Energy and protein supplementation of ammoniated wheat straw diets for growing steers

Eighty-eight yearling beef steers (308 +/- 1.4 kg) were used in two separate trials to determine the protein-sparing value of the N added to wheat straw during the ammoniation process and to determine the effects of supplementing ammoniated straw diets with energy and ruminal escape protein. In Exp. 1, steers were fed untreated straw (US) with either 0, 150, or 500 g of soybean meal (SBM) for 88 d. The addition of SBM to US diets increased (P less than .01) straw intake and average daily gains (ADG), indicating that N was limiting. When ammoniated straw (AS) was substituted for US, the N in the AS was used as efficiently as 500 g of SBM for growth. In Exp. 2, steers had ad libitum access to AS with three levels of supplemental corn (0, 1.23, or 2.45 kg DM.animal-1.d-1) either with or without .41 kg DM of corn gluten meal (CGM) added. Straw intake decreased (P less than .01) as the amount of corn in the diet was increased, but ADG increased (P less than .01) with the addition of corn. Straw consumption was not altered by the addition of CGM, but ADG was increased (P less than .01) by an average .35 kg by CGM. Rumen and blood N components indicated that the N from AS was contributing to the ruminal N pool and that CGM was compensating for microbial protein deficiencies postruminally.     

Diet composition and gains of escape protein-supplemented growing cattle grazing corn residues

Effect of level and method of escape protein (EP) supplementation on weekly steer performance and their diet composition were evaluated in two corn residue grazing trials. In Trial 1, 60 steers (average weight 239 kg) received .8 kg.animal-1.d-1 of a 50% CP supplement to provide one of six levels of EP (60, 88, 116, 144, 172, or 200 g.animal-1.d-1). Steers grazed (2.2 animals/ha) nonirrigated fields (NIF) for 63 d. In Trial 2, 59 steers (average weight 219 kg) grazed either NIF (1.97 animals/ha) or irrigated fields (IF, 3.96 animals/ha) and were supplemented with 60, 95, 130, 165, or 200 g of EP.animal-1.d-1. In a 2 X 5 X 2 factorial arrangement, treatments were IF vs NIF, level of protein, and two supplementation methods: 1) feeding the lowest level of EP (60 g) for 21 d then for the remaining 42 d feeding one of the five EP levels or 2) feeding each EP level continuously. Weekly diet composition was evaluated using four esophageally fistulated steers. In Trial 1, no EP effect (P greater than .05) was found up to 20 d, but EP affected (P less than .05) ADG from d 20 to 34, resulting in 3.35 g of ADG/g of EP. In Trial 2, steers grazing NIF had higher (P less than .01) ADG than those grazing IF (644 vs 414 g/animal). Steer daily gains were increased (P less than .05) by level of EP but were not affected (P greater than .05) by the method of supplementation, indicating that EP supplementation was not needed during the first 21 d.(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 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.     

The effects of grazing, liquid supplements, and implants on feedlot performance and carcass traits of Holstein steers

In each of 2 yr, 20 Holstein steers (185+/-7 kg initial BW) were allocated to each of three treatments: pastured for 4.5 mo on grass/legume pastures and then fed 80% corn diets (DM basis) until slaughter; pastured for 4.5 mo on grass/legume pastures with ad libitum access to molasses-based protein supplements and fed 80% corn diets until slaughter; and placed in a feedlot and fed only 80% corn diets until slaughter (FEEDLOT). Half of the steers in each treatment were initially implanted with Revalor-S and not reimplanted. Supplemented steers on pasture had greater (P < 0.05) ADG than unsupplemented steers, and FEEDLOT steers gained faster and were fatter (P < 0.05) after 4.5 mo. Implanted steers had greater (P < 0.05) ADG with no significant treatment x implant status effect. Supplement intake was variable and related to ambient temperature. During the feedlot phase, steers previously on pasture had greater DMI and ADG (P < 0.05) but were not more efficient than FEEDLOT steers. Percentage of USDA Choice carcasses, fat thickness, dressing percentage, yield grade, and final weight were greater (P < 0.05) for FEEDLOT steers than for steers on other treatments. Implanting increased ADG of all steers but did not affect carcass traits, carcass composition, or feedlot performance during the finishing phase. Holstein steers consuming supplemented and unsupplemented pasture before slaughter will be leaner, have lower carcass weights, and have generally lower quality grades than those fed exclusively in a feedlot when slaughtered at similar ages.     

