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Feedlot cattle (n= 128; BW = 549 ± 60 kg) were used to evaluate the effects of ractopamine hydrochloride (RAC) on growth performance, physiological response to handling, and mobility during shipment for slaughter in a study utilizing a split-plot design with a 2 × 2 factorial arrangement of treatments: 1) diet (CON [no β-adrenergic agonist] vs. RAC [400 mg·animal−1·d−1ractopamine hydrochloride for 28 d]) and 2) handling intensity (HI; low-stress handling [LSH; cattle moved at a walking pace with no electric prod use] vs. high-stress handling [HSH; cattle moved at a minimum of a trot and an electric prod applied while in the alley for posthandling restraint and during loading for shipment to the abattoir]). Cattle fed RAC tended to have greater ADG and G:F (P= 0.06), and had greater HCW and LM area (P= 0.04). The HI treatments were applied on the day after the 28-d growth performance period. Blood samples were collected before HI treatment (baseline), after HI treatments (POSTHAND), after transport to the abattoir (POSTTRANS), and during exsanguination at slaughter. A diet × HI interaction (P= 0.01) was observed in the change in cortisol from baseline to POSTTRANS, and there tended (P≤ 0.07) to be diet × HI interactions for the change in epinephrine from baseline to POSTHAND and for the change in creatine kinase (CK) from baseline to POSTTRANS. Feeding RAC and HSH both increased the change from baseline to POSTHAND in norepinephrine and pH (P≤ 0.05). The HSH cattle also had greater changes from baseline to POSTHAND in blood HCO3, base excess, partial pressure of CO2, lactate, cortisol, and glucose (P≤ 0.01). Ractopamine and HSH both produced greater increases in CK concentrations from baseline to slaughter (P< 0.01). Mobility was not affected by RAC at the feedlot or following an average 6-h lairage (P≥ 0.43). This study confirms RAC improves growth performance and suggests metabolic acidosis, a precursor to fatigued cattle syndrome, develops in cattle allowed to trot without the use of a lead rider regardless of RAC administration. Cattle fed RAC displayed altered hormonal responses to handling and transport stress, and the overall proportion of cattle with compromised mobility appears to increase later in the marketing channel. These findings warrant additional research aimed at better understanding the physiological response to stress and protect the welfare of cattle during shipment for slaughter.

The effects of handling intensity on the physiological response and carcass characteristics of feedlot cattle fed ractopamine hydrochloride were evaluated at the time of transport to slaughter. Eighty steers (BW = 668 ± 36 kg) representing 10 lots of similar breed, frame size, and degree of finish were blocked by lot, stratified by weight, and randomly assigned to 1 of 2 handling intensities (HI) over a 1,600 m dirt alley course: 1) low-stress handling (LSH) or 2) high-stress handling (HSH). For the LSH treatment, 4 penmates were kept at a walk with the use of a lead rider. For the HSH treatment, 4 penmates were kept at a minimum of a trot and received 2 applications of an electric prod (approximately 1 s per impulse) at 2 separate instances: first in the alley before post-handling sampling, and again during loading for transportation to the abattoir. Behavioral observations and physical indicators of stress were recorded a minimum of 1 h before handling (baseline), immediately after handling (POSTHAND), and while in lairage after a 200 km transport to the abattoir. Vital parameters were recorded at baseline and POSTHAND. Venous blood samples were collected via jugular venipuncture at baseline and POSTHAND, and mixed arterial and venous blood samples were collected during exsanguination at slaughter. Muscle tremors tended to be more prevalent in HSH cattle at POSTHAND (P= 0.10). The HSH cattle tended to have greater POSTHAND heart rate (P= 0.08); however, there was no effect of HI on POSTHAND respiration rate or rectal temperature (P ≥0.34). The HSH cattle had greater lactate, epinephrine, norepinephrine, cortisol, and glucose concentrations at POSTHAND (P≤ 0.02). Additionally, HSH cattle had lower POSTHAND blood pH, bicarbonate, base excess, and partial pressure carbon dioxide (P< 0.0001). Bicarbonate concentrations were greater in HSH cattle at slaughter (P= 0.05); however, there were no differences between HI treatments for the remaining blood variables (P ≥0.11). Concentrations of stress hormones and CK were significantly greater at slaughter relative to baseline and POSTHAND for both LSH and HSH cattle (P< 0.001). These findings suggest cattle trotted without a lead rider develop metabolic acidosis, and illustrate the importance of low-stress handling at the time of transport for slaughter. Further research is warranted to develop strategies to mitigate stress at the time of transport and ensure the welfare of beef cattle presented to abattoirs.

Feedlot cattle (n= 1,395; BW = 568 ± 43 kg) were used to evaluate the effects of shade on animal welfare, growth performance, and carcass quality during the summer of 2013 in a Kansas commercial feedlot. Seven lots of predominately black steers and heifers (4 and 3, respectively) visually determined to be approaching the final mo on feed were identified, randomly gate-sorted, and allocated to pens located across the feed alley from each other to receive 1 of 2 treatments: 1) Shade (mean shade area = 1.5 m2/ animal) or 2) No shade. Shade was provided using a 13-ounce polyethylene fabric and pens were oriented northwest to southeast. The mean starting date was June 13 and the mean days on feed for lots while on the study was 38 d. Cattle were fed a 77.67% DM steam-flaked corn-based diet and had ad libitum access to water throughout the duration of the trial. Zilpaterol hydrochloride (ZIL) was included in the finishing ration at an inclusion rate of 8.3 mg/kg of DM for the last 20 d on feed with a 3 d withdrawal period. Pen floor temperatures (PFT) were measured using an infrared thermometer and prevalence of cattle open-mouth breathing (OMB) was recorded on a pen basis. In addition to shade treatment, the effect of temperature humidity index (THI) on PFT and OMB was analyzed by classifying days as either “Alert” (THI < 79) or “Danger” (THI > 79). On the day of slaughter, pens within a replicate were kept separate through all stages of the marketing channel from loading at the feedlot until stunning at the plant. Pen served as the experimental unit for all measurements. There was a THI × shade treatment interaction for PFT and OMB (P< 0.001) where days classified as “Danger” increased PFT and prevalence of OMB compared to “Alert” days in unshaded but not shaded cattle. Shaded cattle had greater DMI (P= 0.01); however, unshaded cattle had greater G:F (P= 0.05) and therefore no differences were observed in ADG (P= 0.39). Shaded cattle had greater dressing percentage (P= 0.01), although HCW, LM area, fat thickness, marbling score, and quality grade did not differ between treatments (P> 0.05). Heat stress, a significant animal welfare concern and cause of reduced performance in feedlot cattle during the final phase of the feeding period, was alleviated in shaded cattle and illustrates the importance of shade provision as 1 tool to protect the welfare and increase feed consumption in large pens of feedlot cattle during hot summer months.

