Cattle, carcass, economic, and estimated emission impacts of feeding finishing steers lubabegron or ractopamine hydrochloride.

Lubabegron (Experior; Elanco, Greenfield, IN, USA) is the first U.S. Food and Drug Administration approved feed additive for reducing gas emissions from feedlot animals or their waste; it does not have live or carcass performance claims. Our primary objective was to determine the effect of lubabegron on feedlot performance and carcass traits in finishing beef steers compared to ractopamine hydrochloride (Optaflexx; Elanco, Greenfield, IN, USA). A commercial feedlot trial using cross-bred beef steers (n = 2,117; 373 ±â€…15 kg initial body weight [BW]) was completed with a randomized complete block design. Treatments consisted of two feed additives: (1) OPT targeted to deliver 300 mg/animal/d of ractopamine hydrochloride for 28 ±â€…7 d out from harvest and (2) EXP targeted to deliver 36 mg/animal/d of lubabegron 56 ±â€…7 d out from harvest and a 4-d preslaughter withdrawal period. Twenty 70 to 142 hd pens with 10 pens per treatment were used. Cattle were weighed at arrival processing and at harvest and fed for an average of 167 d. Data were used to calculate production metrics, partial budgets, and estimated greenhouse gas emissions using published methods, and were analyzed using linear mixed models with pen as the experimental unit and block as a random intercept. A statistical significance threshold of α = 0.05 was determined a priori. There was no evidence for statistically significant differences between treatments for initial BW (P = 0.70), health-related outcomes (P values ≥ 0.43), or mobility scores (P = 0.09). Cattle-fed EXP had increased final BW, ADG, G:F, and decreased dry matter intake (P values ≤ 0.01) compared to OPT. Carcasses were 11 ±â€…1.76 kg (hot carcass weight) heavier in EXP group (P < 0.01), and differed between treatments for both yield grades (YG) and quality grades distributions (P values ≤ 0.01). Cattle-fed EXP had a shift toward more YG 1 and 2, select and sub-select carcasses compared to OPT, which had as shift toward more YG 3, 4, 5, prime and choice carcasses. With increased beef production and efficiency compared to OPT, the estimated CO2 equivalent emissions from production were reduced by 6.2% per unit of carcass weight for EXP (P ≤ 0.01). Estimated net returns/animal shipped were $56.61 ±â€…9.37 more for EXP than OPT (P ≤ 0.01). In conclusion, when cattle were fed for the same total number of days, feeding EXP compared to OPT increased net returns, feedlot performance, and efficiency, but resulted in carcass yield and quality characteristics that may impact marketing programs.

Cattle handling technique can induce fatigued cattle syndrome in cattle not fed a beta adrenergic agonist.

Angus crossbred steers (n = 40; 563 ± 44 kg) were used to examine the effects of handling method and fat thickness on the blood chemistry and physiology of market steers. Steers were blocked by backfat (BF) thickness and were randomly assigned to treatment groups: low-stress handling (LSH) and aggressive handling (AH). Cattle were then ran¬domly assigned to one of 5 blocks containing 4 steers from the LSH and AH treatments. Steers in the LSH treatment were walked and AH cattle were run through a course of 1,540 m. Blood samples were obtained via jugular venipuncture before handling (BASE), at 770 m (LAP1), at 1,540 m (LAP2), and at1 h (1H) and 2 h (2H) after finishing the course. Blood samples were analyzed for plasma lactate (LAC), creatinine kinase (CK), base excess (BE), blood pH (pH), serum cortisol (CORT) concentrations, and venous carbon dioxide (PvCO2) and oxygen (PvO2) pressures. Heart rate (HR), respiratory rate (RR), and rectal temperature (TEMP) were measured at the same intervals. Cattle in the AH treatment had greater ( < 0.05) LAC than those in LSH at BASE (4.1 vs. 3.0 mmol/L), LAP1 (16.5 vs. 2.3 mmol/L), LAP2 (22.3 vs. 2.4 mmol/L), 1H (7.2 vs. 2.7 mmol/L), and 2H (4.0 vs. 2.5 mmol/L), respectively. Creatinine kinase and RR were not different (P > 0.14). Blood pH in AH cattle was decreased compared with that in LSH cattle ( < 0.05) at LAP1 (7.25 vs. 7.45) and LAP2 (7.19 vs. 7.48) but was not different ( > 0.13) at BASE, 1H, or 2H. Heart rate and TEMP were increased in AH cattle compared to LSH ( > 0.01). Serum cortisol was increased ( < 0.05) in AH compared to that in LSH cattle at LAP1 (87.5 vs. 58.9 nmol/L), LAP2 (144.4 vs. 93.1 nmol/L), and 1H (113.5 vs. 53.1 nmol/L). Although RR was not differ¬ent between LSH and AH, PvCO2 was decreased in AH compared to that in LSH ( < 0.05) at LAP2 (30.6 vs. 39.3 mmHg) and PvO2 was increased at LAP1 (42.7 vs. 33.5 mmHg) and at LAP2 (51.5 vs. 36.6 mmHg). Lactate was increased in AH cattle in the thicker BF group at 1H ( < 0.05), and blood pH was decreased at LAP1, LAP2, and 1H ( < 0.05) compared to the thinner BF cohorts. Four AH steers became exhausted (EXH) and did not complete the course. Increased CK, decreased PvCO2, and muscle tremors occurred in EXH steers compared to non-exhausted AH cohorts. Results of this study show that AH causes physiologic and blood chemistry changes in steers, which can be potentially detrimental to cattle, emphasizing the need for low-stress handling practices.