Effect of supplements on growth and forage intake by stocker steers grazing wheat pasture

This experiment was conducted with stocker steers to determine the effects of supplementary fiber and grain on ruminal acid concentrations and OM intake following abrupt dietary change to lush, primary-growth wheat (Triticum aestivum) pasture and to measure the effects of those supplements on weight gain at different levels of herbage mass (HM). Each of four irrigated wheat pastures (2.4, 3.6, 4.9, and 6.1 ha) was stocked with nine Angus crossbred steers (mean = 189 kg). In each pasture, three steers were individually fed a daily supplement of 11.3 g of cottonseed hulls (CSH)/kg BW(.75), three steers were fed a supplement mixture of 11.3 g CSH/kg BW(.75) and 8.5 g corn grain/kg BW(.75), and three steers remained as controls. Body weight and HM changes were measured at 28-d intervals throughout the experiment. Ruminal samples for VFA determination were collected twice during the 1st wk on pasture. Organic matter intake calculations were based on fecal output and OM digestibility estimates made during the 2nd wk on pasture. Fecal outputs were estimated from nonlinear least squares analyses using a two-compartment rumen model of excretion patterns of Yb following a single oral dose. Digestibility of OM was estimated using indigestible NDF in feed and feces as an internal marker. Dietary supplements had no detectable effect on ruminal VFA characteristics. The magnitude of changes in ruminal acetate:propionate ratios between d 3 and 7 on pasture was significantly and negatively related to ADG during the first 28-d growth measurement period. Body condition scores taken on d 0 also had a significant, negative relationship to ADG. Average fecal output was greater for steers fed supplements (36 g/kg BW(.75)) than for control steers (30 g/kg BW(.75)) (P < .03). The supplements also significantly reduced estimates of total diet OM digestibility. However, supplements had no measurable effect on BW changes. Herbage mass up to 1,000 kg/ha had a significant and positive effect on ADG, which was 1.44 kg during Period 1, when HM was apparently not limiting in any pasture. The deduced threshold level of the influence of HM on ADG was 850 kg/ha. Under the conditions of this experiment, the effects of supplemental fiber and(or) grain on fecal output and OM digestibility were detected. However, in the amounts fed, these supplements had no detectable effect on ADG at any level of HM.     

Wheat distillers grains in feedlot cattle diets: feeding behavior, growth performance, carcass characteristics, and blood metabolites

A study was conducted to evaluate feed intake, ADG, carcass quality, eating behavior, and blood metabolites in feedlot beef steers fed diets that varied in proportion of wheat dried distillers grains with solubles (DDGS) replacing barley grain or barley silage. Two hundred crossbred steers (BW = 489 ± 30 kg) were blocked by BW and randomly allotted to 20 pens (5 pens per treatment). Steers were fed 1 of 4 diets: control without DDGS (CON), 25% (25DDGS), 30% (30DDGS), or 35% (35DDGS) wheat DDGS (DM basis). The CON diet consisted of 15% barley silage and 85% barley-based concentrate; the 3 wheat DDGS diets were formulated by substituting 20% barley grain and 5, 10, or 15% silage, respectively, with 25, 30, or 35% wheat DDGS so that the 35DDGS diet contained no silage. The diets were formulated such that wheat DDGS was substituted for both barley grain and barley silage to evaluate whether wheat DDGS can be fed as a source of both energy and fiber in feedlot finishing diets. Dry matter intake of steers fed 25DDGS was greater (P < 0.01), but final BW, ADG, and G:F were not different compared with steers fed CON diet. Carcass characteristics and liver abscess score were not different between CON and 25DDGS. Steers fed 25DDGS had longer eating time (min/d; P < 0.01), greater meal frequency (P < 0.04), but a slower eating rate (P < 0.04). Replacing barley silage with increasing amounts of wheat DDGS (from 25DDGS to 35DDGS) linearly reduced (P < 0.01) DMI. Final BW, ADG, and G:F were not affected by increasing amounts of wheat DDGS. Carcass traits were not different, whereas liver abscess scores linearly (P < 0.01) increased as more barley silage was replaced by wheat DDGS. Eating time (min/d) and duration of each meal linearly (P < 0.02) decreased, whereas eating rate (min/g of DM) linearly (P < 0.01) increased with increasing replacement of barley silage. Blood urea N was doubled (P < 0.01) compared with CON by inclusion of wheat DDGS. Results indicate that wheat DDGS can be used effectively in feedlot diets, decreasing the need for barley grain or silage without negatively affecting growth performance and carcass characteristics. A reduction in the amount of roughage required to maintain growth performance is a potential advantage in feedlot operations because forage is costly and often of limited availability. Thus, DDGS can be a possible alternative as long as they are available and cost effective; however, increased incidence of liver abscess and increased N content of manure need to be considered when greater amounts of wheat DDGS are included in finishing diets.     

