Predicting red meat yields in carcasses from beef-type and calf-fed Holstein steers using the United States Department of Agriculture calculated yield grade.

Analyses were conducted to evaluate the ability of the USDA yield grade equation to detect differences in subprimal yield of beef-type steers and calf-fed Holstein steers that had been fed zilpaterol hydrochloride (ZH; Intervet Inc., Millsboro, DE) as well as those that had not been fed ZH. Beef-type steer (n = 801) and calf-fed Holstein steer (n = 235) carcasses were fabricated into subprimal cuts and trim. Simple correlations between calculated yield grades and total red meat yields ranged from -0.56 to -0.62 for beef-type steers. Reliable correlations from calf-fed Holstein steers were unobtainable; the probability of a type I error met or exceeded 0.39. Linear models were developed for the beef-type steers to predict total red meat yield based on calculated USDA yield grade within each ZH duration. At an average calculated USDA yield grade of 2.9, beef-type steer carcasses that had not been fed ZH had an estimated 69.4% red meat yield, whereas those fed ZH had an estimated 70.7% red meat yield. These results indicate that feeding ZH increased red meat yield by 1.3% at a constant calculated yield grade. However, these data also suggest that the calculated USDA yield grade score is a poor and variable estimator (adjusted R(2) of 0.31 to 0.38) of total red meat yield of beef-type steer carcasses, regardless of ZH feeding. Moreover, no relationship existed (adjusted R(2) of 0.00 to 0.01) for calf-fed Holstein steer carcasses, suggesting the USDA yield grade is not a valid estimate of calf-fed Holstein red meat yield.

Effect of zilpaterol hydrochloride supplementation on cutability and subprimal yield of beef steer carcasses.

Beef steers (n = 11,877) from 7 studies were fed zilpaterol hydrochloride (ZH) for 0 or 20 to 40 d before slaughter to determine the effects of ZH on subprimal weight and yield. Carcasses were selected based on mean HCW of treatment groups for fabrication into boneless, closely trimmed, or denuded subprimals, lean, fat, and bone. Data from the 7 trials were pooled for statistical analysis. Feeding ZH increased (P < 0.05) weights of all major subprimals compared with steers not supplemented with ZH. Also, subprimals from the hindquarter, including valuable cuts like the tenderloin, strip loin, and top sirloin butt, increased (P < 0.05) as a percentage of cold carcass weight from steers fed ZH. The tenderloin was 0.06 percentage units greater (P < 0.05), the strip loin was 0.08 percentage units greater (P < 0.05), and the top sirloin butt was 0.11 percentage units greater (P < 0.05) in ZH-fed steers when compared with steers not fed ZH. Supplementation of ZH greatly increased (P < 0.05) total saleable carcass yield by 1.76 percentage units, whereas ZH inclusion decreased (P < 0.05) the percentage of fat trim and bone by 0.58 and 1.10 percentage units, respectively. Therefore, ZH can be utilized by the beef industry to improve red meat yield efficiency throughout the beef production chain.

Effects of feeding zilpaterol hydrochloride for twenty to forty days on carcass cutability and subprimal yield of calf-fed Holstein steers.

Zilpaterol hydrochloride (ZH) is designed to increase carcass leanness, chilled side weight (CSW), and percent saleable yield. The objective of this study was to evaluate the effect of a single dose of ZH on cutability and subprimal yield of calf-fed Holstein steers when fed for increasing durations. Two hundred forty steers were fed 8.3 mg/kg of ZH on a DM basis for 0, 20, 30, or 40 d, with a 3-d withdrawal before slaughter. After slaughter, steers were fabricated into 4 pieces (round, loin/flank, rib/plate, and chuck), packaged in combos, shipped to 2 locations, and further fabricated into subprimal pieces and trim. Trim was collected from each primal and separated into groups based on composition of 90, 80, and 50% lean. Zilpaterol hydrochloride increased (P = 0.01) CSW by 6.22 kg and saleable yield by 6.4 kg when included in the diet for 20 d. Furthermore, saleable yield as a percentage of CSW was increased (P = 0.03) 1.18 percentage units when included in the diet for 20 d. Steers fed ZH for 20 d had heavier strip loins (4.47 vs. 4.12 kg, P = 0.02), tenderloins (2.75 vs. 2.49 kg, P = 0.02), and ribeye rolls (5.74 vs. 5.30 kg, P = 0.01) than steers not fed ZH. These advantages are further demonstrated as a percentage of CSW. Strip loins (P = 0.06), tenderloins (P = 0.04), and ribeye rolls (P = 0.04) of ZH-fed steers had a greater percentage of CSW than controls. Zilpaterol hydrochloride also increased the percentage of CSW of the 3 primary components of the round when fed for 20 d. The knuckle was 0.10 percentage units heavier (P = 0.11), the top round was 0.24 percentage units heavier (P = 0.04), and the bottom round was 0.22 percentage units heavier (P = 0.03) in ZH-fed steers when compared with steers not fed ZH. Based on these data, it can be concluded that ZH significantly increased subprimal cutting weights, yields, and percentage saleable yield of calf-fed Holstein steers when fed for at least 20 d before slaughter. Zilpaterol hydrochloride increased percentage of CSW of subprimal cuts from Holstein steers in the round and to a lesser degree in the loin.