Effects of the Programmed Nutrition Beef Program on feedlot performance and carcass characteristics.

The objective of this study was to examine the effects of alternative finishing strategies on feedlot performance and carcass characteristics. Beef steers (64 pens; 8 steers/pen) were allocated to a randomized complete block design with a 2 × 2 factorial treatment arrangement. Factor 1 consisted of diet, with cattle fed a conventional (CON) diet or a diet consisting of Programmed Nutrition Beef Program (PN) supplements. The PN treatment included Programmed Nutrition Beef Receiver fed from d 1 through 20 of feeding and Programmed Nutrition Beef Finisher fed from d 21 to harvest. Factor 2 evaluated the presence (EGP+) or absence (EGP-) of exogenous growth promotants (ExGP) in the production system. Steers in the EGP+ treatments were initially implanted with Component E-S, reimplanted with Component TE-IS, and fed 400 mg·animal·dof ractopamine hydrochloride for the final 28 d before harvest. Steers were harvested on d 175, and strip loins were removed from 2 carcasses selected at random from each pen for transport to Kansas State University. One 1.27-cm-thick steak was removed from the anterior face for proximate and long-chain fatty acid analysis. There were no diet × ExGP interactions ( > 0.10) for feedlot performance except for DMI ( = 0.02). Steers in the PN/EGP+ treatment consumed more feed than all other treatments ( < 0.05). Both diet and ExGP affected DMI ( < 0.05), with PN and EGP+ steers consuming more feed than their contemporaries. Gain:feed and ADG were unaffected ( > 0.10) by diet, but ExGP improved these measures ( < 0.01). There were no diet × ExGP interactions for carcass characteristics except KPH fat and percentages of yield grade 3 and 4 carcasses ( < 0.05). Diet affected total incidence of liver abscesses because PN steers had a greater ( = 0.05) incidence of liver abscesses than steers in the CON treatment. Diet did not affect the other carcass characteristics ( > 0.10). Use of ExGP increased ( < 0.05) HCW, LM area, and 12th-rib fat but did not affect ( > 0.10) marbling score. Using ExGP reduced the percentage carcasses grading Premium Choice ( < 0.05). No diet × ExGP interactions or diet effects were detected for long-chain fatty acid profiles ( > 0.10). Use of ExGP increased ( < 0.05) the ratio of saturated:unsaturated fatty acids. In summary, the alternative feeding strategy presented in this study produced similar feedlot performance and carcass characteristics compared with a conventional feedlot system.

Feeding zilpaterol hydrochloride is associated with decreased dry matter intake shortly after initiation of feeding dependent on season and previous intake.

A database of daily feed deliveries for steers and heifers fed at 3 commercial feedyards in Kansas between January 1, 2010, and January 31, 2012 (n = 1,515 pens), was used to investigate the prevalence and extent of changes in DMI after initiation of feeding zilpaterol hydrochloride (ZIL) at 8.3 mg/kg (DM) for 20 d. Season affected the percentage of pens experiencing a decrease in DMI post-ZIL (P < 0.01), but there were significant (P < 0.01) season × sex, season × feedyard, season × pre-ZIL DMI, season × days post-ZIL, and season × period post-ZIL interactions. Average DMI decreased within 1 d after initiation of ZIL feeding in all seasons; however, this initial decrease was greater (P < 0.01) in the summer (-0.30 kg) and winter (-0.27 kg) than in the spring (-0.05 kg) or fall (-0.06 kg). The decrease in DMI averaged across all days post-ZIL was greater in summer than during other seasons for both steers and heifers, and the change in intake was greater in steers than heifers in all seasons but fall. Size of intake change within each season varied by feedyard and by season. The percentage of pens that had a large DMI decrease (≥ 0.9 kg/d) was greatest during the summer (33%), and the percentage of pens with no decrease was the least (15%); during the fall, 34% of pens had no DMI decrease and only 8% of pens had a large decrease in DMI. Intake before ZIL initiation affected size and prevalence of DMI decrease; with increasing pre-ZIL DMI, the percentage of pens with a decrease increased from 62% for pens with pre-ZIL DMI of less than 7.7 kg/d to 82% for pens consuming greater than 10.5 kg/d pre-ZIL (P < 0.01). Of those pens with greater than 10.5 kg/d pre-ZIL DMI, 27% had DMI decrease of greater than 1.4 kg/d compared to only 3% for pens consuming <8.7 kg/d pre-ZIL. The average dosage of ZIL consumed per animal with an average DMI of 7.3, 8.2, 9.1, 10.0, and 10.9 kg/d was calculated to be 61, 68, 76, 83, and 91 mg/animal daily, which may be related to the differences in DMI decrease. Pre-ZIL DMI contributed to DMI decrease during ZIL administration, but the increased occurrence and size of DMI decrease during the summer may indicate an additional physiological mechanism.

Effects of the Programmed Nutrition Beef Program on meat quality characteristics.

