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

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

Effects of ractopamine on genetically obese and lean pigs

Twenty-eight genetically obese and 24 lean barrows (65.0 and 68.7 kg average BW, respectively) were allotted within genotype to a 16% CP corn-soybean meal basal diet or this basal diet + 20 ppm ractopamine (a phenethanolamine beta-adrenergic agonist) and allowed ad libitum access to feed for 48 d. Compared to lean pigs, obese pigs had lower ADG, gain to feed ratio, longissimus muscle area, predicted amount of muscle, and weights of trimmed loin and ham, ham lean, heart, spleen, kidney and gastrointestinal tract (P less than .05). Obese pigs also had shorter carcass but higher dressing percentage, backfat thickness, fat depth, fat area, untrimmed loin weight and fasting plasma urea N concentration (P less than .05). Dietary supplementation with 20 ppm ractopamine reduced daily feed intake and improved gain to feed ratio in both lean and obese pigs (P less than .05). Pigs fed ractopamine had shorter carcasses, less fat depth and fat area, smaller weights of stomach and colon plus rectum, but higher dressing percentages, longissimus muscle areas, weights of trimmed Boston butts, picnics and loins, ham lean and predicted amounts of muscle than pigs not fed ractopamine (P less than .05). Supplemental ractopamine had no effect on fasting plasma concentrations of urea N, nonesterified fatty acids, triglyceride or glucose (P greater than .05). No genotype x ractopamine interactions for the criteria described above were detected (P greater than .05). These results suggest that ractopamine will improve the efficiency of feed utilization and carcass leanness in swine with different propensities for body fat deposition.     

Effects of crude protein concentration and degradability on performance, carcass characteristics, and serum urea nitrogen concentrations in finishing beef steers

Two experiments were conducted at two locations to determine the effects of dietary CP concentration and source on performance, carcass characteristics, and serum urea nitrogen (SUN) concentrations of finishing beef steers. British x Continental steers were blocked by BW (357 +/- 28 and 305 +/- 25 kg initial BW; n = 360 and 225; four and five pens per treatment in Exp. 1 and 2, respectively). Steam-flaked corn-based diets were arranged in a 3 x 3 factorial with three CP concentrations (11.5, 13, or 14.5% of DM) and three sources of supplemental CP (N basis): 100% urea; 50:50 blend of urea and cottonseed meal; or 100% cottonseed meal. Steers in both experiments were initially implanted with Ralgro and reimplanted with Revalor-S on d 56. Performance and carcass data were pooled across locations. Crude protein concentration x source interactions were not observed (P = 0.22 to 0.93) for performance and carcass data. Crude protein concentration affected ADG (P = 0.02) and carcass-adjusted (to a common dressing percent within location) ADG quadratically (P = 0.06). Increasing the concentration of supplemental urea linearly increased carcass-adjusted ADG and G:F (P < 0.05) and carcass-adjusted G:F (P < 0.001). Dry matter intake was not affected (P = 0.93) by either CP concentration or source. Hot carcass weight (HCW; P = 0.02), LM area (P = 0.05), and dressing percent (P = 0.03) increased linearly with increasing urea concentration, whereas increasing CP concentration quadratically affected HCW (P = 0.02), with a maximum at 13% CP. Differences in backfat thickness and yield grade were negligible across treatments. Neither marbling score nor percentage of carcasses grading USDA Choice was affected by CP concentration or source. At all times measured, SUN concentrations increased (P < 0.05) with increasing CP concentration, but effects of CP source were small and variable across time. Results indicate that increasing CP concentrations from 11.5 to 13% slightly increased ADG and carcass-adjusted ADG, whereas increasing the proportion of supplemental urea increased carcass-adjusted ADG, G:F, and carcass-adjusted G:F and increased HCW, LM area, and dressing percent. A CP concentration above 13% seemed detrimental to ADG and HCW. Serum urea N increased over time, with CP concentration having a greater effect than CP source.     

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.     