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Crossbred yearling steers (n= 360; 395 ± 33.1 kg initial BW) were used to evaluate the effects of dry-rolled corn (DRC) particle size in diets containing 20% wet distiller's grains plus solubles on feedlot performance, carcass characteristics, and starch digestibility. Steers were used in a randomized complete block design and allocated to 36 pens (9 pens/treatment, with 10 animals/pen). Treatments were coarse DRC (4,882 μm), medium DRC (3,760 μm), fine DRC (2,359 μm), and steam-flaked corn (0.35 kg/L; SFC). Final BW and ADG were not affected by treatment (P> 0.05). Dry matter intake was greater and G:F was lower (P< 0.05) for steers fed DRC vs. steers fed SFC. There was a linear decrease (P< 0.05) in DMI in the final 5 wk on feed with decreasing DRC particle size. Fecal starch decreased (linear, P< 0.01) as DRC particle size decreased. In situ starch disappearance was lower for DRC vs. SFC (P< 0.05) and linearly increased (P< 0.05) with decreasing particle size at 8 and 24 h. Reducing DRC particle size did not influence growth performance but increased starch digestion and influenced DMI of cattle on finishing diets. No differences (P> 0.10) were observed among treatments for any of the carcass traits measured. Results indicate improved ruminal starch digestibility, reduced fecal starch concentration, and reduced DMI with decreasing DRC particle size in feedlot diets containing 20% wet distiller's grains on a DM basis.

There are several experimental reports claiming to have demonstrated amplification and lasing at 13.5 nm on the Lyman–[MATH] transition in Li2+ions produced by optical field ionization (OFI) of a preformed Li-plasma. We have systematically studied properties of Li-OFI-plasmas by recording simultaneously the time dependent XUV line emission and scattered femtosecond laser signals. Our investigations demonstrate that in the Li vapor (plasma) produced by nanosecond pulse laser ablation of a solid target clusters and microparticles are present that strongly influence the XUV emission. These observations raise doubts on the interpretation of so far reported results on the feasibility of the Lyman–[MATH] Li laser.

Angus crossbred steers (n = 40; 563 ± 44 kg) were used to examine the effects of handling method and fat thickness on the blood chemistry and physiology of market steers. Steers were blocked by backfat (BF) thickness and were randomly assigned to treatment groups: low-stress handling (LSH) and aggressive handling (AH). Cattle were then ran¬domly assigned to one of 5 blocks containing 4 steers from the LSH and AH treatments. Steers in the LSH treatment were walked and AH cattle were run through a course of 1,540 m. Blood samples were obtained via jugular venipuncture before handling (BASE), at 770 m (LAP1), at 1,540 m (LAP2), and at1 h (1H) and 2 h (2H) after finishing the course. Blood samples were analyzed for plasma lactate (LAC), creatinine kinase (CK), base excess (BE), blood pH (pH), serum cortisol (CORT) concentrations, and venous carbon dioxide (PvCO2) and oxygen (PvO2) pressures. Heart rate (HR), respiratory rate (RR), and rectal temperature (TEMP) were measured at the same intervals. Cattle in the AH treatment had greater (P< 0.05) LAC than those in LSH at BASE (4.1 vs. 3.0 mmol/L), LAP1 (16.5 vs. 2.3 mmol/L), LAP2 (22.3 vs. 2.4 mmol/L), 1H (7.2 vs. 2.7 mmol/L), and 2H (4.0 vs. 2.5 mmol/L), respectively. Creatinine kinase and RR were not different (P > 0.14). Blood pH in AH cattle was decreased compared with that in LSH cattle (P< 0.05) at LAP1 (7.25 vs. 7.45) and LAP2 (7.19 vs. 7.48) but was not different (P> 0.13) at BASE, 1H, or 2H. Heart rate and TEMP were increased in AH cattle compared to LSH (P> 0.01). Serum cortisol was increased (P< 0.05) in AH compared to that in LSH cattle at LAP1 (87.5 vs. 58.9 nmol/L), LAP2 (144.4 vs. 93.1 nmol/L), and 1H (113.5 vs. 53.1 nmol/L). Although RR was not differ¬ent between LSH and AH, PvCO2 was decreased in AH compared to that in LSH (P< 0.05) at LAP2 (30.6 vs. 39.3 mmHg) and PvO2 was increased at LAP1 (42.7 vs. 33.5 mmHg) and at LAP2 (51.5 vs. 36.6 mmHg). Lactate was increased in AH cattle in the thicker BF group at 1H (P< 0.05), and blood pH was decreased at LAP1, LAP2, and 1H (P< 0.05) compared to the thinner BF cohorts. Four AH steers became exhausted (EXH) and did not complete the course. Increased CK, decreased PvCO2, and muscle tremors occurred in EXH steers compared to non-exhausted AH cohorts. Results of this study show that AH causes physiologic and blood chemistry changes in steers, which can be potentially detrimental to cattle, emphasizing the need for low-stress handling practices.