The objective of this study was to examine the effects of alternative finishing strategies on beef steak color and cooked meat characteristics. Beef steers (n = 64 pens; 8 steers/pen) were allocated to a randomized complete block design with a 2 × 2 factorial treatment arrangement and initial body weight serving as the blocking factor. Factor 1 consisted of dietary treatment with cattle either being fed a conventional feedlot diet (CON) or a diet that included Programmed Nutrition Beef Program supplements. Cattle in the Programmed Nutrition (PN) treatments were fed in two-stages: 1) the basal diet with Programmed Nutrition Beef Receiver from d 1 to 20 and the basal diet with Programmed Nutrition Beef Finisher from d 21 to harvest. Factor 2 consisted of the inclusion (EGP+) or absence (EGP-) of an exogenous growth promoting program. Steers in the EGP+ treatments were implanted initially with Component E-S, reimplanted with Component TE-IS, and fed 400 mg · d(-1) · steer(-1) of ractopamine hydrochloride for the final 28 d before harvest. Steers were harvested on d 175 of feeding and 1 strip loin was removed from 2 carcasses selected at random from each pen for transport to Kansas State University. After 14 d of aging, loins were fabricated into 2.54-cm thick steaks for objective and trained sensory panel measurement of cooked meat characteristics and objective color measurements during 7 d retail display. There were no interactions (P > 0.10) between feeding strategy and exogenous growth promotants for all objective measures of color and cooked meat characteristics. Throughout the display period, PN steaks were darker (P = 0.02) than CON steaks, but surface percentages of oxymyoglobin and metmyoglobin and metmyoglobin reducing ability were unaffected by feeding strategy (P > 0.10). Loins and steaks from PN cattle possessed decreased moisture loss during aging and cooking (P < 0.01). Trained sensory panel evaluation of cooked meat revealed a dietary program × growth promotant interaction for myofibrillar tenderness, connective tissue amount, and overall tenderness (P = 0.01). Compared to the CON/EGP- and PN/EGP- treatments, steaks from the CON/EGP+ and PN/EGP+ treatments were evaluated by panelists as being less myofibrillar and overall tender (P < 0.05). The alternative feeding strategies presented in this study can favorably impact water-holding capacity without negatively compromising retail display discoloration.

Dried distillers grains with solubles with reduced corn silage levels in beef finishing diets.

Two finishing experiments were conducted to evaluate the use of 25% dried corn distillers grains with solubles (DDG) in beef cattle finishing diets by partially replacing a portion of the grain and soybean meal in the control diets. In Exp.1, crossbred heifers (n = 377; BW 378 +/- 4.1 kg) were fed diets consisting of steam-flaked corn (SFC) with a control diet containing 0% DDG and 15% corn silage (CS), 25% DDG and 15% CS, or 25% DDG and 5% CS. Compared with the control treatment, heifers fed DDG and 15% CS had a greater proportion of USDA yield grade 4 and 5 carcasses (P = 0.04; 5.68 vs. 14.12), and smaller LM area (P = 0.04; 86.09 vs. 82.48 cm(2)). In Exp. 2, crossbred heifers (n = 582; BW = 377 +/- 27.09 kg) were fed diets similar to Exp. 1 except dry-rolled corn (DRC) and SFC were compared as the basal grain sources. Treatments included DRC or SFC: with control diets containing 0% DDG and 15% CS, 25% DDG and 15% CS, or 25% DDG and 5% CS. Feeding SFC decreased DMI (P < 0.01), improved G:F (P < 0.01) and final shrunk BW (P = 0.05) compared with DRC. Average USDA yield grade was greater for cattle fed DRC than for those fed SFC (P = 0.02), but calculated yield grade was not different among treatments (P = 0.71). Feeding DDG and 5% CS, regardless of grain source, led to decreased DMI and greater G:F than feeding DDG and 15% CS (P = 0.02). When comparing the control treatments with the diets containing 25% DDG and 15% CS shrunk final BW, ADG, and G:F were decreased (P < or = 0.05); however, carcass-adjusted measurements were not different (P > 0.52). Results indicate that roughage levels can be reduced in feedlot diets containing 25% DDG with no adverse effects on BW gain, feed efficiency, or carcass quality.

Evaluation of dried distillers grains and roughage source in steam-flaked corn finishing diets.