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.     

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.     

Efficacy of plastic pot scrubbers as a replacement for roughage in high-concentrate cattle diets.

Effects of plastic pot scrubbers on feedlot performance and ruminal metabolism of steers fed all-concentrate diets were determined. In Trial 1, 31 crossbred steers (means initial BW, 290 kg) were penned and fed individually. Treatments were 1) 85% concentrate-15% corn silage diet, 2) 100% concentrate diet, and 3) 100% concentrate diet + ruminal insertion of eight plastic pot scrubbers per steer. During the first 112 d of the trial, steer ADG did not differ (P greater than .10) due to treatment. From d 113 to 152, steers provided with pot scrubbers had 16% greater ADG than those fed the 100% concentrate diet without pot scrubbers (P = .18). In Trial 2, 78 crossbred steers (means initial BW, 315 kg) were penned individually and fed the diets used in Trial 1. Steers fed the 100% concentrate diet received zero, four or eight pot scrubbers. From d 113 to 167, steers provided with four or eight pot scrubbers or fed the 85% concentrate diet had greater (P less than .10) gains than steers fed the 100% concentrate diet without pot scrubbers. In Trial 3, 120 steers (means initial BW, 286 kg) were grouped in 12 pens and limit-fed an all-concentrate diet for 84 d. Sixty steers were provided with six pot scrubbers each. Performance was not affected (P greater than .10) by the use of pot scrubbers during the 84-d growing phase. During the subsequent 84-d finishing phase, half the steers receiving each treatment were switched to either an 85% concentrate-15% corn silage or an 100% concentrate diet offered for ad libitum consumption.(ABSTRACT TRUNCATED AT 250 WORDS)     

Performance and digestibilities of beef cattle fed diets supplemented with either soybean meal or roasted soybeans and implanted with Synovex.

Two 160-d feedlot experiments, each consisting of 20 Angus-Hereford steers (216 +/- 5 kg BW, Exp. 1; 258 +/- 5 kg BW, Exp. 2) and 20 Angus-Hereford heifers (208 +/- 5 kg BW, Exp. 1; 236 +/- 5 kg BW, Exp. 2), were used to investigate the effects of supplementing diets with either roasted soybeans (RSB, roasted at 127 degrees C for 10 min) or soybean meal (SBM) and implanting or not implanting with an estrogenic growth promoter (SYN; Synovex-S, 20 mg of estradiol benzoate plus 200 mg of progesterone or Synovex-H, 20 mg of estradiol benzoate plus 200 mg of testosterone) on performance. The cattle were fed a basal diet of 15% orchardgrass silage, 15% corn silage, and 70% corn-based concentrate. Treatments were 1) no SYN and fed a SBM-supplemented diet, 2) no SYN and fed a RSB-supplemented diet, 3) SYN and SBM, and 4) SYN and RSB. Cattle in the SYN groups were reimplanted at 80 d. Four additional Angus-Hereford steers were used in a digestion and nitrogen balance experiment conducted during the first half of Exp. 1. For the total 160-d feedlot experiments, DMI for RSB compared with SBM was lower (P < .01; 8.5 vs 9.2 kg/d, SEM = .07) and ADG/DMI tended to be higher (P < .10; 165 vs 157 g/kg, SEM = 1.3). Final BW of steers fed RSB was similar (P > .10) to that of steers fed SBM (473 vs 478 kg, SEM = 5.6), as was ADG (1.39 vs 1.43 kg/d, SEM = .02). Dry matter intake for SYN-implanted steers was higher (P < .01) than for steers not implanted (9.2 vs 8.5 kg/d). Likewise, final BW (491 vs 460 kg) and ADG (1.49 vs 1.33 kg/d) were higher (P < .01), and ADG/DMI (166 vs 157 g/kg) tended to be higher (P < .10), for SYN-implanted steers than for steers not implanted. During the more rapid muscle growth period (0 to 80 d), DMI for RSB compared with SBM was lower (P < .01; 7.8 vs 8.6 kg/d, SEM = .07) and ADG/DMI was similar (P > .10; 181 vs 172 g/kg, SEM = 1.8). Dry matter intake for SYN-implanted steers was higher (P < .05) than for steers not implanted (8.4 vs 8.0 kg/d), as was ADG/DMI (P < .01, 182 vs 171 g/kg). During this more rapid growth period, the supplement x implant interaction for ADG was significant (P < .05; 1.35, 1.36, 1.59, and 1.44 kg/d for Treatments 1, 2, 3, and 4, respectively, SEM = .04). There were no differences in digestibilities or N balance. The results suggest that there is no improvement in performance under feedlot conditions when RSB replaces SBM in the diet of beef cattle, and, in young cattle, RSB may reduce the response expected by an estrogenic growth promoter.     

