The effect of roasted soybeans in the diet of feedlot steers and Synovex-S ear implants on carcass characteristics and estimated composition.

Beef steer carcasses from three 2 x 2 factorial feeding experiments (Exp. 1, 20 carcasses; Exp. 2 and 3, 19 carcasses each) were evaluated to study the influence of supplementing with roasted soybeans (RSB; 127 degrees C for 10 min) vs soybean meal (SBM) and implanting with the estrogenic growth promoter Synovex-S (SYN, 20 mg estradiol benzoate and 200 mg progesterone) on carcass merit, composition of dissected 9-10-11th rib section, estimated edible carcass composition, and cooking characteristics of strip loin steaks. In all experiments, steers were fed diets consisting of 15% corn silage, 15% orchardgrass silage, and 70% corn-based concentrate. There were no treatment interactions found in this study. Final BW averaged 480.4, 498.5, and 500.7 kg for Exp. 1, 2, and 3, respectively, and hot carcass weights averaged 288.4, 296.4, and 309.1 kg. Across experiments, hot carcass weight was 8.3 kg less (P < .03) for RSB steers than for SBM steers. Fat weight (P < .01) and percentage of fat (P < .01) were less and percentage of bone (P < .04) was greater in the 9-10-11th rib section of RSB steers than of SBM steers. Estimated percentage of fat (P < .02) was less and percentage of bone (P < .04) was greater in edible carcass of RSB steers than in that of SBM steers. Total 9-10-11th rib section weight tended to be less for RSB steers (P < .08) than for SBM steers. Carcass merit measurements were not affected (P > .10) by supplement, but numerically the percentage of kidney, pelvic, and heart fat was 11% greater for RSB steers than for SBM steers in Exp. 2 and 3. Final BW and carcass weight were 38.7 and 22.6 kg greater (P < .01), respectively, for SYN-implanted steers than for steers not implanted. Longissimus muscle area was greater (P < .01), percentage of kidney, pelvic, and heart fat (P < .02) was less, USDA quality grade tended to be less (P < .09), and shear force of strip loin was greater (P < .01) for SYN-implanted steers than for steers not implanted. The 9-10-11th rib section and estimated carcass compositions were not different (P > .10) between SYN-implanted steers and steers not implanted but reflected a somewhat leaner carcass. The authors conclude from this study that in feedlot steers, either implanted or not implanted, there is no benefit from supplementing with RSB in place of SBM, and that the use of RSB in place of SBM in feedlot diets may reduce the amount of edible carcass.     

Effect of ruminal protein degradability on growth and N metabolism in growing beef steers

The objective of two experiments was to correlate plasma levels of urea N (PUN) and the percentage of urine N in the form of urea (UUN) to weight gain in response to different dietary protein regimens for growing Angus steers. In Exp. 1, 60 steers (302 kg BW) were assigned to various levels of dietary N (control plus supplemental N to provide from 100 to 400 g more crude protein daily) within two sources of supplemental N (soybean meal [SBM] or a mixture of two parts corn gluten meal:one part blood meal [CGM:BM]). In Exp. 2, 27 steers (229 kg BW) were fed two levels of SBM, and half of the steers received growth-promoting implants. Steers were housed in groups of 12 and fed individually for 84 d in both experiments. Corn silage was fed at a restricted rate to minimize orts. Jugular blood and urine samples were collected during the experiments. In Exp. 1, maximal ADG of steers fed SBM (1.0 kg) was reached with 671 g/d total crude protein, or 531 g/d metabolizable protein. Maximal ADG of steers fed CGM:BM (0.91 kg) was reached with 589 g/d total crude protein, or 539 g/d metabolizable protein. The DMI was higher (P < 0.07) for steers fed SBM (6.37 kg/d) than for steers fed CGM:BM (6.14 kg/d). Increasing ruminal escape protein from 36% (SBM) to 65% (CGM:BM) of CP decreased (P < 0.05) endogenous production of urea, as evidenced by lower concentrations of urea in blood and lower UUN. In Exp. 2, increasing supplemental protein from 100 to 200 g/d increased (P < 0.05) ADG and PUN. Implants lowered (P < 0.05) UUN, particularly at the higher level of supplemental protein. Protein supplementation of growing steers can be managed to maintain acceptable ADG yet decrease excretion of urea in the urine.     

Plasma concentrations of thyroid hormone in steers treated with Synovex-S and 3,5,3'-triiodothyronine.

This experiment examined the effect of daily administration of 3,5,3'-triiodothyronine (T3) on plasma profiles of T3, thyroxine (T4), 3,3',5'-triiodothyronine (reverse T3; rT3) and thyrotropin (TSH) in beef steers in which protein accretion was increased by using implants of Synovex-S (SYN). Twenty-four Angus-Hereford steers (302 +/- 16 kg) were individually fed a diet of a corn-based concentrate and silage mixture for 56 d at equal energy intake per steer (ME/unit BW.75). A 2 x 2 factorial arrangement of treatments was used in which treatments were SYN ear implants (200 mg of progesterone and 20 mg of estradiol benzoate) or no implants and s.c. injections of T3 in polyethylene glycol (2 micrograms of T3/kg BW every 48 h) or no injections of T3. Blood samples were collected every 2 wk. Plasma T3 concentration during the experimental period was increased in T3-treated steers (3.0 +/- .1 vs 2.2 +/- .1 ng/mL, P < .01) and was decreased in SYN-implanted steers (2.4 +/- .1 vs 2.7 +/- .1 ng/mL, P < .01). Plasma T4 and rT3 concentrations were reduced (22 +/- 4 vs 75 +/- 2 and .04 +/- .01 vs .12 +/- .01 ng/mL, respectively, P < .01) in T3-treated steers. Concurrently, plasma TSH concentration was decreased in T3-treated steers (.37 +/- .01 vs .51 +/- .02 ng/mL, P < .02). Synovex-S increased BW gain (21.0%, P < .01) and protein gain (35.6%, P < .01) compared with that of nonimplanted steers. Body weight gain and protein gain were not affected by treatment with T3.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Effect of live weight gain of steers during winter grazing: I. Feedlot performance, carcass characteristics, and body composition of beef steers

