Sorghum grain flake density and source of roughage in feedlot cattle diets.

Feedlot performance was studied in a 262-d trial using 126 crossbred beef steers (182 kg initial BW) to determine whether source of dietary roughage influences performance and carcass characteristics by steers fed growing (112 d) and finishing (150 d) diets with various flake densities (FD) of steam-processed sorghum grain. A 3 x 3 arrangement of treatments (two pens of seven steers each) was used, with dietary roughages being chopped alfalfa hay or 50:50 mixtures (equal NDF basis) of cotton-seed hulls or chopped wheat straw with alfalfa hay; sorghum grain was steam-flaked to densities of 386, 322, and 257 g/L (SF30, SF25, and SF20, reflecting bushel weight in pounds). The effects of these same FD on nutrient digestibilities were determined in three experiments with 24 crossbred steers fed finishing diets containing each of the roughage sources. No interactions between FD and roughage type were detected in any performance or carcass measurements (P > .10). Intake of DM decreased linearly (P < .05) in response to decreased FD. Daily rate and efficiency of gain were not altered (P >.10) by FD. Decreasing FD decreased linearly (P < .05) dressing percentage and fat thickness, but not other carcass measurements. Dietary roughage did not affect (P >.10) daily gains or carcass measurements, but DM intake was lower and feed efficiencies were superior (P < .05) when alfalfa hay was the sole source of roughage. Cottonseed hulls and wheat straw were relatively less valuable in the low roughage finishing diets than in higher roughage growing diets. Digestibilities of starch increased linearly as FD was decreased (P = .02) when steers were fed diets containing wheat straw, but not for alfalfa hay or cottonseed hull diets. Digestibilities of DM did not vary with changes in FD; however, changes in CP, NDF, and ADF digestibilities due to FD seemed to differ among experiments. In conclusion, performance and carcass measurement responses by growing-finishing steers to differences in sorghum grain FD were not related to source of dietary roughage, but diets with alfalfa hay as the only source of roughage were most efficient. Decreasing FD of sorghum grain below 386 g/L (30 lb/bu) was not advantageous in improving performance or carcass merit by growing-finishing steers.

Evaluation of biological efficiency of free-grazing beef cows under semidesert conditions.

Effects of cow BW, hip height, and estimated genetic potentials (EBV) for weaning weight direct and milk on cow productivity, fecal OM output, OM intake, and efficiency (kilograms of calf BW/kilogram of OM intake by the cow) were evaluated with 44 free-grazing crossbred cows under semidesert conditions. Calf BW were measured during early, mid-, and late lactation. Data were collected in four periods: Period 1 = late spring (early lactation), Period 2 = late summer (mid-lactation), Period 3 = mid-autumn (late lactation), and Period 4 = mid-winter (nonlactation). Calf BW increased linearly with cow BW (P < .01) in Periods 1, 2, and 3. Fecal OM output and OM intake increased with cow BW in Periods 2 (P < .01) and 4 (P < .01), and on average (P < .02). Overall efficiency decreased with increasing cow BW (P < .04). Taller cows excreted more fecal OM and had greater OM intake throughout the study (P < .02 to P < .11). Overall efficiency decreased with increasing cow hip height (P < .05). Weaning weight direct EBV of cows was related linearly to cow BW (P < .01 to P < .07) and to calf BW (P < .01 to P < .07). Calf weight in all periods increased linearly with milk EBV (P < .001). Overall, fecal OM output, OM intake, and efficiency were not affected by milk EBV.