Supplemental betaine and peroxide-treated feather meal for finishing cattle

These studies evaluated the effects of betaine, provided either as feed-grade betaine or as concentrated separator by-product (CSB; desugared beet molasses), on performance and carcass characteristics of finishing cattle. In Exp. 1, 175 steers (410 kg initial BW) were fed a finishing diet based on steam-flaked and dry-rolled corn, and treatments included 10.5 and 21 g/d feed-grade betaine and 250 and 500 g/d CSB (supplying 15.5 and 31 g/d of betaine, respectively). Steers fed feed-grade betaine had greater (linear and quadratic effects, P < 0.1) DMI than control steers, but ADG and gain efficiencies were not affected by treatment. Dressing percent and backfat thickness was greater (P < 0.1) for steers that received feed-grade betaine than for controls. Longissimus muscle area was lower (P < 0.1) for steers supplemented with either feed-grade betaine or CSB than for control steers. Yield grades were higher for cattle receiving feed-grade betaine (quadratic effect, P < 0.1) than for control steers. Marbling scores were not affected by supplemental betaine, but the percentage of carcasses grading USDA Select was lower (linear and quadratic effects, P < 0.1) for steers fed feed-grade betaine than for control steers, predominantly due to a greater percentage grading USDA Choice. In Exp. 2, 312 heifers (343 kg initial BW) were used in a finishing study to evaluate the effects of graded levels of feed-grade betaine and peroxide-treated feather meal on performance and carcass characteristics. Treatments included two finishing diets (containing peroxide-treated or untreated feather meal) and four levels (0, 4, 8, and 12 g/d) of feed-grade betaine arranged in a 2 x 4 factorial. No significant interactions occurred between treatment of feather meal and betaine. Treatment of feather meal with hydrogen peroxide (5% wt/wt) increased in situ protein degradability but did not alter DMI, ADG, gain efficiencies, or carcass characteristics of heifers when it replaced untreated feather meal in the diet. Top-dressing feed-grade betaine to the diets had no effect on DMI, ADG, and gain efficiencies. Marbling scores were greater (cubic effect, P < 0.05) for heifers fed diets top-dressed with 4 and 12 g/d of feed-grade betaine, but other carcass characteristics were not altered significantly. Overall, feed-grade betaine and CSB did not alter growth performance, but did have minor effects on carcass characteristics.     

Response of barrows to space allocation and ractopamine

An experiment using 264 crossbred barrows was conducted to examine the interaction between space allocation and dietary ractopamine addition on pig performance and carcass characteristics using a 2 x 2 factorial arrangement of treatments. Treatments were 0.55 (19 pigs per pen) or 0.74 (14 pigs per pen) m2/pig from start (29.7 +/- 0.1 kg BW) to slaughter (108 kg BW) in a fully slatted facility and 0 or 10 ppm (as-fed basis) ractopamine for 28 d before slaughter. There were few treatment interactions. Pigs given 0.55 m2/pig had a lower ADG (P = 0.010), ADFI (P = 0.088), 10th-rib backfat depth on d 86 (P = 0.010), and carcass loin muscle depth (P = 0.011) than pigs given 0.74 m2/pig. There was no difference in feed conversion (P = 0.210) as a result of space allocation. Pigs fed diets containing 10 ppm ractopamine had decreased (P = 0.004) ADFI and improved (P = 0.001) feed conversion efficiencies for the 28-d feeding period, along with greater loin depth (P = 0.005) and carcass lean percent (P = 0.001). The improvements in 28-d carcass lean growth associated with feeding 10 ppm ractopamine resulted in an improvement in overall daily fat-free lean gain (P = 0.046). Under these experimental conditions, the response to dietary ractopamine was similar for crowded and uncrowded pigs.     

Effects of increasing dose of live cultures of Lactobacillus acidophilus (Strain NP 51) combined with a single dose of Propionibacterium freudenreichii (Strain NP 24) on performance and carcass characteristics of finishing beef steers

