Authors: Sofia Suarez Lorences, Graduate Student, Animal Science, Lincoln; Jeff Heldt, Selko Company, Indianapolis, IN; Pablo Loza, Former Assistant Professor, PHREC, Scottsbluff; Galen E. Erickson, Professor, Animal Science, Lincoln.
Summary with Implications
A feedlot study evaluated the effects of Renergy™ (Selko USA) and Rumensin® (Elanco Animal Health) on growth performance, carcass traits, and liver abscess severity in finishing beef cattle. Using a 2 × 2 factorial design, cattle were fed one of four diets: control (no additive), Renergy, Rumensin, or both additives combined. A significant interaction between Renergy and Rumensin was observed for feed conversion, with a tendency for interaction in dry matter intake (DMI). Cattle fed Renergy tended to have lower DMI and lower average daily gain, though DMI did not differ between cattle fed both additives and those fed no additives. Rumensin had no effect on cattle performance. Neither additive influenced liver abscess incidence or severity. These results suggest that Renergy and Rumensin impacted feed efficiency and carcass traits without affecting liver health, with Renergy reducing intake and gain, and Rumensin having more notable effects on carcass composition.
Introduction
Maintaining and improving rumen health is crucial for optimal cattle performance in feedyards. In this context, Renergy is a feed additive that combines organic acids that modify rumen fermentation by promoting propionate production from lactic acid and increasing efficiency of lactate-utilizing bacteria. The objective of this study was to evaluate the effects of Renergy™ (Selko USA) and Rumensin® (Elanco Animal Health) on growth performance, carcass traits, and liver abscess severity in finishing beef cattle.
Procedure
An experiment was conducted at the Panhandle Research and Extension Center (PREC; Scottsbluff, NE) to determine the effects of Renergy (Selko USA) on growth performance, carcass characteristics, and liver abscess severity and prevalence in finishing beef cattle. Crossbred steers (n = 320; initial BW 887 ± 51 lb) were used in a randomized block design. Steers were blocked (light, medium and heavy blocks) and stratified by weight and assigned randomly to pen. Pens were assigned randomly to one of the four treatments. Cattle were limit fed at 2% of BW for five days to equalize gut fill and weighed on two consecutive days at the beginning of the experiment to establish initial BW. Cattle were implanted with Revalor-XS (Merck Animal Health) on day 1.
Cattle were stepped up for 21 days, and from day 22 to harvest, cattle were fed a finishing diet containing 20% corn silage, 54% dry rolled corn (DRC), 20% wet distillers grains (WDGS) and 6% supplement (Table 1). Four treatments were evaluated in a total of 32 pens with 10 steers/pen. Treatments were arranged as a 2 x 2 factorial that included no additives, feeding 16 g/steer daily of Renergy; feeding 435 mg/steer daily of Rumensin (assuming 29 lb DMI or 30 g/ton of DM); or a combination of both. Cattle were fed for 141 days, regardless of weight block. At the end of the feeding period, cattle were harvested at a commercial abattoir. Hot carcass weight and liver abscesses were recorded at harvest and marbling score; longissimus muscle area and 12th rib fat depth were recorded after a 48-hour chill. Carcass-adjusted final BW was calculated by assuming a common 63% dressing percentage; and was used to determine average daily gain (ADG) and feed efficiency.
Performance data were analyzed using the Mixed procedure of SAS (SAS Institute, Inc., Cary, N.C.), while incidence and severity of liver abscesses were analyzed using the Glimmix procedure of SAS. Pen was the experimental unit, and treatment and block were fixed effects. Data were analyzed as a 2 x 2 factorial, evaluating an interaction between both feed additives (Renergy and Rumensin). If no significant interaction was observed, then the main effect of feed additive was discussed. Significance was declared at P ≤ 0.05 and a tendency at P ≥ 0.10.
| Ingredient, % | 1 to 7 | 8 to 14 | 15 to 21 | 22 to harvest |
| Corn Silage | 50 | 40 | 30 | 20 |
| Dry Rolled Corn | 24 | 34 | 44 | 54 |
| Wet Distillers Grains | 20 | 20,0 | 20 | 20 |
| Supplement | 6 | 6 | 6 | 6 |
Results
An interaction (P = 0.04; Table 2) between feed additives was observed for feed conversion. Cattle fed Renergy had lower F:G, followed by cattle fed Rumensin and cattle with no feed additive in the diet. However, cattle fed both feed additives had significantly greater F:G compared to feeding none or each additive alone, which was unexpected. This suggests that the feed additives were antagonistic to each other and the effects in the rumen. A tendency for an interaction (P = 0.07) between feed additives was observed for dry matter intake (DMI). Cattle fed Renergy tended to have the lowest intakes (27.4 lb/d), while cattle fed Rumensin had equal intakes compared to cattle fed Renergy + Rumensin (28.3 lb/d), and cattle fed no additives had numerically greater intakes (28.5 lb) compared to the other treatments. No other significant interactions between feed additives were observed.