Two experiments were conducted to examine the effect of previous BW gain during winter grazing on subsequent growth, carcass characteristics, and change in body composition during the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) supplemented with 0.91 kg/d of cottonseed meal. Winter grazing ADG (kg/d) for HGW, LGW, and NR steers were, respectively, 1.31, 0.54, 0.16 (Exp. 1) and 1.10, 0.68, 0.15 (Exp. 2). At the end of winter grazing, four steers were selected randomly from each treatment to measure initial carcass characteristics and chemical composition of carcass, offal, and empty body. All remaining steers were fed a high-concentrate diet to a common backfat end point. Six steers were selected randomly from each treatment for final chemical composition, and carcass characteristics were measured on all steers. Initial fat mass and proportion in carcass, offal, and empty body were greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both experiments. Live BW ADG and gain efficiency during the finishing phase did not differ (P = 0.24) among treatments, but DMI (% of mean BW) for NR and LGW was greater (P < 0.003) than for HGW steers. Final empty-body composition did not differ (P = 0.25) among treatments in Exp. 1. In Exp. 2, final carcass and empty-body fat proportion (g/kg) was greater (P < 0.03) for LGW and NR than for HGW steers. Accretion of carcass fat-free organic matter was greater (P < 0.004) for LGW than for HGW and NR steers in Exp. 1, but did not differ (P = 0.22) among treatments in Exp. 2. Fat accretion in carcass, offal, and empty body did not differ (P = 0.19) among treatments in Exp. 1, but was greater (P < 0.05) for LGW and NR than for HGW steers in Exp. 2. Heat production by NR steers during finishing was greater (P < 0.02) than by HGW steers in Exp. 1 and 2. Differences in ADG during winter grazing and initial body fat content did not affect rate of live BW gain or gain efficiency during finishing. Feeding steers to a common backfat thickness end point mitigated initial differences in carcass and empty-body fat content. However, maintenance energy requirements during finishing were increased for nutritionally restricted steers that were wintered on dormant native range.     

Dose and release pattern of anabolic implants affects growth of finishing beef steers across days on feed

Four experiments evaluated the effect of implant dose and release pattern on performance and carcass traits of crossbred beef steers. In Exp. 1, steers (4 to 7 pens/treatment; initial BW = 315 kg) were fed an average of 174 d. Treatments were 1) no implant (NI); 2) Revalor-S [120 mg of trenbolone acetate (TBA) and 24 mg of estradiol 17β (E(2)); REV-S]; 3) Revalor-IS followed by REV-S (cumulatively 200 mg of TBA and 40 mg of E(2); reimplanted at 68 to 74 d; REV-IS/S); and 4) Revalor-XS (200 mg of TBA and 40 mg of E(2); REV-X). Carcass-adjusted final BW was greater (P < 0.05) for REV-X and REV-IS/S than for REV-S (610, 609, and 598 kg, respectively). Daily DMI did not differ (P > 0.10) among the 3 implants, but carcass-adjusted G:F was greater (P < 0.05) for REV-X and REV-IS/S than for REV-S (0.197 and 0.195 vs. 0.188). Both HCW and LM area were greater (P < 0.05) for REV-X and REV-IS/S than for REV-S. Marbling scores were greatest (P < 0.05) for REV-S and least (P < 0.05) for REV-IS/S; REV-X was intermediate to NI and REV-IS/S. In Exp. 2, steers (10 pens/treatment; initial BW = 391 kg) were fed 131 d, with treatments of REV-S, REV-IS/S (reimplanted at 44 to 47 d), and REV-X. Carcass-adjusted final BW (598 kg), ADG (1.6 kg), DMI (9.4 kg), G:F (0.17), and HCW did not differ (P > 0.10) among treatments. The percentage of Choice was less (P < 0.05) and percentage of Select greater (P < 0.05) for REV-IS/S than for REV-S and REV-X. In Exp. 3, steers (10 pens/treatment; initial BW = 277 kg) were fed 197 d and received either REV-IS/S (reimplanted at 90 to 103 d) or REV-X. Carcass-adjusted final BW (625 vs. 633 kg) and ADG (1.81 vs. 1.76 kg) were greater (P < 0.05) for REV-X-implanted steers. Daily DMI did not differ, but G:F tended (P < 0.10) to be increased and HCW was greater (P < 0.05) for REV-X than for REV-IS/S. In Exp. 4, steers (8 pens/treatment; initial BW = 238 kg) were fed 243 d and received either REV-IS/S (reimplanted at 68 to 71 d) or REV-X. Carcass-adjusted final BW (612 kg), ADG (1.54 kg), DMI (7.55), and G:F (0.21) did not differ (P > 0.10) for REV-IS/S and REV-X-implanted steers. Carcass traits did not differ among implants, but the percentage of Choice carcasses was greater (P < 0.05) and percentage of Select was less (P < 0.05) for REV-X than for REV-IS/S. These data indicate that when TBA/E(2) dose is equal, the altered release rate of REV-X can improve performance and quality grade, but these effects depend on duration of the feeding period and timing of initial and terminal implants.     