Effect of zilpaterol hydrochloride duration of feeding on performance and carcass characteristics of feedlot cattle.

Four trials, each with a randomized complete block design, were conducted with 8,647 beef steers (initial BW = 346 +/- 29.6 kg) in 3 different locations in the United States to evaluate the effects of zilpaterol hydrochloride (ZH) on performance and carcass characteristics of feedlot cattle. Treatments consisted of feeding ZH (8.33 mg/kg of dietary DM) for 0, 20, 30, or 40 d, at the end of the feeding period, followed by a 3-d withdrawal period before slaughter. Cattle were weighed on d 0 and 50 before slaughter (in 3 of the 4 studies), and on the day of slaughter. Data from the 4 trials were pooled for statistical analyses. No differences (P > or = 0.78) were detected among treatments for ADG and G:F from the start of the study until the final 50 d on feed. Final BW was greater for the average of the 3 ZH-treated groups (P < 0.01) than for the 0-d group. Average daily gain was greater for ZH-treated vs. control cattle during the final 50 d on feed (P < 0.01) and for the entire feeding period (P < 0.01). No differences in DMI were noted for any periods of the experiment (P > or = 0.42) for ZH-treated cattle vs. controls. No differences were noted for DMI among the ZH-treated groups for the final 50 d on feed (P = 0.81) or for the overall feeding period (P = 0.31). Feeding ZH for any length of time increased G:F (P < 0.01) for the final 50 d and overall compared with 0-d cattle. In addition, a linear increase with more days of ZH feeding was observed for G:F during the period that ZH was fed (P = 0.01), as well as for the overall feeding period (P = 0.01). The ZH-treated cattle had heavier HCW (P < 0.01), greater dressing percent (P < 0.01), reduced marbling scores (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.01), and a lower USDA yield grade (P < 0.01) than the 0-d cattle, regardless of the duration of ZH feeding. Dressing percent increased linearly (P < 0.01) with increased duration of ZH feeding, whereas 12th-rib fat (P = 0.07), marbling scores (P < 0.01), and USDA calculated yield grade (P = 0.01) decreased linearly with increased duration of ZH feeding. Feeding ZH increased ADG and G:F and decreased overall carcass fatness. In addition, effects of ZH on measures of carcass fatness were enhanced by feeding the product for a greater length of time.

Influence of slow-release urea on nitrogen balance and portal-drained visceral nutrient flux in beef steers.

