Influence of Maternal Carbohydrate Source (Concentrate-Based vs. Forage-Based) on Growth Performance, Carcass Characteristics, and Meat Quality of Progeny

The objective of this research was to investigate the influence of maternal prepartum dietary carbohydrate source on growth performance, carcass characteristics, and meat quality of offspring. Angus-based cows were assigned to either a concentrate-based diet or forage-based diet during mid- and late-gestation. A subset of calves was selected for evaluation of progeny performance. Dry matter intake (DMI), body weight (BW), average daily gain (ADG), gain to feed (G:F), and ultrasound measurements (muscle depth, back fat thickness, and intramuscular fat) were assessed during the feeding period. Carcass measurements were recorded, and striploins were collected for Warner-Bratzler shear force (WBSF), trained sensory panel, crude fat determination and fatty acid profile. Maternal dietary treatment did not influence (p > 0.05) offspring BW, DMI, ultrasound measurements, percent moisture, crude fat, WBSF, or consumer sensory responses. The forage treatment tended to have decreased (p = 0.06) 12th rib backfat compared to the concentrate treatment and tended to have lower (p = 0.08) yield grades. The concentrate treatment had increased (p < 0.05) a* and b* values compared to the forage treatment. These data suggest variation in maternal diets applied in this study during mid- and late-gestation has limited influence on progeny performance.

206 Effects of a Direct Fed Microbial and/or an Enzymatically Hydrolyzed Yeast Product Fed to Beef Steers Provided Ractopamine Hydrochloride 28 d Before Harvest During Summer Months in the Northern Plains

This research determined the influence a direct fed microbial (DFM) and/or enzymatically hydrolyzed yeast (EHY) product (Arm & Hammer Animal and Food Production, Princeton, NJ) have on heat stress measures in beef steers administered ractopamine hydrochloride (RH; 300 mg/steer·d-1) the final 28-d on feed, during summer months in the Northern Plains (NP). At weaning, single-sourced steers (n = 256; initial BW = 246 ± 1.7 kg; n = 64 steers/treatment; 8 steers/pen) were blocked by location in a 2×2 factorial arrangement of DFM (Certillus CP B1801 dry; Bacillus subtilis, Lactobacillus plantarum; 28 g/steer·d-1) and EHY (Celmanax; 18 g/steer·d-1). The final diet provided 1.44 Mcal/kg of NEg and 30 g/907kg of monensin sodium. Temperature-humidity index (THI) was calculated from: 0.81 × ambient temperature + [relative humidity × (ambient temperature - 14.40)] + 46.40. On d 1 and 2 and d 21 and 22 on RH, respiration rate (RR) and panting scores (PS) were determined before and after AM and PM feedings (0700h, 1100h, 1400h, 1700h). RR (n = 3 steers/pen) was calculated from: 600/seconds required for 10 flank movements. PS was determined from: 0 (not distressed) to 4.5 (severely distressed). Two separate heat events occurred and average THI was greater than 75 for 10-d of the 28-d period. A DFM×EHY interaction was noted for the proportion of steers categorized as PS 2.0 at 1100h on d21 (P = 0.03) and RR on d21 at 1400h (P = 0.02). Control steers had a greater proportion of PS 2.0 at 1100h on d21 compared with DFM or EHY steers (P ≤ 0.05), while DFM×EHY steers did not differ from others (P ≥ 0.10). On d21 DFM×EHY steers had greater (P &lt; 0.05) RR compared with DFM steers, control and EHY steers did not differ from others (P ≥ 0.10). DFM and EHY used alone or in combination had minimal effects on heat stress measures in steers fed RH in the NP under minimal heat stress conditions.