Effects of limit feeding corn or dried distillers grains with solubles at 2 intakes during the growing phase on the performance of feedlot cattle

Energy density in growing diets may affect carcass quality of cattle; however, few reports have described the impact of energy source. The objectives of this research were to determine effects of source [dried distillers grains with solubles (DDGS) vs. corn] and amount (limit-fed to gain 0.9 vs. 1.4 kg of BW/d) of energy during the growing phase on feedlot performance and marbling. Angus-cross steers (144 head) were blocked by BW (average initial BW = 252 ± 36 kg), allotted within each block to 8 pens (6 steers/pen, 24 pens total), and randomly assigned to 1 of 4 feeding systems in a 2 × 2 factorial arrangement of treatments: 1) 65% DDGS fed to gain 0.9 kg of BW/d, 2) 65% DDGS fed to gain 1.4 kg of BW/d, 3) 65% corn fed to gain 0.9 kg of BW/d, and 4) 65% corn fed to gain 1.4 kg of BW/d. Fecal grab samples were collected on d 52 of the growing phase to determine digestibility of DM, ADF, NDF, ether extract (EE), and CP. After the 98-d growing phase, all steers were fed the same finishing diet. Steers were slaughtered by pen when average BW within the pen was 544, 522, and 499 kg for the large, medium, and small BW blocks, respectively. Average daily gain and DMI differed (P<0.01) by design during the growing phase. Compared with the corn-based diets, digestibilities of DM, NDF, and EE were decreased (P<0.02) when DDGS-based diets were fed during the growing phase, whereas the digestibility of N was increased (P<0.01). The ADG was greatest (P=0.02) during the finishing phase for steers fed to gain 0.9 kg of BW/d initially, but source of energy during the growing phase did not affect (P=0.24) finishing phase ADG. Steers fed to gain 0.9 kg of BW/d during the growing phase also had less backfat (P=0.08), decreased USDA yield grades (P=0.03), and greater LM area (P<0.01) than steers fed to gain 1.4 kg of BW/d. There was an interaction between energy source and amount for marbling scores (P=0.02). Steers fed corn-based diets to gain 0.9 kg of BW/d during the growing phase had the most marbling, whereas those fed to gain 0.9 kg of BW/d on DDGS had the least marbling; the remaining feeding systems were intermediate. Overall ADG and DMI were affected (P < 0.06) by both source and amount of energy fed during the growing phase. Feeding the DDGS-based diet to achieve greater ADG during the growing phase increased marbling, whereas feeding the corn-based diet to increase ADG during the growing phase decreased marbling.     

Effect of field peas, chickpeas, and lentils on rumen fermentation, digestion, microbial protein synthesis, and feedlot performance in receiving diets for beef cattle

Two experiments were conducted to evaluate the use of pulse grains in receiving diets for cattle. In Exp. 1, 8 Holstein (615 +/- 97 kg of initial BW) and 8 Angus-crossbred steers (403 +/- 73 kg of initial BW) fitted with ruminal and duodenal cannulas were blocked by breed and used in a randomized complete block design to assess the effects of pulse grain inclusion in receiving diets on intake, ruminal fermentation, and site of digestion. Experiment 2 was a 39-d feedlot receiving trial in which 176 mixed-breed steers (254 +/- 19 kg of initial BW) were used in a randomized complete block design to determine the effects of pulse grains on DMI, ADG, and G:F in newly received feedlot cattle. In both studies, pulse grains (field peas, lentils, or chickpea) replaced corn and canola meal as the grain component in diets fed as a total mixed ration. Treatments included 1) corn and canola meal (control); 2) field pea; 3) lentil; and 4) chickpea. Preplanned orthogonal contrasts were conducted between control vs. chickpea, control vs. field pea, and control vs. lentil. In Exp. 1, there were no differences among treatments for DMI (11.63 kg/d, 2.32% of BW daily, P = 0.63) or OM intake (P = 0.63). No treatment effects for apparent ruminal (P = 0.10) and total tract OM digestibilities (P = 0.40) were detected when pulse grains replaced corn and canola meal. Crude protein intake (P = 0.78), microbial CP flow (P = 0.46), total tract CP digestibility (P = 0.45), and microbial efficiency (P = 0.18) were also not influenced by treatment. Total-tract ADF (P = 0.004) and NDF (P = 0.04) digestibilities were greater with field pea vs. control. Total VFA concentrations were lower for field pea (P = 0.009) and lentil (P < 0.001) compared with control. Chickpea, field pea, and lentil had lower (P < or = 0.03) acetate molar proportion than control. Ruminal pH (P = 0.18) and NH3 (P = 0.14) were not different among treatments. In Exp. 2, calves fed chickpea, field pea, and lentil had greater overall DMI (7.59 vs. 6.98 kg/d; P < or = 0.07) and final BW (332 vs. 323 kg; P < or = 0.04), whereas chickpea and lentil had greater ADG (1.90 vs. 1.71 kg/d; P < or = 0.04) than control. Gain efficiency (P = 0.18) did not differ among treatments. Steers fed pulse grains had similar CP and OM digestibilities compared with a combination of corn and canola meal in receiving diets. Pulse grains are a viable alternative for replacement of protein supplements in receiving diets for beef cattle.     

Dietary roughage regimen for feedlot steers: reduced roughage level (2%) during the mid-finishing period.