A database of daily feed deliveries for steers and heifers fed at 3 commercial feedyards in Kansas between January 1, 2010, and January 31, 2012 (n= 1,515 pens), was used to investigate the prevalence and extent of changes in DMI after initiation of feeding zilpaterol hydrochloride (ZIL) at 8.3 mg/kg (DM) for 20 d. Season affected the percentage of pens experiencing a decrease in DMI post-ZIL (P< 0.01), but there were significant (P< 0.01) season × sex, season × feedyard, season × pre-ZIL DMI, season × days post-ZIL, and season × period post-ZIL interactions. Average DMI decreased within 1 d after initiation of ZIL feeding in all seasons; however, this initial decrease was greater (P< 0.01) in the summer (–0.30 kg) and winter (–0.27 kg) than in the spring (–0.05 kg) or fall (–0.06 kg). The decrease in DMI averaged across all days post-ZIL was greater in summer than during other seasons for both steers and heifers, and the change in intake was greater in steers than heifers in all seasons but fall. Size of intake change within each season varied by feedyard and by season. The percentage of pens that had a large DMI decrease (≥0.9 kg/d) was greatest during the summer (33%), and the percentage of pens with no decrease was the least (15%); during the fall, 34% of pens had no DMI decrease and only 8% of pens had a large decrease in DMI. Intake before ZIL initiation affected size and prevalence of DMI decrease; with increasing pre-ZIL DMI, the percentage of pens with a decrease increased from 62% for pens with pre-ZIL DMI of less than 7.7 kg/d to 82% for pens consuming greater than 10.5 kg/d pre-ZIL (P< 0.01). Of those pens with greater than 10.5 kg/d pre-ZIL DMI, 27% had DMI decrease of greater than 1.4 kg/d compared to only 3% for pens consuming <8.7 kg/d pre-ZIL. The average dosage of ZIL consumed per animal with an average DMI of 7.3, 8.2, 9.1, 10.0, and 10.9 kg/d was calculated to be 61, 68, 76, 83, and 91 mg/animal daily, which may be related to the differences in DMI decrease. Pre-ZIL DMI contributed to DMI decrease during ZIL administration, but the increased occurrence and size of DMI decrease during the summer may indicate an additional physiological mechanism.

A meta-analysis of studies evaluating feedlot steer implant programs was conducted to evaluate the differential effects of anabolic implant dosage on feedlot performance and carcass traits. The effect sizes of the implant dosage of interest vs. negative controls and vs. other implant dosages on various dependent variables (ADG, F:G, DMI, dressing percentage [DP], HCW, yield grade, percentage Choice or higher, and marbling score) were calculated. Treatments used for comparisons included no implant, EST (20 mg estradiol benzoate + 200 mg progesterone, 36 mg zeranol, or 72 mg zeranol), ET120 (24 mg estradiol 17β + 120 mg trenbolone acetate [TBA]), and ET200 (28 mg estradiol benzoate + 200 mg TBA or 20 mg estradiol-17β + 200 mg TBA). In the first analysis, the 3 implant dosages were compared to negative control. A second analysis was conducted to compare ET120 vs. ET200 using only studies that included a direct comparison of these 2 dosages. The number of studies included in the analysis for each implant dosage and response variable ranged from 34 to 7. A mixed model was used to evaluate individual implant treatments; implant dosage was a fixed effect, and individual study was included as a random effect. All dosages had greater ADG, DMI, and HCW and lower F:G, percentage Choice, and marbling score vs. negative controls (P< 0.05) In the second direct comparison analysis, ET200 tended to have greater ADG (P =0.10) and HCW (P= 0.07) and had lower F:G (P< 0.01) and percentage of carcasses grading Choice or greater (P< 0.01) vs. ET120. Differences in HCW between ET120 and ET200 diminished numerically with increasing days of implant activity (P< 0.01). All dosages of implants evaluated herein increased performance and decreased quality grade vs. negative controls. Combination implants containing estrogen (E) and 200 mg TBA have greater potency for growth promotion than implants containing E+120 mg TBA resulting in slightly greater performance.

Feedlot and carcass data from steers (n= 16,700) and heifers (n= 6,357) originating from 16 different states and fed in 17 feedlots located in southwest Iowa were used to evaluate the accuracy of the USDA frame score for predicting final BW of fed cattle. Frame score was recorded by USDA or state personnel for cattle either before leaving the state of origin or on arrival at the terminal feedlot. Mixed model procedures were used to investigate relationships between USDA frame score and measures of live performance and carcass traits. Other fixed effects included in the model included USDA muscle score, sex, age classification on feedlot entry (calf: ≤270 d of age, yearling: 271–365 d of age, and long yearling: >365 d of age), BCS on feedlot arrival, number of treatments for respiratory disease, hide color, and site of frame or muscle scoring; the interactions of sex × frame score and hide color × frame score were also included; fat thickness was included as a fixed effect (covariate) in the analysis of ADG, final BW, days on feed, LM area, marbling score, and quality grade. Random effects included in the model were year of feedlot arrival and feedlot in which cattle were fed. The system accurately projects the minimum target final BW for large frame steers and heifers; however, the final BW of the smallest medium frame steers and heifers exceeds the target minimum final BW by 35 and 40 kg, respectively. When frame score was assigned post facto based on actual final BW (adjusted to 1.27 cm fat thickness), it was determined that large frame was over-assigned by graders (62 vs. 35% for steers and 54 vs. 32% for heifers, actual score vs. postharvest score, respectively), medium frame was underassigned (37 vs. 51% and 46 vs. 58% for steers and heifers), and small frame was underassigned (0.7 vs. 15% and 0.6 vs. 10% for steers and heifers; K= 0.01, P< 0.01). Across sexes, of the cattle assigned to small, medium, or large frame score, 40, 59, and 43% actually had final BW (adjusted to 1.27 cm fat thickness) within the guidelines for the target final BW of each of the frame scores (P< 0.01). The present frame score system accurately reflects the modern feedlot cattle population; however, adjustments in the assignment of frame scores to reflect changes in technologies and final weights may be warranted.

An array of management tools exists within the beef industry to improve animal welfare and productivity; however, the ability to assess the outcomes of these tools is needed. Deficiencies in management commonly manifest as bovine respiratory disease complex or nutritional disorders such as acidosis; therefore, lung, liver, and rumen gross pathology lesions present at slaughter were measured as part of the Harvest Audit Program (HAP) and associations with performance determined. Individual gross pathology data from 19,229 cattle at commercial packing plants in Kansas and Texas were collected. Corresponding individual preharvest and carcass data were obtained on a subset of 13,226 cattle. Associations between lesions and performance were modeled using multivariable mixed effect models. Regression coefficients were used for estimation of lesion associative effects on continuous outcomes and odds ratios for dichotomous outcomes. Across the entire population, 67.3% of the cattle had no pulmonary lesions; 22.5 and 9.8% of cattle displayed mild and severe lesions, respectively. Severe pulmonary lesions were associated with a decreased ADG of 0.07 kg and a HCW 7.1 kg less than cohorts with no pulmonary lesions (P< 0.01). Overall, 68.6% of cattle observed had normal livers. Of cattle severely affected by liver abscesses (A+; 4.6%), 14.9% also displayed severe pulmonary lesions and 28.3% displayed mild pulmonary lesions. Rumenitis lesions were observed in 24.1% of the overall study population. Of cattle with mildly abscessed livers (A–), moderately abscessed livers (A), and severely abscessed livers, 20.6, 21.6, and 9.24% displayed mild or severe rumenitis lesions at slaughter. Severe rumenitis lesions were associated with a significant decrease in ADG and HCW (0.025 and 2.20 kg, respectively; P< 0.001). Although the majority of the cattle in this population would be considered low risk, after adjustments for cattle with multiple lesions, 22.9% of cattle in the overall population were observed with a severe lesion (lung, liver, or rumen). In conclusion, a gross pathology monitoring system is feasible and the 22.9% prevalence of severe lesions (lung, liver, or rumen) indicates that significant opportunity exists to improve beef cattle health, well-being, and productivity. Data generated using HAP may be used to support decisions concerning the implementation or removal of managerial practices and health interventions in beef cattle production systems.