Two studies were conducted to evaluate effects of dried distillers grains with solubles (DDGS) and alfalfa hay (AH) or corn silage (CS) on feedlot performance, carcass characteristics, ruminal fermentation, and diet digestibility in cattle fed steam-flaked corn (SFC) diets. In trial 1, crossbred heifers (n = 358; BW = 353 +/- 13 kg) were used in a finishing trial to evaluate interactions between corn-DDGS and roughage source (AH or CS) in terms of impact on feedlot performance and carcass characteristics. Experimental diets (DM basis) consisted of SFC and 11% CS without DDGS (SFC-CS), SFC and 11% CS with 25% DDGS (DDGS-CS), SFC and 6% AH without DDGS (SFC-AH), and SFC with 25% DDGS and 6% AH (DDGS-AH). Heifers were fed for ad libitum intake once daily for 97 d. Results indicated no interaction between DDGS and roughage source with respect to animal performance. Feeding DDGS did not affect ADG (P = 0.19), DMI (P = 0.14), or feed conversion (P = 0.67). Heifers fed CS had greater DMI than those fed AH (P = 0.05), but ADG (P = 0.56) and G:F (P = 0.63) were not different. There were no differences among treatments with respect to HCW, dressing percentage, subcutaneous fat thickness, quality grades, or yield grades (P > 0.20). Cattle fed CS tended (P = 0.10) to have greater marbling scores than those fed AH. There was an interaction (P = 0.02) between roughage and DDGS with respect to incidence of liver abscess. The greatest incidence was observed in cattle fed diets without DDGS when CS was fed, and the least was observed in cattle fed diets without DDGS when AH was used. In the second trial, ruminal fermentation characteristics and diet digestibility were examined in 12 cannulated Holstein steers fed similar diets to those fed in the finishing trial. Ruminal pH for all treatments was below 5.8 for 14 h after feeding. Acetate:propionate ratios were less (P = 0.02) in steers fed 25% DDGS but had greater (P = 0.02) ruminal lactate concentrations compared with cattle fed 0% DDGS. Feeding 25% DDGS decreased (P < 0.01) ruminal ammonia concentrations, and digestion of DM and OM was less (P < 0.01) compared with diets without DDGS. The decrease in digestibility was largely attributable to decreases in digestion of CP (P = 0.03) and NDF (P < 0.01). Feeding strategies aimed at increasing ruminal pH and ruminally available protein may improve digestion of DDGS in steam-flaked corn-based finishing diets.

Effects of increasing levels of dried corn distillers grains with solubles on growth performance, carcass characteristics, and meat quality of yearling heifers.

Three hundred forty-seven crossbred heifers (330 +/- 11 kg initial BW) were used in a randomized complete block study to identify the optimal level of dried corn distillers grains with solubles (DGS) in flaked corn finishing diets. Fifty-four pens were used, with 9 pens per treatment and 6 to 7 heifers per pen. Finishing diets were steam-flaked corn-based and were fed once daily for 148 d. Dietary treatments consisted of 6 levels of DGS (0, 15, 30, 45, 60, and 75%, DM basis). Dry matter intake, ADG, and final BW responded quadratically (P < or = 0.03) to increasing levels of DGS and were maximized at 15% DGS. However, G:F decreased linearly (P = 0.01) as level of DGS increased. Longissimus muscle areas were not different (P > or = 0.27), whereas 12th-rib fat thicknesses decreased linearly (P = 0.05) for heifers fed increasing levels of DGS. Marbling score and USDA yield grades were not different (P > or = 0.06) for heifers fed different levels of DGS. Number of carcasses grading USDA Prime or Choice were not different (P > or = 0.07), whereas number of carcasses grading USDA Select increased (P = 0.02; linear) as dietary level of DGS increased from 0 to 75%. Myofibrillar and overall tenderness increased linearly (P = 0.01) as dietary level of DGS increased from 0 to 75%. Juiciness, off-flavor intensity, and thiobarbituric acid reactive substances were not different (P > or = 0.16) among treatments. Redness of steaks (i.e., a*) was not different (P > or = 0.13) for steaks collected from heifers fed different levels of DGS as evidenced by similar instrumental color measurements after d 0, 3, and 5 of display. However, on d 7, steak color was less red (P = 0.04) and had more metmyoglobin. Concentration of linoleic acid (18:2n-6cis), total n-6 fatty acids, and total PUFA linearly increased (P = 0.01) with increasing levels of DGS.

Optimizing use of distillers grains in finishing diets containing steam-flaked corn.

Two hundred ninety-nine crossbred yearling steers (363 +/- 15 kg initial BW) were fed for an average of 114 d in a finishing study comparing 7 diets in which steam-flaked corn was used as the principal energy source. Forty-nine pens were used in this study with 7 BW blocks, 7 pens per treatment, and 5 to 7 steers per pen. A control diet with no distillers grains with solubles (DGS) was compared with 6 diets containing 15% DGS (DM basis). The diets contained wet sorghum DGS with 0 or 6% alfalfa hay, dried sorghum DGS with 0 or 6% alfalfa hay, wet corn DGS with 6% alfalfa hay, or dried corn DGS with 6% alfalfa hay. Apparent total tract digestibilities were calculated by total collection of fecal material from the concrete-surfaced pens over a 72-h period. Dry matter intake, ADG, G:F, and carcass characteristics were similar (P > or = 0.18) for steers fed finishing diets with or without 15% DGS. However, apparent total tract digestibilities of DM and OM were 2.8% less (P < or = 0.03) for finishing diets containing 15% DGS (DM basis). Dry matter intake, ADG, G:F, apparent total tract digestibility, and carcass characteristics were not different (P > or = 0.09) for steers fed finishing diets containing sorghum or corn DGS. Dry matter intake, ADG, G:F, apparent total tract digestibility, and carcass characteristics also were not different (P > or = 0.10) for steers fed finishing diets containing wet or dried DGS. Steers fed sorghum DGS with 6% hay consumed more DM (P < 0.01) and gained more BW (P < 0.01) than steers fed diets without hay, but G:F were not different (P > 0.78). Sorghum DGS diets containing alfalfa hay were 4% less (P = 0.01) digestible than sorghum DGS diets containing no hay. Carcasses of steers fed sorghum DGS diets without hay were lighter, leaner, and had decreased USDA yield grades (P = 0.01) compared with steers fed sorghum DGS diets containing hay. Feeding moderate levels (i.e., 15%, DM basis) of DGS resulted in growth performance and carcass characteristics similar to those of cattle fed no DGS. In addition, sorghum- and corn-based DGS had similar feeding values, and wet (approximately 31% DM) and dried (approximately 91% DM) DGS also had similar feeding values. Complete removal of alfalfa hay in diets containing DGS improved diet digestibility but reduced growth performance and carcass finish.

