Impact of sorting before feeding zilpaterol hydrochloride on feedlot performance and carcass characteristics of yearling steers.

Two studies evaluated sorting and feeding zilpaterol hydrochloride (ZH) on feedlot performance and carcass characteristics in randomized block-designed finishing trials. In Exp. 1 (initial BW 342 ± 10 kg, = 1,000), 5 treatments included an unsorted non-ZH fed negative control (-CON), an unsorted ZH fed positive control (+CON), and 3 treatments in which the heaviest 20% within the pen were sorted and marketed 28 d early and the remaining 80% were fed ZH. The 20% were identified at the beginning (EARLY), 100 d from slaughter (MIDDLE), or 50 d from slaughter (LATE). Because of sorting, the remaining steers in sorted treatments were fed 14 d longer than -CON and +CON. Average days on feed for control treatments were 165 and 173 d for the EARLY, MIDDLE, and LATE treatments. In Exp. 2 (initial BW 376 ± 29 kg, = 1,400), 4 treatments included -CON; +CON; an early weight sort fed ZH (1-SORT) with the heaviest 20% identified at d 1 and sorted 50 d from harvest and marketed 14 d before -CON and +CON, with the remaining 80% of the pen fed 7 d longer than -CON and +CON; and a 4-way sort 50 d from harvest fed ZH (4-SORT) with steers sorted into HEAVY, MID-HEAVY, MID-LIGHT, and LIGHT groups marketed -14, 0, +7, and +28 d from -CON and +CON, respectively. Average days on feed for control treatments were 154 and 157 d for the 1-SORT and 159 d for 4-SORT. Steers were fed Zilmax at 8.3 mg/kg DM for 20 d followed by a 3 d withdrawal. In Exp. 1, steers fed +CON had 13 kg greater (P < 0.01) HCW than steers fed -CON. Steers sorted EARLY, MIDDLE, and LATE had 28, 25, and 24 kg heavier ( P< 0.01) HCW than -CON steers, respectively. Carcass weight SD was greater (P = 0.01) for +CON than -CON but was not different (P = 0.17) between -CON and ZH sorted treatments. Percentage of overweight carcasses (454 kg) was greater (P ≤ 0.05) in sorted treatments than in -CON. In Exp. 2, HCW for +CON was 15 kg heavier (P < 0.01) than that for -CON, and HCW for 4-SORT was greater (P < 0.02) than that for +CON. Carcass weight SD was not different (P > 0.10) between +CON and -CON, whereas carcass weight SD of 4-SORT was reduced (P < 0.01) compared with that of -CON and +CON. Steers fed ZH had a greater percentage of carcasses over 454 kg than steers fed -CON (P < 0.01). Although not statistically different (P = 0.27), the percentage of carcasses over 454 kg was reduced by 28% for 4-SORT compared with +CON. Feeding ZH increases carcass weight, but sorting reduces variation, allowing further increases in carcass weight while minimizing overweight carcasses.

Effects of nitrogen fertilization and dried distillers grains supplementation: nitrogen use efficiency.

In a 3-yr study, 135 crossbred steers (330 ± 10 kg) were used in a randomized complete block design to evaluate corn dried distillers grains plus solubles (DDGS) fed to yearling steers as a substitute for forage and N fertilizer and its effect on N use efficiency in yearling steers grazing smooth bromegrass pastures. Steers were initially stocked at 6.8 animal unit months (AUM)/ha on nonfertilized smooth bromegrass pastures (CONT), at 9.9 AUM/ha on smooth bromegrass pastures fertilized with 90 kg of N/ha (FERT), or at 9.9 AUM/ha on nonfertilized smooth bromegrass pastures with 2.3 kg (DM) of DDGS supplemented daily per steer (SUPP). Paddock was the experimental unit, with 3 replications per treatment per year for 3 yr. Paddocks were strip-grazed, and put-and-take cattle were used to maintain similar grazing pressure among treatment paddocks during the 160-d grazing season. Steers consumed less forage (P < 0.01), but total N intake for SUPP was greater (P < 0.01) per steer and per hectare than for FERT, and both were greater (P < 0.01) than for CONT. Nitrogen retention for steers in the SUPP treatment was increased (P < 0.01) by 31% compared with N retention in the CONT and FERT treatments. Nitrogen retention per hectare for SUPP was 30 and 98% greater (P < 0.01) than N retention per hectare for FERT and CONT, respectively. Nitrogen excretion per steer and per hectare were also greater (P < 0.01) for SUPP than FERT, and both were increased (P < 0.01) compared with CONT. Animal N use efficiency was similar (P = 0.29) for steers in the CONT, FERT, and SUPP treatments. However, system-based N use improved (P < 0.01) by 144% for SUPP compared with FERT. The DDGS increased N intake and N excretion in yearling steers. However, because of improvements in BW gain and increases in stocking rate of pastures, DDGS can be a useful tool to increase the efficiency of N use in smooth bromegrass grazing systems.