Manger space restriction does not negatively impact growth efficiency of feedlot heifers program fed a concentrate-based diet to gain 1.36 kg daily

The objective of this research was to determine the influence manger space restriction had on program-fed feedlot heifers during the growing phase. Charolais × Angus heifers [initial body weight (BW) = 329 ± 22.1 kg] were used in a 109-d backgrounding study. Heifers were received approximately 60 d prior to study initiation. Initial processing (53 d before study initiation) included individual BW, application of an identification tag, vaccination against viral respiratory pathogens and clostridial species, and administration of doramectin pour-on for control of internal and external parasites. All heifers were administered 36 mg of zeranol at study initiation and were assigned to 1 of 10 pens (n = 5 pens/treatment with 10 heifers/pen) in a randomized complete block design (blocked by location). Each pen was randomly assigned to 1 of 2 treatments: 20.3 cm (8IN) or 40.6 cm (16IN) of linear bunk space/heifer. Heifers were individually weighed on days 1, 14, 35, 63, 84, and 109. Heifers were programmed to gain 1.36 kg daily based on predictive equations set forth by the California Net Energy System. To calculate predictive values, a final BW of 575 kg was assumed to be the mature BW of the heifers and tabular net energy values of 2.05 NEm and 1.36 NEg from days 1 to 22, 2.00 NEm and 1.35 NEg from days 23 to 82, and 1.97 NEm and 1.32 NEg from days 83 to 109 were used. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with manger space allocation as the fixed effect and block as the random effect. No differences (P > 0.35) were observed between 8IN or 16IN heifers for initial BW, final BW, average daily gain, dry matter intake, feed efficiency, variation in daily weight gain within each pen or applied energetic measures. No differences (P > 0.50) were observed between treatments for morbidity. Although not statistically analyzed, 8IN heifers appeared to have looser stools during the first 2 weeks compared to the 16IN heifers. These data suggest restricting manger space allocation from 40.6 to 20.3 cm did not negatively influence gain efficiency or the efficiency of dietary net energy utilization in heifers programmed fed a concentrate-based diet to gain 1.36 kg daily. The use of tabular net energy values and required net energy of maintenance and retained energy equations are effective means to program cattle to a desired rate of daily gain during the growing phase.

Evaluation of the effects of corn silage maturity and kernel processing on steer growth performance and carcass traits

Two experiments were conducted to investigate the effects of feeding kernel processed corn silage to growing calves at 65% inclusion (dry matter [DM] basis; Exp. 1] and finishing beef steers at 20% inclusion (DM basis; Exp. 2). In Exp. 1, steers (n = 184; initial shrunk body weight [BW] = 388 ± 22.3 kg) were used to evaluate the influence that kernel processing of corn silage has on production responses when fed at 65% diet inclusion (DM basis) during a 46-d growing period. Steers were allotted to 1 of 24 pens (12 replicate pens/treatment). Treatments were based upon corn silage that was either kernel processed or not. In Exp. 2, steers (n = 192; initial shrunk BW = 446 ± 28.3 kg) were used in a 112-d finishing experiment. Treatments were grouped in a 2 × 2 factorial arrangement (24 pens total; 8 steers/pen) to evaluate corn silage harvest maturity (1/2 to 2/3 milk line or black layer) and kernel processing (processed or not) at time of corn silage harvest on finishing steer growth performance and carcass traits when corn silage is fed at a dietary DM inclusion of 20%. Both experiments were analyzed as a randomized completed block design with pen as experimental unit. In Exp. 1, final BW tended (P = 0.07) to be increased by 3 kg in kernel processed corn silage. Daily weight gain and DM intake were increased (P ≤ 0.04) by 6% and 2%, respectively, in steers fed kernel processed corn silage compared to controls; however, gain efficiency was not appreciably influenced by treatment (P = 0.15). In Exp. 2, there were no harvest maturity × kernel processing interactions (P ≥ 0.26) for any growth performance measures or any parameters related to efficiency of dietary NE utilization. No harvest maturity × kernel processing interactions (P ≥ 0.08) were observed for any carcass traits except for the distribution of USDA Prime carcasses (P = 0.04). Steers fed 2/3 milk line and unprocessed corn silage had a lower (P = 0.05) proportion of carcasses grade USDA Prime (0.0%) compared to all other treatments (12.0%). Harvest time (P ≥ 0.07) and kernel processing (P ≥ 0.07) of corn silage had no appreciable influence on any other carcass trait measures. These data indicate that kernel processed corn silage fed to growing calves at 65% diet inclusion (DM basis) enhances intake and daily gain, while kernel processed corn silage fed to finishing steers at 20% diet inclusion (DM basis) does not appreciably influence daily gain, efficiency of gain, or carcass parameters.