Evaluation of sulfur content of dried distillers grains with solubles in finishing diets based on steam-flaked corn or dry-rolled corn

Crossbred yearling steers (n=80; 406 ± 2.7 kg of BW) were used to evaluate the effects of S concentration in dried distillers grains with solubles (DDGS) on growth performance, carcass characteristics, and ruminal concentrations of CH(4) and H(2)S in finishing steers fed diets based on steam-flaked corn (SFC) or dry-rolled corn (DRC) and containing 30% DDGS (DM basis) with moderate S (0.42% S, MS) or high S (0.65% S, HS). Treatments consisted of SFC diets containing MS (SFC-MS), SFC diets containing HS (SFC-HS), DRC diets containing MS (DRC-MS), or DRC diets containing HS (DRC-HS). High S was achieved by adding H(2)SO(4) to DDGS. Ruminal gas samples were analyzed for concentrations of H(2)S and CH(4). Steers were fed once daily in quantities that resulted in traces of residual feed in the bunk the following day for 140 d. No interactions (P ≥ 0.15) between dietary S concentration and grain processing were observed with respect to growth performance or carcass characteristics. Steers fed HS diets had 8.9% less DMI (P < 0.001) and 12.9% less ADG (P=0.006) than steers fed diets with MS, but S concentration had no effect on G:F (P=0.25). Cattle fed HS yielded 4.3% lighter HCW (P = 0.006) and had 16.2% less KPH (P=0.009) than steers fed MS. Steers fed HS had decreased (P=0.04) yield grades compared with steers fed MS. No differences were observed among treatments with respect to dressing percentage, liver abscesses, 12th-rib fat thickness, LM area, or USDA quality grades (P ≥ 0.18). Steers fed SFC had less DMI (P < 0.001) than steers fed DRC. Grain processing had no effect (P > 0.05) on G:F or carcass characteristics. Cattle fed HS had greater (P < 0.001) ruminal concentrations of H(2)S than cattle fed MS. Hydrogen sulfide concentration was inversely related (P ≤ 0.01) to ADG (r=-0.58) and DMI (r=-0.67) in cattle fed SFC, and to DMI (r=-0.40) in cattle fed DRC. Feeding DDGS that are high in dietary S may decrease the DMI of beef steers and compromise the growth performance and carcass characteristics of feedlot cattle.     

