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Research Abstracts in Antibiotics


General Management

Therapy & Preventative with Antibiotics

(Abstracts and links to articles are listed oldest to newest publication)
J Dairy Sci.1985 Aug;68(8):2033-7
Effect of Colostral Immunoglobulin G1 and Immunoglobulin M Concentrations on Immunoglobulin Absorption in Calves.

Besser TE, Garmedia AE, Mcguire TC, Gay CC

Twenty-three calves were fed colostrum at 110 ml/kg body weight divided into two feedings at 1 and 13 h of age. The concentrations of immunoglobulins were measured in the colostrum fed and in the calves’ sera following colostrum feeding. Apparent efficiency of immunoglobulin absorption was calculated for each calf. Significant negative correlations between efficiency of absorption and mass of immunoglobulin fed were observed for both immunoglobulins. A separate group of 225 calves born on a commercial dairy
were fed 2.84 L of colostrum by 4 h of age. Concentrations of immunoglobulin G 1 in the colostrum fed and in the calves’ sera at 48 h were measured. Negative correlation was observed between the efficiency of absorption and the mass of immunoglobulin G1 fed. These results suggest a physiologic limitation to the mass of immunoglobulin that can be absorbed to serum from a given volume of colostrum. No indication of a selective immunoglobulin absorption mechanism was observed.

Prev Vet Med. 2002 Feb 14;53(1-2):103-15.
Influence of arrival weight, season and calf supplier on survival in Holstein beef calves on a calf ranch in California, USA.
Moore DA, Sischo WM, Festa DM, Reynolds JP, Robert Atwill E, Holmberg CA.


On a yearly basis, large calf ranches rear thousands of neonatal cattle for replacement heifers, veal or dairy beef. Dairy beef ranches obtain bull-calves from multiple sources and with questionable colostrum intake histories. Such ranches accumulate large amounts of data that could be used to help them with calf purchasing and on-farm management practices to avoid losses. Our purpose was to describe some calf purchase factors associated with mortality in neonatal calves raised on a single large calf ranch. Computerized records describing 120,197 bull-calves purchased between January 1997 and November 1998 were used in a survival analysis. Risk factors for mortality within the first 4 weeks after arrival on the ranch included body weight on arrival, month of arrival, and the calf supplier. The strength of the effects was conditional on the week after arrival to the ranch.

Prev Vet Med. 2003 Oct 15;61(2):91-102.
Assessing antibiotic resistance in fecal Escherichia coli in young calves using cluster analysis techniques.
Berge AC, Atwill ER, Sischo WM.


This study uses cluster analysis techniques to describe the antibiotic susceptibility patterns seen in calf fecal Escherichia coli (E.coli). Cohorts of 30 dairy calves at six farms were sampled at 2-week intervals during the pre-weaning period. At each sampling occasion five fecal E. coli isolates per calf were analyzed for antibiotic susceptibility to 12 antibiotics using the disk diffusion method. All isolates had a profile consisting of the aggregate measured inhibition zone size for each of the evaluated antibiotics. Several cluster analytic algorithms were assessed to partition the E. coli isolates. For our data, Ward’s minimum variance method met the objectives of the study. Relative to the number of possible combinations of resistance clusters, a parsimonious set of 14 patterns was developed. This set of E. coli isolates exhibited a limited set of resistance patterns to the different antibiotics indicating that certain resistance genes may be linked.
(Supported by the Center of Disease Control)

J Am Vet Med Assoc. 2003 Nov 1; 223(9):1329-33.
Evaluation of flunixin meglumine as an adjunct treatment for diarrhea in dairy calves.
Barnett SC, Sischo WM, Moore DA, Reynolds JP.


OBJECTIVE: To assess the use of flunixin meglumine as an adjunct treatment for diarrhea in calves.

DESIGN: Clinical trial.