Two experiments were conducted to evaluate the effects of slow-release urea (SRU) versus feed-grade urea on portal-drained visceral (PDV) nutrient flux, nutrient digestibility, and total N balance in beef steers. Multi-catheterized steers were used to determine effects of intraruminal dosing (Exp. 1; n = 4; 319 +/- 5 kg of BW) or feeding (Exp. 2; n = 10; 4 Holstein steers 236 +/- 43 kg of BW and 6 Angus steers 367 +/- 46 kg of BW) SRU or urea on PDV nutrient flux and blood variables for 10 h after dosing. Intraruminal dosing of SRU (Exp. 1) prevented the rapid increase in ruminal ammonia concentrations that occurred with urea dosing (treatment x time P = 0.001). Although apparent total tract digestibilities of DM, OM, NDF, and ADF were not affected by treatment (P > 0.53, Exp. 2), SRU increased fecal N excretion (49.6 vs. 45.6 g/d; P = 0.04) and reduced apparent total tract N digestibility (61.7 vs. 66.0%; P = 0.003). Transfer of urea from the blood to the gastrointestinal tract occurred for both treatments in Exp. 1 and 2 at all time points with the exception for 0.5 h after dosing of urea in Exp. 1, when urea was actually transferred from the gastrointestinal tract to the blood. In both Exp. 1 and 2, both urea and SRU treatments increased arterial urea concentrations from 0.5 to 6 h after feeding, but arterial urea concentrations were consistently less with SRU (treatment x time P < 0.001, Exp. 1; P = 0.007, Exp. 2). Net portal ammonia release remained relatively consistent across the entire sampling period with SRU treatment, whereas urea treatment increased portal ammonia release in Exp. 1 and tended to have a similar effect in Exp. 2 (treatment x time P = 0.003 and P = 0.11, respectively). Urea treatment also increased hepatic ammonia uptake within 0.5 h (treatment x time P = 0.02, Exp. 1); however, increased total splanchnic release of ammonia for the 2 h after urea treatment dosing suggests that PDV ammonia flux may have exceeded hepatic capacity for removal. Slow-release urea reduces the rapidity of ammonia-N release and may reduce shifts in N metabolism associated with disposal of ammonia. However, SRU increased fecal N excretion and increased urea transfer to the gastrointestinal tract, possibly by reduced SRU hydrolysis or effects on digestion patterns. Despite this, the ability of SRU to protect against the negative effects of urea feeding may be efficacious in some feeding applications.

Influence of slice baling on feeding value of alfalfa hay in receiving and finishing diets for feedlot cattle.

Three studies were conducted to evaluate the feeding value of slice alfalfa hay in feedlot diets. In Exp. 1, 108 steer calves (183.1 +/- 1.2 kg initial BW; 6 pens/treatment) were used in a completely randomized design to evaluate the effect of baling method on performance and morbidity of newly received calves. The study lasted 28 d. Treatments consisted of a 65% concentrate receiving diet containing 1) ground or 2) slice alfalfa hay. Steer calves were fed daily at 0800 h. Animals also received long-stem sudangrass hay the first 7 d. Steers were weighed on d 0, 16, and 28. Feed, sudangrass hay, or feed plus sudangrass hay intakes were not affected (P > 0.25) by treatment. Conversely, ADG from d 0 to 16 was greater (P < 0.001) for slice than ground (1.27 vs. 0.81 +/- 0.067 kg/d, respectively) and from d 0 to 28 (1.23 vs. 0.91 +/- 0.042 kg/d, respectively). In addition, G:F was greater (P < 0.001) for slice than ground hay from d 0 to 16 (0.39 vs. 0.25 +/- 0.021), and from d 0 to 28 (0.31 vs. 0.24 +/- 0.013 for slice and ground, respectively). Moreover, morbidity (40.5 +/- 3.9%; P = 0.20) and retreatment rates (30.7 +/- 7.5%; P = 0.14) were similar for slice and ground. In Exp. 2, 176 crossbred steers (393.9 +/- 10.8 kg initial BW) were used in an 84-d feeding experiment (4 pens/treatment) in a randomized complete block experimental design with a 2 x 2 factorial arrangement of treatments to evaluate effects of alfalfa baling method (ground or slice) and forage level (8 or 14%) on growth performance. Experimental diets were based on steam-flaked corn. Daily BW gain was greater (P = 0.10) for steers consuming ground compared with the slice hay diet. A baling method x forage level interaction (P = 0.07) was observed for DMI. Baling method did not (P = 0.98) influence DMI with 8% roughage level. But with 14% roughage, DMI was greater (P = 0.02) for steers consuming ground hay than the slice diet. The G:F ratio was affected (P = 0.03) only by forage level (0.194 vs. 0.182 +/- 0.003 for 8 and 14% roughage, respectively). In Exp. 3, 4 ruminally cannulated mixed-breed steers were used in a 4 x 4 Latin square design to evaluate effects on digestive function. No baling method effects (P >or= 0.16) were detected for DM, OM, CP, or NDF intakes or DM, OM, and NDF total tract digestibility. Digestibility of NDF and OM were greater (P

Nutrient net absorption across the portal-drained viscera of forage-fed beef steers: Quantitative assessment and application to a nutritional prediction model.

