barley and lambs fed the 40 vs 80% barley diets. Ruminal pH was lower(P = .05) and in situ barley digestion greater(P = .03) over time in lambs fed the 80% barley diet than in lambs fed the 40% barley diet. Feedlot lamb ADG was not always greatest with high l evels of barley; however, gain:feed improved at the higher barley leve ls. The higher barley levels seemed to result in fatter lambs.