ANIMALS: 115 calves with diarrhea that were 1 to 21 days old at enrollment. PROCEDURE: Calves that developed diarrhea were randomly assigned to receive no flunixin meglumine (controls), a single dose of flunixin meglumine (2.2 mg/kg [1.0 mg/lb]), or 2 doses of flunixin meglumine administered 24 hours apart. Serum IgG concentration and PCV were measured prior to enrollment in the trial. Calves were evaluated daily to determine rectal temperature, fecal consistency, demeanor, and skin elasticity score. The primary analytic outcome was days of sickness (morbid-days). RESULTS: Calves with fecal blood and treated with a single dose of flunixin meglumine had fewer morbid-days and antimicrobial treatments, compared with controls. Although not significant, calves given 2 doses of flunixin meglumine in 24 hours had fewer morbid-days than untreated control calves. Regardless of severity of diarrhea, calves without fecal blood did not benefit from the use of flunixin. For calves with fecal blood, failure of passive transfer (low serum IgG concentration) was an independent risk factor for increased morbid-days. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with a single dose of flunixin meglumine resulted in fewer antimicrobial treatments and morbid-days in calves with fecal blood. As observed in other studies, calves with failure of passive transfer were at high risk for poor outcomes. This emphasizes the importance of developing and implementing effective colostrum delivery programs on dairy farms.

J Dairy Sci. 2005 Jun;88(6):2166-77.
A clinical trial evaluating prophylactic and therapeutic antibiotic use on health and performance of preweaned calves.
Berge AC, Lindeque P, Moore DA, Sischo WM.


The objective of this clinical trial was to evaluate the influence of prophylactic and therapeutic antibiotics on health and performance in preweaned dairy calves on a calf ranch. One hundred twenty 1-d-old calves were enrolled into 3 management systems for antibiotic use and raised until 4 wk of age. Sixty calves were not eligible to receive prophylactic or therapeutic antibiotics. Thirty calves were eligible to receive individual antibiotic treatment for disease, but no prophylactic antibiotics in milk replacer. The remaining 30 calves received milk replacer medicated with neomycin and tetracycline HCl, and could be treated with antibiotics. Health status and treatments were monitored and recorded daily. The primary study outcomes were weight gain, morbidity, and mortality. The most important factor associated with morbidity and mortality was passive immune transfer through colostrum. In-feed antibiotics delayed onset of morbidity, decreased overall morbidity, and increased weight gain. Nonantibiotic therapies for clinical disease were associated with increased mortality and morbidity compared with antibiotic treatments. The study has shown that minimizing or eliminating the use of antibiotics in the feed requires measures to ensure adequate passive transfer of immunity, but that in the face of inadequate passive transfer of immunity, animal welfare may be endangered by replacing medicated milk replacer with nonmedicated milk replacer, and therapeutic antibiotics with nonantibiotic alternatives.
(Supported by the California Dairy Research Foundation, Center for Food Animal Health-SVM University of California, and NIFSI-CSREES)

Prev Vet Med. 2005 Jun 10;69(1-2):25-38.
Animal and farm influences on the dynamics of antibiotic resistance in faecal Escherichia coli in young dairy calves.
Berge AC, Atwill ER, Sischo WM.


It is believed that the intensive use of antibiotics in the management of disease in pre-weaned calves contributes to high levels of antibiotic resistance in commensal and pathogenic bacteria. We described the temporal dynamics of antibiotic-susceptibility patterns seen in bovine enteric Escherichia coli in pre-weaned calves on dairy farms and dedicated calf-rearing facilities. Cohorts of 30 calves at each of six farms were sampled at 2-week intervals during the pre-weaning period. Faecal E. coli isolates were analyzed for antibiotic susceptibility to 12 antibiotics with the disk-diffusion method and grouped using cluster analysis of inhibition-zone patterns. The influences of calf age, farm-type, and individual-calf antibiotic therapy on the clustering’s were assessed using stratified analyses and cumulative multinomial logistic regression using generalized estimating equation with antibiotic-resistance cluster as an ordinal-dependent variable. The model controlled for farm and cohort by a nested design and included a repeated measure on calf at each sampling occasion. E. coli from calves 2 weeks of age were more likely to be increasingly multiply resistant than E. colifrom day-old calves (OR = 53.6), as were 4- and 6-week-old calves (OR = 29.8 and 16.4, respectively). E. coli from calves on dedicated calf-rearing facilities were more likely to be increasingly multiply resistant than E. coli from dairy-reared calves (OR = 2.4). E. coli from calves treated with antibiotics within 5 days prior to sampling were also more likely to be increasingly multiply resistant than E. coli from calves not exposed to individual antibiotic therapy (OR = 2.0).
(Supported by the Center of Disease Control )

Reprod Nutr Dev. 2005 Jul-Aug; 45(4):427-40.
Effect of feeding live yeast products to calves with failure of passive transfer on performance and patterns of antibiotic resistance in fecal Escherichia coli.
Galvao KN, Santos JE, Coscioni A, Villasenor M, Sischo WM, Berge AC.