This study aimed to establish the relationship between ME intake and energy and nutrient absorption across the portal-drained viscera (PDV) of forage-fed beef steers. Eight Angus (328 +/- 40 kg of BW) steers were surgically fitted with portal, mesenteric arterial, and mesenteric venous catheters, and were fed alfalfa cubes in a replicated 4 x 4 Latin square design with 4 levels of energy intake between 1 and 2 times maintenance energy requirements. On d 28 of each experimental period, p-aminohippuric acid was infused to measure blood and plasma flow across the PDV, and blood samples (1 every hour, for 6 h) were collected simultaneously from arterial and venous catheters for net absorption measurements. Oxygen utilization, and therefore energy utilization, increased (P < 0.05) linearly in relation to ME intake. Glucose net uptake was unaffected, but lactate net release increased linearly in response to ME intake (P < 0.05). Net absorption of all AA except tryptophan, glutamate, and glutamine increased linearly with ME intake (P < 0.05). The constant net absorption of glutamate and glutamine indicated increased net utilization of these AA when dietary supply was increased. These data provide quantitative measures of the PDV effects on energy and AA availability for productive tissues, and suggest that the greater net utilization of some AA when ME intake is increased could relate to their catabolism for energy production. Prediction estimates of small intestinal AA absorption, based on the Cornell Net Carbohydrate and Protein System (CNCPS), exceeded observed net AA PDV absorption. Mean bias represented the greatest proportion (87 to 96%) of the deviation between individual AA absorption and observed net AA PDV absorption, suggesting that the CNCPS model may be used to predict AA net absorption when factors describing AA utilization by the PDV are applied to model predictions.

Effects of long- or short-term exposure to a calf identified as persistently infected with bovine viral diarrhea virus on feedlot performance of freshly weaned, transport-stressed beef heifers.

A single experiment with a completely randomized design was conducted to evaluate the effects of long- or short-term exposure to a calf identified as persistently infected with bovine viral diarrhea virus (PI-BVD) on feedlot performance and carcass characteristics of freshly weaned, transport-stressed beef heifers. Two hundred eighty-eight heifers that had been vaccinated for BVD before weaning and transport were processed and given a metaphylactic antibiotic treatment at arrival and were fed common receiving, growing, and finishing diets for a 215-d period. Treatments were designed to directly or adjacently expose the cattle to a PI-BVD heifer. Directly exposed treatments were 1) negative control with no PI-BVD calf exposure (control), 2) PI-BVD calf commingled in the pen for 60 h and then removed (short-term exposure), and 3) PI-BVD calf commingled in the pen for the duration of the study (long-term exposure); and spatially exposed treatments were 1) negative control with no PI-BVD calf exposure (adjacent pen control), 2) PI-BVD calf commingled in the adjacent pen for 60 h and then removed (adjacent pen short-term exposure), and 3) PI-BVD calf commingled in the adjacent pen for the duration of the study (adjacent pen long-term exposure). Exposure to a PI calf transiently (60 h) or for the duration of the feeding period (215 d) did not affect (P > or = 0.25) final BW compared with heifers that were not exposed. Neither period nor overall DMI was affected (P > or = 0.37) by PI-BVD calf exposure, and no differences (P > or = 0.44) were observed between short- and long-term exposed heifers in the direct or spatially exposed groups. Likewise, total trial ADG was not affected (P > or = 0.36) and overall efficiency of gain (P > or = 0.19) was unaffected by PI-BVD calf exposure in the direct or spatially exposed groups. The results from this study suggest that exposing previously vaccinated, freshly weaned, transport- stressed beef calves to a calf that is persistently infected with bovine viral diarrhea virus has little, if any, marked effects on health, performance, or carcass characteristics.

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.

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.

Dietary supplementation with Lactobacillus- and Propionibacterium-based direct-fed microbials and prevalence of Escherichia coli O157 in beef feedlot cattle and on hides at harvest.