Crossbred horned steers and heifers (n= 40; BW = 311.8 ± 4.7 kg) were used to determine the effect of dehorning methods on pain, cattle behavior, and wound healing. Cattle were blocked by weight and randomly assigned to 1 of 4 treatments: 1) control (CON), 2) banded using high tension elastic rubber (BAND), 3) mechanically removed (MECH), or 4) tipped (TIP). Vocalization and behavior were recorded during the dehorning process. Wound healing scores, attitude, gait and posture, appetite, and lying were recorded daily. Vocalization scores were highest for MECH cattle and BAND cattle vocalized more than TIP and CON (P< 0.05). Attitude (P= 0.06), gait and posture (P= 0.06), and lying scores (P< 0.05) were higher for BAND cattle in the days following procedures compared to MECH, TIP, and CON cattle. Cattle in the BAND treatment tended (P< 0.13) to have higher appetite scores than the other methods. Wound healing scores (horn bud and bleeding) were higher for BAND cattle than MECH, TIP, and CON cattle (P< 0.05). These data indicate that MECH is a painful procedure for cattle at the time of the procedure. Banding to remove horns from cattle is not recommended based on the data and observations from this study.

Auction-derived feeder calves (n = 1,601; initial BW = 273.5 ± 4.7 kg) were used to examine effects of delayed administration of the initial steroid implant on health, performance, and carcass characteristics of feedlot cattle. Steers were procured from multiple auction markets in the southeastern United States and shipped to a central Kansas feedyard over a 6-wk period from December 2009 to January 2010. Steers were rested overnight before processing, then were randomly assigned, within arrival block, to 1 of 2 treatments: 1) implanted with Revalor-XS (40 mg estradiol and 200 mg trenbolone acetate) immediately upon arrival or 2) implanted with Revalor-XS 45 d postarrival. Cattle were weighed by pen using a group scale immediately after processing of each block. Feed deliveries were measured using load cells on feed trucks and recorded daily. Cattle were evaluated daily for morbidity and mortality by feedyard health personnel. Sick or injured cattle were removed from the home pen for further diagnosis and treatment. Individual animal health data were obtained and recorded daily. Final BW was calculated by dividing HCW by average dressing percent of the pen. Carcass data (quality grade and yield grade) were obtained by USDA personnel; presence of lung lesions, pleural adhesions, and liver abscesses were evaluated by trained university personnel. Delaying the initial implant tended to reduce morbidity (24.7 vs. 28.5%; P= 0.13) and reduced the percentage of animals requiring early salvage harvest due to chronic, nonresponsive respiratory disease (1.8 vs. 3.3%; P= 0.02). However, there were no effects of timing of implant administration (P≥ 0.31) on rates of retreatment, mortality, lung lesions, or pleural adhesions. Implanting immediately upon feedlot arrival resulted in no effect on ADG or feed conversion (P≥ 0.30). Cattle implanted upon arrival had numerically greater HCW and yield grade vs. cattle implanted on d 45; however, these differences were not significant (P≥ 0.16). Delaying the initial implant 45 d did not greatly influence animal health, performance parameters, or carcass characteristics in feeder calves at high risk of developing bovine respiratory disease.

The use of herbicides on crop fields has created shifts in weed populations and the emergence of herbicide resistance. Because of this phenomenon, there is interest in the exploitation of allelopathic activity of crop plants. This was assessed in field experiments at the Tygerhoek Research Farm (19°54″ E, 34°08″ S), South Africa, to determine whether significant weed control could be achieved via allelopathy. This locality contains weakly developed residual soils (pH 5.1) of Mispah (Entisol) type containing 22% clay and 1.6% carbon. Uniform scattering of a quantity of plant residues preceded drilling. The rotational plant species planted into the plant residues consisted of barley (Hordeum vulgareL. variety Clipper), canola (Brassica napusL. variety ATR Hyden), wheat (Triticum aestivumvariety SST 88), lupines (Lupinus albusL. variety Tanjil), alfalfa (Medicago sativaL. variety SA standard), medic (Medicago truncatulaGaertn. variety Parabinga), and ryegrass (Lolium multiflorumLam. variety Energa). These crops are used in crop rotation in this grain production area. Six plant species were used in the second experiment, planted at 90° angle across the first after the latter was harvested, namely barley, wheat (variety SST 027), lupines (variety Tanjil and variety Quilinock), ryegrass and ryegrass weed type (L. multiflorum× perenne). Broadleaf weeds comprised 88.5% of total weed spectrum. Medic suppressed ryegrass weed type while lupines suppressed grass weeds. An acceptable production practice using allelopathic crops for weed control will likely consist of combining continued limited amounts of herbicides with leguminous crop residues.

Two finishing experiments were conducted to evaluate the use of 25% dried corn distillers grains with solubles (DDG) in beef cattle finishing diets by partially replacing a portion of the grain and soybean meal in the control diets. In Exp.1, crossbred heifers (n = 377; BW 378 ± 4.1 kg) were fed diets consisting of steam-flaked corn (SFC) with a control diet containing 0% DDG and 15% corn silage (CS), 25% DDG and 15% CS, or 25% DDG and 5% CS. Compared with the control treatment, heifers fed DDG and 15% CS had a greater proportion of USDA yield grade 4 and 5 carcasses (P= 0.04; 5.68 vs. 14.12), and smaller LM area (P= 0.04; 86.09 vs. 82.48 cm2). In Exp. 2, crossbred heifers (n = 582; BW = 377 ± 27.09 kg) were fed diets similar to Exp. 1 except dry-rolled corn (DRC) and SFC were compared as the basal grain sources. Treatments included DRC or SFC: with control diets containing 0% DDG and 15% CS, 25% DDG and 15% CS, or 25% DDG and 5% CS. Feeding SFC decreased DMI (P< 0.01), improved G:F (P< 0.01) and final shrunk BW (P= 0.05) compared with DRC. Average USDA yield grade was greater for cattle fed DRC than for those fed SFC (P= 0.02), but calculated yield grade was not different among treatments (P= 0.71). Feeding DDG and 5% CS, regardless of grain source, led to decreased DMI and greater G:F than feeding DDG and 15% CS (P= 0.02). When comparing the control treatments with the diets containing 25% DDG and 15% CS shrunk final BW, ADG, and G:F were decreased (P≤ 0.05); however, carcass-adjusted measurements were not different (P> 0.52). Results indicate that roughage levels can be reduced in feedlot diets containing 25% DDG with no adverse effects on BW gain, feed efficiency, or carcass quality.