Fifty-two newborn Holstein calves with serum IgG concentrations less than 0.73 g.dL(-1) were randomly assigned to one of four treatments: no added live yeast (control), 0.5 g of live yeast added to the grain for 84 d (SC; Saccharomyces cerevisiae), 0.5 g of live yeast added to the milk for 42 d (SB; S. cerevisiae, spp. boulardii), and 0.5 g of live yeast added to the grain for 84 d and to the milk for 42 d (SCSB). Calves were offered 440 g of milk replacer DM for the first 42 d and grain for ad libitum intake throughout the study. Plasma was analyzed weekly for concentrations of glucose and beta-hydroxybutyrate. Escherichia coli isolated from fecal samples collected every 2 weeks were used for determination of antibiotic resistance patterns. Calves receiving SC consumed more grain DM, had increased weight gain prior to weaning, and increased plasma glucose concentrations compared to controls. Days with diarrhea were reduced by feeding live yeast to calves. Antibiotic resistance in fecal E. coli was associated with the age of calves with highest levels of resistance observed in the 3 d calves. While calves receiving SCSB had higher levels of antibiotic resistance than controls, this effect was not associated with any of the other treatments. Improvements in performance of calves with failure of passive transfer were observed when live yeast was added only to the grain.
(Supported by Lallemand Animal Nutrition)

Prev Vet Med. 2006 Feb 24;73(2-3):203-208

Stakeholder position paper: Dairy producer.

Sischo WM.

Bacterial antimicrobial resistance is a problem common to both animal and public health. An important public policy issue is to develop and implement prudent use practices where antimicrobials are used. As policy develops, there are questions regarding the use of antimicrobials in animal agriculture and whether these uses constitute prudent use. A series of papers assessing the risk to the public health from agricultural use of antimicrobials have consistently concluded that risk estimation is hampered by the lack of data that describe the amount, types, and uses of antimicrobials in animal agriculture. The absence of information has spurred efforts to develop a framework to collect these data. However, the reasons and benefit of collecting these data should be carefully defined. The dairy industry, contrasted to other major animal commodities, is not focused on meat production but on milk production. Milk production is constrained by disease and antimicrobial treatment is a common management tool, but unlike many other animal agricultural systems where the value and safety of the product is measured in the future; the value of milk is zero when an antimicrobial is used in a lactating cow and milk must be discarded because of residues. While there are exceptions, e.g. non-lactating cow therapy, this difference results in antimicrobials being used sporadically and directed at therapy rather than prophylactic uses. In the dairy industry, antimicrobial use data and its consequences may exist in sufficient detail or could be estimated from existing data sets without the expense of additional surveys. Finally, the main food product milk is mainly pasteurized and all shipments of milk from the farm to the processing plant are tested for the presence of antimicrobials. This makes the likelihood of farm-origin antimicrobials or bacteria appearing in finished product very low. This suggests that the use and quantity of antimicrobials in the dairy system has little impact on public health. This does not imply that the dairy industry does not have a significant role in developing guidelines for appropriate and careful application of antimicrobials, but the effort and cost to collect additional data should be used to fund efforts that improve our diagnostic and managerial skills. These data would change the use of antimicrobials by decreasing the rates of disease and ultimately decreasing prophylactic, metaphylactic and therapeutic use of antimicrobial. These studies and outcome are as important to the dairy industry as to public health.

Appl Environ Microbiol. 2006 Jun; 72(6):3872-8.
Field trial evaluating the influence of prophylactic and therapeutic antimicrobial administration on antimicrobial resistance of fecal Escherichia coli in dairy calves.
Berge AC, Moore DA, Sischo WM.