Because roughage in feedlot diets is one of the most expensive ingredients on an energy basis, regimens that minimize roughage usage are of interest. Crossbred steers of British breeds (n = 112, initial BW = 405 kg) were used to compare the feeding of diets containing 2% roughage from d 22 through 84 and 10% roughage from d 85 to finish (d 133; 2/10%) to the feeding of 10% roughage throughout the finishing period (10/10%); all diets were based on steam-flaked sorghum grain and contained monensin and tylosin. When the 2% roughage diet was fed, steers consumed less feed (6.8 vs 7.8 kg/d, P less than .01), tended to gain less (1.11 vs 1.20 kg/d, P = .13), and were numerically more efficient (16.5 vs 15.5 kg of gain/100 kg of DMI, P greater than .2) than steers fed the 10% roughage diet (10/10%). After the roughage content was increased from 2 to 10% on d 85 (all steers fed 10% roughage), steers fed the 2/10% regimen had greater DMI (8.4 vs 8.0 kg/d, P = .08) and ADG (1.29 vs 1.09 kg, P = .06), and tended to be more efficient (15.4 vs 13.6 kg of gain/100 kg of DMI, P = .10) than steers fed the 10/10% regimen. Steers fed the two regimens had similar (P greater than .2) overall gain performance. The 2/10% regimen tended to have a greater percentage of Choice carcasses (58 vs 42%, P = .14) and numerically more liver abscesses (24 vs 15%, P greater than .2) than the 10/10% regimen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Optimizing nitrogen utilization in growing steers fed forage diets supplemented with dried citrus pulp

Our objectives were to compare the effects of sources of supplemental N on ruminal fermentation of dried citrus pulp (DCP) and performance of growing steers fed DCP and bahiagrass (Paspalum notatum) hay. In Exp. 1, fermentation of DCP alone was compared with that of isonitrogenous mixtures of DCP and solvent soybean meal (SBM), expeller soybean meal (SoyPLUS; SP), or urea (UR). Ground (1 mm) substrates were incubated in buffered rumen fluid for 24 h, and IVDMD and fermentation gas production kinetics and products were measured. Nitrogen supplementation increased (P < 0.10) ruminally fermentable fractions, IVDMD, pH, and concentrations of NH3 and total VFA, but reduced the rate of gas production (P < 0.10) and the lag phase (P < 0.01). Supplementation with UR vs. the soy-based supplements increased ruminally fermentable fractions (P < 0.05) and concentrations of total VFA (P < 0.10) and NH3 (P < 0.01), but these measures were similar (P > 0.10) between SBM and SP. In Exp. 2, 4 steers (254 kg) were fed bahiagrass hay plus DCP, or hay plus DCP supplemented with CP predominantly from UR, SBM, or SP in a 4 x 4 Latin square design, with four 21-d periods, each with 7 d for DMI and fecal output measurement. Nitrogen-supplemented diets were formulated to be isonitrogenous (11.9% CP), and all diets were formulated to be isocaloric (66% TDN). Intake and digestibility of DM, N, and ADF were improved (P < 0.05) by N supplementation. Compared with UR, the soy-based supplements led to greater (P < 0.05) DM and N intakes and apparent N and ADF digestibilities. Plasma glucose and urea concentrations increased (P < 0.10) with N supplementation and were greater (P < 0.01) for the soy-based supplements than for UR. Intake, digestibility, and plasma metabolite concentrations were similar (P > 0.1) for SBM and SP. In Exp. 3, 24 steers (261 kg) were individually fed bahiagrass hay plus DCP (control), or hay plus DCP supplemented with CP predominantly from UR or SBM. Over 56 d, DMI and ADG were greatest (P < 0.05) in steers fed SBM. Nitrogen supplementation increased (P < 0.05) DMI, ADG, and G:F. However, SBM supplementation produced greater (P < 0.05) DMI and ADG and similar (P > 0.05) G:F compared with UR supplementation. We conclude that supplemental N is important to optimize ruminal function and performance of growing steers fed forage diets supplemented with DCP. Diets with supplemental N mainly from SBM improved diet digestibility and animal performance beyond that achieved by UR.     

Effects of intake level on metabolic response to estrogenic growth promoters in beef steers

Effects of diethylstilbestrol (DES, 10 mg/d orally, Trial 1) or Synovex-S (SYN, 220 mg ear implant, Trial 2) on gain and N balance (g/d) were determined in steers that consumed 1.3, 2.7, 4.4 and 7.4 kg DM/d (Trial 1) and 1.3, 2.9, 4.3 and 6.6 kg DM/d (Trial 2). Each trial was a replicated 4 x 4 Latin square with four pairs of steers per trial (BW:322 kg, Trial 1; 278 kg Trial 2) and a control and growth promoter steer in each pair. Steers were fed a pelleted 75% concentrate diet containing 16.7% (DM basis). Each period consisted of 1 wk of intake adaptation, 5 wk of feeding and 1 wk in metabolism crates (2-d adjustment and 5-d collection). Steers were switched among DMI but not among promoter treatments. Intercept and slope, respectively, for the regression of BW gain (kg/d) on DMI (kg/d) were -.66 and .276 for control vs -.84 and .328 for DES steers and -.69 and .276 for control vs -.89 and .356 for SYN steers. Similar regression values for N balance (g/d) on DMI (kg/d) were -10.3 and 6.91 for control vs -17.2 and 9.10 for DES steers and -4.5 and 4.67 for control vs -7.6 and 5.85 for SYN steers. Across trials, slopes differed from zero (P less than .01), and promoter slopes differed from controls for gain (P less than .01) and N balance (P less than .10). During an extra period at the end of each trial, all steers were fed the high intake level for 6 wk, followed by N balance determinations the last 3 d of a 7-d fast.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of grazing dormant native range or winter wheat pasture on subsequent finishing cattle performance, carcass characteristics, and ruminal metabolism

