Effects of Restricted and Ad Libitum Intakes of Diets Containing Wheat Middlings During the Growing Phase on Performance and Carcass Composition of Early Weaned Steers

Three experiments were conducted to evaluate the effects of restricting the intake of 25% wheat middling diets during the growing phase on finishing phase performance and carcass composition of early weaned steers. In Exp. 1, early weaned Wagyu cross steers were used to compare effects of ad libitum (AL) intake vs restricted (RS; 75% AL) intake of a high concentrate diet. In Exp. 2, early weaned Continental cross steers were used to compare effects of AL intake vs RS intake of a high concentrate diet or hay for AL intake during the growing phase on finishing phase performance and carcass composition. In Exp. 3, early weaned Wagyu cross steers were used to evaluate the same treatments as Exp. 2. Steers were fed until they had ca. 1.0-cm subcutaneous fat cover. In Exp. 1, because steers fed for AL intake were leaner than RS-fed steers, backfat was used as a covariate for finishing phase performance and carcass composition. For Exp. 1, 2, and 3, steer performance for the finishing phase was adjusted to a common dressing percentage. In the growing phase of Exp. 1, steers fed AL gained 18.6% more (P<0.05) than RS-fed steers. However, feed efficiencies were similar for steers fed for AL intake and for RS-fed steers. In the finishing phase, ADG was similar for steers fed AL and for RS-fed steers. Steers fed AL tended (P<0.12) to be heavier at time of slaughter. During the growing phase of Exp. 2, steers fed high concentrate diets AL or RS gained more (P<0.01) than steers fed hay AL. Gain to feed ratio was higher (P<0.01) for AL steers than for steers fed hay AL. When growing and finishing phase performances were combined, steers fed AL had higher (P<0.01) daily gains than did steers fed hay AL. Also, feed efficiencies were improved (P<0.01) for steers fed AL and RS-fed steers more than for steers fed hay AL. Dressing percentages were higher (P<0.01) for steers fed AL and RS-fed steers when compared with steers fed hay AL. In Exp. 3, growing phase daily gains (P<0.04) and gain to feed ratio (P<0.03) were higher for steers fed AL and RS-fed steers than for steers fed hay AL. When growing and finishing phase performances were combined, steers fed for AL intake gained faster (P<0.03) than did steers fed hay AL. Feed efficiencies were improved (P<0.02) for steers fed AL and RS-fed steers compared with steers fed hay AL. Yield grades were higher (P<0.01) for AL steers than for steers fed hay AL.     

Corn processing method in finishing diets containing wet corn gluten feed

Two trials were conducted to determine the effect of corn processing method on performance and carcass traits in steers fed finishing diets containing wet corn gluten feed (WCGF). In Trial 1, 480 steer calves (303 kg initial BW) were fed eight finishing diets: 1) dry-rolled corn (DRC) without; and 2) with 32% (DM basis) WCGF; 3) steam-flaked corn (SFC) without; and 4) with WCGF; 5) a combination of DRC and SFC without WCGF; 6) finely-ground corn (FGC) with WCGF; 7) high-moisture corn (HMC) with WCGF; and 8) whole corn (WC) with WCGF. Feeding WC + WCGF increased (P < 0.10) DMI and decreased gain:feed compared with all other treatments. Feeding DRC + WCGF increased (P < 0.10) DMI and decreased (P < 0.10) gain:feed compared with treatments other than WC + WCGF. Steers on treatments that included WCGF gained similarly, regardless of corn processing method, and at a rate 6% faster (P < 0.10) than steers fed diets that did not include WCGF. Gain:feed did not differ among steers fed SFC, SFC + WCGF, SFC + DRC, and HMC + WCGF. Steers fed SFC or SFC + WCGF were more efficient (P < 0.10) than steers fed DRC or FGC + WCGF. In Trial 2, 288 steer calves (382 kg initial BW) were fed six finishing diets: 1) DRC without; and 2) with 22% (DM basis) WCGF; 3) SFC without; and 4) with WCGF; 5) finely rolled corn (FRC) with WCGF; and 6) HMC corn with WCGF. Steers fed DRC + WCGF or FRC + WCGF consumed more DM (P < 0.10) than steers fed DRC, SFC, or SFC + WCGF. Feed intake did not differ between steers fed SFC + WCGF and HMC + WCGF. All treatment groups receiving WCGF consumed more DM (P < 0.10) feed than steers fed DRC or SFC without WCGF. Steers fed SFC + WCGF gained 8% faster (P < 0.10), and steers fed DRC 9.5% slower (P < 0.10) than steers receiving all other treatments. Daily gains did not differ among other treatment groups. Steers fed SFC or SFC + WCGF gained 10% more (P < 0.10) efficiently than all other treatment groups. Feed efficiency did not differ among steers fed DRC, DRC + WCGF, FRC + WCGF, and HMC + WCGF. Estimates for the NEg of WCGF calculated from animal performance indicated that WCGF contained approximately 25.3% more energy when fed with SFC than when fed with DRC. In general, more intensively processing corn improved gain:feed in finishing diets containing WCGF.     