The effects of feeding flaxseed during the receiving period on morbidity, mortality, performance, and carcass characteristics of heifers.

Two experiments were conducted at the Kansas State University Beef Cattle Research Center to determine the effects of feeding ground flaxseed (flax) during the receiving period on the growth, health, and subsequent finishing performance of heifers. Crossbred heifers (Exp. 1: n = 363, 214 +/- 1 kg of initial BW; Exp. 2: n = 377, 222 +/- 1 kg of initial BW) were purchased during January and April of 2006. Heifers were fed receiving rations based on steam-flaked corn with 0, 2, 4, or 6% ground flax (DM basis) for 56 d. Following the receiving period, cattle in Exp. 1 and 2 were fed steam-flaked corn-based diets for 150 and 147 d, respectively, and then slaughtered. Heifers were implanted 91 and 109 d before slaughter for Exp. 1 and 2, respectively. In Exp. 1, DMI during the receiving period tended to increase linearly (P = 0.09) with increasing flax in the diet. Average daily gain was 1.46, 1.56, 1.58, and 1.61 kg for heifers fed 0, 2, 4, and 6% flax, respectively (linear, P = 0.03). Final BW in Exp. 1 after the finishing period was increased (linear, P = 0.04) with increasing inclusion of flax in the receiving diets. In Exp. 2, growth performance and mortality during the receiving period were not different among treatments (P > 0.12). During the receiving period in Exp. 2, incidence of the first respiratory treatment tended to be greatest (P = 0.09) for heifers fed 4% flax. During the finishing period, DMI were 8.4, 8.4, 8.0, and 8.1 kg/d for 0, 2, 4, and 6% flax, respectively (linear, P = 0.05). In Exp. 2, LM areas were greatest (quadratic, P = 0.04) for cattle fed 2% flax at receiving. In general, feeding flax during the receiving period may have the potential to improve growth performance; however, performance between experiments was variable, and many factors excluding flax feeding may have contributed to this response.

Efficacy of monensin and tylosin in finishing diets based on steam-flaked corn with and without corn wet distillers grains with solubles.

Three hundred seventy-one crossbred-yearling heifers (299 +/- 9 kg initial BW) were obtained from a common source and used in a randomized complete-block designed finishing study. A 2 x 3 factorial arrangement of treatments was used with one factor being diet: based on steam-flaked corn finishing diet (SFC) or SFC plus 25% (dry basis) corn wet distillers grains with solubles (WDGS). The second factor was feed additives: no added antibiotics (NONE), 300 mg of monensin daily (MONENSIN), or 300 mg of monensin + 90 mg of tylosin daily (MON+TYL). Main effect of diet resulted in no difference in DMI (P = 0.34). Heifers fed SFC gained 9% faster (P = 0.01) and were 7% more efficient (P = 0.01) than heifers fed WDGS. In addition, heifers fed SFC had 3% heavier (P = 0.01) HCW; 1% greater (P = 0.01) dress yield; and had 3% larger (P = 0.05) LM area. Marbling score and carcasses that graded USDA Choice or better were both greater (P /= 0.12) among feed additive treatments. Kidney, pelvic, and heart fat and s.c. fat thickness at the 12th rib were also not different (P >/= 0.55) for main effects of diet and feed additive. There was a tendency (P = 0.09) for a diet x feed additive interaction for the most severe (A+) liver abscesses. Heifers fed NONE yielded the greatest percentage (16%) of A+ livers in the SFC treatment, whereas heifers fed MON+TYL yielded the greatest percentage (10%) in the WDGS treatment. Including wet distillers grains with solubles in diets based on steam-flaked corn decreased finishing heifer performance, HCW, and marbling. Tylosin addition tended to decrease severity of liver abscesses in diets containing SFC, but not in diets containing WDGS. These data indicate that monensin and tylosin may not be as effective when used in steam-flaked corn diets with 25% WDGS.

Corn distillers grains with solubles derived from a traditional or partial fractionation process: Growth performance and carcass characteristics of finishing feedlot heifers.

Six hundred ten crossbred-yearling heifers (347 +/- 5 kg of initial BW) were obtained and used in a randomized complete-block design finishing study. Finishing diets were based on steam-flaked corn and ground alfalfa hay. The control (CONT) treatment contained no distillers grains with solubles (DGS), the second diet was formulated to contained 13% (DM basis) dried corn DGS derived from a traditional dry-grind ethanol process (TRAD), and the third diet was formulated to contained 13% (DM basis) dried corn DGS derived from a partial fractionation dry-grind process (FRAC). Dry matter intake, ADG, and gain efficiency were not different (P >/= 0.48) for yearling heifers fed CONT when compared with heifers fed DGS. Heifers fed TRAD consumed more (P = 0.01) feed than heifers fed FRAC. However, ADG and feed efficiency were not different (P >/= 0.07) for heifers fed DGS. Moderate inclusion levels of DGS in finishing flaked corn diets yielded satisfactory performance. Growth performance was not different for heifers fed DGS originating from either ethanol processing method.