Effects of supplemental energy and/or degradable intake protein on performance,grazing behavior,intake, digestibility,and fecal and blood indices by beef steers grazed on dormant native tallgrass prairie

To evaluate the effects of balancing total diet degradable intake protein with dietary total digestible nutrients (TDN), we conducted two studies during 2 yr with 100 (302 +/- 8 kg initial BW) mixed-breed yearling steers and 12 ruminally cannulated steers (526 +/- 28 kg). Steers individually received one of four supplements 5 d/wk while grazing dormant native tallgrass prairie. Supplements included: 1) corn and soybean meal, balanced for total diet degradable intake protein in relation to total diet TDN (CRSBM), 2) corn and soybean hulls, equal in supplemental TDN to CRSBM (CORN), 3) soybean meal, equal in supplemental degradable intake protein to CRSBM (SBM), or 4) a cottonseed hull-based control supplement (CONT). At each feeding (5 d/wk), steers consumed 13.6, 13.6, or 4.2 g of dry matter/kg of body weight, or 178 g of DM, respectively, of supplement. Steers fed CRSBM had greater (P < 0.01) average daily gain than cattle fed CORN or SBM. Feeding soybean meal (CRSBM, SBM) resulted in improved (P < 0.01) efficiency of supplement. Grazing time, intensity, and harvesting efficiency were reduced (P < 0.05) by corn supplementation (CRSBM and CORN), whereas the number of grazing bouts per day was increased (P < 0.08). Intake and digestibility of forage organic matter were reduced (P < 0.01) for steers supplemented with corn (CORN and CRSBM) vs cattle not fed corn (SBM and CONT). Total diet digestibility (P < 0.12) and digestible organic matter intake (P < 0.01) were greater for CRSBM-fed steers than for cattle fed either CORN or SBM. Steers fed CRSBM had greater (P < 0.01) fecal nitrogen and serum insulin than cattle fed CORN or SBM. Corn-fed cattle had lesser (P < 0.01) fecal pH and ADF concentrations than steers not consuming grain. Cattle fed supplements with soybean meal (CRSBM and SBM) had greater (P < 0.01) serum urea nitrogen than steers fed supplements without soybean meal (CORN, CONT). Supplemented steers grazing dormant tallgrass prairie had a greater rate of gain, with the greatest response in animal performance occurring when grain supplements were balanced for total diet degradable intake protein in relation to total diet TDN. These results lead us to suggest that grain-supplemented cattle grazing dormant tallgrass prairie require a balance of total diet degradable intake protein in relation to total diet TDN to optimize animal performance.     

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.     

Grazing methods and stocking rates for direct-seeded alfalfa pastures: I. Plant productivity and animal performance

A 4-yr study was conducted to determine the effects of two grazing methods (GM) at two stocking rates (SR) on alfalfa pasture plant productivity and animal performance and to ascertain the effect of grazing systems on subsequent performance of steers fed a high-concentrate diet. Eight pasture plots (.76 ha) were seeded in 1988 with alfalfa (Medicago sativa L. var. WL225) and divided into two blocks of four pastures each. Grazing methods consisted of a traditional four-paddock or an intensive 13-paddock system. Pastures were managed to allow a 36-d rest period with an average grazing season of 110 d. The low and high SR were 5.9 vs 11.7, 5.3 vs 10.5, 5.3 vs 7.9, and 5.3 vs 7.9 steers/ha for years 1989 to 1992, respectively. Following the grazing season, steers were placed in a feedlot and fed a high-concentrate diet (81% high-moisture corn, 14% corn silage, 5% protein-mineral supplement) for an average of 211 d. There was no effect of GM on herbage mass, pasture phase ADG, or live weight gain/hectare. Increasing the number of paddocks was beneficial when herbage mass was limited and stocking rate was above 7.9 steers/ha. Increasing SR above 7.9 steers/ha decreased herbage mass and pasture-phase ADG. As forage allowance increased, pasture-phase ADG increased quadratically (R2 = .82, P < .001), reached a plateau, and then decreased. Previous grazing system did not influence the performance of steers in the feedlot or their carcass characteristics. Optimum SR is dependent on herbage mass produced.     

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.     