A winter grazing/feedlot performance experiment repeated over 2 yr (Exp. 1) and a metabolism experiment (Exp. 2) were conducted to evaluate effects of grazing dormant native range or irrigated winter wheat pasture on subsequent intake, feedlot performance, carcass characteristics, total-tract digestion of nutrients, and ruminal digesta kinetics in beef cattle. In Exp. 1, 30 (yr 1) or 67 (yr 2) English crossbred steers that had previously grazed native range (n = 38) or winter wheat (n = 59) for approximately 180 d were allotted randomly within previous treatment to feedlot pens (yr 1 native range = three pens [seven steers/pen], winter wheat = two pens [eight steers/pen]; yr 2 native range = three pens [eight steers/pen], winter wheat = four pens [10 or 11 steers/pen]). As expected, winter wheat steers had greater (P < 0.01) ADG while grazing than did native range steers. In contrast, feedlot ADG and gain efficiency were greater (P < 0.02) for native range steers than for winter wheat steers. Hot carcass weight, longissimus muscle area, and marbling score were greater (P < 0.01) for winter wheat steers than for native range steers. In contrast, 12th-rib fat depth (P < 0.64) and yield grade (P < 0.77) did not differ among treatments. In Exp. 2, eight ruminally cannulated steers that had previously grazed winter wheat (n = 4; initial BW = 407 +/- 12 kg) or native range (n = 4; initial BW = 293 +/- 23 kg) were used to determine intake, digesta kinetics, and total-tract digestion while being adapted to a 90% concentrate diet. The adaptation and diets used in Exp. 2 were consistent with those used in Exp. 1 and consisted of 70, 75, 80, and 85% concentrate diets, each fed for 5 d. As was similar for intact steers, restricted growth of cannulated native range steers during the winter grazing phase resulted in greater (P < 0.001) DMI (% of BW) and ADG (P < 0.04) compared with winter wheat steers. In addition, ruminal fill (P < 0.01) and total-tract OM digestibility (P < 0.02) were greater for native range than for winter wheat steers across the adaptation period. Greater digestibility by native range steers early in the finishing period might account for some of the compensatory gain response. Although greater performance was achieved by native range steers in the feedlot, grazing winter wheat before finishing resulted in fewer days on feed, increased hot carcass weight, and improved carcass merit.     

Effects of restricted versus conventional dietary adaptation on feedlot performance,carcass characteristics,site and extent of digestion,digesta kinetics,and ruminal metabolism

Three experiments were conducted to determine effects of restricting intake of the final finishing diet as a means of dietary adaptation compared with diets increasing in grain over a period of 20 to 22 d on overall cattle performance, carcass characteristics, digestibility, digesta kinetics, and ruminal metabolism. In Exp. 1, 84 Angus x Hereford yearling steers (initial BW = 418 +/- 29.0 kg) were fed for 70 d. Restricting intake during adaptation had no effect (P > 0.10) on overall ADG:DMI, but decreased (P < 0.05) DMI compared with ad libitum access to adaptation diets, which resulted from differences during the initial 28 d of the experiment. In Exp. 2, 150 mixed crossbred steer calves (initial BW = 289 +/- 22.9 kg) were fed for an average of 173 d. Restricting intake decreased (P < 0.01) overall daily gain (1.51 vs 1.65 kg/d) and DMI (8.68 vs 9.15 kg/d) compared with ad libitum fed steers; however, ADG:DMI was not influenced (P > 0.10) by adaptation method. Experiment three used eight ruminally and duodenally fistulated steers (initial BW = 336 +/- 20 kg) in a completely random design. Total tract digestibility, digesta kinetics and ruminal metabolism were determined. Restricting intake reduced (P < 0.10) daily DMI variation from d 1 through 7, 8 through 14, and 22 through 28 compared with ad libitum feeding of three adaptation diets. Restricted steers had reduced (adaptation method x period interaction, P < 0.05) intakes and fecal excretions of ADF and greater OM digestibilities on d 4 through 7, 11 through 14, and 18 through 21. Digesta kinetics and ruminal metabolism were generally not affected (P > 0.10) by adaptation method. Our results suggest that restricted-feeding of the final diet as a means of dietary adaptation can be used in finishing cattle with few problems from acidosis or related intake variation. In light-weight steers (Exp. 2), disruptions in intake during the adaptation period might have resulted in restriction for an extended period, which decreased (P < 0.01) hot carcass weight compared with calves fed ad libitum. Effects of limit feeding during the initial 28 d of the feeding period on site and extent of digestion, digesta kinetics, and ruminal metabolism were minimal, supporting few differences in performance across the finishing period for yearling cattle.     

Effect of dietary cation-anion difference on urinary pH, feedlot performance, nitrogen mass balance, and manure pH in open feedlot pens