The effects of ractopamine-hydrogen chloride (Optaflexx) on performance, carcass characteristics, and meat quality of finishing feedlot heifers.

Two experiments were conducted at the Kansas State University Beef Cattle Research Center to determine the effects of ractopamine-HCl (Optaflexx) on growth performance, carcass characteristics, and meat quality of finishing feedlot heifers. In Exp. 1, heifers implanted with Revalor-H (n = 302, initial BW = 479 kg) were fed steam-flaked corn diets with 0 (control) or 200 mg of ractopamine-HCl (OPT) per heifer daily for 28 d before slaughter. Average daily gain and DMI were not different between treatments (P > 0.17); however, OPT cattle tended to have a greater G:F (P = 0.06). Treatments did not differ with respect to final BW, HCW, dressing percentage, USDA yield grade, USDA quality grade, marbling score, LM area, KPH, Warner-Bratzler shear force, weight loss during cooking, or L*, a*, or b* colorimetric values during a 7-d retail display or purge loss from loin steaks during retail display (P > 0.19). In Exp. 2, nonimplanted crossbred heifers (n = 281, BW = 451 +/- 2 kg) were fed finishing diets based on steam-flaked corn. A control diet (no ractopamine) was compared with diets providing 200 mg of OPT per heifer daily for periods of 28 or 42 d (200 x 28 and 200 x 42, respectively), 300 mg/d for 28 d (300 x 28), and a step-up regimen consisting of 14 d at 100 mg, followed by 14 d at 200 mg, and the final 14 d at 300 mg of OPT (step-up). Feeding OPT had no effect on carcass weight gain among treatments (P = 0.18). The efficiency of carcass gain was 34 and 35% greater (P = 0.06) for the 200 x 42 and step-up groups compared with control, respectively. Feeding OPT at 300 mg for 28 d reduced DMI compared with the control, 200 x 28, and 200 x 42 (P < 0.05) groups. Administration of OPT had no effect on marbling score, yield grade, LM area, KPH, or percentages of carcasses grading USDA Choice (P > 0.10). Feeding ractopamine-HCl (Optaflexx) to finishing heifers generally improved the efficiency of carcass gain with minimal effect on carcass characteristics. These effects were most pronounced in heifers fed ractopamine for 42 d.

Influence of processed grains on fecal pH, starch concentration, and shedding of Escherichia coli O157 in feedlot cattle.

Manipulation of cattle diets has been proposed as a possible preharvest control measure for Escherichia coli O157. Altering hindgut fermentation through diet changes may be a means to reduce fecal shedding of E. coli O157. In Exp. 1, the objective was to determine whether fecal shedding of E. coli O157 was related to fecal starch concentration. Beginning on d 20, and every week thereafter until d 61, steers in 54 pens (6 to 7 steers per pen) were sampled (n = 122) by fecal collection and rectoanal mucosal swabs (RAMS) for E. coli O157 and fecal starch concentration determinations. Escherichia coli O157 prevalence was 3.3% in fecal samples, 4.1% as measured by RAMS, and 4.9% by fecal or RAMS samples. Steers positive for E. coli O157 contained 21% more (P < 0.05) fecal starch than steers that were negative for E. coli O157. In Exp. 2, we attempted to alter the concentration of starch escaping rumen fermentation by feeding finishing diets based on steam-flaked corn (SFC) and dry-rolled corn (DRC) to 30 heifers prescreened for being culture positive for fecal E. coli O157. Beginning on d 13, heifers were sampled (feces and RAMS) weekly to monitor fecal pH and starch concentration, and prevalence of E. coli O157. Prevalence of E. coli O157 remained above 30% for the first 13 d, but declined (P < 0.05) over the entire 7-wk period. Based on RAMS, the prevalence of E. coli O157 tended to be greater (P = 0.08) for heifers fed SFC than for those fed the DRC diet. After d 20, heifers fed DRC had greater (P < 0.05) fecal starch and lower (P < 0.05) fecal pH than heifers fed SFC. Fecal pH was negatively correlated (r = - 0.34; P < 0.05; n = 143) with fecal starch concentration. Fecal starch concentration and pH were not different (P > 0.05) for heifers that were positive or negative for E. coli O157. Our data suggest that fecal shedding of E. coli O157 was not related to fecal pH or starch concentration in cattle fed grain-based diets.

Effects of melengestrol acetate on the inflammatory response in heifers challenged with Mannheimia haemolytica.

