Procedures—Via IM injection, each calf received a fresh whole-blood inoculum (day 0) calculated to contain 2 × 106 lymphocytes. Blood samples for the ELISA and PCR assay were collected from calves immediately prior to inoculation and weekly thereafter for 7 weeks. Mean and median number of weeks to PCR-detected conversion of BLV status and seroconversion were calculated. Point sensitivity and cumulative sensitivity of the 2 assays were calculated at each sample collection. At each sampling time, the proportion of calves identified as infected by the cumulative weekly ELISA and PCR assay results was compared by use of a Fisher exact test.
Results—In 5 calves, conversion of BLV status was detected via PCR assay before seroconversion was identified. However, seroconversion preceded PCR-detected conversion in 2 calves. In 1 calf, both assays yielded positive results at the same test date. These differences were not significant.
Conclusions and Clinical Relevance—In experimentally inoculated BLV-negative calves, conversion of BLV status was detected via PCR assay more quickly than via ELISA; this difference was not significant and probably not clinically important. The PCR assay may be useful as a confirmatory test in animals of exceptional value; tests based on viral identification may become critically important if vaccines against BLV infection are developed and marketed.
Objective—To determine serum lactoferrin concentrations
(SLFC) in neonatal calves before and after
ingestion of colostrum and to develop models that
predict SLFC as a function of colostral lactoferrin concentrations
(CLFC) in calves.
Animals—13 Holstein calves.
Procedure—Calves were fed 4 L of colostrum via
oroesophageal feeder within 3 hours after birth.
Serum samples were collected before ingestion of
colostrum (day 0) and 2, 4, 6, and 7 days after birth.
Colostrum and serum IgG concentrations were measured
by use of radial immunodiffusion. The CLFC and
SLFC were determined by use of an ELISA.
Results—Mean ± SD SLFC on days 0, 2, 4, 6, and 7
were 2.5 ± 1.6 (range 0.47 to 7.1), 6.0 ± 3.0 (range 2.0 to
16.6), 12.0 ± 12.4 (range 0.0 to 43.5), 17.1 ± 13.6 (range
2.2 to 39.4), and 13.6 ± 16.4 (range 0.0 to 43.8) mg/ml,
respectively. The SLFC on days 6 and 7 differed significantly
from SLFC on day 0. The model that best estimated
SLFC on day 6 predicted that (SLFC)2 was a function
of the logarithm of relative efficiency of passive
transfer (REPT) and ([CLFC]2 × [REPT]2), where R2 = 0.4.
The model for SLFC on day 7 predicted that (SLFC)2 was
a function of log(REPT), where R2 = 0.44.
Conclusions and Clinical Relevance—Definitive evidence
for passive transfer of lactoferrin via colostrum
is lacking, because SLFC on day 2 or 4 were not significantly
different than day 0. Relative efficiency of
lactoferrin absorption was directly related to SLFC on
day 6 but inversely related to SLFC on day 7.
(Am J Vet Res 2002;63:476–478)
Veterinary medicine has a unique role in modern society with regard to the production of a safe, wholesome, and economical food supply; protection from zoonotic diseases of livestock origin; and participation in the arena of biodefense. These roles are often collectively referred to as food supply veterinary medicine (FSVM).1–3 Employment opportunities in FSVM include those in the private and public sectors, such as the traditional curative care of livestock; production medicine consulting services; pharmaceutical and biologics firms; and positions related to food safety, biosecurity, process assurance, and biodefense. Several authors4–8 have asserted that the US veterinary
A series of surveys1–3 supported by the Food Supply Veterinary Medicine Coalition has highlighted issues related to the supply and demand for food animal veterinarians in the United States. Food supply veterinary medicine (FSVM) embraces traditional preventive care and treatment of livestock; production medicine consulting services; pharmaceutical and biologics industry employment; and employment related to food safety, biosecurity, process assurance, and biodefense. In contrast to results for the KPMG LLP study4 (often referred to as the Megastudy), several recent reports5–11 have asserted that the training and supply of food supply veterinarians does not meet
Objective—To evaluate the use of a polymerase
chain reaction (PCR) assay in detecting bovine leukosis
virus (BLV) in adult dairy cows.
Animals—223 adult dairy cows.