The objective of this study was to describe the influence of in-feed and therapeutic antimicrobials on resistance in commensal fecal Escherichia coli isolated from preweaned calves. Four groups of 30, day-old calf-ranch calves were enrolled and raised until 4 weeks of age. Groups 1 to 3 were raised without antimicrobials in the feed. Group 1 was isolated from the other groups and received no antimicrobial therapy. Group 2 was housed on the calf ranch and did not receive antimicrobial therapy, whereas groups 3 and 4 could be treated with antimicrobials. Group 4 was fed neomycin and tetracycline HCl in the milk replacer. Fecal samples were collected from calves on days 1, 14, and 28. Three E. coli isolates per sample were evaluated for susceptibility to 12 antimicrobials. Cluster analysis was used to group isolates having similar susceptibility patterns. Cumulative logistic regression was used to evaluate factors associated with increasing levels of multiple antimicrobial resistance. In-feed antimicrobials were associated with higher levels of multiple antimicrobial resistance in fecal E. coli.  In calves not receiving in-feed antimicrobials, older calves had higher levels of resistance compared to day-old calves. Individual antimicrobial therapy increased resistance in these calves but appeared to be transient. There was no environmental influence on resistance in E. coli populations among study groups.
(Supported by the California Dairy Research Foundation, Center for Food Animal Health-SVM University of California, and NIFSI-CSREES)

Am J Vet Res. 2006 Sep; 67(9):1580-8.
Prevalence and antimicrobial resistance patterns of Salmonella enterica in preweaned calves from dairies and calf ranches.
Berge AC, Moore DA, Sischo WM.


OBJECTIVE: To evaluate serovar and antimicrobial resistance patterns of Salmonella enterica isolated from preweaned calves and identify management risk factors associated with fecal shedding of S enterica.

SAMPLE POPULATION: Cohorts of 10 to 15 preweaned calves (1 to 84 days of age) on 26 dairies and 7 calf ranches and cross-sectional samples of preweaned calves on smaller farms.

PROCEDURES: Calves were evaluated every 2 weeks during a 6-week period.  Salmonella isolates obtained from rectal fecal swabs underwent antimicrobial susceptibility testing against 12 antimicrobials. Cluster analysis enabled description of antimicrobial susceptibility patterns. Calf, cohort, and farm risk factors associated with both the prevalence of S enterica and multiple-antimicrobial-resistant S enterica in preweaned calves were identified with repeated-measure logistic regression models. RESULTS: Salmonella enterica was detected on > 50% of farms and in 7.5% of 3,686 fecal samples. Many isolates (33%) were resistant to multiple antimicrobials. Shedding of Salmonella spp was negatively associated with increasing calf age, herds being closed to incoming cattle, and antimicrobial supplementation of milk replacer; prophylactic antimicrobial treatment in day-old calves increased shedding. No association between farm management and presence of multiple-antimicrobial-resistant S enterica or between calving management and presence of S enterica in calves < or = 1 week old was detected.

CONCLUSIONS AND CLINICAL RELEVANCE: In preweaned calves, the most important factors associated with decreased likelihood of fecal shedding of S enterica were the use of antimicrobial-supplemented milk replacer and maintenance of a closed herd. Infection with multiple-antimicrobial-resistant S enterica was not associated with antimicrobial administration.
(Supported by National Integrated Food Safety Initiative-Cooperative State Research, Education, and Extension Service)

J Vet Diagn Invest. 2008 Jul;20(4): 497-500.
Antimicrobial resistance in Salmonella enterica subspecies enterica serovar Dublin from dairy source calves in the central San Joaquin Valley, California during the years 1998-2002.
Anna Catharina B. Berge,1 Elizabeth Thornburg, John M. Adaska, Robert B. Moeller, Patricia C. Blanchard

Abstract. This study describes antimicrobial resistance patterns of Salmonella enterica subspecies enterica serovar Dublin (S.Dublin) in clinical submissions from calves and temporal and farm-type trends in antimicrobial resistance patterns of the isolates. A total of 300 isolates of S. Dublin were obtained from fecal or internal organs of from calves less than 120 days of age originating from 84 dairies and 18 calf-ranches from July 1998 to December 2002. The isolates were susceptibility tested to a panel of 10 antimicrobials using the disk diffusion assay. Temporal and farm-type trends in individual antimicrobial inhibition zone sizes were assessed and antimicrobial resistance patterns were described using cluster analysis. Isolates obtained from calf ranches compared to dairies exhibited decreased susceptibility to ampicillin, florfenicol, gentamicin, neomycin, sulfisoxazole, sulfamethoxazole/trimethoprim, and tetracycline. During the years 1998 to 2002 decreasing susceptibility was seen for ceftiofur, enrofloxacin, florfenicol, sulfisoxazole, sulfamethoxazole/trimethoprim, and tetracycline. There were 22 different antimicrobial resistance patterns in the isolate set, indicating that S. Dublin has the ability to transfer and pick up resistance genes with relative ease. The trends seen in antimicrobial resistance in S. Dublin may likely be linked to antimicrobial drug use in young calves.

