Three experiments were conducted to evaluate supplementation of dried distillers grains with solubles (DGS) to spring-calving beef cows (n = 120; 541 kg of initial BW; 5.1 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplemental treatments included (DM basis) 1) 0.77 kg/d DGS (DGSL); 2) 1.54 kg/d DGS (DGSI); 3) 2.31 kg/d DGS (DGSH); 4) 1.54 kg/d of a blend of 49% wheat middlings and 51% cottonseed meal (POS); and 5) 0.23 kg/d of a cottonseed hull-based pellet (NEG). Feeding rate and CP intake were similar for DGSI and POS. In Exp. 1, cows were individually fed 3 d/wk until calving and 4 d/wk during lactation; total supplementation period was 119 d, encompassing 106 d of gestation and 13 d of lactation. Tall-grass prairie hay (5.6% CP, 50% TDN, 73% NDF; DM basis) was fed for ad libitum intake throughout the supplementation period. Change in cow BW and BCS during gestation was similar for DGSI and POS (-5.0 kg, P = 0.61 and -0.13, P = 0.25, respectively) and linearly increased with increasing DGS level (P < 0.01). Likewise, during the 119-d supplementation period, BW and BCS change were similar for DGSI and POS (-72 kg, P = 0.22 and -0.60, P = 0.10) and increased linearly with respect to increasing DGS (P < 0.01). The percentage of cows exhibiting luteal activity at the beginning of breeding season (56%, P = 0.31), AI conception rate (57%, P = 0.62), or pregnancy rate at weaning (88%, P = 0.74) were not influenced by supplementation. In Exp. 2, 30 cows from a separate herd were used to evaluate the effect of DGS on hay intake and digestion. Supplementation improved all digestibility measures compared with NEG. Hay intake was not influenced by DGS (P > 0.10); digestibility of NDF, ADF, CP, and fat linearly increased with increasing DGS. In Exp. 3, milk production and composition were determined for cows (n = 16/treatment) of similar days postpartum from Exp. 1. Daily milk production was not influenced by supplementation (6.3 kg/d, P = 0.25). Milk fat (2.1%) and lactose (5.0%) were not different (P > 0.10). Milk protein linearly increased as DGS increased (P < 0.05) and was greater for DGSI compared with POS. Similar cow performance was achieved when cows were fed DGS at the same rate and level of CP as a traditional cottonseed meal-based supplement. Increasing amounts of DGS did not negatively influence forage intake or diet digestibility.

In a 3-yr study, 139 fall-born steers (Angus and Angus x Charolais; BW=287±31 kg in mid-April) were allotted to 1 of 4 treatments in a 2 x 2 factorial arrangement. Weaning date treatments were 1) mid-April at 212±12 d of age (normal weaning; NW) and 2) mid-July at 300±15 d of age (late weaning). Finishing system treatments were feedlot placement in 1) July, with a mean calf age of 310±14 d (calf-fed; CF), and 2) October, with a mean calf age of 394±15 d (yearling-fed; YF). Steers assigned to the NW treatment were returned to native tall grass prairie rangeland after weaning each year. Steers assigned to the YF treatment grazed abundant native tall grass prairie pasture for an additional 84-d period. The number of days on feed was greater (P<0.01) for CF compared with YF. Late-weaned steers were 16 kg heavier (P<0.01) at the time of feedlot entry compared with NW steers. No other differences (P>0.05) for time of weaning were detected, nor were there any interactions (P>0.05) between weaning and finishing system. Yearling-fed steers were heavier (34 kg; P<0.01) at the time of feedlot placement, had greater (P<0.01) DMI, and had greater (P<0.01) feedlot ADG (1.80 vs. 1.68 kg) than CF, resulting in greater final BW and hot carcass weight (P<0.01). No other differences (P>0.05) were detected for any carcass traits measured. System economic analysis showed no differences in break-even selling price or system profitability.