Effects of Feed Intake Restriction on Performance and Carcass Characteristics of Finishing Beef Steers,

Crossbred steers (n = 264, 311 ± 1.6 kg initial BW) were blocked by BW, randomly assigned to one of four treatments (28 pens, 7 pens per treatment), and fed a common 90% concentrate diet to determine the effects of the severity of caloric restriction on animal performance and carcass characteristics. Treatments were 1) ad libitum access to feed for 151 d (AL100); 2) 75% of DMI by AL100 for 65 d, 95% of DMI by AL100 for 65 d, and ad libitum access to feed for 21 d (AL85); 3) 80% of DMI by AL100 for 65 d, 100% of DMI by AL100 for 65 d, and ad libitum access to feed for 21 d (AL90); and 4) 85% of DMI by AL100 for 65 d, 105% of DMI by AL100 for 65 d, and ad libitum access to feed for 21 d (AL95). Feed was offered for AL85, AL90, and AL95 based on DMI by AL100 the previous week. All steers were fed a similar quantity of DM for 4 d prior to initial, interim, and final BW determinations to minimize gastrointestinal fill differences. Overall DMI was greater (P<0.01) for AL100 than for the average of the remaining treatments and decreased linearly (P<0.01) among AL95, AL90, and AL85. Overall ADG (carcass-adjusted) was less (P<0.01) for AL85, AL90, and AL95 than for AL100, whereas overall ADG:DMI (carcass-adjusted) did not differ (P>0.10) between AL100 and the average of the remaining treatments. Overall ADG and ADG:DMI (carcass-adjusted) responded quadratically (P<0.05) with increasing DMI restriction. Hot carcass weight, longissimus area, and kidney, pelvic, and heart fat percentage were greater (P<0.05) for AL100 than for the remaining treatments and responded quadratically (P<0.10) among AL85, AL90, and AL95. Marbling score was greater (P<0.10) for AL100 than for the average of the remaining treatments, and the number of carcasses grading Prime + Choice tended to be higher (P<0.15) for AL100 and AL95. Restricting feed intake of finishing yearling steers to an average of 85 to 95% of ad libitum for 130 d of a 151-d feeding period generally resulted in slower ADG, lesser marbling scores, and carcasses that were lighter and leaner compared with yearling steers allowed ad libitum to feed and harvested after an equal number of days on feed.     

Effects of grain processing and dietary lipid source on performance, carcass characteristics, plasma fatty acids, and sensory properties of steaks from finishing cattle

An experiment was conducted to evaluate the effects of grain processing and lipid addition to finishing diets on cattle performance, carcass characteristics, and meat quality. Eighty Hereford x Angus steers (384 kg +/- 17 kg of BW) were fed diets containing steam-flaked corn (SFC) or dry-rolled corn (DRC) with and without the addition of tallow (SFC/Fat and DRC/Fat) or steam-flaked corn with ground flaxseed (SFC/Flax). Ribeye steaks from steers fed SFC, SFC/Fat, or SFC/ Flax were used to evaluate the effects of fat source on meat quality. Cattle fed SFC and SFC/Fat tended to have greater ADG, G:F, HCW, and USDA yield grade, compared with those fed DRC and DRC/Fat (P < 0.10). Steaks from steers fed SFC/Flax developed a detectable off-flavor (P < 0.05) compared with steaks from steers fed SFC and SFC/Fat, and steaks from steers fed SFC retained desirable color longer than those from steers fed SFC/Flax (P < 0.05). Feeding SFC/Flax increased deposition of alpha-linolenic acid in muscle tissue compared with feeding SFC or SFC/Fat (P < 0.01). Dietary treatment did not cause differences in tenderness, juiciness, or flavor intensity. Ground flaxseed can replace tallow in finishing diets without loss in performance, but flax may affect flavor and color stability of beef. Feeding flaxseed can effectively alter composition of carcass tissues to yield beef that is high in n-3 fatty acids.     

