Abstract
Dietary manipulations to include tannins can change the proportion and amount of nitrogen (N) excreted in the urine and feces as well as improve N-use efficiency in ruminants. Our objective was to determine the effects of different levels of phytogenic supplementation (Actifor®) on intake, digestibility, carcass measures, and N balance of lambs offered a corn-based finishing diet. Twenty-six lambs (31.5 ± 5.39 kg BW) were allocated randomly to 1 of 3 corn-based finishing diets (85% concentrate) that were offered for ad libitum consumption. Lambs were housed individually in 1 × 1.5-m pens with plastic-coated grate flooring (n = 18; 6/trt) or 1.5 × 4.3-m pens with rubber mat flooring (n = 8; 2 or 3/trt). Diets were not supplemented or supplemented with 4 or 8 g/d of Actifor® (n = 8, 9, and 9 lambs/trt, respectively). A 7-d total fecal and urine collection period (n = 6 lambs/trt) began on d 43. On d 50, rumen samples were taken at 0800, 1100, and 1400 h for measurement of pH and VFA concentrations. Data were analyzed using the MIXED procedure of SAS, and orthogonal linear and quadratic contrasts were used to assess phytogenic supplementation level effects. Intake and digestibility of DM and OM were not different across treatments (P ≥ 0.32). Average fecal N and lamb shrink before slaughter increased linearly (P ≤ 0.05) with increasing levels of phytogenic supplementation. Propionate and acetate:propionate decreased (P ≤ 0.05) and acetate, valerate, and pH tended to increase quadratically (P ≤ 0.08) with increasing phytogenic inclusion. Back-fat and yield grade tended (P = 0.06) to decrease linearly and dressing percentage tended (P = 0.06) to decrease quadratically with increasing phytogenic inclusion. Phytogenic supplementation increased average fecal N and improved some carcass measures, but did not affect diet digestibility.
170 Effects of Dietary Phytogenic Supplementation to a Finishing Diet on Intake, Digestibility, Nitrogen Balance and Carcass Measures