Effect of inclusion rate of Fermenten on performance, carcass traits, and apparent total tract digestibility of growing Angus crossbred steers.

In Phase 1 (d 0 to 56) of a two-phase experiment, 81 steers (initial body weight = 189 ± 22 kg) were arranged in a generalized randomized block design, allocated to 9 pens (9 steers/pen) and assigned to 1 of 3 dietary treatments. Treatments consisted of different inclusion rates of Fermenten (FER) in a backgrounding diet fed ad libitum, and were as follow: 0 (CON), 2, or 4% FER in the diet dry matter (DM). Steer was considered the experimental unit, and individual DM intake was measured using the GrowSafe system. In Phase 2 (d 57 to 112), treatments were discontinued and steers were relocated to a paddock with free access to a common basal diet, to assess potential residual effects of FER. Effect of treatment was measured on performance, concentration of serum urea nitrogen (SUN), non-esterified fatty acids (NEFA) and glucose, and apparent total tract digestibility of nutrients. On d 56, steers fed 4% FER had lesser (P = 0.01) body weight (BW) than 2% FER steers. Steers fed CON also tended (P = 0.08) to have greater BW than 4% FER steers. Average daily gain (ADG) was not different (P = 0.96) between CON and 2% FER steers, whereas steers in the 4% FER treatment had lesser (P ≤ 0.01) ADG than CON and 2% FER. Steers in the 4% FER treatment had lesser (P = 0.04) DM intake than CON, and were less feed efficient (P ≤ 0.04) than 2% FER and CON steers. However, DM intake as a percentage of the BW did not differ (P = 0.07) across treatments. A treatment effect was observed for final BW on d 112 (P = 0.05), where 4% FER tended (P = 0.07) to have lesser BW than CON. In Phase 2, ADG was not different (P = 0.18) among treatments. However, overall ADG (d 0 to 112) was lesser (P = 0.02) for steers fed 4% FER when compared with CON. There was no difference (P ≥ 0.12) in longissimus muscle area gain or 12 th rib fat depth gain. There was a treatment × day interaction for serum concentrations of glucose (P < 0.001), NEFA (P < 0.001) and SUN (P < 0.001). Steers fed 4% FER had greater (P < 0.001) DM, organic matter (OM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude protein (CP) apparent total tract digestibility than CON. Similarly, 4%FER steers had greater (P ≤ 0.02) DM, OM, NDF, and ADF digestibility than 2% FER. Results show that although inclusion of FER increased apparent total tract digestibility of nutrients, DM intake and overall performance of growing beef cattle was negatively affected, mainly when FER was included at 4% of the diet DM.