Influence of Betaine on Pasture,Finishing, and Carcass Performance in Steers

Two experiments were conducted to investigate the effects of supplemental betaine on steer performance, fat deposition, and carcass characteristics. In Exp. 1 (grazing phase), 80 steers (317 kg) were fed either 1.0 kg of a control supplement (30% CP) or 1.0 kg of the control supplement plus 20 g of betaine per head per day. Betaine supplementation had no effect on overall gain or fat deposition (P>0.10) but increased ADG (P<0.10) during d 46 to 90 (0.64 vs 0.72 kg; control vs betaine, respectively). The pasture groups remained intact and were moved to the feedlot for 141 d and fed a control diet or the control diet plus 20 g of betaine per head per day. Betaine had no overall effect on finishing gain (P>0.10); however, this response was variable by period. Betaine increased final fat thickness and fat thickness change (P<0.10), but did not affect marbling or longissimus area (P>0.10). Supplemental betaine on pasture increased feed intake, final BW, and hot carcass weight (P<0.05) and increased final fat thickness and fat thickness change (P<0.10) during the finishing phase. In Exp. 2, supplemental betaine (40 g/d) was fed to steers (averaging 584 kg) in 11 replications during the last week before harvest. The overall weighted average increase in dressing percentage when betaine was fed was +0.34% (P<0.05). There was no effect (P>0.10) on fat thickness or marbling. Season of year did not affect response.     

Use of dried distillers grains throughout a beef production system: effects on stocker and finishing performance, carcass characteristics, and fatty acid composition of beef

A 2-yr study was conducted using a 3 × 2 factorial arrangement of treatments to evaluate the effects of feeding dried distillers grains throughout a beef production system on performance, carcass characteristics, and fatty acid profile of beef. Factors were wheat pasture supplement [no supplement (CON), dry-rolled corn (DRC), and dried distillers grains (DDG)] fed at 0.5% BW daily and finishing diet [steam-flaked corn based diet containing 0 (SFC) or 35% (35DDG) DDG]. Each year, 60 preconditioned Hereford steers (initial BW = 198 kg ± 3) grazed winter wheat pasture with or without supplement. Body weight gain was 8% greater for steers consuming DDG supplement compared with CON and DRC steers (P < 0.01). After the grazing period, pastures within supplement treatment were randomly assigned to SFC or 35DDG. There was no supplement by finishing diet interaction for any performance or carcass variable of interest (P ≥ 0.41). Previous supplementation on winter wheat affected BW at feedlot entry and adjusted G:F (P ≤ 0.05) but had no effect on finishing ADG or carcass traits (P ≥ 0.12). On a carcass-adjusted basis, steers consuming 35DDG had reduced final BW, ADG, G:F, and total BW gain throughout the system (P ≤ 0.04) compared with SFC. Additionally, steers consuming 35DDG had reduced HCW, dressing percent, and fat thickness (P ≤ 0.03) compared with SFC. There was a supplement by finishing diet interaction (P = 0.02) for 18:0, in which cattle supplemented with DRC and fed the SFC finishing diet had the lowest concentration of 18:0 but DRC supplemented steers fed the 35DDG diet had the greatest concentration. The interaction was not significant (P ≥ 0.18) for other fatty acids. Main effects of supplement and finishing diet affected (P ≤ 0.05) several other fatty acids of interest, particularly 18:2, which is associated with reduced flavor-stability of beef. The use of DDG as a supplement to wheat pasture resulted in greater ADG during wheat grazing and heavier BW at feedlot entry, but final BW was not different from CON or DRC groups. Feeding DDG at 35% DM in steam-flaked corn-based finishing diets reduced ADG, G:F, and HCW, and affected the fatty acid composition of beef.     

Effects of Dietary Phosphorus and Microbial Phytase Level on Beef Finishing Performance