205 Evaluation of a Direct Fed Microbial and/or an Enzymatically Hydrolyzed Cell Wall + Yeast Culture Product on Growth Performance, Dietary Net Energy Utilization, and Carcass Traits in Beef Steers

This research determined the influence a direct fed microbial (DFM) and/or enzymatically hydrolyzed yeast (EHY) product (both from Arm & Hammer Animal and Food Production, Princeton, NJ) have on growth performance and carcass characteristics in beef steers fed in the Northern Plains (NP). Single-sourced, newly weaned steers (n = 256; initial BW = 246 ± 1.7 kg; n = 8 pens/treatment with 8 steers/pen) were blocked by location in a 2×2 factorial treatment arrangement of DFM (Certillus CP B1801 dry; Bacillus subtilis, Lactobacillus plantarum; 28 g/steer·d-1) and EHY (Celmanax; 18 g/steer·d-1). Steers were individually weighed on d 1, 14, 42 (end of receiving phase; implant with 200 mg progesterone and 20 mg estradiol benzoate), 77, 105 (end of growing phase), 133, 161 (implant with 200 mg trenbolone acetate and 28 mg estradiol benzoate), 182, 230 (start ractopamine HCl at 300 mg/steer·d-1) and 258. No DFM × EHY interactions (P ≥ 0.05) were observed for cumulative growth performance. No health parameters were influenced by treatment (P ≥ 0.08). EHY steers had reduced (P = 0.04) dry matter intake compared with DFM and had a tendency (P &lt; 0.08) for improved applied energetics measures. A DFM × EHY interaction (P = 0.02) was noted for the distribution of USDA yield grade (YG) 1 carcasses. Control steers had a greater proportion (P &lt; 0.05) of YG1 carcasses compared with other treatments. A DFM × EHY interaction (P = 0.04) was noted for the distribution of USDA Prime carcasses. Steers from DFM × EHY had a greater proportion (P &lt; 0.05) of USDA Prime carcasses compared with DFM or EHY, but did not differ from control, which were similar to DFM and EHY. Use of DFM and EHY alone or in combination had minimal effects on growth performance and carcass traits in NP steers.

225 Effect of Increasing Doses of Encapsulated Butyric Acid and Zinc on Beef Feedlot Steer Growth Performance, Dietary Net Energy Utilization, and Carcass Characteristics

The objective of this study was to determine the effects that increasing doses of encapsulated butyric acid and zinc (BPZ) have on beef feedlot steer growth performance, dietary net energy utilization, and carcass characteristics. Steers (n = 272; shrunk BW = 360 kg ± 74 kg) were assigned to dietary treatment [0 (CON), 1, 2, or 3 g BPZ/kg diet DM] in a randomized complete block design (RCBD) with pen (n = 32) as experimental unit. Cattle were fed until visually assessed to have 1.27 cm rib-fat and were shipped for harvest at a commercial beef abattoir. Carcass and liver health data was recorded. Feedlot performance data was calculated on a carcass-adjusted basis (HCW/0.625). Data were analyzed as a RCBD with fixed effects of BPZ inclusion level and block was considered a random effect; pre-planned contrasts for CON vs. BPZ, plus linear, and quadratic responses were tested. No differences (P ≥ 0.14) were observed for final BW, DMI, ADG, feed conversion efficiency, observed dietary NEm and NEg, observed-to-expected dietary NEm and NEg, HCW, REA, rib-fat thickness, marbling score, estimated EBF, or distribution of USDA YG 1, 3, 4, 5, and USDA quality grade among treatments. A tendency (P = 0.10) was observed for CON vs. BPZ for calculated YG. Tendencies were detected for USDA YG 2 carcass distribution (linear; P = 0.07) and for normal and abscessed liver prevalence (quadratic; P = 0.08). Dressed yield tended to be greater (P = 0.08) for BPZ vs. Con and increased with dose (linear; P = 0.05). Supplementation of BPZ in finishing cattle diets does not appreciably influence growth performance, but increases dressed yield. Data from this study suggests that the addition of BPZ to feedlot finishing diets for decreasing the prevalence of abscessed livers should be further investigated.

