This study examined the sensitivity, specificity, predictive values, and classification accuracy of 3 commonly used screening tests for failure of passive transfer: the sodium sulfite turbidity test, the zinc sulfate turbidity test, and refractometry relative t o serum immunoglobulin G1 (IgG,) concentrations determined by radial immunodiffusion. Serum samples were obtained from 242 calves ranging from 1 t o 8 days of age. Using a serum concentration of 1,000 mg/dL IgG, t o define adequate passive transfer, the zinc sulfate test had a sensitivity of 1.00 and a specificity of 0.52 in the detection of inadequate passive transfer. The endpoint of the test appeared t o be higher than desired; calves testing negative had mean serum lgG, concentration of 955 mg/ dL and a large proportion of calves with adequate passive transfer were misclassified as positive for failure of passive transfer. Using the qualitative zinc sulfate test, the percentage of calves correctly classified with regard t o passive transfer status was less than that observed with either the sodium sulfite test or refractornetry. The sensitivity of the sodium sulfite assay was 0.85 at a 1 + endpoint and 1.00 at alves are born without appreciable serum concentra-C tions of immunoglobulin (Ig). Ig requirements are satisfied by ingesting and absorbing colostral 1gs.l.' Adequate passive transfer of Igs is a critical determinant of calf health and s~r v i v a l .~~' Several assays have been used to measure serum Ig concentrations in neonatal livestock. These include refractometer determination of total serum protein concentration, zinc sulfate and sodium sulfite turbidimetry, immunoassays, and the glutaraldehyde clot test.'.*-'' Assay procedures should be adapted to a practice setting. Immediacy of results permits practitioners to provide feedback to calfrearing personnel and make clinical decisions regarding the necessity of targeted intervention in individual calves with failure of passive transfer (FPT).Immunoassay procedures detecting bovine IgG have not been successfully adapted to a practice setting. Additionally, the time constraints of sample collection, sample submission, and assays procedures often relegate the results of immunoassays to historical interest. Labor and expense also have limited the widespread on-farm application of immunoassay procedures. The recently developed and marketed whole blood glutaraldehyde coagulation test attempted to address these timing and economic constraints; however, the sensitivity and specificity of the assay proved inadequate for routine diagnostic use." The primary goal of this study was to compare the sensitivity, specificity, and predictive values of 3 commonly used screening tests for the detection of FPT in calves. These test procedures included refractometry, the qualitative zinc sulfate turbidity test, and the semiquantitative sodium sulfite turbidity test. All 3 assays are readily adapted to a farm or practice setting. Assay results were compared with serum IgG I concentrations determined by radial immu...
This study examined the relationship between serum gamma-glutamyl-transferase (GGT) activity and passive transfer status in beef calves less than 18 days of age. Immunoglobulin G1 (IgG1) concentrations were measured in 69 commercial beef calves between the ages of 24 and 72 hours. GGT activities were then measured in these same calves at various ages between 3 and 18 days of age. Models were developed predicting serum IgG1 concentration as a function of calf age and serum GGT activity. Minimal association was present between initial serum IgG1 concentration and serum GGT activity when all calves less than 18 days of age were considered (r2 = 0.065). When the study population was restricted to calves less than 8 days of age, the fit of the developed model was greatly improved (r2 = 0.438). Serum GGT activity has no apparent advantage relative to other assay procedures for predicting passive transfer status in beef calves. If serum GGT activity is to be used to assess passive transfer status in beef calves, application of this procedure should be restricted to calves less than 8 days of age.