Two experiments, each with a randomized complete block design, were conducted to evaluate the effects of feeding live cultures of Lactobacillus acidophilus plus Propionibacterium freudenreichii on performance and carcass characteristics of feedlot cattle. British and British x Continental steers (240 steers in each experiment; 12 pens/treatment in each study; average initial BW = 370 +/- 6 kg) were fed a 92% concentrate diet based primarily on steam-flaked corn. Four treatments were evaluated, which included a control diet (lactose carrier only) or diets containing 1 x 10(9) cfu/(steer x d) of P. freudenreichii (strain NP 24) with 1 x 10(7) (L), 1 x 10(8) (M), or 1 x 10(9) (H) cfu of L. acidophilus strain NP 51/(steer x d). Data were pooled for the 2 experiments. No differences (P > 0.10) were detected among treatments for final BW, final BW based on HCW, or DMI during various stages of the feeding period or overall. Likewise, no differences among treatments were observed for either ADG or carcass-adjusted ADG (P > 0.10), except for the tendency for a quadratic effect of NP 51 dose for the overall feeding period (P = 0.10), in which cattle fed M had a lower ADG than those fed L and H. Gain efficiency on a live BW basis was improved (P = 0.02) by NP 51 treatments compared with the control, with G:F responding quadratically to NP 51 dose for the overall feeding period (P = 0.05). In contrast to G:F based on live BW, carcass-adjusted G:F tended (P = 0.14) to decrease linearly with increasing NP 51 dose because the dressing percent tended (P = 0.12) to be less for steers fed direct-fed microbial compared with control cattle. Within the direct-fed microbial treatments, there also was a tendency (P = 0.13) for a linear decrease in the dressing percent as the NP 51 dose increased. No differences were observed in other carcass characteristics (P > 0.10), except tendencies for a quadratic increase in marbling score (P = 0.11) and percentage of USDA Choice cattle (P = 0.10). These data indicate that live cultures of L. acidophilus strain NP 51 plus P. freudenreichii strain NP 24 increased G:F of feedlot cattle fed steam-flaked corn-based diets by approximately 2%, but the effects depended on the dose of Lactobacillus.     

Impact of dietary energy level and ractopamine on growth performance, carcass characteristics, and meat quality of finishing pigs

A total of 54 finishing barrows (initial BW = 99.8 ± 5.1 kg; PIC C22 × 337) reared in individual pens were allotted to 1 of 6 dietary treatments in a 2 × 3 factorial arrangement of treatments with 2 levels of ractopamine (0 and 7.4 mg/kg) and 3 levels of dietary energy (high, 3,537; medium, 3,369; and low, 3,317 kcal of ME/kg) to determine the effects of dietary ractopamine and various energy levels on growth performance, carcass characteristics, and meat quality of finishing pigs. High-energy diets were corn-soybean-meal-based with 4% added fat; medium-energy diets were corn-soybean meal based with 0.5% added fat; and low-energy diets were corn-soybean meal based with 0.5% added fat and 15% wheat middlings. Diets within each ractopamine level were formulated to contain the same standardized ileal digestible Lys:ME (0 mg/kg, 1.82; and 7.4 mg/kg, 2.65 g/Mcal of ME). Individual pig BW and feed disappearance were recorded at the beginning and conclusion (d 21) of the study. On d 21, pigs were slaughtered for determination of carcass characteristics and meat quality. No ractopamine × energy level interactions (P > 0.10) were observed for any response criteria. Final BW (125.2 vs. 121.1 kg), ADG (1.2 vs. 1.0 kg/d), and G:F (0.31 vs. 0.40) were improved (P < 0.001) with feeding of ractopamine diets. Feeding of the low-energy diet reduced (P = 0.001) final BW and ADG compared with the high- and medium-energy diets. Gain:feed was reduced (P = 0.005) when the medium-energy diets were fed compared with the high-energy diets. Additionally, G:F was reduced (P = 0.002) when the low-energy diets were compared with the high- and medium-energy diets. Feeding ractopamine diets increased (P < 0.05) HCW (93.6 vs. 89.9 kg) and LM area (51.2 vs. 44.2 cm(2)). The LM pH decline was reduced (P ≤ 0.05) by feeding ractopamine diets. The feeding of low-energy diets reduced (P = 0.001) HCW when compared with the high- and medium-energy diets and reduced (P = 0.024) 10th-rib backfat when compared with the high- and medium-energy diet. These data indicate that feeding ractopamine diets improved growth performance and carcass characteristics, while having little or no detrimental effect on meat quality. Reductions in energy content of the diet by adding 15% wheat middlings resulted in impaired ADG, G:F, and 10th-rib backfat. There were no ractopamine × energy level interactions in this trial, which indicates that the improvements resulting from feeding ractopamine were present regardless of the dietary energy levels.     

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.     