Two experiments were conducted to evaluate the effect of feeding microbial phytase on P availability and feedlot performance of beef steers fed a whole corn-based diet. In Experiment 1, six crossbreed steers were used in a replicated 3 x 3 Latin square design. Steers were paired according to BW, and each pair was assigned to one of three treatment groups: 1) 0 FTU phytase [the quantity of phytase needed to hydrolyze 1 μM of inorganic P/min (37.2˚C and pH 5.5)]; 2) 250 FTU phytase; and 3) 500 FTU phytase. Treatments were rotated so that each pair of steers received each treatment for a 20-d period. During the last 5 d of each rotation period, steers were placed in metabolism stalls, and feed and feces were collected for mineral analyses. Apparent digestibilities for P, Ca, Mg, and Cu responded quadratically (P<0.05) as phytase level increased from 0 to 500 FTU. There were no differences in fecal mineral content (DM basis) or Zn apparent digestibility among treatments. In Experiment 2, 288 steers were used in a completely randomized experimental design to evaluate the effects of P and microbial phytase level on feedlot performance, carcass data, and apparent mineral availability. Steers were assigned to one of four treatment gruaps: 1) 0.35% dietary P and 0 FTU phytase, 2) no supplemental dietary P and 0 FTU phytase 3) no supplemental dietary P and 200 FTU phytase, and 4) no supplemental dietary P and 400 FTU phytase. Diets without supplemental dietary P averaged 0.30% P. Each treatment group consisted of six pens of 11 or 12 steers each. Steers from two pens of each treatment were used to assess the apparent digestibility of P, Ca, Mg, Cu, and Zn. Chromic oxide was used as a digestion marker and was fed, in a pellet, to steers in each pen for 17 d. During the last 3 d of each period, feed and feces were collected. There were no significant differences observed among treatments for feedlot performance or slaughter data. Fecal P percentage for steers receiving the 0.35% P and 0 FTU phytase treatment was significantly greater than that for steers receiving the other treatments. Apparent digestibility of Ca and P responded linearly and quadratically (P<0.05) as phytase level increased from 0 to 400 FTU. Magnesium, Cu, and Zn apparent digestibility responded linearly (P<0.10) as phytase level increased. These experiments suggest that supplementing microbial phytase enhanced mineral apparent digestibility in ruminants and that supplementing P did not improve feedlot performance.     

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

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

Effects of dry, wet, and rehydrated corn bran and corn processing method in beef finishing diets

Two finishing trials were conducted to determine the effects of adding different types of corn bran, a component of corn gluten feed, on cattle performance. In Trial 1, 60 English crossbred yearling steers (283 +/- 6.7 kg) were used in a completely randomized design with four dietary treatments. Treatments were diets with no corn bran, dry corn bran (86% DM), wet corn bran (37% DM), and rehydrated dry bran (37% DM). Bran was fed at 40% of dietary DM. All finishing diets had (DM basis) 9% corn steep liquor with distillers solubles, 7.5% alfalfa hay, 3% tallow, and 5% supplement. Gain efficiency and ADG were greater (P < 0.01) for cattle fed no corn bran compared with all treatments containing corn bran; however, no differences were detected across corn bran types. In Trial 2, 340 English crossbred yearling steers (354 +/- 0.6 kg) were used in a randomized block design with treatments assigned based on a 2 x 4 + 2 factorial arrangement (four pens per treatment). One factor was the corn processing method used (dry-rolled corn, DRC; or steam-flaked corn, SFC). The other factor was corn bran type: dry (90% DM), wet (40% DM), or dry bran rehydrated to 40 or 60% DM. Bran was fed at 30% of dietary DM, replacing either DRC or SFC. Two control diets (DRC and SFC) were fed with no added bran. All finishing diets contained (DM basis) 10% corn steep liquor with distiller's solubles, 3.5% alfalfa hay, 3.5% sorghum silage, and 5% supplement. Corn bran type did not affect DMI (P = 0.61), ADG (P = 0.53), or G:F (P = 0.10). Dry matter intake was greater (P < 0.01) by steers fed bran compared with those fed no bran, and was greater by steers fed DRC than by steers fed SFC (P < 0.01). Interactions occurred (P < 0.01) between grain source and bran inclusion for ADG and G:F. The ADG by steers fed the SFC diet without bran was greater (P < 0.01) than by steers fed SFC diets with bran, whereas the ADG by steers fed DRC diets with or without bran was similar. Daily gain was 15.2% greater (P < 0.01) by steers fed SFC without bran than by steers fed DRC without bran. Gain efficiency was 16.9% greater (P < 0.01) for steers fed SFC without bran compared with steers fed DRC without bran. In DRC and SFC diets, feeding bran decreased (P < 0.01) G:F by 5.2 and 13.8%, respectively. The moisture content of corn bran had no effect on finishing steer performance, and drying corn bran did not affect its energy value in finishing cattle diets.     