Effect of feeding combinations of wet distillers grains and wet corn gluten feed to feedlot cattle.

Three experiments were conducted to evaluate the use of combinations of wet corn gluten feed (WCGF) and wet distillers grain plus solubles (WDGS) in dry-rolled and high-moisture corn-based finishing diets for beef cattle. In Exp. 1, 250 steers (BW = 343 +/- 13.5 kg) were fed 5 treatments consisting of a corn-based, control diet with 0% coproducts, and diets including 30% WCGF, 30% WDGS, 15% WCGF plus 15% WDGS, or 30% WCGF plus 30% WDGS. No associative effects resulted from feeding 15% WCGF plus 15% WDGS; DMI, ADG, and G:F were intermediate between steers fed WCGF or WDGS at 30% of diet DM. Feeding coproducts in combinations at 30 and 60% of diet DM increased ADG, G:F, and final BW (P < 0.05) compared with the corn-based diet. In Exp. 2, 280 yearling steers (BW = 370 +/- 0.45 kg) were used to evaluate feeding 0, 25, 50, or 75% coproducts as a combination of 50% WCGF:50% WDGS (DM basis). Additional diets were fed containing decreased alfalfa hay at 5, 2.5, and 0% (DM basis) as coproduct blend inclusions increased at 25, 50, and 75% (DM basis), respectively. No interactions were observed between alfalfa hay and coproduct blend levels, and no effects on ADG or G:F (P > 0.21) were observed due to alfalfa hay. Intake, ADG, and G:F responded quadratically (P < 0.05) across coproduct levels, with the greatest ADG and G:F at 25 and 50% blend, and similar ADG and G:F for the 0 and 75% blend levels. In Exp. 3, 504 steers (BW = 376 +/- 16 kg) were fed to evaluate 0, 10, 15, 20, 25, and 30% (DM basis) WDGS in diets containing 30% WCGF (DM basis) as well as a control diet with no coproducts. The inclusion of 30% WCGF in the diets increased DMI, ADG, and G:F (P < 0.05) when compared with control. Response to inclusion level of WDGS tended to be quadratic for DMI (P = 0.12), quadratic for ADG (P = 0.05), and no effect for G:F (P = 0.96). Greatest ADG was achieved with 15 to 20% WDGS inclusion in diets containing 30% WCGF. The use of combinations of WCGF and WDGS in finishing diets resulted in similar or improved steer performance compared with corn, suggesting replacement of corn with coproduct combinations up to 75% diet DM is possible if a roughage source is fed.

Manipulating grain processing method and roughage level to improve feed efficiency in feedlot cattle.

The effects of feeding finishing diets containing whole corn with no roughage on performance and carcass characteristics of feedlot steers were evaluated in 6 trials conducted at commercial research facilities (Bos Technica Research Services Inc., Salina, KS) in the Southern Plains of the United States. One hundred and two feedlot pens containing 6,895 steers were represented. All trials were designed as randomized complete blocks with pen serving as the experimental unit. Steers were fed and managed similarly across all trials. Treatments consisted of a typical control finishing diet with various grain sources and processing methods that contained roughage and a finishing diet containing whole corn (8 to 23% of diet DM) but without added roughage. Final BW was greater (P < 0.1) for steers fed typical finishing diets than for steers fed whole corn diets without roughage in 5 of the 6 trials. Feeding finishing diets containing whole corn but without roughage resulted in decreased (P < 0.1) ADG and carcass ADG in 5 of the 6 trials. However, DMI also was less (P < 0.1) for steers fed whole corn finishing diets without roughage in all trials such that feeding whole corn diets without roughage improved (P < 0.05) G:F (BW basis) in 2 of the 6 trials, and improved (P < 0.1) G:F based on carcass weight in 5 of the 6 trials. Dry matter intake as a percentage of BW daily across trials was well predicted from percentage of dietary NDF from roughage, being 1.906 + 0.0199 (+/-0.0012) NDF (P < 0.05). Performance-based NE(g) content of the diet was greater (P < 0.07) for steers fed whole corn diets without roughage. Differences in USDA yield and quality grades were inconsistent. Results indicate that feeding diets containing whole corn with no added roughage tends to decrease DMI and ADG in finishing steers, but improves feed efficiency and performance-calculated dietary NE(g).