Two studies were conducted to evaluate effects of dried distillers grains with solubles (DDGS) and alfalfa hay (AH) or corn silage (CS) on feedlot performance, carcass characteristics, ruminal fermentation, and diet digestibility in cattle fed steam-flaked corn (SFC) diets. In trial 1, crossbred heifers (n = 358; BW = 353 ± 13 kg) were used in a finishing trial to evaluate interactions between corn-DDGS and roughage source (AH or CS) in terms of impact on feedlot performance and carcass characteristics. Experimental diets (DM basis) consisted of SFC and 11% CS without DDGS (SFC-CS), SFC and 11% CS with 25% DDGS (DDGS-CS), SFC and 6% AH without DDGS (SFC-AH), and SFC with 25% DDGS and 6% AH (DDGS-AH). Heifers were fed for ad libitum intake once daily for 97 d. Results indicated no interaction between DDGS and roughage source with respect to animal performance. Feeding DDGS did not affect ADG (P= 0.19), DMI (P= 0.14), or feed conversion (P= 0.67). Heifers fed CS had greater DMI than those fed AH (P= 0.05), but ADG (P= 0.56) and G:F (P= 0.63) were not different. There were no differences among treatments with respect to HCW, dressing percentage, subcutaneous fat thickness, quality grades, or yield grades (P> 0.20). Cattle fed CS tended (P= 0.10) to have greater marbling scores than those fed AH. There was an interaction (P= 0.02) between roughage and DDGS with respect to incidence of liver abscess. The greatest incidence was observed in cattle fed diets without DDGS when CS was fed, and the least was observed in cattle fed diets without DDGS when AH was used. In the second trial, ruminal fermentation characteristics and diet digestibility were examined in 12 cannulated Holstein steers fed similar diets to those fed in the finishing trial. Ruminal pH for all treatments was below 5.8 for 14 h after feeding. Acetate:propionate ratios were less (P= 0.02) in steers fed 25% DDGS but had greater (P= 0.02) ruminal lactate concentrations compared with cattle fed 0% DDGS. Feeding 25% DDGS decreased (P< 0.01) ruminal ammonia concentrations, and digestion of DM and OM was less (P< 0.01) compared with diets without DDGS. The decrease in digestibility was largely attributable to decreases in digestion of CP (P= 0.03) and NDF (P< 0.01). Feeding strategies aimed at increasing ruminal pH and ruminally available protein may improve digestion of DDGS in steam-flaked corn-based finishing diets.

A metabolism study was conducted to evaluate ruminal fermentation and apparent total tract digestibilities of cattle finishing diets. Holstein steers (n = 16, 351 kg of BW) with ruminal cannulas were fed diets consisting of 0 or 25% dried corn distillers grains (DDG), using dry-rolled corn (DRC) or steam-flaked corn (SFC) as the principal energy source (2 × 2 factorial arrangement). The study was conducted in 2 periods, with 4 steers per treatment in each period. Periods consisted of a 12-d adaptation phase and a 3-d collection phase. Compared with DRC, feeding SFC decreased intakes of DM, OM, starch, NDF, and ether extract (P< 0.01), and steers fed SFC excreted less DM, OM, starch, NDF, and ether extract (P< 0.01). Compared with SFC, feeding DRC decreased ruminal concentrations of acetate, butyrate, isobutyrate, and isovalerate, and decreased the acetate-to-propionate ratio (P< 0.01). Compared with SFC, DRC decreased ruminal propionate, valerate, and lactate concentrations (P< 0.01). When compared with cattle fed SFC, ruminal pH of cattle fed DRC was less at 0 h and greater at 6 h postfeeding (P< 0.01). Ruminal ammonia concentrations were greater for DRC vs. SFC at h 0, 6, 10, 12, 14, 16, 18, 20, and 22 postfeeding (P< 0.05). Feeding DDG decreased consumption of starch and ether extract, but increased NDF intake (P< 0.01). Fecal excretion of ether extract was increased by adding DDG compared with diets without DDG (P< 0.05), resulting in less apparent total tract digestibility of ether extract for cattle fed DDG (P< 0.01). Ruminal lactate concentrations were increased with addition of DDG compared with diets without DDG (P= 0.01). Ruminal ammonia concentrations were less for steers fed 25 vs. 0% DDG at 2, 4, 6, 8, and 10 h postfeeding (P< 0.05). We conclude, based on these results, that ruminal fermentation and apparent total tract digestibility of DDG are affected by grain processing.

Conventional feeding systems use pharmaceutical products not allowed in natural or organic systems for finishing cattle. This review of data compares the performance effects (ADG, G:F, DMI) of technologies used in conventional feeding programs that are prohibited in organic programs, natural programs, or both. The technologies evaluated were steroid implants, monensin, tylosin, endectocides, and metaphylaxis with any antimicrobial. For inclusion in this analysis, studies were conducted in North America, reported randomization to treatment group, used beef cattle, contained an untreated control group, and were sourced from peer-reviewed journals. Forest plots were used to examine the data visually for trends toward a uniform effect of the technology on the outcomes of interest (ADG, DMI, G:F). Technologies that displayed a uniform response on the forest plot compared with negative controls were then analyzed using mixed models. Examination of forest plots for endectocides, steroid implants, monensin, and metaphylaxis technologies appeared to show performance advantages for treated cattle relative to cattle in negative control groups. An insufficient number of studies met the inclusion criteria to conduct meta-analyses comparing endectocides, monensin, or tylosin with negative controls. Average daily gain in feeder cattle given metaphylaxis on arrival was 0.11 kg/d (P< 0.01) greater relative to cattle that did not receive metaphylaxis on arrival. Implanting heifers increased ADG by 0.08 kg/d compared with nonimplanted controls (P= 0.09). Implants had no effect on G:F (P= 0.14) in heifers or on DMI (P= 0.44) relative to nonimplanted control heifers. Implanting steers was associated with greater ADG, by 0.25 kg/d (P< 0.01), and DMI, by 0.53 kg/d (P< 0.01), relative to nonimplanted control steers. Implants also improved G:F in steers relative to nonimplanted steers, by 0.02 (0.17 vs. 0.15; implanted vs. controls, P< 0.01; n = 21 studies). When average estimated differences in ADG and G:F for implanted and nonimplanted steers were incorporated into a breakeven model, implanted steers had a $77/animal lower cost of production than nonimplanted steers and a $349/animal lower cost of production than organically raised steers. These data illustrate the importance of capturing premiums when operating natural and organic production systems to maintain economic viability.