Eight ruminally cannulated steers (BW = 753 +/- 48 kg) were used to evaluate in situ N, NDF, and DM degradation characteristics of by-product feeds and their application for beef cows consuming low-quality forage. Experimental feedstuffs included (DM basis) 1) extruded-expelled cottonseed meal (ECSM; 33% CP and 55% NDF), 2) extruded-expelled cottonseed meal with linters (ECSML; 25% CP and 41% NDF), 3) dried distillers grains with solubles (DGS; 33% CP and 36% NDF), 4) solvent-extracted cottonseed meal (CSM; 43% CP and 29% NDF), and 5) a blend of 76% wheat middlings with 18% CSM (WMCSM; 23% CP and 40% NDF). Steers were fed chopped prairie hay (4.8% CP, 69% NDF; DM basis) ad libitum and received 0.38 kg/100 kg of BW of WMCSM daily. In situ degradation kinetics of N, NDF, and DM components included the following fractions: A (immediately soluble), B (potentially degradable), and C (undegradable). Calculated rumen degradable protein (RDP) for ECSM was the greatest among all feedstuffs (83.8%; P < 0.01), which was composed of a large A fraction of N (41%). Similar RDP values were observed for DGS and ECSML (50.7 and 50.9%, respectively, P = 0.93). The B fraction N for ECSML was large (88.9%); however, most of this was unavailable for ruminal degradation. The amount of RDP in CSM and WMCSM was similar (78.2 and 73.5%, respectively; P = 0.12) though the A fraction of N was greater for WMCSM compared with CSM (P < 0.01). Degradability of NDF was greatest (P < 0.01) for DGS (67.4%) and was similar (P = 0.48) for WMCSM and CSM (54.5 and 57.0%, respectively). The least degradability of NDF was calculated for ECSM (29.3%; P < 0.01), attributed to greater lignin content (13.3%, DM). Degradability of DM was greatest (P < 0.01) for CSM and WMCSM (63.7 and 59.4%, respectively) and least (P < 0.01) for ECSM (36.5%) and ECSML (40.6%). Ruminal N degradation characteristics of ECSM were similar to more traditional supplements containing CSM and WMCSM. The RDP for ECSML and DGS N was less compared with other feedstuffs, indicating these feeds may need to be blended with other ingredients containing greater concentrations of degradable N, particularly in situations in which forage RDP is low.

To evaluate the effects of feeding increasing levels of dried distillers grains with solubles (DDGS) during preconditioning, weaned steer (n = 64) and heifer (n = 64) calves were stratified by BW and allotted to receiving pens for a randomized complete block design. Dietary treatments included DDGS at 0.30, 0.75, 1.20, or 1.65% of mean pen BW. Throughout 56 d, prairie hay (4.8% CP, 68.8% NDF) was fed ad libitum, and refusals were measured weekly. After 56 d, steer calves grazed wheat pasture before entering the feedlot; heifers were placed in the feedlot. Calves readily consumed DDGS at all levels fed. As DDGS level increased, ADG increased quadratically (P < 0.01), hay intake decreased linearly (P < 0.01) and G:F improved quadratically (P < 0.01). Wheat pasture ADG was greatest for steers fed the lowest DDGS level (P < 0.01) and decreased linearly across treatments (P < 0.01). For steers, hot carcass weight and marbling score increased numerically (linear, P = 0.13; linear, P = 0.12, respectively) with increasing DDGS during preconditioning. Other measured carcass characteristics were not influenced by DDGS level for steers or heifers (P > 0.20). Optimal G:F was estimated at 1.5 and 1.36% DDGS feeding for steers and heifers, respectively. At 1.65% of BW, visual symptoms of polioencephalomalacia were not observed. We suggest a maximum DDGS feeding rate of 1.25% of BW for growing calves consuming native tall grass prairie hay as long as maximum dietary sulfur concentrations are not exceeded.

Three experiments were conducted to evaluate the efficacy of supplemental energy and extruded-expelled cottonseed meal (ECSM; 30.6% CP; 44% NDF, 10.2% fat; DM basis) as a protein supplement (SUP) to spring-calving beef cows (n = 96; 535 kg initial BW; 5.4 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplementation of ECSM was compared with 2 traditional cottonseed meal-based SUP. For all experiments, SUP provided equal CP. On a DM basis, SUP included 1) a blend of 76% wheat middlings and 18% solvent-extracted cottonseed meal (WMCSM); 2) solvent-extracted cottonseed meal (CSM); and 3) delinted, extruded-expelled cottonseed meal (ECSM). In Exp. 1, cows were individually fed SUP 3 d/wk until calving and 4 d/wk during lactation; total SUP period was 95 d. Tall-grass prairie hay (4.4% CP; 74% NDF; DM basis) was provided during the SUP period. Changes in cow BW during gestation (P = 0.23), over the SUP period (P = 0.27), and over the 301-d experiment (P = 0.56) were similar. Changes in BCS were similar during gestation (P = 0.78), over the SUP period (P = 0.95) and over the 301-d experiment (P = 0.37). Calf birth weights (P = 0.21) and BW at weaning (P = 0.76) were not different. Percentage of cows exhibiting luteal activity at the beginning of breeding season (P = 0.59), AI conception rate (P = 0.71), and pregnancy rate at weaning (P = 0.88) were not different. In Exp. 2, 18 cows in early lactation from Exp. 1 were used to determine the effect of SUP on hay intake and digestion. Hay intake tended (P = 0.10) to be greater for CSM than ECSM. Intake of OM and DM was greater for WMCSM (P 0.10). Similarly, 24-h milk production was not different (P = 0.25). Neither greater energy intake of cows consuming WMCSM nor greater fat intake of cows consuming ECSM influenced cow performance measures or calf weaning weight. Cow response to SUP with ECSM compared with traditional cottonseed meal-based SUP indicates that ECSM is a viable source of supplemental protein for beef cows consuming low-quality forage.

