***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The prophylactic administration of injectable tilmicosin for pneumonia in weaned beef calves was investigated in 1,806 animals . Comparisons were made among calves receiving an " on-arrival " injection of tilmicosin , calves receiving a single injection of long-acting oxytetracycline , and calves receiving no prophylaxis .  Morbidity and mortality attributable to pneumonia , morbidity and mortality attributable to all causes , and case fatality were significantly lower in the group of calves that received tilmicosin , compared with calves that received long-acting oxytetracycline and calves that received no prophylactic antibiotic .  Mean time to initial pneumonia treatment was significantly extended in calves that received prophylaxis , compared with those that received no antibiotic on arrival at the feedlot . Calves that received tilmicosin  gained significantly more weight than calves that received oxytetracycline . Calves that were not treated for pneumonia during the trial period gained significantly more weight than did those calves that were treated for pneumonia regardless of experimental group . The majority of mortalities were attributable to fibrinous pneumonia ( 31/34 ) . Important bacterial isolates ( Pasteurella spp , Haemophilus somnus , Actinomyces pyogenes ) obtained at necropsy did not have resistance to tilmicosin in association with administration of tilmicosin as prophylaxis for pneumonia . However , bacterial resistance to trimethoprim/sulfonamide and to oxytetracycline were commonly found in these postmortem isolates The objectives of this study were to determine ( i ) whether an association exists between individual pharmacokinetic parameters and treatment outcome when feeder cattle were diagnosed with bovine respiratory disease ( BRD ) and treated with gamithromycin ( Zactran ( ® ) )  at the label dose and ( ii ) whether there was a stronger association between treatment outcome and gamithromycin concentration in plasma or in the pulmonary epithelial lining fluid ( PELF ) effect compartment . The study design was a prospect i ve , blinded , r and omized clinical trial utilizing three groups of 60 ( 362 - 592 lb ) steers/bulls r and omly allocated within origin to sham injection or gamithromycin mass medication . Cattle were evaluated daily for signs of BRD by a veterinarian blinded to treatment . Animals meeting the BRD case definition were enrolled and allocated to a sample collection scheme consisting of sample s for bacterial isolation ( bronchoalveolar lavage fluid and nasopharyngeal swabs ) and gamithromycin concentration determination ( PELF and plasma ) .  Gamithromycin susceptibility of M. haemolytica ( n = 287 ) and P. multocida ( n = 257 ) were determined using broth microdilution with frozen panels containing gamithromycin at concentrations from 0.03 to 16 μg/mL. A two-compartment plasma pharmacokinetic model with an additional compartment for gamithromycin in PELF was developed using rich data sets from published and unpublished studies . The sparse data from our study were then fit to this model using nonlinear mixed effects modeling to estimate individual parameter values . The result ing parameter estimates were used to simulate full time-concentration profiles for each animal in this study . These profiles were analyzed using noncompartmental methods so that PK/PD indices ( AUC24 /MIC , AUC∞ /MIC , CMAX /MIC ) could be calculated for plasma and PELF ( also T > MIC ) for each individual . The calculated PK/PD indices were indicative that for both M. haemolytica and P. multocida a higher drug exposure in terms of concentration , and duration of exposure relative to the MIC of the target pathogen , was favorable to a successful case outcome . A significant association was found between treatment success and PELF AUC0 - 24 /MIC for P. multocida . The calves in this study demonstrated an increased clearance and volume of distribution in plasma as compared to the healthy calves in two previously published reports . Ultimately , the findings from this study indicate that higher PK/PD indices were predictive of positive treatment outcomes The conduct of r and omized controlled trials in livestock with production , health , and food-safety outcomes presents unique challenges that may not be adequately reported in trial reports . The objective of this project was to modify the CONSORT ( Consoli