Effects of level of condensed distillers solubles in corn dried distillers grains on intake, daily body weight gain, and digestibility in growing steers fed forage diets1.

Three experiments were conducted examining the effects of feeding different levels of dried distillers grains (DDG) and different proportions of condensed distillers solubles (CDS) added to DDG on performance and digestibility in forage-fed steers. In Exp. 1, a total of 120 individually fed crossbred steers (276 +/- 31 kg) were used in a randomized complete block design with a 4 x 5 factorial arrangement of treatments. Factors included DDG supplementation level (0.25, 0.50, 0.75, or 1.0% of BW daily) and proportion of CDS in DDG (0.0, 5.4, 14.5, 19.1, and 22.1% of DDG DM). A basal diet of 58.8% alfalfa hay, 39.2% sorghum silage, and 2% vitamin and mineral supplement (DM basis) was fed for ad libitum intake. As the level of DDG increased, intake of forage decreased linearly (P < 0.01), intake of DDG increased linearly (P < 0.01), and total DMI increased quadratically (P = 0.06). A DDG level x CDS level interaction (P < 0.01) was observed for ADG and G:F. The 0.0, 5.4, 14.5, 19.1, and 22.1% CDS treatments had the greatest ADG when DDG was supplemented at 0.75, 1.0, 1.0, 0.75, and 0.50% of BW daily, respectively. In Exp. 2, four crossbred steers (295 +/- 19 kg) were used in a 3-period switchback design. A basal diet of 58.8% alfalfa hay, 39.2% brome hay, and 2% vitamin and mineral supplement (DM basis) was fed at 95% of ad libitum intake. Treatments were DDG containing 0.0 or 22.1% CDS supplemented at 1.0% of BW daily. Apparent total tract digestibility was measured by total fecal collection. No differences between treatments were observed for digestibility of DM, OM, or NDF (P >/= 0.14). Digestibility of ether extract was greater (P = 0.02) in steers supplemented with DDG containing 22.1% CDS. In Exp. 3, two ruminally and duodenally cannulated Holstein steers (663 +/- 24 kg) were used to estimate DM and CP digestion of the DDG fed in Exp. 1 using the mobile bag technique. Basal diets were the same as fed in Exp. 1 and steers were supplemented with DDG at 0.5% of BW daily. Ruminal DM digestibility increased linearly (P < 0.01), and postruminal and total tract DM digestibility increased quadratically (P = 0.02 and P = 0.03, respectively) as the level of CDS increased. Level of CDS may affect growing steer performance because depressions in ADG and G:F were observed as intake of ether extract increased. A clear explanation for the interaction between the DDG supplementation level and the CDS level on growing steer performance was not evident in the digestion experiments.

Effects of nitrogen fertilization and dried distillers grains supplementation: forage use and performance of yearling steers.