Six experiments were conducted to evaluate dietary cation-anion difference (DCAD) in concentrate diets on urinary pH, feedlot performance, and N mass balance. In Exp. 1, 15 wether lambs (33.5 ± 3.0 kg) in five 3 × 3 Latin squares were fed a basal diet of 82.5% dry-rolled corn (DRC), 7.5% alfalfa hay, 5% molasses, and 5% supplement with different proportions of anionic and cationic salts. The DCAD was -45, -24, -16, -8, 0, +8, +16, +24, +32, and +40 mEq per 100 g of DM with the control basal diet (DCAD = +8) included in each square. Urinary pH increased (cubic, P < 0.01) as DCAD increased and DMI increased linearly (P < 0.01) with increasing DCAD. In Exp. 2 and 3, 8 Holstein steers (312 ± 24 kg) were used in 2 consecutive 4 × 4 Latin squares. Steers were fed either the same basal diet as Exp. 1 or a basal diet with 20% wet distillers grains (WDGS) replacing DRC. In Exp. 2, DCAD was adjusted to -2, -12, and -22 mEq per 100 g of DM from the basal diet (DCAD = +8) and DCAD was adjusted in Exp. 3 to -12, -22, and -32 mEq per 100 g of DM from the basal WDGS diet (DCAD = -2). Urinary pH decreased linearly as DCAD decreased (P < 0.01) in both experiments, whereas DMI decreased linearly in Exp. 2 (P = 0.02) but not Exp. 3 (P = 0.96). In Exp. 4, 6 crossbred steers (373 ± 37 kg) were used in a 2-period crossover design. Steers were fed the same basal diet as Exp. 3 with DCAD of -16 (NEG) and +20 (POS) mEq per 100 g of DM. Urinary pH and DMI (P < 0.05) were less for cattle fed the NEG diet compared with POS. In 2 experiments, steers (n = 96 each) were fed NEG or POS as calves (260 ± 22 kg of BW) for 196 d from November to May (Exp. 5) or as yearlings (339 ± 32 kg of BW) for 145 d from June to October (Exp. 6). Final BW, DMI, ADG, and HCW were not different (P > 0.11) among treatments in either experiment. Efficiency of BW gain was increased (P = 0.05) for steers fed NEG compared with POS in Exp. 5 but was not different (P = 0.11) in Exp. 6. Amount of N intake, retention, excretion, and manure N (kg/steer) were not different (P > 0.11) among treatments in either experiment. Manure pH (soil, feces, and urine) was decreased (P < 0.01) in pens fed NEG compared with POS in both experiments. Amount of N lost (kg/steer) was not different (P = 0.44) in Exp. 5, but tended (P = 0.09) to be 10.6% greater for POS compared with NEG in Exp. 6. Urinary pH was decreased by reducing DCAD, but this had minimal effect on N losses in open feedlot pens in these experiments.     

Effect of cattle age, forage level, and corn processing on diet digestibility and feedlot performance

Three experiments were conducted to determine the effects of cattle age and dietary forage level on the utilization of corn fed whole or ground to feedlot cattle. In Exp. 1, 16 steers were used to investigate the effects of cattle age and corn processing on diet digestibility. Two cattle age categories were evaluated (weanling [254 +/- 20 kg BW] and yearling [477 +/- 29 kg BW]; eight steers per group), and corn was fed either ground or whole to each cattle age category. Cattle age and corn processing did not affect (P > 0.10) diet digestibility of DM, OM, starch, CP, NDF or ADF, and no interactions (P > 0.10) between these two factors were detected. In Exp. 2, the effects of forage level and corn processing on feedlot performance and carcass characteristics were evaluated. One hundred eighty steers (310 +/- 40 kg BW) were allotted to 24 pens, and were fed one of the following diets: high-forage (18.2% corn silage) cracked corn (HFCC); high-forage shifting corn (whole corn for the first half of the trial, then cracked corn until harvest; HFSC); high-forage whole corn (HFWC); low-forage (5.2% corn silage) cracked corn (LFCC); low-forage shifting corn (LFSC); and low-forage whole corn (LFWC). For the high-forage diets, steers fed cracked corn had 7% greater DMI than those fed whole corn, whereas for the low-forage diets, grain processing did not affect DMI (interaction; P = 0.02). No interactions (P > 0.10) between forage level and corn processing were found for ADG and G:F. Total trial ADG and G:F, and percentage of carcasses grading USDA Choice, and carcass yield grade were not affected (P > 0.10) by corn processing. Cattle with fewer days on feed grew faster and more efficiently when cracked corn was fed, whereas cattle with longer days on feed had greater ADG and G:F when corn was fed whole (interaction; P < 0.10). In Exp. 3, the effects of forage level and corn processing on diet digestibility were evaluated. The high-forage cracked corn, high-forage whole corn, low-forage cracked corn, and low-forage whole corn diets used in Exp. 2 were fed to 16 steers (350 +/- 27 kg BW) in a digestion trial. No interactions (P > 0.10) between forage level and corn processing were detected for starch digestibility. Forage level and corn processing (grinding) did not affect (P > 0.10) diet DM, OM, starch, CP, and NDF digestibility. Processing corn did not provide additional benefits to feedlot cattle performance under these experimental conditions.     

Effects of an artificial sweetener on health, performance, and dietary preference of feedlot cattle

Two experiments examined the effects of a saccharin-based artificial sweetener (Sucram) on health, performance, and dietary preference of feedlot cattle. In Exp. 1, 200 steer calves (initial BW = 190.4 +/- 1.47 kg) were fed a 65% concentrate diet supplemented with or without 200 mg of Sucram/kg (DM basis) during a 56-d receiving-growing period. Feeding Sucram did not affect overall (P = 0.19) DMI; however, from d 29 to 56, there was a trend (P = 0.10) for increased DMI with Sucram (5.71 vs. 6.02 kg/d, respectively). From d 0 to 28 and d 0 to 56, there were trends (P = 0.11 and 0.12, respectively) for increased ADG and for increased d-56 BW (P = 0.07) for calves fed Sucram. No differences were detected (P = 0.82) for receiving (REC) period morbidity. During the finishing (FIN) period, 180 steers from the REC period were assigned (9 pens/treatment in a 2 x 2 factorial design) to the following treatments: 1) control REC/control FIN; 2) control REC/Sucram FIN; 3) Sucram REC/control FIN; and 4) Sucram REC/ Sucram FIN. Over the FIN period, ADG tended (P = 0.12) to be greater for Sucram; however, carcass-adjusted ADG did not differ among treatments. Daily DMI was affected by a REC x FIN interaction (P = 0.08), which was the result of greater DMI by cattle in the Sucram REC/Sucram FIN treatment and decreased DMI by cattle in the Sucram REC/control FIN treatment. In general, changes in carcass characteristics were minor. In Exp. 2, 12 steers (initial BW = 395.6 +/- 6.17 kg) were used in a simultaneously replicated 3 x 3 Latin square preference test. Each square consisted of 3 pens, with 2 steers/pen, and 3 time periods. Bunks had dividers at their midpoint, and equal quantities of diet (as-fed basis) were delivered randomly on either side of the divider daily. Treatments were: 1) control; 2) Sucram = basal diet supplemented with 200 mg of Sucram/kg of DM; and 3) choice = control and Sucram on separate sides of the divider. Dietary preference differed on d 1 (P = 0.01) and d 3 (P = 0.02) for control vs. choice and Sucram vs. choice, with the choice group consuming 0.49 and 1.72 kg of DM more of the Sucram diet than the control diet, respectively. This effect, however, was not consistent across days, and average DMI did not differ (P = 0.81) among treatments. Addition of Sucram to the diet of newly received cattle tended to increase receiving period ADG; however, its effects on morbidity, finishing performance, and dietary preference were limited.     