Steers (n = 15,631) and heifers (n = 5,897) fed at 18 feedlots (total confinement, partial confinement, or open lots) in southwest Iowa between 2002 and 2006 as part of the Tri-County Steer Carcass Futurity sponsored by Iowa State University were used to correlate various phenotypic traits with feedlot performance and carcass traits. Dependent variables [ADG, respiratory morbidity, HCW, fat thickness, calculated yield grade, marbling score, presence or absence of lung damage, loin muscle area (LMA), and LMA × 100/HCW] were evaluated on the basis of various phenotypic traits [initial BW, disposition score (1 = calm, 6 = extremely excitable), muscle score, frame score, BCS, number of treatments for respiratory disease, presence of lung lesions, breed makeup, and percentage Angus genetics]. Subjectively evaluated phenotypic traits were evaluated by Iowa State University or USDA personnel. Cattle with greater disposition score (more excitable) had decreased initial BW, final BW, ADG, HCW, yield grade, quality grade, marbling score, and mortality (P< 0.01). Respiratory morbidity was negatively correlated with initial BW, ADG, yield grade, HCW, and marbling score (P< 0.01). As initial BW increased, final BW and HCW increased and respiratory morbidity decreased (P< 0.01). Cattle with greater BCS on arrival had greater initial BW but were lighter at slaughter (P< 0.01). Increased number of treatments for respiratory disease was associated with decreased ADG, greater mortality rate, and greater incidence of lung lesions (P< 0.01). Body weight gain was similar between English- and Continental-breed cattle (P> 0.05), although final BW and HCW were greater and yield grade and yield grade-adjusted marbling score were less for Continental-breed cattle (P< 0.01). Cattle with a poorer muscling score had reduced HCW and LMA and greater yield grade, marbling score, and quality grade (P< 0.01). Animal disposition, health, breed type, and frame score have dramatic effects on live feedlot performance and carcass traits.

Five studies were conducted to evaluate the effects of lipid source on performance and health of stressed feeder cattle. A total of 332 heifers (195 ± 2.37 kg initial BW) in trial 1 and 336 heifers (206 ± 1.70 kg initial BW) in trial 2 were fed diets containing ground flaxseed (FLAX), rolled full-fat soybeans (SOY), or tallow (TAL) at 13, 20, or 4%, respectively (DM basis). All diets were formulated to be isonitrogenous and isocaloric. The ADG and G:F for the first 7 d and for the entire feeding period were greater (P< 0.05) for TAL and FLAX than for SOY. Percentage of animals treated and retreated for bovine respiratory disease did not differ among dietary treatments. The FLAX treatment increased (P< 0.05) total n-3 PUFA concentrations in the plasma, whereas SOY increased (P< 0.05) plasma concentrations of total n-6 PUFA. In trial 3, 18 steers were individually fed diets containing TAL and 18 steers were fed a diet containing SOY (20% of DM). In trials 4 and 5, 18 steers were individually fed diets containing TAL and 18 steers were fed diets containing FLAX (12.9% of DM). On d 14 and 17 of study 3, 4, and 5, 16 steers from each dietary treatment were injected i.v. with Escherichia coliO55:B5 lipopolysaccharide (LPS), and 2 steers from each diet were injected with saline. Rectal temperatures after LPS challenge were lower (P< 0.05) for SOY and FLAX than for TAL, and plasma TNF was greater (P< 0.05) for SOY than for TAL. Serum haptoglobin and blood fibrinogen increased and white blood cell count decreased in response to LPS, but none of these variables was affected by treatment. Although this research failed to measure an effect of lipid source on feedlot morbidity or mortality, these studies indicate that altering the source and type of dietary fatty acids may modify the immune response in stressed feeder cattle and that performance may be hindered by feeding full-fat soybeans to receiving cattle.

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 × 28 and 200 × 42, respectively), 300 mg/d for 28 d (300 × 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 × 42 and step-up groups compared with control, respectively. Feeding OPT at 300 mg for 28 d reduced DMI compared with the control, 200 × 28, and 200 × 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.

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

Two experiments were conducted to investigate the effects of ractopamine-HCl (RAC) and implant strategy or days on feed (DOF) on feedlot performance and expression of β-adrenergic receptors (AR). In Exp. 1, 1,147 feedlot heifers weighing 282 ± 3 kg were used with implant treatments of Revalor-200 (R200) at arrival, or Revalor-IH at arrival with reimplantation with Finaplix-H on d 58 (RF). Ractopamine (0 vs. 200 mg/d) was fed the last 28 d in both experiments. Treatments were randomly assigned to 16 pens. At slaughter, semimembranosus muscle tissue was excised for RNA isolation. Ractopamine administration increased (P< 0.05) ADG, G:F, HCW, and LM; decreased (P< 0.05) 12th rib fat depth; and improved (P< 0.05) yield grade. There was no effect (P> 0.10) on the expression of β1-AR mRNA; however, there was a tendency (P= 0.10) for RAC feeding to increase β2-AR mRNA levels. For β3-AR mRNA, there was an implant by RAC interaction (P= 0.05), with RAC numerically increasing β3-AR mRNA in heifers implanted with RF, but a decrease (P< 0.05) in expression in heifers implanted with R200. Ractopamine also decreased (P< 0.05) IGF-I mRNA in heifers implanted with RF. In Exp. 2, 2,077 heifers were used to investigate the effects of RAC and DOF. Days on feed were 129, 150, and 170, and RAC was administered the last 28 d. Ractopamine improved (P< 0.05) G:F, but had no other effects (P> 0.05) on performance. Average daily gain decreased (P< 0.05) as DOF increased. Hot carcass weight, LM area, 12th rib fat, G:F, calculated yield grade, and marbling score increased (P< 0.05) and the percentage of KPH fat decreased (P< 0.05) as DOF increased. These data aid in our understanding of the effects of steroidal implants, DOF, and RAC administration in feedlot heifers.