In a 3-yr study, corn dried distillers grains plus solubles (DDGS) were evaluated as a substitute for forage and N fertilizer in yearling steers grazing smooth bromegrass. A total of 135 steers (330 +/- 10 kg) were used in a randomized complete block design to measure the effects of DDGS supplementation and N fertilization on animal and pasture performance. Steers were initially stocked at 6.8 animal unit month (AUM)/ha on nonfertilized smooth bromegrass pastures (CONT), at 9.9 AUM/ha on smooth bromegrass pastures fertilized with 90 kg of N/ha (FERT), or at 9.9 AUM/ha on nonfertilized smooth bromegrass pastures with 2.3 kg of DDGS DM supplemented daily (SUPP). Paddock was the experimental unit, with 3 replications per year for 3 yr. Paddocks were strip-grazed and put-and-take cattle were used to maintain similar grazing pressure among treatment paddocks during the 160-d grazing season. In vitro DM disappearance declined quadratically (P < 0.01), whereas CP and standing crop showed cubic responses (P < 0.01) throughout the grazing season. Crude protein was greater (P < 0.05) for FERT compared with CONT and SUPP. Standing crop was 18% greater (P < 0.01) for FERT than CONT and was 10% greater (P < 0.01) than SUPP. Adjusted stocking rates (AUM/ha) were greater (P < 0.01) for FERT and SUPP compared with CONT. Final BW were greater (P < 0.01) for SUPP steers compared with CONT and FERT steers. Similar results were observed for ADG, with SUPP steers gaining more (P < 0.01) compared with CONT and FERT steers. Total BW gain per hectare was increased (P < 0.01) by 53% with FERT and by 105% with SUPP. Feedlot ADG was similar among treatments (P = 0.88), and SUPP steers maintained their BW advantage through the finishing phase. Dried distillers grains can be used to substitute effectively for N fertilizer by increasing the performance of yearling steers grazing smooth bromegrass and increasing stocking rates compared with nonfertilized pastures.

Effect of corn processing method and corn wet distillers grains plus solubles inclusion level in finishing steers.

Two experiments were conducted to determine the effect of corn processing method and corn wet distillers grains plus solubles (WDGS) level on steer performance and metabolism. In Exp. 1, 480 crossbred steer calves (314 +/- 18 kg of BW) were used in a finishing experiment with a randomized complete block design and a 3 x 4 treatment structure. Diets were based on dry-rolled (DRC), high-moisture (HMC), or steam-flaked corn (SFC) with increasing levels of WDGS (0, 15, 27.5, or 40%; DM basis). A corn processing x WDGS level interaction (P < 0.01) was observed for ADG and G:F. Average daily gain and G:F increased linearly (P < 0.01) in steers fed DRC; ADG increased quadratically (P = 0.04) and G:F increased linearly (P = 0.02) in steers fed HMC; and ADG decreased quadratically (P = 0.02) with no change in G:F (P = 0.52) in steers fed SFC as WDGS increased. In Exp. 2, 7 ruminally fistulated steers (440 +/- 41 kg of BW) were used in a 6-period crossover design with 3 x 2 factorial treatment structure. Diets were the same as those fed in Exp. 1, except they contained only 2 levels of WDGS (0 or 40% of diet DM). Total tract starch digestibility was greater (P < 0.01) for steers fed SFC than for steers fed DRC or HMC. Minimum ruminal pH was less (P < 0.01) for steers fed SFC than for steers fed HMC or DRC. Variance of ruminal pH was different among all 3 processing methods with DRC < HMC < SFC (P < 0.10). In situ 22-h DM digestibility of DRC and HMC and starch digestibility of DRC were greater (P < 0.10) in steers fed DRC compared with steers fed HMC or SFC. Steers fed 0% WDGS had less (P < or = 0.02) intake of DM, OM, NDF, and ether extract compared with steers fed 40% WDGS. Total tract digestibility of DM and OM was greater (P < or = 0.08) and digestibility of ether extract tended (P = 0.11) to be less for steers fed 0% WDGS compared with steers fed 40% WDGS. Maximum ruminal pH and pH variance were greater (P < or = 0.08) in steers fed 0% WDGS. A corn processing x WDGS level interaction (P = 0.09) was observed for ruminal acetate to propionate ratio (A:P). Within diets containing 0% WDGS, A:P in steers fed SFC was less (P < or = 0.08). In diets containing 40% WDGS, A:P was similar between processing methods and not different from the SFC with 0% WDGS. The corn processing x WDGS level interaction observed in the finishing experiment may be due to the decreased ruminal A:P in DRC and HMC diets with 40% WDGS.

Performance and digestibility characteristics of finishing diets containing distillers grains, composites of corn processing coproducts, or supplemental corn oil.