Effect of Dietary Cottonseed Meal Concentration on Feedlot Performance and Carcass Characteristics of Cull Beef Cows

Cull beef cows (n = 232, initial BW = 450 + 6 kg) stratified by body condition score and number of permanent incisors were used in a randomized complete block design (8 pens/treatment, 9 to 11 cows/pen) to evaluate graded levels of supplemental cottonseed meal during a 57-d feeding period. Basal 92% concentrate diets were formulated to contain 0.9% urea and were based on unprocessed corn. Supplemental cottonseed meal and tallow replaced corn in isocaloric (NE_g) test diets formulated to contain dietary CP of 11.5, 13.0, or 14.5% of DM (0, 4, and 8% of diet DM; degradable intake protein = 7.01, 8.52, and 10.02% of diet DM). Cows were adapted to diets by offering a restricted amount of the 92% concentrate diet on d 1, and DMI was gradually increased until ad libitum access was achieved (by d 30). Overall DMI (9.2, 9.3, 9.5 + 0.15 kg/d) increased linearly (P=0.08) as dietary cottonseed meal increased. Live ADG (1.23, 1.24, and 1.36 + 0.07 kg/d) tended to increase linearly (P=0.14), whereas live ADG:DMI (133, 133, and 143 + 7 g/kg), carcass-adjusted ADG (1.27, 1.25, and 1.38 + 0.07 kg/d), and carcass-adjusted ADG:DMI (138, 134, and 145 + 7 g/kg) did not differ (P>0.22) among treatments. Hot carcass weight, fat thickness, longissimus area, internal fat percentage, average yield grade, lean and fat color, and carcass conformation did not differ (P>0.18) among treatments. Carcass maturity and quality-grade distributions were not statistically analyzed because of prior stratification of animals by chronological age. However, overall carcass maturity (includes lean and bone maturity) averaged across treatments was 2.63% A, 4.39% B, 40.79% C, 52.19% D, and 0% E. The distribution of carcass quality grades averaged across treatments was 0.44% Choice, 1.32% Select, 5.70% Standard, 5.70% Commercial, 78.07% Utility, and 8.77% Canner. The incidence of A-, A, or A+ liver abscesses responded quadratically (P=0.07; 13.7, 21.8, and 11.7% for 0, 4, and 8% cottonseed meal, respectively), but liver abscess severity was not analyzed because of limited observations in each category. The incidence of other hepatic defects (distoma, telangiectasis, cirrhosis) did not differ (P=0.24) among treatments. Increasing dietary CP using cottonseed meal increased feed intake and tended to increase live BW gain of feedlot cull beef cows.     

Vitamin E supplementation in beef finishing diets containing 35% wet distillers grains with solubles: feedlot performance and carcass characteristics

Supplementation of vitamin E has indications for improving cattle health, performance, and retail characteristics when included in grain-based diets. This experiment was conducted to determine performance and carcass characteristics of steers fed diets containing wet distillers grains with solubles (WDGS) and supplemented with vitamin E. Steers of mixed Bos indicus and Bos taurus breeding (n = 199; BW = 363 ± 32 kg) were blocked by BW and assigned to 1 of 4 supplemental vitamin E (VITE) treatments [0 (control), 125, 250, and 500 IU·steer(-1)·d(-1)], which were fed for the last 97 d of the feeding period. Two blocks were on feed 129 d, and 3 blocks were fed for 150 d. Steers were fed a dry-rolled corn-based finishing diet with 35% WDGS (DM basis). Individual BW were measured initially, the initial day of vitamin E supplementation, and the day of slaughter. Carcass weights were collected at slaughter, and carcass data were collected after a 36-h chill. Body weight and ADG were not affected by VITE (P ≥ 0.34). There was a tendency for a linear (P = 0.08) increase in carcass-adjusted BW with increasing VITE. Use of carcass-adjusted final BW resulted in a linear increase (P = 0.04) in ADG with increasing VITE. Pre-vitamin E and vitamin E feeding period DMI were not affected (P ≥ 0.24) by VITE, but there was a tendency (P = 0.08) for a linear increase in overall DMI with increasing VITE. No difference (P ≥ 0.29) occurred in G:F measures using BW gains, but G:F using carcass-adjusted BW gains resulted in a trend (P = 0.11) for G:F to increase linearly with increasing VITE. Hot carcass weights tended (P = 0.08) to increase linearly with increasing dietary vitamin E. Vitamin E supplementation resulted in no effects (P ≥ 0.13) on measured carcass characteristics. Calculated yield grades (YG) were also not affected (P ≥ 0.37). However, the distribution of calculated YG resulted in a quadratic effect (P = 0.02) for YG 3 with the control and 500 VITE being greater than the 2 intermediate amounts. However, the percentage of carcasses grading YG 3 or less were not affected by vitamin E supplementation (P = 0.64). No differences were observed in the distribution of quality grades based on marbling scores (P ≥ 0.57). Data from this study suggest that vitamin E supplemented above basal requirements during the last 97 d of the feeding period in finishing diets containing 35% WDGS results in slight to no effect on animal performance or carcass characteristics.     