PSVIII-B-17 Supplemental Organic Trace Minerals and a Yeast Culture Product in Newly Weaned Steer Calves: Effects of Use and Delivery Method on Growth Performance, Efficiency, and Hepatic Trace Minerals

The objective was to determine if delivery method of organic trace minerals and Saccharomyces cerevisiae yeast culture product influence growth performance, feed efficiency, and hepatic trace mineral measures in newly-weaned steers. Crossbred steers (n = 192; 256 ± 14 kg) were used in a 49-d receiving experiment. Within 36h of weaning, steers were weighed, allotted to 24 pens (n = 8 steers/pen; 8 pens/treatment) and randomly assigned to treatments: traditional receiving diet (Con); traditional receiving diet plus the “stress-pack” directly in the diet (Force); traditional receiving diet plus a low-moisture, cooked molasses block fortified with the “stress-pack” (Tub). “Stress-pack” was offered the first 28 d of the 49-d. Biopsy samples were collected from a subsample of steers (n = 14 steers) on the day of weaning and subsequent samples were collected from the same steer (n = 1 steer/pen) on d 14, 28 and 49 for hepatic trace mineral concentration determination. A treatment × day interaction (P≤0.01) for hepatic Cu concentration was noted. Force had greater hepatic Cu (P≤0.05) compared to Tub and Con for the entire period. Tub had greater hepatic Cu compared to Con on d 14 and 28 (P &lt; 0.05), but was similar to Con on d 49 (P&gt;0.10). Force tended (P=0.08) to have greater DMI compared to Tub from d 1 to 14. From d 15 to 28, steers offered “stress-pack” had greater DMI (P=0.01) and tended (P=0.07) to have greater ADG compared to Con by 12.5%. From d 29 to 49, “stress-pack” steers had greater DMI (P=0.01) and Force consumed 6.9% more DM compared to Tub (P=0.01). Cumulative DMI (P=0.01) and ADG (P=0.05) was greater for Force compared to Tub by 5.4% and 9.4%, respectively. Application of “stress-pack” in diets offered to newly-weaned cattle enhanced production responses, but delivery method influences DMI and daily gain.

Supplemental organic trace minerals and a yeast culture product in newly weaned steers: effects of use and delivery method on growth performance and hepatic trace mineral content

The objective of this study was to determine if supplementation and delivery method of a "stress pack" composed of organic trace minerals and Saccharomyces cerevisiae yeast culture product influenced growth performance, feed efficiency, and hepatic trace mineral concentration in newly weaned steers. Crossbred steers (n = 192; 256 ± 14.0 kg) were used in a 49-day receiving phase experiment. Within 36 hours of weaning, steers were weighed, allotted to 24 pens (n = 8 steers/pen; 8 pens/treatment), and randomly assigned to treatments: 1) a traditional receiving diet (CON), 2) a traditional receiving diet plus the "stress-pack" directly in the diet (FORCE), and 3) a traditional receiving diet plus a low-moisture, cooked molasses block fortified with the "stress-pack" (TUB). The "stress-pack" was offered the first 28 day of the 49-day receiving period. Due to adverse weather conditions forecasted on day 1, biopsy samples were collected from a subsample of steers (n = 14 steers) on day 1 to establish hepatic trace mineral concentration baseline. Steers were selected based on the mean body weight (BW) from allotment (day -1) of the pen for collection of subsequent samples (n = 1 steer/pen) on days 14, 28, and 49 for hepatic trace mineral concentration determination. Cumulative dry matter intake (DMI) (P = 0.01) was greater for FORCE compared to CON and TUB. Final BW and average daily gain (ADG) tended (P ≤ 0.10) to be greater for FORCE compared to TUB and CON by 5.4% and 9.4%, respectively. Feed efficiency did not differ between treatments (P = 0.28). A treatment × day interaction (P ≤ 0.01) for hepatic Cu concentration was noted. The FORCE treatment had greater hepatic Cu compared to TUB and CON for the entire period. The steers that received TUB had greater hepatic Cu compared to CON on days 14 and 28, but similar to CON on day 49. The addition of a "stress-pack" to diets offered to newly weaned cattle enhanced hepatic trace mineral concentration, and delivery method influences DMI and daily gain.