For the main effects of feed additive, cattle fed Renergy tended (P = 0.07) to have lower average daily gain (ADG) compared to cattle not fed Renergy (3.25 vs 3.53 lb, respectively). Hot carcass weight, dressing percentage, ribeye area, 12th rib backfat thickness, marbling score, quality grade, yield grade, and liver abscess incidence and severity were not affected (P ≥ 0.15) by the addition of Renergy to the diet.
Cattle fed Rumensin showed no differences in ADG and HCW (P ≥ 0.19) compared to cattle with no Rumensin in the diet. Cattle fed Rumensin had lower (P < 0.01) dressing percentage compared to cattle with no Rumensin in the diet. Also, cattle fed Rumensin had smaller (P = 0.02) ribeye area than cattle fed no Rumensin. Cattle fed Rumensin had greater (P = 0.04) marbling score compared to cattle not fed Rumensin (527 vs 506, respectively). When looking at 12th rib backfat thickness, cattle fed Rumensin tended (P = 0.07) to have greater backfat thickness than cattle fed no Rumensin. Calculated yield grade was greater (P = 0.01) for cattle fed Rumensin compared to cattle with no Rumensin in the diet; however, quality yield grade was not different. Liver abscess incidence and severity were not affected (P ≥ 0.18) by the addition of Rumensin in the diet.
| Treatment | Control | Renergy | Rumensin | Ren+Rum | SEM | Int.1 | Renergy2 | Rum3 |
| Performance | ||||||||
| Initial BW, lb | 888 | 891 | 887 | 889 | 2.7 | 0.98 | 0.26 | 0.63 |
| Live FBW, lb | 1318b | 1323b | 1349a | 1316b | 8.8 | 0.04 | 0.13 | 0.19 |
| Adj FBW4, lb | 1360 | 1359 | 1360 | 1339 | 7.5 | 0.19 | 0.15 | 0.21 |
| DMI, lb/d | 28.5 | 27.4 | 28.3 | 28.3 | 0.28 | 0.07 | 0.08 | 0.22 |
| ADG5, lb | 3.35 | 3.32 | 3.36 | 3.19 | 0.054 | 0.19 | 0.07 | 0.29 |
| F:G | 8.91 ab | 8.96 a | 8.71 a | 9.17 b | 0.04 | 0.47 | 0.11 | |
| Carcass characteristics | ||||||||
| HCW, lb | 857 | 856 | 857 | 844 | 4.7 | 0.19 | 0.15 | 0.2 |
| Dressing, % | 65 | 64.8 | 63.6 | 64.1 | 0.3 | 0.2 | 0.62 | 0.002 |
| LM area6 in2 | 14.4 | 14.2 | 13.9 | 14 | 0.17 | 0.48 | 0.95 | 0.02 |
| Fat, in | 0.5 | 0.51 | 0.55 | 0.53 | 0.019 | 0.56 | 0.81 | 0.07 |
| Marbling7 | 511 | 500 | 526 | 529 | 10.3 | 0.49 | 0.69 | 0.04 |
| Calc. yield grade | 2.8 | 2.86 | 3.09 | 2.96 | 0.075 | 0.24 | 0.65 | 0.01 |
| Liver abscess, % | 33.3 | 26.7 | 29.9 | 37.7 | 0.05 | 0.18 | 0.74 | 0.44 |
1 a-b Within a row, means without common superscript differ (P < 0.05) 1 P-value for the interaction between Renergy™ and Rumensin 2P-value for the main effect of Renergy™ 3P-value for the main effect of Rumensin 4 Calculated from hot carcass weight, adjusted to a common 63% dressing percentage 5 Calculated from carcass adjusted FBW 6 LM area = longissimus muscle (ribeye) area 7 Marbling score 400 = Small00; 500 = Modest00; 600 = Moderate00. | ||||||||
Conclusions
The addition of Renergy to a finishing diet tended to decrease ADG without affecting any other performance or carcass traits; while adding Rumensin to a finishing diet resulted in lower dressing percentage, smaller ribeye area, greater marbling score, greater calculated yield grade, and tended to increase 12th rib backfat thickness with no effect on ADG and HCW. Liver abscess incidence and severity were not affected by treatment.
Acknowledgment
Funding provided by Micronutrients USA.
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