Yearling steers (n = 2,552; 314 kg of initial BW) were used to evaluate the effects of ractopamine-HCl (RAC) and days on feed on performance, carcass characteristics, and skeletal muscle gene expression in finishing steers. Treatment groups included serial slaughter dates of 150, 171, or 192 d on feed. Within each slaughter date, steers either received RAC (200 mg/steer) daily for the final 28 d or were not fed RAC. All steers were initially implanted with Revalor-IS and were reimplanted with Revalor-S after 75 d on feed. At slaughter, muscle samples from the semimembranosus were collected for mRNA analysis of the β-adrenergic receptors (β-AR). Ractopamine administration increased (P< 0.05) ADG, G:F, and HCW and increased (P= 0.08) LM area. Ractopamine did not affect the dressing percentage, USDA yield grade, or quality grade (P> 0.3). There was no change in overall feed intake across the entire feeding period; however, feed intake was increased during the 28-d period during which the steers were fed RAC (P≤ 0.05). Greater days on feed decreased (P< 0.05) ADG, G:F, DMI, and the number of yield grade 1 and 2 carcasses. Also, greater days on feed increased (P< 0.05) HCW, dressing percentage, and the number of prime and choice carcasses, as well as the number of yield grade 4 and 5 carcasses. Increasing days on feed decreased (P< 0.05) the abundance of β1-AR and β3-AR mRNA and increased (P< 0.05) the abundance of β2-AR mRNA in skeletal muscle samples obtained at slaughter. Ractopamine had no effect (P> 0.10) on the abundance of β1-AR or β3-AR mRNA, but tended (P= 0.09) to increase β2-AR mRNA. Additional time-course studies with primary muscle cell cultures revealed that advancing time in culture increased (P< 0.001) β2-AR mRNA but had no effect (P> 0.10) on β1-AR or β3-AR mRNA. We conclude that days on feed and RAC are affecting β-AR mRNA levels, which could, in turn, impact the biological response to RAC feeding in yearling steers.

In vitro experiments were performed to investigate the effects of melengestrol acetate (MGA) or progesterone (P4) on bovine muscle satellite cells and C2C12myoblasts. Addition of MGA at physiological and supraphysiological concentrations resulted in a dose-dependent decrease (P< 0.05) in DNA synthesis as measured by 3H]-thymidine incorporation (TI). Similarly, P4 addition (0.01 nM) reduced (P< 0.05) TI. Addition of MGA (10 nM) increased (P< 0.05) IGF-I mRNA abundance but did not affect myogenin mRNA. Progesterone addition (10 nM) increased myogenin mRNA abundance (P< 0.05). In C2C12cultures, P4 addition resulted in a dose-dependent decrease in TI. The antiprogestin RU486, in combination with MGA or P4, also resulted in reduced (P< 0.05) TI. Treatment with RU486 alone had a negative effect (P< 0.05) on TI that was similar to the progestins. Treatment of C2C12myoblasts with MGA (100 nM) resulted in an increase (P< 0.05) in myogenin mRNA. These studies suggest that progestins may reduce satellite cell proliferation, ultimately affecting carcass composition.

Two studies utilizing 1,862 yearling heifers were conducted to determine the effects of a fenbendazole oral drench in addition to an ivermectin pour-on (SG+IVPO), compared with an ivermectin pour-on (IVPO) or a doramectin injectable (DMX) alone, on parasite burden, feedlot performance, and carcass merit of feedlot cattle. In the first study, heifers receiving the SG+IVPO had fewer (P= 0.02) cattle retreated for disease and 73% fewer (P= 0.06) worm eggs per fecal sample 98 d after treatment than heifers treated with IVPO. Heifers treated with SG+IVPO consumed more DM, had greater ADG, were heavier at slaughter, and had heavier carcasses than IVPO-treated heifers (P< 0.05). Heifers treated with SG+IVPO also had more (P= 0.07) carcasses grading USDA Prime or Choice than IVPO-treated heifers. In the second study, heifers treated with SG+IVPO had fewer (P< 0.01) worm eggs per fecal sample 35 d after treatment and had fewer numbers of adult and larval Cooperiaand Trichostrongylusspp. in the small intestine at slaughter (P< 0.10) compared with heifers treated with DMX. Heifers treated with SG+IVPO consumed more DM, were heavier at slaughter, and had heavier carcasses than DMX-treated heifers (P< 0.01). The SG+IVPO-treated heifers also had greater ADG (P< 0.10). The broad-spectrum effectiveness of a combination of a fenbendazole oral drench and an ivermectin pour-on reduced parasite burden and increased feed intake, ADG, and carcass weight in feedlot heifers compared with treatment with an endectocide alone.

In this study we determined airborne concentrations of Halon 1301 (CBrF3) and the associated blood levels which produce cardiac arrhythmias in dogs. Beagle dogs were exposed by inhalation to Halon 1301 concentrations ranging from 5 to 20% and, after five minutes of exposure, were given epinephrine by intravenous injection (8-10 µg/kg). Electrocardiograms were recorded. Serious cardiac arrhythmias were produced with concentrations of 7.5% or greater. A second group of dogs with cannulas surgically implanted in the common carotid artery and external jugular vein were exposed to 5%, 7.5% and 10% Halon 1301 for 60 minutes. The blood concentration of Halon 1301 increased rapidly during the first five minutes of exposure, plateaued within twenty minutes, and declined rapidly after exposure. The mean blood concentrations at equilibrium were directly proportional to airborne concentrations: at a concentration of 5% in air - arterial 19.2 µg/mL, venous 14.6 µg/mL; at 7.5% in air - arterial 30.6 µg/mL, venous 28.4 µg/mL; and at 10% in air -arterial 402 µg/mL, venous 32.1 µg/mL. Since there was no rapid increase in blood fluorocarbon concentration after the first five minutes of exposure, it does not seem likely that risk of cardiac sensitization would increase with increased length of exposure to a given concentration.

