| Abstrakt: |
The influence of a 50% concentrate: 50% roughage diet (control) and of this control diet plus 1.85% viable yeast culture, 2.5% NaHCO3, 5.0% NaHCO3or 33 ppm monensin on liquid dilution rate (LDR), rumen fermentation and feedlot performance of growing steers, and on diet digestibility and N retention by lambs, was evaluated in three trials. The effects of five experimental diets on LDR and rumen fermentation were evaluated in trial 1. The LDR for steers fed monensin (9.0%/hr) was lower (P<.10) than that for steers fed yeast culture (11.0) or 5% NaHCO3(11.9), but similar to the LDR for steers fed the control (10.3) or 2.5% NaHCO3(10.3) diets. Liquid turnover time (hours) was longer (P<.10) for steers fed diets with monensin than for those fed the other diets, but rumen liquid volumes were not affected by diet. Acetate concentrations and acetate: propionate ratios were lower (P<.01) and propionate concentrations higher (P<.01) for steers fed monensin than for steers fed other diets. Ruminal ammonia concentrations were not affected (P>.05) by diet. In trial 2, 20 white-faced lambs were used in a conventional digestion trial evaluating effects of the five diets on digestibility and N retention. Digestibility of dry matter (DM), organic matter (OM), crude protein (CP) and acid detergent fiber (ADF) did not differ among diets; however, digestibility of DM, OM and CP tended to be higher with monensin. N retention in lambs fed monensin (9.1 g/day) was higher (P<.05) than that in lambs fed the control (7.1), yeast culture (7.0) or 2.5% NaHCO3(5.7) diet and tended to be higher than N retention in lambs fed 5% NaHCO3 (7.6). Seventy-four crossbred steers were used in a 73-day growing trial (trial 3) to evaluate feedlot performance with the five diets. Average daily gains (kilograms) and feed conversions (kilograms DM/kilograms gain) for steers fed control, yeast culture, 2.5% NaHCO3, 5% NaHCO3and monensin diets were 1.34, 6.42; 1.39, 6.32; 1.37, 6.19; 1.32, 6.26, and 1.46, 5.90, respectively. Although differences were not significant, average daily gain and feed conversion tended to be improved by monensin. |