The accuracy of a commercially available whole blood glutaraldehyde clot test in the detection of failure of passive transfer (serum immunoglobulin [IglG, <1,000 mg/dL) in neonatal calves was evaluated. Serum samples were obtained from 242 calves ranging in age from 1 to 8 days, and comparisons were made with serum lgG, concentrations determined by radial immunodiffusion. Both the sensitivity and specificity of the currently marketed whole blood glutaraldehyde clot test are inadequate for routine diagnostic use. Concerns alves are born with negligible concentrations of immu-C noglobulin (Ig). Ig requirements are met by ingesting and absorbing the colostral 1gs.l.' This process, termed passive transfer, is not the result of an active immune response by the neonate. In this regard, passive transfer of Ig is a critical determinant of calf health.' Although colostra vary with regard to their Ig concentration, the timing and volume of colostrum intake also are critical in assuring adequate passive transfer of Ig; colostral Ig absorption is best at birth and declines within hours. ' Routine monitoring of passive transfer in calves can be used to assess management and husbandry practices. Test results can be used to critique calf rearing practices and develop intervention strategies to optimize calf health and farm productivity. In calves of exceptional value or genetic merit, quantification of serum Ig concentration permits identification of calves which require Ig supplementation. Tests of this type also are useful in a clinical setting because they assist with the diagnosis and prognosis of individual sick neonates.A variety of assay procedures have been developed to measure serum Ig concentrations in neonatal livestock. These include refractometer determination of total serum protein concentration, zinc sulfate and sodium sulfite turbidity assays, immunoassays, and the glutaraldehyde gelation assay.',' Any assay procedure used should be readily adapted to on-farm application. Immediacy of results permits feedback to calf rearing personnel, and creates incentives for optimal management practices. Additionally, rapidly available test results may permit targeted treatment of individual calves. Consequently, test procedures should provide rapid and reliable results, require minimal instrumentation, and be inexpensive.A whole blood glutaraldehyde gelation assay which apparently addresses many of these concerns has recently been marketed. In this assay, whole blood is added to a reagent tube containing glutaraldehyde and the time required for clot formation is measured. Gelation times less than 5 minutes are considered indicative of adequate passive transfer. Because the test is performed on whole blood rather than serum, this test has advantages relative to turbidity tests and refractometry, which require instrumentation (eg, centrifuge, temperature-compensated refractometer), and sample processing before a test can be performed.Use of glutaraldehyde gelation of Ig as an assay for serum Ig concentration is hardly a no...
This study examined the relationship between serum gamma-glutamyl-transferase (GGT) activity and passive transfer status in beef calves less than 18 days of age. Immunoglobulin G1 (IgG1) concentrations were measured in 69 commercial beef calves between the ages of 24 and 72 hours. GGT activities were then measured in these same calves at various ages between 3 and 18 days of age. Models were developed predicting serum IgG1 concentration as a function of calf age and serum GGT activity. Minimal association was present between initial serum IgG1 concentration and serum GGT activity when all calves less than 18 days of age were considered (r2 = 0.065). When the study population was restricted to calves less than 8 days of age, the fit of the developed model was greatly improved (r2 = 0.438). Serum GGT activity has no apparent advantage relative to other assay procedures for predicting passive transfer status in beef calves. If serum GGT activity is to be used to assess passive transfer status in beef calves, application of this procedure should be restricted to calves less than 8 days of age.
The effect of vaccination with a commercially available R-mutant coliform mastitis vaccine on the survival of comingled dairy calves on a farm with endemic salmonellosis was examined. A total of 864 calves were randomly assigned to either vaccine (n = 435) or control (n = 429) groups. Passive transfer status of each calf was determined using refractometer determination of serum total protein concentration. Logistic models were developed to determine the effects of vaccine group and passive transfer status on calf survival to 100 days of age. In a model in which serum protein concentration was treated as a categorical variable, increasing serum total protein concentrations were associated with decreased mortality until these concentrations exceeded 6.0 g/dL. Calves with serum protein concentrations > 6.0 g/dL had increased risk for mortality compared with calves with serum protein concentrations > 5.5 g/dL but < or = 6.0 g/dL. This increased risk for mortality was supported by the results of a logistic model in which serum protein concentration was treated as a continuous variable. The increased risks associated with high serum protein concentration probably reflect the effect of dehydration in calves with occult disease. Neither model demonstrated any significant association between vaccination status and survival to 100 days of age. Based on these results, the routine immunization of calves cannot be recommended as a strategy to prevent mortality on farms with endemic salmonellosis.
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