Effects of an Estradiol Implant on Locoweed Consumption,Toxicity, and Recovery in Growing Beef Steers

Two experiments were conducted to determine effects of an estradiol implant (Compudose®) on locoweed consumption and toxicity in growing steers. In Exp. 1, 16 crossbred steers (185.3 ± 6.1 kg) were randomly assigned to two replicated treatments and received either an estradiol implant or no implant. Steers were assigned to one of four pastures and were rotated through all pastures, which differed in locoweed distribution, to allow equal access. Bite counts were recorded twice daily at 0600 and 1700 h during a period when steers were likely to consume locoweed. For bite counts, steers were observed for 5 min each, starting at 0600 and at 1700 h, and the number of bites taken of cool- and warm-season grasses, forbs, and locoweed were recorded. Blood was collected on d 0, 7, 28, 35, 63, and 119, and individual BW was recorded on d 0, 35, 63, and 119. Proportion of bites of locoweed consumed by implanted vs nonimplanted steers did not differ (P>0.10). Likewise, ADG, serum alkaline phosphatase activity, and thyroxine concentrations did not differ (P>0.10) between implanted and nonimplanted steers. In Exp. 2, 20 crossbred steers (212.3 ± 6.1 kg) were divided into four groups and individually fed in a 2 × 2 factorial arrangement of treatments. Treatments included: 1) estradiol implant + locoweed, 2) implant, no locoweed, 3) no implant + locoweed, and 4) no implant, no locoweed. Steers were implanted at d 0 and fed either a ground forage diet containing 80% sudangrass hay and 20% locoweed, or a diet of 100% sudangrass hay. Implanted steers had improved ADG vs nonimplanted steers (P<0.10) through 63 d on trial, but no differences were observed in steers fed locoweed vs sudangrass hay diets (P>0.90; locoweed x implant, P>0.10). Alkaline phosphatase activity was greater (P<0.05) for steers fed locoweed vs those not receiving locoweed on d 7, 14, and 21, whereas, thyroxine concentration was lower (P<0.06) in steers fed locoweed than those not fed locoweed on d 14 and 21. Estradiol concentrations were greater in implanted steers vs those not implanted (P<0.05). These results suggest no effect of an estrogen implant on locoweed consumption or on severity of locoweed toxicity by beef steers.     

Effects of supplemental zinc concentration and source on performance, carcass characteristics, and serum values in finishing beef steers

Three studies were conducted to examine the effects of zinc concentration or source in diets of finishing beef steers. In Exp. 1, 108 (British x Continental) beef steers were supplemented with concentrations of added zinc (as ZnSO4) at 20, 100, or 200 mg/kg of dietary DM. No differences (P > 0.10) were noted among treatments for ADG or gain:feed for the 112-d finishing period. However, a linear (P < 0.10) decrease was noted in daily DMI with increasing zinc concentrations for the overall finishing period. No differences (P > 0.10) were noted in hot carcass weight; dressing percentage; longissimus muscle area; percentage of kidney, pelvic, and heart fat; or marbling score. There were, however, quadratic increases in s.c. fat thickness (P < 0.05) and yield grade (P < 0.01) with added zinc. In Exp. 2, 12 beef steers were used to examine effects of added dietary zinc on serum concentrations of cholesterol and fatty acid profiles. No differences (P > 0.10) were observed in cholesterol or fatty acids among the supplemental zinc levels. In Exp. 3, 84 Brangus- and Angus-sired steers were fed a steam-flaked corn-based diet containing 30 mg of supplemental zinc per kilogram of dietary DM from one of the following sources: 1) ZnSO4, 2) Zn amino acid complex, or 3) a zinc polysaccharide complex. No differences (P > 0.10) were noted for the overall 126-d trial for ADG, DMI, or gain:feed ratio. Percentage kidney, pelvic, and heart fat was increased (P < 0.10) in steers supplemented with ZnSO4 vs the average of Zn amino acid and Zn polysaccharide complexes. However, s.c. fat thickness was greater (P < 0.10) in steers supplemented with Zn amino acid and Zn polysaccharide complexes vs ZnSO4. Serum zinc concentration did not differ (P > 0.10) among zinc sources. Supplemental zinc concentration in finishing diets did not seem to influence feedlot performance and had a minimal impact on carcass quality. Either the organic or inorganic source can be included in finishing diets without affecting feedlot performance.     

Combinations of alfalfa hay and wet corn gluten feed in limit-fed growing diets for beef cattle