Influence of forage level on passage rate, digestibility and performance of cattle

Two trials (feedlot and metabolism) were conducted to evaluate the influence of level of chopped tall fescue hay (FH) in high concentrate diets on average daily gain (ADG), liquid and particulate passage rates, digestibility and in situ digestibility of corn. In the feedlot trial, 36 Hereford steers were fed diets containing 15, 30 and 50% FH in combination with 74, 59 and 39% whole shelled corn (WSC) and a soybean meal supplement. Steers offered 15, 30 and 50% FH consumed 9.0, 9.0 and 7.6 kg dry matter (DM) per d; gained 1.19, .89 and .67 kg; and had DM to gain ratios of 7.6, 10.1 and 11.5, respectively. A negative correlation was observed between fecal pH and ADG (r = -.52) and between fecal pH and fecal starch (r = -.40). In a 4 X 4 Latin-square trial, four cannulated steers were fed 4, 8, 16 or 24% FH in combination with 86, 82, 74 or 66% WSC and a soybean meal supplement. After 14 d of adaptation, steers were offered ytterbium (Yb)-labelled WSC and were ruminally pulse-dosed with chromium ethylenediaminetetraacetic acid (Cr-EDTA) on the first day of the collection period. Steers fed 4, 8, 16 or 24% FH had the following particulate passage rates: 2.3, 2.7, 2.7 and 2.9%/h from fecal analyses; 2.3, 1.7, 2.4 and 2.8%/h from ruminal analyses; 6.0, 5.3, 6.3 and 8.1%/h for liquid, respectively. With increasing FH level, liquid passage rate exhibited linear and quadratic effects (P less than .05), while particulate passage rate (rumen sampling) showed linear and cubic effects (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of haylage and monensin supplementation on performance, carcass characteristics, and ruminal metabolism of feedlot cattle fed diets containing 60% dried distillers grains

The objectives of this research were to determine the interaction of monensin and haylage supplementation for steers fed 60% dried distillers grains (DDGS) on 1) mineral status, performance, and carcass characteristics, and on 2) ruminal pH, H(2)S, and short-chain fatty acid concentrations. In Exp. 1, Angus-cross steers (n=168; BW=277 ± 67 kg) were blocked by BW and allotted in a 2 × 2 factorial arrangement of treatments to 24 pens. Dietary treatments were 1) 0 mg of monensin/kg of diet + 0% haylage, 2) 33 mg of monensin/kg of diet + 0% haylage, 3) 0 mg of monensin/kg of diet + 10% haylage, and 4) 33 mg of monensin/kg of diet + 10% haylage. The remainder of the diet was 60% DDGS, 10% corn silage, 15% supplement, and corn (either 5 or 15%) on a DM basis. When supplemented with 0 mg of monensin/kg of diet, added haylage increased ADG by 5.7%, whereas when supplemented with 33 mg of monensin/kg of diet, added haylage increased ADG by 13% (P < 0.01). No interactions of monensin and haylage were observed for DMI or G:F (P ≥ 0.36). Haylage inclusion increased (P < 0.01) DMI and decreased (P < 0.01) G:F. No interactions (P > 0.05) on plasma mineral concentrations were observed; however, over time, plasma Cu concentrations decreased (P < 0.01), whereas plasma ceruloplasmin and S concentrations increased (P < 0.01). There were no treatment effects (P ≥ 0.08) on carcass characteristics. Cattle fed the 60% DDGS diets benefitted from increased dietary forage, and the effects of monensin and forage were additive for ADG and final BW. In Exp. 2, ruminally fistulated steers (n=8; BW = 346 ± 34 kg) were used in a replicated 4 × 4 Latin square design and were randomly assigned to the diets used in Exp. 1. Haylage inclusion increased ruminal pH from 1.5 through 12 h postfeeding, and the effects of monensin supplementation were additive (P < 0.05). From 1.5 through 9 h postfeeding, steers fed 33 mg of monensin/kg of diet tended to have reduced (P ≤ 0.10) concentrations of H(2)S when compared with steers fed 0 mg of monensin/kg of diet. Acetate:propionate ratios at 6 h postfeeding were 0.94, 0.93, 1.29, and 1.35 for diets 1 to 4, respectively (P < 0.01); total lactate was decreased regardless of treatment (range: 0.94 to 1.42 μmol/mL). Sulfuric acid in DDGS, not ruminal short-chain fatty acids, may be responsible for the low rumen pH observed and may influence the maximum inclusion of DDGS in cattle diets. Monensin supplementation decreased H(2)S concentration and may decrease the risk of polioencephalomalacia for cattle fed high-DDGS diets.     