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 a dietary Aspergillus oryzae extract containing alpha-amylase activity on performance and carcass characteristics of finishing beef cattle

Three experiments were conducted to examine the effects of an Aspergillus oryzae extract containing alpha-amylase activity on performance and carcass characteristics of finishing beef cattle. In Exp. 1, 120 crossbred steers were used in a randomized complete block design to evaluate the effects of roughage source (alfalfa hay vs. cottonseed hulls) and supplemental alpha-amylase at 950 dextrinizing units (DU)/kg of DM. Significant roughage source x alpha-amylase interactions (P < 0.05) were observed for performance. In steers fed cottonseed hulls, supplemental alpha-amylase increased ADG through d 28 and 112 and tended (P < 0.15) to increase ADG in all other periods. The increases in ADG were related to increased DMI and efficiency of gain during the initial 28-d period but were primarily related to increased DMI as the feeding period progressed. Supplemental alpha-amylase increased (P = 0.02) the LM area across both roughage sources. In Exp. 2, 96 crossbred heifers were used in a randomized complete block design with a 2 x 3 factorial arrangement of treatments to evaluate the effects of corn processing (dry cracked vs. high moisture) and supplemental alpha-amylase concentration (0, 580, or 1,160 DU/kg of DM). Alpha-amylase supplementation increased DMI (P = 0.05) and ADG (P = 0.03) during the initial 28 d on feed and carcass-adjusted ADG (P = 0.04) across corn processing methods. Longissimus muscle area was greatest (quadratic effect, P = 0.04), and yield grade was least (quadratic effect, P = 0.02) in heifers fed 580 DU of alpha-amylase/kg of DM across corn processing methods. In Exp. 3, 56 crossbred steers were used in a randomized complete block design to evaluate the effects of supplemental alpha-amylase (930 DU/kg of DM) on performance when DMI was restricted to yield a programmed ADG. Alpha-amylase supplementation did not affect performance when DMI was restricted. We conclude that dietary alpha-amylase supplementation of finishing beef diets may result in increased ADG through increased DMI under certain dietary conditions and that further research is warranted to explain its mode of action and interactions with dietary ingredients.     

Effects of treating corn silage with alpha-amylase and(or) sorbic acid on beef cattle growth and carcass characteristics

The effects on beef cattle growth performance and carcass characteristics of feeding silages produced by altered fermentations were determined. Alpha-amylase was added at 0 or .05% (wet basis) and sorbic acid was added at 0 or .10% (wet basis) to chopped whole corn plants before ensiling in a 2 x 2 factorial arrangement of treatments. For three successive years, 40 beef heifers (224 kg) were fed these silages for 80 d, finished on corn-and-cob meal (107 d) and slaughtered when backfat thickness over the 13th rib reached 12 mm. Silages treated with alpha-amylase had a slightly higher percentage of N-free extract (P less than .10). Silages treated with sorbic acid had lower percentages of ADFN (P less than .10). During the silage-feeding phase, heifers fed silages treated with alpha-amylase gained more (P less than .01) daily than heifers fed the other two silages (.84 vs .78 kg) and they were more efficient (P less than .01) in weight gain per unit of dry feed consumed (.149 vs .139 kg). During the finishing phase, heifers that previously had been fed the alpha-amylase-treated silage continued to have higher (P less than .05) ADG (.93 vs .87 kg), although all were fed the same diet during this period. Added sorbic acid had no effect on ADG in either period. The percentage of kidney fat in heifers on the alpha-amylase treatments was increased (P less than .02, 2.2 vs 2.0). The biological mechanisms associated with the beneficial results of alpha-amylase addition are not understood yet.     