Two trials were conducted to determine the effects of steam-flaked sorghum grain bulk density on animal performance, cost of production, and propensity to induce ruminal acidosis in feedlot steers. In Trial 1, 336 yearling steers (343 kg; SEM = .346) were fed diets for 125 d that contained sorghum grain (82.5%, DM basis) flaked to .283 (L), .322 (M), or .361 (H) kg/L (i.e., 22, 25, and 28 lb/bu). Steers fed L consumed 3.2% less DM than those fed H (linear, P< .05), resulting in 6.9% lower ADG (linear, P= .02) and 3.6% lower gain efficiency (linear, P< .15). Sorghum grain flaked to M and L had 16 and 46% greater starch gelatinization than H (measured using differential scanning calorimetry; linear, P= .002). Dressing percentage increased linearly (P< .05) with increasing flake density, but no other carcass measurements were affected by treatment. Increasing flake density increased mill production rate linearly (P< .01), resulting in the lowest energy usage per unit of flaked grain for the H treatment. Trial 2 was an acidosis challenge study that incorporated six ruminally cannulated steers (422 kg; SEM = .129) into a replicated 3 × 3 Latin square experiment. Reducing flake density resulted in linear reductions in ruminal pH following intake challenge at 3, 33, and 36 h after the d-12 challenge (P< .05). There was a linear increase in the area between the pH vs time curve and a line at pH 5.5 (P< .01) and 5.0 (P= .09) with decreasing flake density (28.0, 25.2, and 18.2 pH-hours below 5.5 and 9.6, 7.3, and 3.9 pH-hours below 5.0 for L, M, and H, respectively). Cattle consuming L also tended to have higher VFA concentrations (mM) at 36 h after challenge (P= .12). There was no significant treatment effect on ruminal lactate. Flaking sorghum grain to .283 and .322 kg/L resulted in reduced intake and poorer animal performance compared with .361 kg/L (58.7% starch gelatinization), higher susceptibility to subacute acidosis, and higher costs of production.

We conducted two trials to examine the effects of restricted vs full feeding and of grain processing method on feedlot performance, digestion, and mastication efficiency by Holstein steers in different growing-finishing systems. In Trial 1, 272 Holstein steers (177 ± 9.98 kg) were blocked by weight and assigned to growing phase diets based on corn silage (SIL), steam-flaked corn that was either limit-fed (SFLF) or full-fed (SFFF), or whole corn that was limit-fed (WCLF) or full-fed (WCFF). Limit-fed steers were fed at levels predicted to allow daily gain of 1 kg/d. On d 112, all steers were switched to WCFF or SFFF diets until the mean BW of each treatment group was 545 kg. Overall, steers fed WCLF and SFLF during the growing phase and finished on SF were 8.1 and 6.6% more efficient at converting dietary ME to gain (P= .02 and .04, respectively) than steers in the SFFF group. In Trial 2, three ruminally and duodenally cannulated Holstein steers were fed whole (WC) and rolled corn (RC) diets at FF and LF intake in an incomplete replicated 2 × 2 switchback design. Ad libitum access to feed resulted in higher (P= .02) ruminal starch digestibility than did limit-feeding, and calves had higher total tract DM (P= .05) and starch (P= .03) digestion at the heavier BW. Limit-feeding whole corn resulted in increased particle size of masticate (P= .06) compared with full-feeding whole corn. Because of apparent differences in mastication efficiency between limit-fed and full-fed calves, grain processing method during periods of restriction and compensatory growth may be important considerations for managing growth in systems that incorporate limit-feeding.

Immature ovaries ofDrosophila mercatorumwere injected into young larvae and into adult males ofD. mercatorum, D. melanogaster, D. hydei, D. virilis, andZaprionius vittiger. These homo- and heteroplastic transplantations allow normal vitellogenesis to occur in the donor ovary. By SDS gel electrophoresis, we identified the major species-specific yolk proteins of mature eggs (stage 14) which were exclusively of donor-specific origin. Other experiments withD. hydeiandZ. vittigershowed that, when females were used as hosts, the host-specific yolk proteins became incorporated into the donor eggs. When two immature ovaries, one ofD. mercatorumand one ofD. hydei, were co-cultured in males, again only the donor-specific yolk proteins were found in the mature eggs implying that these yolk proteins were not released into the host hemolymph.

The nature of alloantigens seen by T lymphocytes, in particular the role of peptides in allorecognition, has been studied intensively whereas knowledge about the in vivo emergence, diversity, and the structural basis of specificity of alloreactive T cells is very limited. Here we describe human T cell clones that recognize HLA-B35 alloantigens in a peptide-dependent manner. TCR sequence analysis revealed that several of these allospecific clones utilize homologous TCR: they all express TCRAV2S3J36C1 and TCRBV4S1J2S7C2 chains with highly related CDR3 sequences. Thus peptide-specific alloreactivity is reflected in homologous CDR3 sequences in a manner similar to that described for T cells that recognize nominal peptide/self-MHC complexes. The in vivo frequency of this TCR specificity was studied in unstimulated PBL of the responding cell donor who was not sensitized against HLA-B35. The vast majority (approximately 75%) of the VA2S3J36 junctional regions obtained from two samples of PBL, isolated at a 9-yr interval, encode CDR3 identical or homologous to those of the functionally characterized HLA-B35 allospecific T cells. These data are most easily explained by a model of alloreactivity in which persistent or recurrent exposure to a foreign peptide/self-MHC complex led to the in vivo expansion and long-term maintenance of specific T cells that show fortuitous crossrecognition of an HLA-B35/peptide complex and dominate the alloresponse against HLA-B35.

The treatment of hydrofluoric acid (HF) burns has been in a state of flux in the past, with numerous remedies being tried. This presentation offers a somewhat different approach which centers around the use of certain high-molecular-weight quaternary ammonium compounds. The treatment consists basically in thorough and immediate flushing with water, followed by iced alcohol or aqueous Hyamine soaks. A review of over 200 case records confirms the efficacy of this treatment when compared to that in prior use, especially in the treatment of second-degree burns.

Human volunteers were exposed to fluorocarbon 113 at concentrations of 500 and 1000 ppm for five days, three hours in the morning and three hours in the afternoon at each concentration, to determine the effect of repeated exposures to this compound. A control period preceded the exposures. Clinical observations, laboratory tests, subjective impressions, and measurement of psychomotor performance were used to determine possible compound effects. These tests and observations did not reveal evidence of any adverse effects resulting from the exposures. A general improvement in the psychomotor test scores occurred and may have been due to a continued learning effect, Analysis of breath samples did not indicate a significant body buildup of fluorocarbon 113.