Effect of feed delivery fluctuations and feeding time on ruminal acidosis, growth performance, and feeding behavior of feedlot cattle

Research was conducted to determine whether fluctuations in the amount of feed delivered and timing of feeding affect ruminal pH and growth of feedlot cattle. In Exp. 1, the effects of constant (C) vs. fluctuating (F) daily feed delivery on ruminal pH were assessed in a crossover experiment (two 28-d periods) involving six mature, ruminally cannulated steers. The diet consisted of 86.8% barley grain, 4.9% supplement, and 8.3% barley silage (DM basis) and was offered ad libitum for 2 wk to estimate DMI by individual steers. Steers in group C were offered a constant amount of feed daily equal to their predetermined DMI, whereas steers in group F were offered 10% more or less than their predetermined DMI on a rotating 3-d schedule. Ruminal pH of each steer was measured continuously via an indwelling electrode placed in the rumen during the last 6 d of each period. Mean pH tended to be lower (0.10 units) for F than C (5.63 vs. 5.73; P = 0.15), and ruminal pH of steers in group F tended to remain below 5.8 (P = 0.03) or 5.5 (P = 0.14) for greater proportions of the day than steers in group C. Inconsistent delivery of feed lowered ruminal pH, suggesting increased risk of subclinical acidosis. In Exp. 2, a 2 x 2 factorial was used to study the effects of pattern (C vs. F) and feeding time (morning [0900] vs. evening [2100]) on the feeding behavior and performance of 234 (310 +/- 23 kg) Charolais x Hereford beef steers during backgrounding and finishing phases over 209 d. One pen per treatment was equipped with a radio frequency identification (GrowSafe Systems Ltd., Airdrie, Canada) system that monitored bunk attendance by each steer throughout the trial. Pattern of feed delivery did not affect (P = 0.16) DMI (7.36 kg/d), ADG (1.23 kg/d), G:F (0.17), or time spent at the bunk (141 min/d), nor were pattern of feed delivery x time of feeding interactions observed (P = 0.18). Late feeding increased (P < 0.05) daily DMI (7.48 vs. 7.26 kg), ADG (1.28 vs. 1.00 kg/d), and G:F (0.21 vs. 0.15). These studies indicate that the risk of subclinical acidosis was increased with fluctuating delivery of feed, but the greater risk of acidosis did not impair growth performance by feedlot cattle. Consequently, daily intake fluctuations of 10% DMI or less that do not alter overall intake by feedlot cattle are unlikely to have any negative consequences on growth performance.     

Effects of feeding growing cattle high-concentrate diets at a restricted intake on feedlot performance

Three trials were conducted to compare effects of restricted intake of high-concentrate diets vs ad libitum intake of corn silage diets during the growing phase on feedlot cattle performance. In Trial 1, 120 steers (initial BW, 246 kg) were fed 1) a corn silage-based diet ad libitum, 2) a high-moisture corn-corn silage-based diet with intake restricted to a level 20% less than that of the corn silage diet or 3) a high-moisture corn-based diet with intake restricted to a level 30% less than that of the corn silage diet. Steers fed the 20% restricted corn-corn silage-based diet tended (P = .07) to gain slower than those fed the corn silage or 30% restricted high-concentrate diet. Feed efficiency and diet digestibility were greatest for steers fed the 30% restricted-intake, high-concentrate diet (P less than .01). Performance of steers during the subsequent 118-d finishing period was not affected (P greater than .65) by source of energy during the growing period. In Trial 2, ADG of steers fed the 30% intake-restricted, high-concentrate diet was lower (P less than .01) than that of steers with ad libitum access to corn silage. During the 84-d growing period, steers fed supplemental blood meal had 8.3% greater gains and a 6% greater efficiency of feed use than those fed supplemental soybean meal (P less than .01). Monensin did not affect (P = .82) performance of steers fed 30% restricted-intake diets. During the 76-d finishing period, gains and feed conversion were improved (P less than .01) for steers fed the restricted-intake diet in the growing period compared with those given ad libitum access to corn silage. During the growing period in Trial 3, ADG of steers restricted-fed an all-concentrate diet were slightly greater (P less than .10) than ADG of those given ad libitum access to corn silage. Gains did not differ (P = .37) during the subsequent finishing period when steers were switched to 85 or 100% concentrate diets. We concluded that intake of all concentrate diets can be restricted to achieve gains equal to those of steers given ad libitum access to corn silage-based diets without detrimental effects on finishing performance.