The effects of degradable and undegradable intake protein on the performance of lactating first-calf heifers

Two 60-d experiments were conducted to evaluate the effects of supplementing degradable (DIP) and(or) undegradable (UIP) intake protein on the performance of lactating first-calf heifers. Diets were formulated to meet the requirements for either DIP, metabolizable protein (MP), or both when diets contained low-quality grass hay and an efficiency of microbial protein synthesis estimate of 10%. In Exp. 1, 32 individually fed first-calf heifers (avg 395 kg) were allotted to a 2 x 2 factorial arrangement of treatments (main effects of DIP, MP, and DIP x MP interaction) 1 d after calving. Cows consumed a basal diet of chopped crested wheat grass hay (4.3% CP, 67% DIP) ad libitum. Supplemental DIP and UIP were supplied by varying the ratios of soybean meal (75% DIP) and a heat-treated, protected soybean meal (70% UIP). Cow weight gain was better (P < 0.01) when adequate DIP was supplied than when DIP was deficient. However, calf weight gain was not increased by supplementing the cow with DIP. Supplemental UIP did not (P > 0.40) improve cow or calf weight gain. Blood urea N levels were higher (P < 0.01) for cows receiving supplemental DIP and UIP. However, milk production estimates were similar among treatments, as were digestibilities of OM and ADF. Nitrogen digestibility was greater when supplemental DIP was fed, but providing additional UIP did not (P = 0.15) change N digestibilities. Experiment 2 evaluated similar supplements using the same experimental design to determine changes in cow and calf weight gain, body condition score, and pregnancy rate. Seventy-two first-calf heifers (avg 441 kg) were allotted to supplement treatments 1 d after calving and were fed grass hay (5% CP, 53% DIP, 10% microbial efficiency) for ad libitum consumption for 60 d. Supplements were individually fed three times/week. Varying the ratios of soybean meal, heat-treated soybean meal, and corn gluten meal provided additional DIP and UIP. Unlike in Exp. 1, supplemental UIP improved (P < 0.05) cow weight gain. Calves from dams supplemented with DIP gained 5 kg more weight after 60 d than calves from dams deficient in DIP. Pregnancy rates in the fall were similar (P = 0.90) among treatments. These data suggest that DIP was more limiting in Exp. 1 than was UIP. Supplementing UIP in Exp. 2 improved cow weight gains but did not improve calf gains. Data suggest that the efficiency of microbial protein synthesis for this forage-based diet was probably less than 10%.     

Digestibility and utilization of ammonia-treated and urea-supplemented peanut skin diets fed to cattle

A metabolism study and two feedlot trials were conducted to evaluate urea supplementation of peanut skin (PS) diets and ammoniation of PS as methods of reducing detrimental effects of tannins in PS on nutrient digestibility and performance of beef cattle. Tannin content of PS was reduced by 42% after ammoniation. Digestibility coefficients for dry matter, crude protein, nitrogen free extract, energy and total digestible nutrients were higher (P less than .05) for the control diet without PS compared with urea-supplemented PS (UPS) and ammoniated PS (APS) diets. Ether extract digestibility was higher (P less than .05) for UPS and APS diets compared with the control diet. Fecal N was higher (P less than .05) and N retention was lower (P less than .05) in steers fed UPS and APS diets compared with controls, which suggested that in UPS and APS diets dietary protein was being complexed with tannins and excreted. Steers fed the APS diet had lower (P less than .05) plasma urea nitrogen compared with control and UPS diets at 2, 4 and 6 h post-feeding. Eighteen heifers were fed control, UPS and APS diets individually for 84 d, resulting in similar (P less than .05) feedlot performance and carcass traits for heifers on all dietary treatments. Rumen fluid propionic acid levels were similar for control and APS heifers and somewhat lower (P greater than .05) for UPS heifers at 3 and 6 h post-feeding on d 62 of the trial. The experimental diets were fed to 54 steers (360 kg initial wt) ad libitum. After 98 d on dietary treatments average daily gains (ADG), final weights, carcass weights and carcass quality grades were not different (P greater than .05) for control and APS steers. Live weight and ADG were lower (P less than .05) for UPS steers on d 98 compared with control and APS steers, and UPS steers continued in the feedlot through d 147. After 98 d on control or APS diets 72.2% of the beef carcasses produced on each diet graded USDA Choice, and 100% of the carcasses of steers fed UPS graded USDA Choice after 147 d. A urea-supplemented PS diet or a diet containing ammoniated PS was ineffective in improving digestibility and N retention of PS diets when limit-fed to steers. However, ad libitum feeding of an ammoniated PS diet was effective in overcoming detrimental effects of tannins on feedlot performance of heifers and steers.     