Previous research from our laboratory has indicated that melengestrol acetate (MGA) added to the diet during the first 35 d after arrival in the feedlot improves growth rates and tends to reduce chronic respiratory disease in heifers naturally challenged with bovine respiratory disease. The current study was conducted to provide further insight into the possible immunomodulatory effects of MGA. Crossbred heifers (n = 48; 232 +/- 5.5 kg of BW) were used in a randomized complete block design to determine the effects of MGA on lung pathology and markers of inflammation after Mannheimia haemolytica challenge. On d 0, cattle were blocked by BW and randomly assigned, within block, to diets (54% concentrate) that provided 0 or 0.5 mg of MGA per heifer daily for the duration of the experiment. Inoculum containing from 1.3 x 10(9) to 1.7 x 10(9) cfu of M. haemolytica (20 mL) was instilled at the bifurcation of the trachea on d 14. Blood samples were collected, clinical observations were made, and rectal temperatures were recorded for each animal at 0, 12, 24, 48, 72, 96, 120, and 138 h after inoculation. Heifers fed MGA had greater circulating concentrations of eosinophils and postchallenge concentrations of segmented neutrophils and white blood cells (P < 0.01) than controls, as well as elevated plasma protein, serum haptoglobin, and fibrinogen after M. haemolytica challenge (P < 0.01). Heifers fed MGA had lower plasma glucose (P < 0.01), greater plasma urea N (P = 0.02), and elevated respiratory indices (P < 0.01) compared with controls. Necropsies performed on d 6 after inoculation suggested that M. haemolytica challenge was relatively mild, because lesions were confined to a small portion of the lungs. On a 0 to 100 scale, average lung lesion scores were 3 and 1 for MGA-fed and control groups, respectively (P < 0.06). Heifers fed MGA before mild M. haemolytica challenge were more susceptible to infection, as evidenced by a greater number of heifers fed MGA exhibiting pulmonary lesions 138 h after inoculation than controls (14 out of 23 vs. 6 out of 24 for MGA and controls, respectively; P < 0.02).

Dry-rolled or steam-flaked grain-based diets and fecal shedding of Escherichia coli O157 in feedlot cattle.

Hindgut is a major colonization site for Escherichia coli O157 in cattle. In this study, diets were formulated to effect changes in hindgut fermentation to test our hypothesis that changes in the hindgut ecosystem could have an impact on fecal shedding of E. coli O157. Feedlot heifers (n = 347) were prescreened for the prevalence of E. coli O157 by fecal and rectoanal mucosal swab cultures. A subset of 40 heifers identified as being positive for fecal shedding of E. coli O157 was selected, housed in individual pens, and randomly allocated to 4 dietary treatments. Treatments were arranged as a 2 x 2 factorial, with factor 1 consisting of grain type (sorghum or wheat) and factor 2 being method of grain processing (steam-flaking or dry-rolling). Four transition diets, each fed for 4 d, were used to adapt the animals to final diets that contained 93% concentrate and 7% roughage. The grain fraction consisted of dry-rolled sorghum, steam-flaked sorghum, a mixture of dry-rolled wheat and steam-flaked corn, or a mixture of steam-flaked wheat and steam-flaked corn. Wheat diets contained 52% wheat and 31% steam-flaked corn (DM basis). Fecal and rectoanal mucosal swab samples were obtained 3 times a week to isolate (enrichment, immunomagenetic separation, and plating on selective medium) and identify (sorbitol negative, indole production, and agglutination test) E. coli O157. The data were analyzed as repeated measures of binomial response (positive or negative) on each sampling day. Method of processing (dry-rolled vs. steam-flaked), sampling day, and the grain type x day interaction were significant (P < 0.05), but not the method of processing x grain type interaction. The average prevalence of E. coli O157 from d 9 was greater (P < 0.001) in cattle fed steam-flaked grains (65%) compared with those fed dry-rolled grains (30%). Average prevalence in cattle fed sorghum (51%) or wheat (43%) were similar (P > 0.10) on most sampling days. Results from this study indicate that feeding dry-rolled grains compared with steam-flaked grains reduced fecal shedding of E. coli O157. Possibly, dry-rolling allowed more substrate to reach the hindgut where it was fermented, thus making the hindgut inhospitable to the survival of E. coli O157. Dietary intervention to influence hindgut fermentation offers a simple and practical mitigation strategy to reduce the prevalence of E. coli O157 in feedlot cattle.

Effects of ractopamine and protein source on growth performance and carcass characteristics of feedlot heifers.

An experiment was conducted to determine the relationship between feeding ractopamine and different amounts of MP on growth and carcass characteristics of feedlot heifers. Seventy-two crossbred heifers (475 kg of initial BW) were fed individually a diet based on steam-flaked corn for ad libitum intake for 29 d. Heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17beta 60 d before the experiment. Treatments were arranged as a 2 x 3 factorial and included 0 or 200 mg of ractopamine-HCl (23 ppm)/ d, and urea, solvent soybean meal, or expeller soybean meal (ESBM) as the predominant protein supplement. The amounts of MP supplied by the urea, solvent soybean meal, and ESBM diets were 688, 761, and 808 g/ d, respectively, calculated according to level 1 of the NRC model. Body weights were obtained 1 d before ractopamine feeding and at slaughter. Blood samples were obtained 1 d before starting the experiment and 13 d later. Ractopamine improved ADG, efficiency of gain, carcass-adjusted ADG, and carcass-adjusted efficiency of gain (P < 0.01). For ADG, heifers demonstrated a ractopamine x protein source interaction (P < 0.05); heifers not fed ractopamine had greater ADG when fed ESBM than when fed urea, whereas for heifers fed ractopamine there were no differences (P > or = 0.10) among protein supplements. This interaction was not observed for carcass-adjusted ADG (P = 0.60). Final live weights (P = 0.02) and carcass weights (P = 0.01) were greater with ractopamine feeding. Carcass marbling scores and yield grades were not affected by ractopamine or protein source (P > or = 0.39). Plasma total alpha-amino N and glucose concentrations decreased more from pretreatment concentrations when heifers were fed ractopamine (P < 0.05). Feeding ractopamine to heifers for 28 d before slaughter improved ADG and efficiency of gain without any large effects on carcass characteristics. The MP supply does not need to be increased from that provided by finishing diets based on steam-flaked corn with urea as the primary N supplement to allow the maximal response to ractopamine by finishing heifers.