Maternal Nutrition and Meat Quality of Progeny

The concept of fetal programming is based on the idea that nutritional status and environmental conditions encountered by the dam during pregnancy can have lifetime impacts on her offspring. These changes in the gestational environment have been shown to influence fetal development and subsequent growth performance, carcass composition, and meat quality characteristics. Beef fetuses can be particularly prone to experiencing variations in the maternal environment during development owing to a relatively long duration of pregnancy potentially exposing the dam to environmental temperature stress and/or seasonal conditions that can compromise feed quality or quantity. If feed is limited or forage conditions are poor, a maternal deficiency in protein and/or energy can occur as well as fluctuations in body condition of the dam. As a result, the fetus may receive inadequate levels of nutrients, potentially altering fetal development. There are critical windows of development during each stage of gestation in which various tissues, organs, and metabolic systems may be impacted. Skeletal muscle and adipose tissue are particularly vulnerable to alterations in the gestational environment because of their low priority for nutrients relative to vital organs and systems during development. The timing and severity of the environmental event or stressor as well as the ability of the dam to buffer negative effects to the fetus will dictate the developmental response. Much of the current research is focused on the influence of specific nutrients and timing of nutritional treatments on offspring carcass composition and meat quality, with the goal of informing strategies that will ultimately allow for the use of maternal nutritional management as a tool to optimize performance and meat quality of offspring.

331 Effects of on-Arrival Application of a Modified-Live Respiratory and Clostridia Vaccination on Health, Growth Performance, and Antibody Titers of Newly Weaned Calves

The objective of this research was to evaluate health, growth performance, and antibody titers to IBR, BVD 1 and 2, PI3, and BRSV for calves administered a respiratory and clostridia vaccine compared with no vaccination upon arrival. Single-sourced, newly weaned steers (n = 70; initial body weight (BW) = 254±5.9 kg) were allotted to 10 pens (n = 5 pens/treatment with 7 steers/pen). Steers were blocked by BW in a RCBD of VAC (vaccinated for IBR, BVD 1 and 2, PI3, and BRSV and clostridial upon arrival) or NOVAC (not vaccinated upon arrival). Steers were individually weighed on d 0 (arrival), 1, 21, and 42 for growth performance measures. Whole blood samples were collected (n = 3 steers/pen closest to the pen mean BW) on d 1, 21, and 42 via jugular venipuncture for antibody titer responses. Depression scores of 0 (normal) to 4 (moribund) were recorded for each individual steer for 21 d. Body weight gain and feed efficiency were not influenced (P ≥ 0.10) by treatment. However, dry matter intake tended (P &lt; 0.07) to increase as a percentage of BW by 3.5% for NOVAC compared with VAC. No treatment by day interactions (P &gt; 0.05) were observed for depression scores or BVD 1 and 2 or PI3 titers. However, a treatment by day interaction (P &lt; 0.03) was observed for IBR and BRSV titers. VAC steers had decreased (P &lt; 0.05) titers for both IBR and BRSV on d 1 compared with d 21 but were similar (P &gt; 0.05) to d 42, which were also similar (P &gt; 0.05) to d 21 titers. Additionally, VAC steers had a 27% increase (P &lt; 0.03) in PI3 titers compared with NOVAC steers. Collectively, growth performance was unaffected by vaccination, and vaccinated calves had increased antibody titer responses, as expected.

Case study: effects of low-stress weaning on calf growth performance and carcass characteristics