Three experiments evaluated the lipids in distillers grains plus solubles compared with corn or other sources of lipid in finishing diets. Experiment 1 utilized 60 individually fed yearling heifers (349 +/- 34 kg of BW) fed treatments consisting of 0, 20, or 40% (DM basis) wet distillers grains plus solubles (WDGS), or 0, 2.5, or 5.0% (DM basis) corn oil in a finishing diet based on high-moisture corn (HMC) and dry-rolled corn. Cattle fed 20 and 40% WDGS had greater (P < 0.10) G:F than cattle fed 0% WDGS. Cattle fed the 5.0% corn oil had less overall performance than cattle fed the other diets. Results from Exp. 1 indicated that adding fat from WDGS improves performance, whereas supplementing 5.0% corn oil depressed G:F, suggesting that the fat within WDGS is different than corn oil. Experiment 2 used 234 yearling steers (352 +/- 16 kg of BW) fed 1 of 5 treatments consisting of 20 or 40% (DM basis) dry distillers grains plus solubles, 1.3 or 2.6% (DM basis) tallow, or HMC. All diets contained 20% (DM basis) wet corn gluten feed as a method of controlling acidosis. No differences between treatments for any performance variables were observed in Exp. 2. The dry distillers grains plus solubles may be similar to tallow and HMC in finishing diets containing 20% wet corn gluten feed. Experiment 3 used 5 Holstein steers equipped with ruminal and duodenal cannulas in a 5 x 5 Latin square design. Treatments were a 40% WDGS diet, 2 composites, one consisting of corn bran and corn gluten meal; and one consisting of corn bran, corn gluten meal, and corn oil; and 2 dry-rolled corn-based diets supplemented with corn oil or not. Cattle fed the WDGS diet had numerically less rumen pH compared with cattle fed other treatments. Cattle fed WDGS had greater (P < 0.10) molar proportions of propionate, decreased (P < 0.10) acetate:propionate ratios, greater (P < 0.10) total tract fat digestion, and a greater (P < 0.10) proportion of unsaturated fatty acids reaching the duodenum than cattle fed other treatments. Therefore, the greater energy value of WDGS compared with corn may be due to more propionate production, greater fat digestibility, and more unsaturated fatty acids reaching the duodenum.

Effects of grazing residues or feeding corn from a corn rootworm-protected hybrid (MON 863) compared with reference hybrids on animal performance and carcass characteristics.

One grazing and two feeding experiments were conducted to compare the feeding value of corn residue or corn grain from a genetically enhanced corn hybrid (corn rootworm-protected; event MON 863) with nontransgenic, commercially available, reference hybrids. In Exp. 1, two 13.7-ha fields, containing corn residues from either a genetically enhanced corn root-worm-protected hybrid (MON 863), or a near-isogenic, nontransgenic control hybrid (CON) were divided into four equal-sized paddocks. Sixty-four steer calves (262 +/- 15 kg) were stratified by BW and assigned randomly to paddock to achieve a stocking rate of 0.43 ha/steer for 60 d, with eight steers per paddock and 32 steers per hybrid. A protein supplement was fed at 0.45 kg/steer daily (DM basis) to ensure protein intake did not limit performance. Steer ADG did not differ (P = 0.30) between steers grazing the MON 863 (0.39 kg/d) and CON (0.34 kg/d) corn residues for 60 d. The four treatments for the feeding experiments (Exp. 2 and 3) included two separate reference hybrids, the near-isogenic control hybrid (CON), and the genetically enhanced hybrid (MON 863) resulting in two preplanned comparisons of CON vs. MON 863, and MON 863 vs. the average of the reference hybrids (REF). In Exp. 2, 200 crossbred yearling steers (365 +/- 19 kg) were fed in 20 pens, with five pens per corn hybrid. In Exp. 3, 196 crossbred yearling steers (457 +/- 33 kg) were fed in 28 pens, with seven pens per corn hybrid. In Exp. 2, DMI and G:F did not differ (P > 0.10) between MON 863 and CON; however, steers fed MON 863 had a greater (P = 0.04) ADG than steers fed CON. Gain efficiency was greater (P = 0.05) for MON 863 cattle than for REF cattle in Exp. 2, but other performance measurements (DMI and ADG) did not differ (P > 0.10) between MON 863 and REF. No differences (P > 0.10) were observed for performance (DMI, ADG, and G:F) between MON 863 and CON or MON 863 and REF in Exp. 3. In terms of carcass characteristics, no differences (P > 0.10) were observed between MON 863 and CON, as well as MON 863 and REF, for marbling score, LM area, or 12th rib fat thickness in both Exp. 2 and 3. Overall, performance was not negatively affected in the corn residue grazing or feedlot experiments, suggesting the corn rootworm-protected hybrid (event MON 863) is similar to conventional, nontransgenic corn grain and residues when utilized by beef cattle.