Effects of wet corn gluten feed and roughage levels on performance, carcass characteristics, and feeding behavior of feedlot cattle

Two experiments were conducted to evaluate the effects of feeding different levels of wet corn gluten feed (WCGF) and dietary roughage on performance, carcass characteristics, and feeding behavior of feedlot cattle fed diets based on steam-flaked corn (SFC). In Exp. 1, crossbred steers (n = 200; BW = 314 kg) were fed 4 dietary treatments (DM basis): a standard SFC-based diet containing 9% roughage (CON) and 3 SFC-based diets containing 40% WCGF, with either 9, 4.5, or 0% roughage. A linear (P = 0.04) increase in final BW and DMI (P < 0.01) was observed in diets containing WCGF as dietary roughage increased. Steers fed WCGF and higher levels of roughage had greater (P = 0.01) ADG than steers fed lower levels of roughage. Steers fed the CON diet had lower (P = 0.04) daily DMI and greater (P = 0.03) G:F than those fed WCGF. Most carcass characteristics of steers fed CON did not differ (P > 0.10) from those of steers fed WCGF. Based on feed disappearance and visual scan data, consumption rate did not differ (P > 0.10) among treatments; however, feeding intensity (animals present at the bunk after feeding) was greater for steers fed CON (P < 0.01) than for steers fed WCGF. In Exp. 2, yearling crossbred steers (n = 1,983; BW = 339 kg) were fed 4 dietary treatments (DM basis): a standard SFC-based control diet that contained 9% roughage (CON) and 3 SFC-based diets containing either 20% WCGF and 9% roughage or 40% WCGF with 9 or 4.5% roughage. Steers fed the CON diet tended to have lower final BW (P = 0.14), ADG (P = 0.01), and DMI (P < 0.01) than steers fed diets containing WCGF. Steers fed the 20% WCGF diet had greater (P = 0.08) G:F than steers fed the 40% WCGF diets. With 40% WCGF, increasing roughage from 4.5 to 9% decreased (P < 0.01) G:F and increased (P = 0.06) DMI. Gain efficiency was improved (P < 0.01) for steers fed CON vs. those fed diets containing WCGF, whereas HCW (P = 0.02) and dressing percentage (P < 0.01) were greater for steers fed WCGF. Percentage of cattle grading USDA Choice was greater (P = 0.02) for cattle fed WCGF. Results suggest that replacing SFC with up to 40% WCGF increased ADG and decreased G:F when 4.5 to 9.0% roughage was supplied. More CON steers were present at the feed bunk during the first hour after feeding than WCGF steers, suggesting that including WCGF at 40% of the diet affected feeding behavior.     

Effects of phase feeding of protein on performance, blood urea nitrogen concentration, manure nitrogen:phosphorus ratio, and carcass characteristics of feedlot cattle

Two experiments with a randomized complete block design were conducted to determine the effects of phase feeding of CP on performance, blood urea nitrogen (BUN), manure N:P ratio, and carcass characteristics of steers fed in a feedlot. In Exp. 1, 45 crossbred steers (initial BW = 423 +/- 3.3 kg) were individually fed a diet formulated to contain 13.0% CP (DM basis) for 62 d. On d 63, the dietary CP was maintained at 13.0% or formulated to contain 11.5 or 10.0% CP until slaughter. Actual CP values were 12.8, 11.8, and 9.9%, respectively. Reducing the CP concentration of the diet did not affect ADG of steers from d 62 to 109 (P = 0.54) or over the 109-d feeding period (1.45, 1.50, and 1.49 kg/d for 13.0, 11.5, and 10.0% CP, respectively; P = 0.85). No differences (P > 0.12) among treatments were detected for BUN concentrations on d 0, 62, or 109. Gain:feed, DMI, and carcass characteristics did not differ among treatments (P > 0.10). In Exp. 2, 2 trials were conducted using 184 (initial BW = 406 +/- 2.6 kg) and 162 (initial BW = 342 +/- 1.9 kg) crossbred steers. Data from the 2 trials were pooled for statistical analysis, and trial effect was added to the statistical model. Steers were fed a diet formulated to contain 13.0% CP until reaching approximately 477 kg. When the average BW of the pen was 477 kg, diets were maintained at 13.0% CP or reduced to contain 11.5 or 10.0% CP. Actual CP values were 12.4, 11.5, and 9.3% CP for treatments 13.0, 11.5, and 10.0% CP, respectively. Reducing the CP content of the diet did not affect ADG after the diet changed (P = 0.16) or throughout the finishing period (P = 0.14). Immediately before slaughter, steers fed the 13.0% CP diet had greater (P < 0.001) BUN concentrations than steers fed the 11.5 and 10.0% CP diets. Carcasses from cattle fed the 11.5% CP diet had greater (P = 0.02) fat thickness than the 13.0 and 10.0% CP treatments, whereas carcasses from cattle fed 13.0% CP had greater (P = 0.004) marbling scores than steers fed the 11.5 or 10.0% CP diets. Other carcass characteristics, DMI, and G:F did not differ (P > 0.10) among treatments. The N:P ratio was increased with the 10.0% CP diet (P = 0.02) compared with the 11.5 or 13.5% CP treatments; however, manure composition did not differ (P > 0.10) among treatments. These results indicate that reduced CP concentration during the finishing period does not affect feedlot performance but can improve the N and P relationship in the manure.     