date d St and ards of Reporting Trials ) statement to reflect the unique aspects of reporting these livestock trials . A two-day consensus meeting was held on November 18 - 19 , 2008 in Chicago , IL , United States of America , to achieve the objective . Prior to the meeting , a Web-based survey was conducted to identify issues for discussion . The 24 attendees were biostatisticians , epidemiologists , food-safety research ers , livestock-production specialists , journal editors , assistant editors , and associate editors . Prior to the meeting , the attendees completed a Web-based survey indicating which CONSORT statement items may need to be modified to address unique issues for livestock trials . The consensus meeting result ed in the production of the REFLECT ( Reporting Guidelines For R and omized Control Trials ) statement for livestock and food safety ( LFS ) and 22-item checklist . Fourteen items were modified from the CONSORT checklist , and an additional sub-item was proposed to address challenge trials . The REFLECT statement proposes new terminology , more consistent with common usage in livestock production , to describe study subjects . Evidence was not always available to support modification to or inclusion of an item . The use of the REFLECT statement , which addresses issues unique to livestock trials , should improve the quality of reporting and design for trials reporting production , health , and food-safety outcomes Feedlot calves ( n = 3784 ) were systematic ally r and omized and allocated in a 2 × 2 factorial study to receive metaphylactic oxytetracycline ( OTC ) on arrival or no antimicrobial , as well as florfenicol once subcutaneously or twice intramuscularly ( 48 h apart ) if diagnosed with bovine respiratory disease ( BRD ) . Calves of different treatment groups were comingled and followed from placement to re-implantation ( ~100 days ) . Animals receiving OTC had a reduced risk of BRD , an increased risk of arthritis , and no significant differences in average daily gain , BRD relapse , overall mortality , or BRD mortality . There were no significant differences between treatment protocol s. Deep nasal swabs ( n = 233 ) taken at arrival ( n = 122 ) , treatment ( n = 77 ) , and swabs from lungs and joints at postmortem ( n = 34 ) were cultured for Mycoplasma bovis from 61 animals ill or dying of chronic pneumonia and arthritis and from 61 healthy calves . There was significant variation in diversity among isolates ( n = 51 ) between study years and different cattle . Metaphylaxis or antimicrobial treatment did not affect the diversity of isolates . Except for tilmicosin , isolates were largely susceptible to tested antimicrobials The efficacy of tulathromycin in the treatment ( phase 1 ) and prevention ( phase 2 ) of bovine respiratory disease ( BRD ) was evaluated on commercial farms in France , Germany , Italy , and Spain . In phase 1 , commingled cattle with clinical BRD were treated with tulathromycin ( n = 128 ) or florfenicol ( n = 125 ) on day 0 . Similar percentages of animals showed sustained clinical improvement at day 14 ( tulathromycin 83.3 % versus florfenicol 81.0 % ) and had not relapsed by day 60 ( tulathromycin 63.3 % versus florfenicol 58.4 % ) . In phase 2 , healthy in-contact cattle were treated with tulathromycin ( n = 492 ) , tilmicosin ( n = 494 ) , or saline ( n = 265 ) on day 0 . Significantly more ( P = .0001 ) tulathromycin-treated cattle remained healthy to day 14 ( 92.4 % ) than tilmicosin-treated ( 83.7 % ) or saline-treated ( 63.7 % ) cattle , and this was maintained through day 60 ( tulathromycin 85.4 % versus tilmicosin 75.1 % and saline 56.2 % ) . Tulathromycin was highly effective in the treatment and prevention of BRD OBJECTIVE To determine effects of vaccination prior to transit and prophylactic administration of florfenicol at time of arrival at a feedyard on health of cattle and colonization of the nasopharynx by Mannheimia haemolytica ( MH ) . ANIMALS 121 steers from Tennessee and 84 steers from New Mexico . PROCEDURE Half of the steers were vaccinated before transport to a feedyard . Steers from Tennessee were vaccinated with MH bacterin-toxoid , and steers from New Mexico were vaccinated intranasally with modified-live leukotoxin-deficient MH . Half of the vaccinates and nonvaccinates were r and omly selected to receive florfenicol on arrival at the feedyard . Steers were observed daily for respiratory