J. Dairy Sci. 2009 Sep. 92(9):4707-4714

Targeting therapy to minimize antimicrobial use in preweaned calves: Effects on health, growth, and treatment costs.

A. C. B. Berge*, D. A. Moore, T. E. Besser, W. M. Sischo

* Berge Veterinary Consulting, Helsingborg, Sweden
College of Veterinary Medicine, Washington State University, Pullman 99164

Prophylactic and therapeutic antimicrobial use in food animals is questioned because of the potential for development of resistant bacteria and future inability to use some antimicrobials for human or animal disease. The objectives of this study were to determine the effect of raising preweaned dairy calves without antimicrobials in the milk and minimizing therapeutic antimicrobial treatment on morbidity, mortality, weight gain, and treatment costs. Newborn calves (n = 358) were allocated to 1 of 4 groups, housed outdoors in individual hutches, and monitored for 28 d. Calves in the conventional therapy (CT) group were treated as per dairy protocol with sulfamethoxazole/trimethoprim, spectinomycin, penicillin, and bismuth-pectin for diarrhea. The targeted therapy (TT) group included bismuth-pectin for diarrhea and antimicrobial treatment only in cases of fever or depressed attitude. Within CT and TT groups, calves were equally assigned to receive neomycin and tetracycline in their milk for the first 2 wk of life (AB-milk) or no antimicrobials (NoAB-milk). Daily health evaluations included fecal consistency, respiratory disease, attitude, and hydration status as well as milk and grain consumption. A negative binomial model evaluated the total number of days with diarrhea days in each group. General linear models were used to assess average daily weight gain and grain consumption. Conventionally treated calves had 70% more days with diarrhea than TT calves, and AB-milk calves had 31% more days with diarrhea compared with NoAB-milk calves. The TT calves tended to have a higher average daily gain by 28 d and consumed more grain compared with CT calves. If antimicrobials were used only for diarrhea cases with fever, inappetence, or depression and no in-milk antimicrobials were used, a $10 per calf savings could be realized. Targeting antimicrobial therapy of calf diarrhea cases is prudent not only to save the drugs for future use but also to prevent the potential for antibiotic-associated diarrhea and reduce calf-rearing costs.

J.Dairy Sci, 2009 Jan;92(1):286-95.
Evaluation of the effects of oral colostrum supplementation during the first fourteen days on the health and performance of preweaned calves.
Berge AC, Besser TE, Moore DA, Sischo WM.

College of Veterinary Medicine, Washington State University, Pullman 99164, USA.

Increasing concerns about antimicrobial resistance have led to the development and implementation of alternatives to antimicrobial use in animal production. The objective of this clinical trial was to determine the effect of colostrum supplementation of the milk replacer ration on morbidity, mortality, feed intake, and weight gain of preweaned calves. Ninety 1-d-old calves on each of 3 commercial calf ranches were randomly allocated to 1 of 3 groups. Treatment-group calves received 10 g of supplemental immunoglobulin G (IgG) in the form of 70 g of colostrum powder in the milk replacer twice daily for 14 d. The placebo-group calves received a nutritionally equivalent supplement lacking IgG in the milk replacer twice daily for 14 d. Control calves received milk replacer without supplements twice daily. Calves were housed in individual hutches and were weighed on d 1, 28, and 60. Serum was collected on d 2 for serum IgG determination. Daily health evaluations for the first 28 d of life were performed by study personnel blinded to treatment group assignment. Observed illness was treated based on health assessment, rectal temperature, and specific calf ranch protocols. Feed consumption (milk and grain) was recorded. Calves receiving supplemental colostrum had less diarrhea and received fewer antimicrobial treatments than control and placebo calves. The results indicated that calf diarrhea was associated with low serum IgG levels and low-weight calves. Grain consumption and weight gain over the first 28 d of life were significantly greater in colostrum-supplemented calves compared with control calves. No differences in mortality or respiratory disease incidence among groups were detected. Supplemental colostrum during the first 2 wk of life can reduce diarrheal disease in preweaned calves on calf ranches and thereby reduce the amount of antimicrobial treatments needed.