The objective of this study was to compare the influence of two low-stress weaning methods with conventional weaning on post-weaning performance and carcass characteristics of beef steers. Single-sourced steer calves (n = 89) were stratified by body weight (BW) and dam age into three groups in a completely randomized design (n = 29 or 30 steers/treatment): ABRUPT (calves isolated from dams on the day of weaning), FENCE (calves separated from dams via a fence for 7 d prior to completely weaning), and NOSE (nose-flap inserted and calves remained with dams for 7 d prior to completely weaning). At day +7 post-weaning, calves were transported to a commercial feedlot where they received standard step-up and finishing rations typical for a Northern Plains feedlot. BWs were recorded in study day -7 (PreTreat), 0 (Weaning), 7 (PostWean), 26 (Receiving), 175 (Ultrasound), and 238 or 268 (Final), and average daily gains (ADG) were calculated for each time period. Blood samples were collected via coccygeal venipuncture at d -7 (PreTreat), 0 (Weaning), and +7 (PostWean) from a subsample of calves (n = 10 per treatment) and analyzed for haptoglobin (acute-phase stress protein) concentrations using a bovine haptoglobin ELISA kit. On day 175, ultrasound fat thickness and intramuscular fat were determined and utilized to project marketing dates when steers reached 1.27 cm of backfat (day 238 or 268). Carcass measurements were recorded at the time of harvest. The weaning method interacted (P < 0.01) with a time period for ADG and BW. Calf ADG was greater (P < 0.01) in the NOSE treatment during PreTreat to Weaning than ABRUPT or FENCE. In the Weaning to PostWean period, the FENCE calves had greater (P < 0.01) ADG than ABRUPT and NOSE. During the Postwean to Receiving period ADG was greater (P < 0.04) for ABRUPT compared to FENCE and NOSE. Calf ADG was similar (P > 0.05) among treatments for the remainder of the feeding period. Calf BW did not differ among treatments (P > 0.05) at all times of weighing. Haptoglobin was undetectable in all samples except two samples collected on day -7. The weaning method did not influence (P > 0.05) carcass measurements. Collectively these data suggest low-stress weaning methods do not significantly improve post-weaning growth performance or carcass characteristics compared to using conventional methods despite minor, short-term alterations in ADG during the weaning period.

Longitudinal Assessment of Prevalence and Incidence of Salmonella and Escherichia coli O157 Resistance to Antimicrobials in Feedlot Cattle Sourced and Finished in Two Different Regions of the United States

The objective was to investigate the influence of cattle origin and region of finishing on the prevalence of Salmonella, Escherichia coli O157:H7, and select antimicrobial resistance in E. coli populations. Yearling heifers (n = 190) were utilized in a 2 × 2 factorial arrangement. After determining fecal Salmonella prevalence, heifers were sorted into one of four treatments: heifers originating from South Dakota (SD) and finished in SD (SD-SD); heifers originating from SD and finished in Texas (SD-TX); heifers originating from TX and finished in SD (TX-SD); and heifers originating from TX and finished in TX (TX-TX). Fecal, pen, and water scum line samples were collected longitudinally throughout the study; hide swab and subiliac lymph node (SLN) samples were collected at study end. A treatment × time interaction was observed (p ≤ 0.01) for fecal Salmonella prevalence, with prevalence being greatest for TX-TX and TX-SD heifers before transport. From day (d) 14 through study end, prevalence was greatest for TX-TX and SD-TX heifers compared with SD-SD and TX-SD heifers. Salmonella prevalence on hides were greater (p ≤ 0.01) for heifers finished in TX compared with SD. Salmonella prevalence in SLN tended (p = 0.06) to be greater in TX-TX and SD-TX heifers compared with TX-SD and SD-SD. Fecal E. coli O157:H7 prevalence had a treatment × time interaction (p = 0.04), with SD-TX prevalence being greater than TX-SD on d 56 and SD-SD and TX-TX being intermediate. A treatment × time interaction was observed for fecal trimethoprim-sulfamethoxazole-resistant and cefotaxime-resistant E. coli O157:H7 prevalence (p ≤ 0.01). Overall, these data suggest that the region of finishing influences pathogenic bacterial shedding patterns, with the initial 14 d after feedlot arrival being critical for pathogen carriage.