Value of sunflower seed in finishing diets of feedlot cattle

The value of sunflower seed (SS) in finishing diets was assessed in two feeding trials. In Exp. 1, 60 yearling steers (479 +/- 45 kg) were fed five diets (n = 12). A basal diet (DM basis) of 84.5% steam-rolled barley, 9% barley silage, and 6.5% supplement was fed as is (control), with all the silage replaced (DM basis) with rolled SS, or with grain:silage mix replaced with 9% whole SS, 14% whole SS, or 14% rolled SS. Liver, diaphragm, and brisket samples were obtained from each carcass. In Exp. 2, 120 yearling steers (354 +/- 25 kg) were fed corn- or barley-based diets containing no SS, high-linoleic acid SS, or high-oleic acid SS (a 2 x 3 factorial arrangement, n = 20). Whole SS was included at 10.8% in the corn-based and 14% in the barley-based diets (DM basis). In Exp. 1, feeding whole SS linearly increased DMI (P = 0.02), ADG (P = 0.01), and G:F (P = 0.01). Regression of ME against level of whole SS indicated that SS contained 4.4 to 5.9 Mcal ME/kg. Substituting whole for rolled SS did not significantly alter DMI, ADG, or G:F (8.55 vs. 8.30 kg/d; 1.36 vs. 1.31 kg; and 0.157 vs. 0.158, respectively). Replacing the silage with rolled SS had no effect on DMI (P = 0.91) but marginally enhanced ADG (P = 0.10) and improved G:F (P = 0.01). Dressing percent increased linearly (P = 0.08) with level of SS in the diet. Feeding SS decreased (P < 0.05) levels of 16:0 and 18:3 in both diaphragm and subcutaneous fats, and increased (P = 0.05) the prevalence of 18:1, 18:2, cis-9,trans-11-CLA and trans-10,cis-12-CLA in subcutaneous fat. In Exp. 2, barley diets supplemented with high-linoleic SS decreased DMI (P = 0.02) and ADG (P = 0.007) by steers throughout the trial, whereas no decrease was noted with corn (interaction P = 0.06 for DMI and P = 0.01 for ADG). With barley, high-linoleic SS decreased final live weight (554 vs. 592 kg; P = 0.01), carcass weight (329 vs. 346 kg; P = 0.06), and dressing percent (58.5 vs. 59.4%; P = 0.04). Steers fed high-linoleic SS plus barley had less (P < 0.05) backfat than those fed other SS diets. No adverse effects of SS on liver abscess incidence or meat quality were detected. Although they provide protein and fiber useful in formulating finishing diets for cattle, and did improve performance in Exp. 1, no benefit from substituting SS for grain and roughage was detected in Exp. 2. Because of unexplained inconsistencies between the two experiments, additional research is warranted to confirm the feeding value of SS in diets for feedlot cattle.     

Effect of feeding glyphosate-tolerant (roundup-ready events GA21 or nk603) corn compared with reference hybrids on feedlot steer performance and carcass characteristics

Three experiments were conducted to compare the feeding value of genetically enhanced corn (Roundup Ready corn events GA21 and nk603) with nontransgenic hybrids. The four treatments included two separate reference hybrids (REF), the near-isogenic control hybrid (CON), and the genetically enhanced corn (RR), resulting in two preplanned comparisons of CON vs. RR and RR vs. the average of REF. In Exp. 1 (RR event GA21), 175 steers (BW = 427 kg) were fed in 25 pens with seven pens per corn hybrid, except CON, which contained four pens due to limited quantities of that hybrid. In Exp. 2 (RR event nk603), 196 steers (BW = 420 kg) were fed in 28 pens with seven pens per corn. In Exp. 3 (RR event nk603), 200 steers were fed in 20 pens, with a similar treatment design to Exp. 2 and five pens per corn. All experiments were conducted as completely randomized designs and utilized corn produced at University of Illinois (Exp. 1 and 2) and University of Nebraska (Exp. 3) research farms under identity-preserved protocols. In all experiments, DMI, ADG, and feed efficiency were similar (P > 0.30) between RR and REF. In Exp. 1 and Exp. 2, RR was not different (P > 0.25) than CON for growth performance. In Exp. 3, RR was not different from CON for ADG and DMI (P > 0.15) or for feed efficiency (P = 0.08). No differences were observed between RR and CON or RR and REF for carcass weight, longissimus dorsi area, and marbling scores in any of the experiments. Subtle differences were observed between RR and either CON or REF for fat depth in each experiment; however, cattle fed RR were not consistently greater and varied from either the CON or the REF (but not both contrasts) within an experiment. Based on these results, insertion of glyphosate-tolerant genes had no significant effect on nutritive quality of corn. Performance and carcass characteristics were not influenced, which suggests that Roundup Ready corn is similar to conventional, nontransgenic corn when fed to finishing feedlot cattle.