Two experiments were conducted to evaluate the effects of alfalfa hay (AH) and wet corn gluten feed (WCGF) combinations on ADG and gain efficiency of cattle limit-fed growing diets. In Exp. 1, crossbred beef steers (n = 220; initial BW = 262 kg) were limit-fed diets consisting of steam-flaked corn and 40% WCGF (DM basis) with 0, 10, or 20% ground AH (0AH, 10AH, and 20AH, respectively). A fourth diet containing 20% ground AH and steam-flaked corn served as a control. All diets were fed once daily at 1.8% of BW (DM basis). Growing period ADG, gain efficiency, and dietary NE calculated from performance data decreased linearly (P < 0.01) with addition of AH to diets containing WCGF. Rate of DMI increased linearly (P < 0.05) with AH addition to diets containing WCGF. Following the growing period, steers were finished on a common diet offered ad libitum. Gain efficiencies during the finishing period were higher (P < 0.05) for steers fed the 20AH diet than for steers fed the control diet. In Exp. 2, crossbred beef heifers (n = 339; initial BW = 277 kg) were limit-fed diets containing steam-flaked corn with 10, 20, or 30% ground AH and 0, 40, or 68% WCGF in a 3 x 3 factorial arrangement, fed once daily at 1.6% of BW (DM basis). An AH x WCGF interaction occurred (P < 0.05) for growing period ADG and gain efficiency. Increasing AH or WCGF decreased cattle ADG, gain efficiency, and dietary NE with the exception of heifers fed 30AH/40WCGF, which had ADG that did not differ (P > 0.10) from that of heifers fed 20AH/0WCGF or 30AH/0WCGF, and which had greater gain efficiencies (P < 0.05) than heifers fed 30AH/0WCGF. Rate of DMI increased linearly (P < 0.01) with increasing AH and decreased linearly (P < 0.01) with increasing WCGF. Heifers were finished on diets containing 33% WCGF with 0 or 0.5% added urea (DM basis) offered ad libitum. Increasing WCGF in growing diets tended (linear, P < 0.10) to increase finishing ADG and gain efficiency, whereas increasing AH decreased (linear, P < 0.05) kidney, pelvic, and heart fat, and the percentage of carcasses grading USDA Prime. Urea tended to increase ADG (P < 0.10), but decreased (P < 0.04) the percentage of carcasses grading USDA Choice. Results suggest that the value of WCGF relative to steam-flaked corn in limit-fed growing diets might be improved in diets containing 30% AH relative to diets containing 10 or 20% AH.     

Effects of feeding whole cottonseed and cottonseed products on performance and carcass characteristics of finishing beef cattle

Three experiments were conducted to determine the effects of whole cottonseed or cottonseed products on performance and carcass characteristics of beef cattle. In Exp. 1, 120 beef steers (initial BW = 381 +/- 31.7 kg) were fed steam-flaked corn-based finishing diets with 10% (DM basis) basal roughage, and whole cottonseed or individual cottonseed components (cottonseed hulls, meal, and oil). Over the entire feeding period, ADG did not differ (P = 0.95), but DMI increased (P = 0.07) and G:F decreased (P = 0.06) for steers fed the cottonseed diets compared with the control diet. Dressing percent (P = 0.02) and marbling scores (P = 0.02) of carcasses from steers fed the cottonseed diets were less than for steers fed the control diet. In Exp. 2, 150 beef steers (initial BW = 364 +/- 9.9 kg) were used to determine the effects of whole cottonseed or pelleted cottonseed (PCS) on performance and carcass characteristics. Cattle were fed steam-flaked corn-based finishing diets in which whole cottonseed or PCS replaced all of the dietary roughage, supplemental fat, and supplemental natural protein of the control diet. Over the entire feeding period, steers fed the cottonseed diets had lower (P = 0.04) DMI and greater (P < 0.01) G:F than steers fed the control diet. Carcass characteristics did not differ (P = 0.16 to 0.96) among dietary treatments. In Exp. 3, 150 beef heifers (initial BW = 331 +/- 17.1 kg) were used to determine the effects of PCS or delinted, whole cottonseed (DLCS) on performance and carcass characteristics. Heifers were fed rolled corn-based finishing diets in which cottonseed replaced the dietary roughage, supplemental fat, and all or part of the supplemental natural protein of the control diet. Over the entire feeding period, ADG, DMI, and G:F of heifers fed the control diet did not differ (P = 0.19 to 0.80) from those of the cottonseed diets; however, heifers fed the diets containing PCS had greater ADG (P = 0.03) and G:F (P = 0.09) than heifers fed diets containing DLCS. Carcass characteristics of heifers fed the control diet did not differ (P > or = 0.28) from those fed the cottonseed diets. Heifers fed the diets containing PCS had greater (P < or = 0.03) HCW, dressing percent, and LM area than those fed DLCS. Based on our results, whole cottonseed, or products derived from processing whole cottonseed, can replace feedstuffs commonly used in beef cattle finishing diets with no adverse effects on animal performance or carcass characteristics.     