tract disease ( RTD ) . RESULTS Administration of florfenicol at time of arrival reduced the incidence of RTD , delayed the interval before onset of RTD , and reduced the incidence of MH colonization of the nasopharynx for at least 4 days , but vaccination did not have any effect . Vaccination elicited an increase in serum antibody titers to MH . Administration of florfenicol at time of arrival reduced the development of serum antibody titers in intranasally vaccinated steers and both groups of nonvaccinated steers , but intranasal vaccination did not affect colonization by wild-type MH . CONCLUSIONS AND CLINICAL RELEVANCE Administration of florfenicol at time of arrival decreased the incidence of MH organisms in the nasopharynx and delayed the onset of RTD . Prophylactic use of suitable antibiotics is likely to reduce the incidence of acute RTD in calves for several days after arrival at feedyards , which is the period when they are most susceptible to infectious organisms The effectiveness of a feed-additive antimicrobial combination for improving feedlot performance and health was tested using 4325 high-risk feeder calves r and omly allocated to a control group or an experimental group . The experimental group received the conventional ration plus a feed additive containing 700 mg per head/day of chlortetracycline and sulfamethazine from arrival at the feedlot to day 56 of the feeding period . The inclusion of the feed additive to the ration significantly improved average daily gain for days 0 - 28 ( P = 0.0163 ) and 0 - 56 ( P = 0.0001 ) , and the feed conversion for days 0 - 28 ( P = 0.0061 ) and 0 - 56 ( P = 0.0004 ) . Additionally , the use of the feed additive significantly reduced the rate of bovine respiratory disease morbidity for days 0 - 28 ( P = 0.0014 ) and 0 - 56 ( P = 0.0001 ) , the rate of relapses and mortality for days 0 - 56 ( P = 0.0151 and P = 0.0209 , respectively ) , and the rate of animals diagnosed with chronic respiratory disease for days 0 - 28 and 0 - 56 ( P = 0.0009 and P = 0.0002 , respectively ) . Performance and health improvements produced by the use of the feed additive were cost-effective Three trials were conducted to evaluate the use of tilmicosin phosphate ( Micotil ) as a prophylactic medication for newly received , stressed beef cattle . In Trial 1 , 57 beef calves ( average initial BW = 170 kg ) were shipped to the research feedlot from Tennessee and either given no antibiotic at processing or treated with Micotil at 10 mg of tilmicosin phosphate/kg of BW . During a 28-d receiving period , treatment at processing with Micotil did not affect daily gain ( P < .17 ) or DMI ( P < .22 ) compared to control calves . Prophylactic treatment with Micotil decreased ( P < .01 ) the percentage of calves treated for symptoms of bovine respiratory disease from 46.4 to 0 % . In Trial 2 , 117 calves ( average initial BW = 191 kg ) were shipped from Tennessee and allotted r and omly to the same two treatments as in Trial 1 . All calves grazed a 24-ha pasture of irrigated winter wheat during the 28-d receiving period . Treatment of calves with Micotil at the time of arrival processing did not affect ( P > .50 ) daily gain during the trial ; however , as in Trial 1 , mass treatment with Micotil decreased ( P < .01 ) the percentage of calves treated for respiratory disease from 32.8 % to 12.1 % . In Trial 3 , two truckloads of beef calves ( 183 total ; average initial BW = 232 kg ) shipped from Tennessee were allotted r and omly to the same two treatments used in Trials 1 and 2 or to a third treatment that consisted of administration of Micotil at arrival processing if the rectal temperature of the calf was > or = 39.7 degrees C. ( ABSTRACT TRUNCATED AT 250 WORDS The objectives of this study were to 1 ) quantify effects of metaphylactic treatment for bovine respiratory disease ( BRD ) on growth performance , 
    Output:
    
Antimicrobial prophylaxis and metaphylaxis demonstrated moderate , yet highly variable relative risk reductions in BRD morbidity .
These were dependent on the antimicrobial classes used , dependent on metaphylaxis definition , BRD attack rates and duration of the RCTs .
Best relative risk reductions were from broad‐spectrum critically important antimicrobials , or combinations .
BRD prophylaxis/metaphylaxis represents major antimicrobial consumption for highly variable short‐term gains in absolute risk reduction of morbidity/mortality .