Influence of steam-flaked corn moisture level and density on the site and extent of digestibility and feeding value for finishing cattle.

Performance and digestibility experiments were conducted to determine the influence of moisture and flake density (FD) on the feeding value of steam-flaked corn (SFC). Dietary treatments consisted of finishing diets that contained 78% (DM basis) SFC that was tempered using 0, 6, or 12% moisture and processed to either 360 (SF28) or 310 (SF24) g/L. A 3 x 2 factorial arrangement of treatments was used. In Exp. 1, 78 steers were individually fed the respective treatments for 106 d. Moisture added during tempering tended (linear; P < 0.10) to increase starch availability but linearly decreased (P < 0.01) particle size. Decreasing flake density increased (P < 0.001) starch availability and also decreased (P < 0.001) particle size. Starch availability (P < 0.001), moisture (P < 0.001), and particle size (P = 0.05) were all greater for SFC that was collected the day of processing compared with SFC that had been processed the previous day. Steers fed diets containing SF24 consumed less DM as the moisture level increased, whereas steers fed diets containing SF28 had increased DMI as moisture level increased (moisture x FD interaction; P < 0.01). Nonetheless, ADG, G:F, and most carcass characteristics did not differ among treatments. In Exp. 2, 6 multicannulated Jersey steers were used in a 6 x 6 Latin square using the same treatments as in Exp. 1. Increasing moisture intake linearly decreased (P < 0.05) starch intakes. Organic matter and N intakes followed similar trends but were not different. Decreasing FD tended to increase (P < 0.10) microbial N flow to the duodenum and increased microbial efficiency (P < 0.05). Ruminal starch digestibility was 90.5%, and total tract starch digestibility was 99.5% without adding moisture or processing beyond SF28. Moisture additions to corn before steam flaking resulted in few differences in performance or digestibility, despite increases in starch availability that occurred as moisture increased. Processing corn more extensively than SF28 may be unnecessary and cost-prohibitive.

Comparison of rectoanal mucosal swab cultures and fecal cultures for determining prevalence of Escherichia coli O157:H7 in feedlot cattle.

We compared fecal samples with samples collected with rectoanal mucosa swabs (RAMS) to determine the prevalence of Escherichia coli O157 in feedlot cattle (n = 747). Escherichia coli O157 was detected in 9.5% of samples collected with RAMS and 4.7% of samples tested by fecal culture. Pulsed-field gel electrophoresis analysis of isolates suggested that the strains colonizing the rectoanal junction were the same as those from the feces. Mucosal swab sampling was more sensitive than fecal sampling for determining the prevalence of E. coli O157 in feedlot cattle.

Effects of dried full-fat corn germ and vitamin E on growth performance and carcass characteristics of finishing cattle.

Two experiments were conducted to evaluate dried full-fat corn germ (GERM) as a supplemental fat source in cattle finishing diets. In Exp. 1, 24 pens totaling 358 crossbred beef steers with an initial BW of 319 kg were allowed ad libitum access to diets containing dry-rolled corn, 35% wet corn gluten feed, and 0, 5, 10, or 15% GERM on a DM basis. Increasing GERM decreased (linear; P < 0.02) DMI and increased (quadratic; P < 0.02) ADG. Steers fed 10% GERM had the greatest ADG (quadratic; P < 0.02) and G:F (quadratic; P < 0.05). The addition of GERM increased (linear; P < 0.05) fat thickness, KPH, and the percentage of USDA Yield Grade 4 carcasses (quadratic; P < 0.03), with steers fed 15% GERM having the greatest percentage of USDA Yield Grade 4 carcasses. In Exp. 2, 48 pens totaling 888 crossbred beef heifers with an initial BW of 380 kg were allowed ad libitum access to diets containing steam-flaked corn, 35% wet corn gluten feed, and either no added fat (control), 4% tallow (TALLOW), or 10 or 15% GERM on a DM basis, with or without 224 IU of added vitamin E/kg of diet DM. No fat x vitamin E (P > or = 0.08) interactions were detected. Fat addition, regardless of source, decreased (P < 0.01) DMI, marbling score, and the number of carcasses grading USDA Choice. Among heifers fed finishing diets containing TALLOW or 10% GERM, supplemental fat source did not affect DMI (P = 0.76), ADG (P = 0.54), G:F (P = 0.62), or carcass characteristics (P > or = 0.06). Increasing GERM decreased DMI (linear; P < 0.01) and ADG (quadratic; P < 0.02), with ADG by heifers fed 10% GERM slightly greater than those fed control but least for heifers fed 15% GERM. Increasing GERM improved (quadratic; P < 0.03) G:F of heifers, with heifers fed 10% GERM having the greatest G:F. Increasing GERM decreased HCW (linear; P < 0.02), marbling score (linear; P < 0.01), and the percentage of carcasses grading USDA Choice (linear; P < 0.01). The addition of vitamin E increased (P < 0.04) the percentage of carcasses grading USDA Select and decreased (P < 0.01) the percentage of carcasses grading USDA Standard. These data suggest that GERM can serve as a supplemental fat source in cattle finishing diets, and that the effect of vitamin E did not depend on source or concentration of supplemental fat.