Effects of pantothenic acid on growth performance and carcass characteristics of growing-finishing pigs fed diets with or without ractopamine hydrochloride

Two experiments evaluated effects of added pantothenic acid on performance of growing-finishing pigs. In Exp. 1, 156 pigs (PIC, initial BW = 25.7 kg) were used in a 3 x 2 x 2 factorial to evaluate the effects of added pantothenic acid (PA; 0, 22.5, or 45 ppm), ractopamine.HCl (RAC; 0 or 10 mg/kg), and sex on growth performance and carcass traits. Pigs were fed increasing PA from 25.7 to 123.6 kg (d 0 to 98) and RAC for the last 28 d before slaughter. Increasing the amount of added PA had no effect (P > 0.40) on ADG, ADFI, or G:F from d 0 to 70. A PA x sex interaction (P < 0.03) was observed for ADG and G:F from d 71 to 98. Increasing the amount of added PA increased ADG and G:F in gilts, but not in barrows. Increasing the amount of added PA had no effect (P > 0.38) on carcass traits. Added RAC increased (P < 0.01) ADG and G:F for d 71 to 98 and d 0 to 98 and increased (P < 0.01) LM area and percentage lean. In Exp. 2, 1,080 pigs (PIC, initial BW = 40.4 kg, final BW = 123.6 kg) were used to determine the effects of increasing PA on growth performance and carcass characteristics of growing-finishing pigs reared in a commercial finishing facility. Pigs were fed 0, 22.5, 45.0, or 90 mg/kg of added PA. Increasing the amount of added PA had no effect (P > 0.45) on ADG, ADFI, or G:F, and no differences were observed (P > 0.07) for carcass traits. In summary, adding dietary PA to diets during the growing-finishing phase did not provide any advantages in growth performance or carcass composition of growing-finishing pigs. Furthermore, it appears that the pantothenic acid in corn and soybean meal may be sufficient to meet the requirements of 25- to 120-kg pigs.     

Effect of reconstituting field-dried and early-harvested sorghum grain on the ensiling characteristics of the grain and on growth performance and carcass merit of feedlot heifers.

The objective of this study was to determine whether reconstituting field-dried and early-harvested sorghum grain affected the fermentation characteristics and feed value of the ensiled grain when fed to feedlot heifers. In Trial 1, sorghum grain was harvested at 14% moisture, rolled, and reconstituted to 25, 30, or 35% moisture, then ensiled in laboratory-scale silos. Lactic acid concentration increased (d 5 to 90) and pH decreased more rapidly (d 3 to 90) as moisture level increased (P < .05). Acetic acid concentration increased (P < .05) with moisture and day postfilling. Concentration of ethanol was highest (P < .05) in the 30 and 35% moisture grains from d 1 to 5, but by d 90 the ethanol concentration in the 25% moisture grain exceeded (P < .05) that of the two higher-moisture grains. Ammonia N concentration was lowest (P < .05) in the 25% moisture grain at all sampling times postfilling. In Trial 2, 288 heifers (BW = 286+/-83 kg) were used to compare the feeding value of rolled, ensiled sorghum grain harvested at 25% moisture to the same grain reconstituted to 30 or 35% moisture. A steam-flaked corn (SFC) diet served as the control. Final live weight; ADG; hot carcass weight; backfat depth; marbling score; kidney, pelvic, and heart fat; and liver abscess score were not affected by grain treatment (P > .10). Dry matter intake was highest (P < .10) for heifers fed the 25 or 30% moisture sorghum grain diets and lowest for those fed the SFC diet; DMI for heifers fed the 35% moisture sorghum grain diet was intermediate. Feeding 35% moisture sorghum grain improved gain efficiency (P < .10) compared with feeding 25 or 30% moisture sorghum grain by 9.0 and 5.7%, respectively. We conclude that reconstituting sorghum grain beyond the typical moisture levels of 25 to 30% would enhance the fermentation characteristics of the ensiled grain and improve gain efficiency in feedlot heifers.     