ABSTRACT: Three experiments were conducted to evaluate the efficacy of extruded-expelled cottonseed meal (ECSM) as a protein supplement (SUP) to spring-calving beef cows (n = 102; 535 kg of initial BW; 5.4 initial BCS) consuming,low-quality forage during late gestation and early lactation. Supplementation of ECSM was compared,to two traditional cottonseed meal-based SUP. For all Experiments, SUP provided equal CP and included (DM basis): 1) 2.02 kg/d cottonseed meal and wheat midds-based SUP (CSM20); 1.02 kg/d 40% cottonseed meal-based SUP (CSM40); and 1.50 kg/d ECSM. In Exp. 1, cows were individually fed SUP 3 d/wk until calving and 4 d/wk during lactation; total SUP period was 96-d. Tall-grass prairie hay was provided ad libitum during the SUP period. Change in cow BW during SUP period was similar (-69 kg; P= 0.23). Cow BW was not different at weaning (508 kg; P= 0.77). Cow BCS was similar when SUP ended (4.54; P = 0.55) and at weaning (4.34; P= 0.43). Calf birth weight (35 kg; P= 0.20) and BW at weaning (213 kg; P= 0.76) were not different. Percentage of cows exhibiting luteal activity at beginning of breeding season (24%; P= 0.59) and pregnancy rate at weaning (84%; P= 0.88) were not different among SUP. In Exp. 2, cows (n = 20/trt) from Exp. 1, of similar d post-partum were machine-milked to evaluate the effect of SUP on milk production and

Moderate-framed Angus steers from a single cow herd were utilized in a 2-yr study that evaluated performance, carcass traits, and production economics of calf-fed vs. yearling systems. After a brief preconditioning period, weaned steer calves were placed on a high concentrate finishing diet (CF; n = 63) or grazed wheat pasture 164 d before feedlot entry (YF; n = 62). Resulting feedlot entry weight and days on feed were 228 kg and 169 d, respectively, for CF and 445 kg and 88 d, respectively, for YF. Final BW for YF was 87 kg heavier than CF (P < 0.01). For YF, ADG and DMI was greater and G:F was less than CF steers (P < 0.05). Hot carcass weight was 55 kg greater and LM area was 8 cm2 larger for YF compared with CF steers (P < 0.01). Dressing percentage was not different between systems (P = 0.90). System did not affect 12th-rib fat, USDA YG, or marbling score (P > 0.27). Profitability tended (P = 0.09) to favor the CF over the YF system, although breakeven selling price was greater (P < 0.01) for CF vs. YF. Live and carcass price was greater (P = 0.02) for the CF system. Net profit for CF and YF was not different (P > 0.10) when quality or yield grid markets were applied. Inclusion of a long-term winter wheat grazing period increased hot carcass weight by 17% with no detrimental effects on carcass characteristics.

Two experiments evaluated the effects of conventional and natural feedlot management systems (MS) on ractopamine-HCl (RAC) response in yearling steers. Feedlot performance, carcass characteristics, skeletal muscle gene expression, and circulating IGF-I concentrations were measured. The conventional system included a combined trenbolone acetate and estradiol implant, Revalor-S (IMP), as well as monensin-tylosin feed additives (IA). Treatments were arranged in a 2 x 2 factorial and included: 1) natural (NAT): no IMP-no IA, no RAC; 2) natural plus (NAT+): no IMP-no IA, RAC; 3) conventional (CON): IMP-IA, no RAC; and 4) conventional plus (CON+): IMP-IA, RAC. In Exp. 1, one hundred twenty crossbred steers (initial BW = 400 +/- 26 kg) were allotted randomly to treatment in a randomized complete block design (BW was blocking criteria); pen was the experimental unit. In Exp. 2, twenty-four individually fed crossbred steers (initial BW = 452 +/- 25 kg) were used in a randomized complete block design (BW was blocking criteria) and assigned to the same treatments as Exp. 1, with 6 steers/treatment. In Exp. 2, serum was harvested on d 0 and 31 and within the 28-d RAC feeding period, at d 0, 14, and 28. Longissimus biopsy samples were taken on d 0, 14, and 28 of the RAC feeding period for mRNA analysis of beta-adrenergic receptors and steady-state IGF-I mRNA. In Exp. 1, ADG, G:F, final BW, and HCW were greatest for CON+ (P < 0.01). During the final 37 d, RAC increased ADG (P = 0.05) and increased overall G:F (P = 0.02). Marbling score was reduced (P = 0.02), and yield grade was improved with RAC (P = 0.02), but RAC did not affect dressing percentage (P = 0.96) or HCW (P = 0.31). In Exp. 2, MS x RAC interactions were detected in ADG and G:F the last 28 d, overall ADG and overall G:F, final BW, and HCW (P < 0.01). Dressing percentage, yield grade, and marbling score were not altered by MS or RAC (P > 0.10). Circulating IGF-I concentration was increased on d 31 by the conventional MS, and concentration was greater throughout the study than NAT steers (P < 0.01). Circulating IGF-I concentrations were not changed by RAC (P = 0.49). Abundance of beta(1)-AR mRNA tended to increase (P = 0.09) with RAC, but RAC did not affect beta(2)-AR, beta(3)-AR, or IGF-I mRNA (P > 0.40). Management system did not affect beta(1)-AR, beta(2)-AR, beta(3)-AR, or IGF-I mRNA (P > 0.18), yet a trend (P = 0.06) for MS x RAC for beta(2)-AR mRNA was detected. These results indicate that response to RAC is affected by feedlot management practices.