Canola Meal Compared with Urea in a Barley and Potato Processing Residue Finishing Diet for Feedlot Steers

Five combinations of canola meal and urea were compared in a titration study using yearling beef steers (n = 120, initial weight = 383 kg ± 6.25) consuming barley and potato processing residue-based diets. The steers were allotted to 20 pens in a randomized block design and fed for 86 d. Diets were formulated to contain 30% potato processing residue, 45% barley, 15% corn silage, and 10% supplement (DM basis). Nitrogen source was the only difference in the diets. Supplements were formulated to be isonitrogenous with the N source being either urea or canola meal (C) to provide a calculated dietary CP of 11.5%. Treatments were: 100% urea supplement (0C); 25% canola meal supplement, 75% urea supplement (25C); 50% canola meal supplement, 50% urea supplement (50C); 75% canola meal supplement, 25% urea supplement (75C); and 100% canola meal supplement (100C). Average daily gain and DMI were similar for all treatments (P>0.05). Gain to feed ratio was larger (P<0.05) for 75C than 0C (163.2 vs 151.5 g/kg). Marbling scores were greater (P<0.05) from steers fed 0C than from those fed 50C or 75C. Longissimus muscle area and hot carcass weights were greater for 25C than 0C (P<0.05). Longissimus muscle area for 100C was also larger than 0C (P<0.05). The yield grade of 25C steers was lower (P<0.05) than that found in the 0C, 50C, and 100C steers (P<0.05). The 25C treatment had the highest apparent NDF digestibility of all treatments (P<0.05). Additional return of $14.50 per steer fed canola was found (P>0.05). The changes in carcass composition toward a leaner carcass with natural protein (the 25C fed steers) indicate potential benefits from the use of canola meal in barley and potato processing residue-based diets instead of urea as the sole supplemental N source.     

Effects of High Dietary Calcium Propionate and Dietary Cation-Anion Balance on Calcium Metabolism and Longissimus Muscle Tenderness in Finishing Steers,

Forty-eight Angus and Angus-cross steers (initial BW = 657 ± 5.7 kg) were used in a 2 × 2 factorial design to determine whether feeding an anionic diet or high dietary concentrations of a soluble calcium (Ca propionate) source or both would alter Ca metabolism and subsequently longissimus tenderness. Treatments consisted of 1) control, 2) 4% Ca propionate (CaProp), 3) 2% NH ₄Cl (anionic diet), and 4) CaProp plus 2% NH₄Cl. Experimental diets were fed for 7 d prior to slaughter. Steers were individually fed using electronic Calan gate feeders. Blood samples were obtained on d 3 and 7 at 2 h post feeding for plasma Ca determination. A striploin steak was obtained from each carcass at 48 h post harvest for muscle Ca analysis and Warner-Bratzler shear force (WBSF) determination. Addition of CaProp or NH₄Cl to the high concentrate finishing diet reduced (P < 0.01) ADG and DMI during the 7-d feeding period. The anionic diet reduced ADG to a greater extent than did CaProp. Average daily gain and DMI were lowest for steers fed both NH₄Cl and CaProp, indicating that their effects were additive. Carcass characteristics were not affected by CaProp, but the anionic diet tended to reduce hot carcass weights (P=0.13) and longissimus areas (P=0.09). Plasma Ca concentrations were slightly greater in steers fed CaProp on d 3 (P < 0.10) and 7 (P < 0.01) of the study. The anionic diet did not affect plasma Ca. Muscle Ca concentrations and WBSF values were not affected by either CaProp or the anionic diet. Results indicate that beef tenderness was not enhanced in steers fed a diet high in CaProp or those fed an anionic diet.     

The Immune Response and Performance of Calves Supplemented with Zinc from an Organic and an Inorganic Source

Two experiments were conducted to determine the effects of supplemental zinc (Zn) from an organic and an inorganic source on growth performance, serum Zn concentrations, and immune response of beef calves. Treatments consisted of: i) control (no supplemental Zn), ii) Zn sulfate, or iii) Zn-amino acid complex. Zinc sources were supplemented to provide 360 mg of Zn/d. Experiment 1 was a 28-d study using 84 steers (240 ± 1.5 kg) fed bermudagrass hay (21 mg Zn/kg DM) with 1.8 kg/d of the appropriate corn-based supplement. In Exp. 2, 75 heifers (176 ± 2.5 kg) were fed bermudagrass hay (38 mg Zn/kg DM) and the supplements for 140 d. In Exp. 1, ADG was greater (P<0.05) from d 15 to 28 in calves fed supplemental Zn-amino acid compared with those fed Zn sulfate, but ADG did not differ (P>0.10) among treatments for the entire 28-d study. In Exp. 2, there was no effect (P>0.10) on ADG as a result of Zn supplementation. In Exp. 2, Zn-supplemented heifers had a greater response (P=0.06) tophytohemagglutinin 24 h after an intradermal injection. In Exp. 2, calves supplemented with Zn-amino acid complex had a greater antibody response to a second vaccination for bovine respiratory syncytial virus than did control or Zn sulfate-supplemented calves (treatment by day interaction, P=0.06). There was not a consistent benefit of supplemental Zn on growth of calves, but there was a positive impact of supplemental Zn on some immune response measurements.     