373 Growth Performance, Efficiency of Dietary net Energy Utilization, and Carcass Traits of Lambs Supplemented Encapsulated Butyric Acid and Zinc Abruptly Transitioned to a Finishing Diet

The objective of this study was to determine if supplementing encapsulated butyric acid and zinc (BZ) in lambs abruptly transitioned to a finishing diet has effects on growth performance, efficiency of dietary net energy utilization, and carcass traits following a 59.5 d finishing period. Polypay wethers (n = 32; initial shrunk BW = 39 kg ± 4.8 kg) were grouped by initial shrunk BW and assigned to dietary treatment (CON: 0 g BZ/kg diet DM; BZ: 2 g BZ/kg diet DM) in a randomized complete block design (RCBD) with pen (n = 16) as experimental unit. Wethers were abruptly transitioned from growing diet (based upon grass hay, dried distillers grains plus solubles, and a soybean meal based pellet; 1.65 Mcal/kg NEm, 0.95 Mcal/kg NEg) to finishing diet (based upon whole corn, soybean hulls, and a soybean meal pellet; 2.02 Mcal/kg NEm, 1.33 Mcal/kg NEg) upon study initiation. Lambs were harvested at the South Dakota State University meat lab and empty body measures and carcass traits were recorded. Growth performance was calculated on a shrunk live basis (BW × 0.96). Data were analyzed as an RCBD with fixed effect of treatment and random effect of block. No differences (P ≥ 0.15) were observed for final shrunk BW, ADG, DMI, feed conversion efficiency, observed-to-expected (O:E) DMI, O:E NEm, O:E NEg, EBW, dressed yield, or HCW. Percentage of boneless closely trimmed retail cuts (BCTRC) and red meat yield (RMY) were decreased (P = 0.03) for BZ vs. CON. Body wall thickness was increased (P = 0.02) for BZ vs. CON. Supplementing wethers BZ during an abrupt transition to a finishing diet had no effects on growth performance, efficiency of dietary net energy, or empty body measures and had minor effects on body wall thickness, percentage BCTRC, and RMY.

Evaluation of long-term supplementation of a direct-fed microbial and enzymatically hydrolyzed yeast cell culture product on feedlot growth performance, efficiency of dietary net energy utilization, heat stress measures, and carcass characteristics in beef steers

The objective of this research was to determine the influence of long-term supplementation (258 d) of a direct-fed microbial (DFM) and yeast cell wall (YCW) product used alone or in combination on growth performance, dietary net energy utilization, and carcass characteristics in beef steers finished under climatic conditions in the Northern Plains (NP). Single-sourced Charolais × Red Angus steers [n = 256; body weight = 246 ± 1.68 kg] were blocked by pen location in a 2 × 2 factorial arrangement of DFM and YCW. Steers were administered a series of diets common to the NP and administered ractopamine hydrochloride (RH; 300 mg/kg) during the last 28 d of the finishing phase. Steers were vaccinated and poured at processing and individually weighed on days 1, 14, 42, 77, 105, 133, 161, 182, 230, and 258. Temperature-humidity index (THI) was calculated during RH supplementation. For 98% of the experiment, the THI was lower than 72 and thus cattle were not under high-ambient temperature. On days 1, 2, 21, and 22 of RH supplementation, respiration rates (RR), and panting scores (PS) were determined before and after AM and PM feedings (0700 h, 1100 h, 1400 h, and 1700 h). A DFM + YCW interaction was noted for the proportion of steers categorized as PS 2.0 at 1100 h on day 21 (P = 0.03) and RR on day 21 at 1400 h (P = 0.02). Control steers had a greater proportion of PS 2.0 compared to DFM or YCW steers (P ≤ 0.05), while DFM + YCW steers did not differ from others (P ≥ 0.05); DFM + YCW steers had greater (P < 0.05) RR compared to DFM steers, while control and YCW steers did not differ from others (P ≥ 0.05). No DFM + YCW interactions or main effects (P ≥ 0.05) were observed for cumulative growth performance measures. However, YCW steers had 2% lower (P = 0.04) dry matter intakes compared to steers not fed YCW. No DFM + YCW interactions or main effects (P ≥ 0.05) were observed for carcass traits or liver abscess severity. However, a DFM + YCW interaction (P < 0.05) was noted for the distribution of USDA yield grade (YG) 1 and Prime carcasses. Control steers had a greater proportion (P < 0.05) of YG 1 carcasses compared to other treatments. DFM+YCW steers had a greater proportion (P < 0.05) of USDA Prime carcasses compared to DFM or YCW but were similar to control steers, which were also similar to DFM or YCW. Overall, the use of DFM and YCW alone or in combination had minimal effects on growth performance, carcass traits, and heat stress measures in steers finished in NP climatic conditions.