The objective of this study was to describe the prevalence of Escherichia coli O157 in the feces and on the hides of finishing beef cattle fed a standard diet and those fed diets supplemented with direct-fed microbials. Two hundred forty steers received one of four treatments throughout the feeding period: (i) control: no added microbials; (ii) HNP51: high dose of Lactohacillius acidophilus strain NP 51 (10(9) CFU per steer daily) and Propionibacterium freudenreichii (10(9) CFU per steer daily); (iii) HNP51+45: high dose of NP 51 (10(9) CFU per steer daily), P. freudenreichii (10(9) CFU per steer daily), and L. acidophilus NP 45 (10(6) CFU per steer daily); or (iv) LNP51+45: low dose of NP 51 (10(6) CFU per steer daily), P. freudenreichii (10(9) CFU per steer daily), and NP 45 (10(6) CFU per steer daily). Samples were collected from each animal and analyzed for the presence of E. coli O157 using immunomagnetic separation methods on day 0 (feces), 7 days before harvest (feces), and at harvest (feces and hide). At the end of the feeding period, cattle receiving HNP51 were 57% less likely to shed detectable E. coli O157 in their feces than were the controls (P < 0.01). For animals receiving HNP51+45 and LNP51+45, fecal prevalence did not differ from that of the controls. The prevalence of positive hide samples was least among cattle receiving HNP51+45 (3.3%); these animals were 79% less likely (P < 0.06) to have a positive hide sample than were the controls (prevalence = 13.8%). There was poor agreement of the culture results between fecal and hide samples collected from the same animal (kappa = 0.08; confidence interval = -0.05 to 0.2). Cattle supplemented with a high dose of NP 51 had reduced E. coli O157 prevalence in both fecal and hide samples, indicating that this treatment may be an efficacious preharvest intervention strategy.

Effects of live cultures of Lactobacillus acidophilus (strains NP45 and NP51) and Propionibacterium freudenreichii on performance, carcass, and intestinal characteristics, and Escherichia coli strain O157 shedding of finishing beef steers.

In Exp. 1, 240 beef steers (initial BW = 332.8 kg) were used to determine the effects of Lactobacillus acidophilus (LA) plus Propionibacterium freudenreichii (PF) on performance, carcass, and intestinal characteristics; serum IgA concentrations; and the prevalence of Escherichia coli O157 (EC). Cattle were fed a steam-flaked corn-based, 92% concentrate diet, and the four direct-fed microbial (DFM) treatments (12 pens/treatment) included in a randomized complete block design were as follows: 1) control, lactose carrier only (CON); 2) 1 x 10(9) cfu of LA NP51 plus 1 x 10(6) cfu of LA NP45 plus 1 x 10(9) cfu of PF NP24 per animal daily (LA45-51H); 3) 1 x 10(9) cfu of LA NP51 plus 1 x 10(9) cfu of PF NP24 per animal daily (LA51); and 4) 1 x 10(6) cfu of LA NP51 plus 1 x 10(6) cfu of LA NP45 plus 1 x 10(9) cfu of PF NP24 per animal daily (LA45-51L). No differences (P > 0.10) were detected for pen-based performance data. The average lamina propria thickness for LA51 and LA45-51H steers was less (P = 0.02) than the average for CON and LA45-51L steers. Moreover, LA51 and LA45-51H steers had a lower (P = 0.06) prevalence of EC shedding than CON and LA45-51L steers. In Exp. 2, 660 steers fed 91% concentrate, steam-flaked corn-based diets were used to determine the effects of the following DFM treatments (10 pens/treatment) on performance, carcass, and intestinal characteristics: 1) control, lactose carrier only (CON); 2) 5 x 10(6) cfu of LA NP51 plus 5 x 10(6) cfu of LA NP45 plus 1 x 10(9) cfu of PF NP24 per animal daily (LA45-51L); and 3) 1 x 10(9) cfu of LA NP51 plus 5 x 10(6) cfu of LA NP45 plus 1 x 10(9) cfu of PF NP24 per animal daily (LA45-51H). Steers were from two weight groups (WG). One group (SDOF; BW at arrival = 351.5 kg) had grazed before arrival, and the other group (LDOF; BW at arrival = 314 kg) had been in a grower yard. A split plot was used with WG as the whole-plot factor and DFM in the split plot. There was an interaction of WG and DFM for ADG (P = 0.05) and for carcass-adjusted ADG (P = 0.08). The simple-effect ADG and carcass-adjusted ADG means for DFM treatments differed (P < or = 0.01) between WG classifications. Within SDOF, ADG for CON and LA45-51L did not differ (P = 0.70), but both were less (P < or = 0.08) than for LA45-51H. Overall, these data indicate that live cultures of LA plus PF did not greatly affect feedlot performance and carcass characteristics. Some of the DFM used decreased fecal EC shedding, which might be related to the results for ileal lamina propria thickness.