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.     

Evaluation of a Forage-Fat Blend as an Isocaloric Substitute for Steam-Flaked Wheat in Finishing Diets for Feedlot Cattle: Growth Performance and Digestive Function

Two trials were conducted to evaluate the addition of a forage-fat blend (FFB) as a substitute for grain in finishing diets for feedlot cattle. Treatments consisted of a steam-flaked wheat-based finishing diet containing 15, 29, or 45% FFB. The FFB contained 80% chopped alfalfa hay and 20% yellow grease and was formulated to have NE_m and NE_g values similar to that of wheat. In Trial 1, 126 crossbred steers (225 ± 5.4 kg) were used to evaluate treatment effects on growth performance and dietary NE. In Trial 2, three Holstein steers (448 ± 21 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. Increasing the FFB did not affect (P>0.10) ADG, but decreased gain efficiency (linear effect, P<0.05) and dietary NE concentration (linear effect, P<0.01). Increasing the FFB did not affect (P>0.10) ruminal digestion of starch, N, or microbial N (MN) efficiency, but decreased (linear effect, P<0.10) ruminal digestion of OM and increased (linear effect, P<0.10) ruminal digestion of ADF. Increasing the FFB did not affect (P>0.10) postruminal digestion of OM, starch, and N, but decreased postruminal digestion of fatty acids (linear effect, P<0.05). Increasing the FFB did not affect (P>0.10) percentage of total tract starch, N, and ADF digestion, but decreased the percentage of total tract digestion of OM (linear effect, P<0.01) and DE (linear effect, P<0.05). We conclude that an isocaloric FFB can replace grain at levels of up to 45% of dietary DM without affecting ADG in feedlot cattle. However, when dietary inclusion rates are > 15%, dietary NE and, hence, BW gain efficiency may decrease. The magnitude of the effect of FFB inclusion rate on energy recovery is a predictable function of the relationship between fatty acid intake and intestinal fatty acid digestion.     

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.     

Influence of Both Endophyte Infestation in Fescue Pastures and Calf Genotype on Subsequent Feedlot Performance of Steers

Three experiments were conducted to determine the influence of both the concentration of endophytic fungus infestation in tall fescue pastures and calf genotype on the subsequent health and performance of steers in the feedlot. In Exp. 1 and 2, Angus steers grazed fescue pastures in Georgia containing low, moderate, or high endophyte infestations for 182 d (Exp. 1) or 78 d (Exp. 2) with 12 steers per treatment. Steers were transported 1,600 km to Texas in October (Exp. 1) and July (Exp. 2), were fed a 93% concentrate diet during the finishing period, and were harvested at an estimated backfat thickness of 12 mm. In both trials, DMI over the entire feeding period and carcass characteristics were not affected (P>0.05) by endophyte infestation. In both trials, pasture ADG decreased, and feedlot ADG and gain to feed ratio increased as the previous pasture endophyte infestation increased (P<0.05). Serum cholesterol concentrations tended (P<0.10) to decrease with increasing endophyte infestation during the first 14 d in the feedlot. In Exp. 3, Angus and Brahman × British crossbred steers grazed fescue pastures in Georgia containing low, moderate, or high endophyte in each of 2 yr. Six steers of each breed group were on each treatment each year. Steers were transported to Texas in late August of each year, were fed a 93% concentrate finishing diet, and were harvested at an estimated individual backfat thickness of 12 mm. As endophyte infestation increased, serum urea N concentrations and gain to feed ratios increased (P<0.05), whereas pasture ADG, initial BW, transit shrink, serum cholesterol concentrations, final BW, and carcass weights decreased (P<0.05) in Angus steers, but not in Brahman-cross steers. In these studies, the adverse effects of high endophyte infestations in fescue pastures appeared to carry over to the feedlot for ca. 14 d. However, steers from highly infested pastures can compensate for poor pasture performance with improved performance in the feedlot when no adverse health effects occur. Any impact of the endophyte seems to be similar in Brahman-cross and Angus steers.