Efficacy of actaplanin fed on a twice-weekly basis to grazing stocker heifers

Brahman (16), Brangus (32) and Simmental X Brahman (16) open heifers were assigned to four treatment levels and two body weight categories. The weight categories were light (250 kg) and heavy (306 kg). Treatment groups were 0, 600, 900 and 1,200 mg actaplanin.head-1.feeding-1 with feeding only on Monday and Friday. Heifers were group-fed .91 kg/head of supplement (95% soybean meal: 5% molasses) containing actaplanin. Heifers grazed eight Coastal bermudagrass pastures throughout the experiment (July 29 to November 15, 1982). After 75 d on experiment, an additional 1.36 kg of a commercial 14% crude protein supplement was fed on the days that actaplanin was not fed. All heifers were weighted and rotated among pastures at 14-d intervals (last weight period was 11 d) as an attempt to equalize forage availability among groups. Over the entire experiment (109 d), light-weight heifers that were fed actaplanin responded (P less than .01) with greater average daily gain (ADG; .37, .35, .21 kg/d; 600, 900, 1,200) compared with controls (0 mg; .18 kg/d). A trend in response (P less than .10) to actaplanin feeding occurred for heavy-weight heifers (.23, .38, .34 kg/d; 600, 900, 1,200 mg vs controls (.22 kg/d). For light-weight heifers, ADG decreased lineraly (P less than .01) as actaplanin increased from 600 to 1,200 mg, while ADG for heavy-weight heifers increased linearly (P less than .10).(ABSTRACT TRUNCATED AT 250 WORDS)     

Intake restriction strategies and sources of energy and protein during the growing period affect nutrient disappearance, feedlot performance, and carcass characteristics of crossbred heifers.

Two trials were conducted to evaluate intake restriction, energy, and protein source on the performance and carcass merit of heifers limit-fed corn gluten feed. Trial 1 crossbred heifers (n = 140) were allotted to ad libitum wet corn gluten feed (WCGF)-hay, ad libitum WCGF-corn, WCGF-corn continuously limit-fed to achieve a gain of 1.1 kg/d or WCGF-corn fed in the following sequence: 70% of ad libitum for 20 d, ad libitum for 20 d, and 2 d common intake during the 84-d growing period. One-half of these restricted-refed heifers received a rumen-undegraded protein supplement, and the other half received a rumen degraded protein supplement. Heifers were fed a common finishing diet ad libitum subsequent to the growing period. Heifers offered ad libitum WCGF-hay and WCGF-corn were slaughtered at a common compositional fat end point. Heifers limit-fed WCGF-corn were slaughtered at the same time as heifers offered ad libitum WCGF-corn, regardless of subcutaneous fat cover. Limit-feeding WCGF-corn diets to growing heifers reduced ADG (P < or = 0.01) but did not compromise feed efficiency. Method of intake restriction, continuous or ad libitum-interrupted, and supplemental protein source did not affect combined growing-finishing performance. However, when fed for a common length of time, the average of the limit-fed heifers had lighter carcass weights (P < or = 0.01) and lower (P = 0.04) marbling scores. Heifers offered ad libitum WCGF-hay gained slower (P < or = 0.01) and less efficiently (P < or = 0.01) than heifers offered WCGF-corn. Trial 2 crossbred heifers (n = 222) were allotted to dry corn gluten feed (DCGF)-corn ad libitum or restricted to 80% of ad libitum for 42, 84, or 126 d; or ad libitum corn silage or DCGF-corn silage at 80% of ad libitum for 84 d. Feed efficiency (P = 0.07) and ADG (P = 0.08) tended to behave quadratically, being poorer for heifers limit-fed for 126 d during the growing period. Heifers limit-fed DCGF-corn gained more efficiently (P = 0.05) than heifers grown on ad libitum corn silage. Limit-feeding CGF-corn to growing beef heifers can be used to achieve moderate rates of gain without compromising feed efficiency. However, limit-feeding during the growing period may result in lighter weight carcasses with lower quality grades if not fed to the same fat end point as heifers grown with free access to concentrate.