Yearling steers (n = 2,552; 314 kg of initial BW) were used to evaluate the effects of ractopamine-HCl (RAC) and days on feed on performance, carcass characteristics, and skeletal muscle gene expression in finishing steers. Treatment groups included serial slaughter dates of 150, 171, or 192 d on feed. Within each slaughter date, steers either received RAC (200 mg/steer) daily for the final 28 d or were not fed RAC. All steers were initially implanted with Revalor-IS and were reimplanted with Revalor-S after 75 d on feed. At slaughter, muscle samples from the semimembranosus were collected for mRNA analysis of the beta-adrenergic receptors (beta-AR). Ractopamine administration increased (P < 0.05) ADG, G:F, and HCW and increased (P = 0.08) LM area. Ractopamine did not affect the dressing percentage, USDA yield grade, or quality grade (P > 0.3). There was no change in overall feed intake across the entire feeding period; however, feed intake was increased during the 28-d period during which the steers were fed RAC (P:E, 0.05). Greater days on feed decreased (P < 0.05) ADG, G:F, DMI, and the number of yield grade 1 and 2 carcasses. Also, greater days on feed increased (P < 0.05) HCW, dressing percentage, and the number of prime and choice carcasses, as well as the number of yield grade 4 and 5 carcasses. Increasing days on feed decreased (P < 0.05) the abundance of beta(1)-AR and beta(3)-AR mRNA and increased (P < 0.05) the abundance of beta(2)-AR mRNA in skeletal muscle samples obtained at slaughter. Ractopamine had no effect (P > 0.10) on the abundance of beta(1)-AR or beta(3)-AR mRNA, but tended (P = 0.09) to increase beta(2)-AR mRNA. Additional time-course studies with primary muscle cell cultures revealed that advancing time in culture increased (P < 0.001) beta(2)-AR mRNA but had no effect (beta > 0.10) on beta(1)-AR or beta(3)-AR mRNA. We conclude that days on feed and RAC are affecting beta-AR mRNA levels, which could, in turn, impact the biological response to RAC feeding in yearling steers.

Two-thousand two-hundred fifty-two yearling steers (690 lb) were used to evaluate the effects of Optaflexx and days on feed on finishing steer performance and carcass characteristics. Treatment groups included serial harvest dates of 150, 171, or 192 days. Within each harvest date, steers either received Optaflexx (200 mg/steer daily of ractopamineHCl) for the final 28 days, or did not receive Optaflexx. All steers were initially implanted with Revalor-IS and were re-implanted with Revalor-S after 75 days on feed. At harvest, muscle samples from the inside round were obtained for mRNA analysis of the βadrenergic receptors (AR). Optaflexx increased daily gains, hot carcass weight, and ribeye area, and improved feed efficiency. Optaflexx did not affect dressing percentage, USDA yield grade, or quality grade. Optaflexx did not change overall feed intake across the entire feeding period, but feed intake was increased during the 28-day period that steers received Optaflexx. As expected, greater days on feed decreased daily gains, overall feed intake, and the number of yield grade 1 and 2 carcasses, and worsened feed efficiency. Also, greater days on feed increased hot carcass weight, dressing percentage, and the number of prime and choice carcasses, as well as the number of yield grade 4 and 5 carcasses. Increasing days on feed decreased the abundance of mRNA for β1-AR and β3-AR, and increased the abundance of β2AR mRNA. Optaflexx had no effect on abundance of mRNA for β1-AR or β3-AR, but it increased the abundance of mRNA for β2-AR. Optaflexx may affect expression of the β2-AR gene in skeletal muscle, which could impact the performance responses to Optaflexx feeding in steers.