Procedure—Cows were tested for BLV status by use
of an ELISA and a PCR assay. Sensitivity, specificity,
predictive values of positive and negative tests, and
the percentage of cows correctly classified by PCR
assay were calculated. Ninety-five percent confidence
intervals were calculated for sensitivity and
Results—Sensitivity and specificity were 0.672 and
1.00, respectively. Prevalence of BLV in this herd was
0.807. Predictive value of a positive test was 1.00,
and predictive value of a negative test was 0.421. The
percentage of cows correctly classified by PCR assay
Conclusions and Clinical Relevance—A positive
PCR assay result provided definitive evidence that a
cow was infected with BLV. Sensitivity and negative
predictive value for PCR assay were low.
Consequently, PCR assay alone is unreliable for routine
detection of BLV in herds with high prevalence of
the disease. (J Am Vet Med Assoc 2003;222:983–985)
Objective—To determine the prevalence of detectable serum IgG concentrations in calves prior to ingestion of colostrum and to assess whether a detectable IgG concentration was related to dam parity, calf birth weight, calf sex, season of calving, or infectious agents that can be transmitted transplacentally.
Animals—170 Holstein dairy calves.
Procedures—Serum samples were obtained from calves prior to ingestion of colostrum, and serologic testing for bovine viral diarrhea virus (BVDV) and Neospora caninum was performed. Relative risk, attributable risk, population attributable risk, and population attributable fraction for calves with a detectable serum IgG concentration attributable to positive results for N caninum and BVDV serologic testing were calculated. Logistic regression analysis was used to determine whether dam parity, calf sex, season of calving, and calf weight were associated with precolostral IgG concentration.
Results—90 (52.9%) calves had a detectable total serum IgG concentration (IgG ≥ 16 mg/dL). Relative risk, attributable risk, population attributable risk, and population attributable fraction for calves with a detectable serum IgG concentration attributable to positive results for N caninum serologic testing were 1.66, 0.34, 0.014, and 0.03, respectively. Calf sex, calf birth weight, and season of calving were not significant predictors for detection of serum IgG in precolostral samples.
Conclusions and Clinical Relevance—Prevalence of IgG concentrations in precolostral serum samples was higher than reported elsewhere. There was no apparent link between serum antibodies against common infectious agents that can be transmitted transplacentally and detection of measurable serum IgG concentrations.
Objective—To characterize gelatinases in bronchoalveolar
lavage fluid (BALF) and gelatinases produced
by alveolar macrophages of healthy calves.
Sample Population—Samples of BALF and alveolar
macrophages obtained from 20 healthy 2-month-old
Procedure—BALF was examined by use of gelatin
zymography and immunoblotting to detect gelatinases
and tissue inhibitor of metalloproteinase (TIMP)-1
and -2. Cultured alveolar macrophages were stimulated
with lipopolysaccharide (LPS), and conditioned
medium was subjected to zymography. Alveolar
macrophage RNA was used for reverse transcriptasepolymerase
chain reaction assay of matrix metalloproteinases
(MMPs), cyclooxygenase-2, and inducible
nitric oxide synthase.
Results—Gelatinolytic activity in BALF was evident at
92 kd (14/20 calves; latent MMP-9) and 72 kd (18/20;
latent MMP-2). Gelatinolytic activity was evident at 82
kd (10/20 calves; active MMP-9) and 62 kd (17/20;
active MMP-2). Gelatinases were inhibited by metal
chelators but not serine protease inhibitors.
Immunoblotting of BALF protein and conditioned
medium confirmed the MMP-2 and -9 proteins.
Endogenous inhibitors (ie, TIMPs) were detected in
BALF from all calves (TIMP-1) or BALF from only 4
calves (TIMP-2). Cultured alveolar macrophages
expressed detectable amounts of MMP-9 mRNA but
not MMP-2 mRNA.
Conclusions and Clinical Relevance—Healthy
calves have detectable amounts of the gelatinases
MMP-2 and -9 in BALF. Endogenous inhibitors of
MMPs were detected in BALF (ie, TIMP-1, all calves;
TIMP-2, 4 calves). Lipopolysaccharide-stimulated alveolar
macrophages express MMP-9 but not MMP-2
mRNA. The role of proteases in the pathogenesis of
lung injury associated with pneumonia has yet to be
determined. (Am J Vet Res 2004;65:163–172)
Objective—To evaluate 3 refractometers for detection
of failure of passive transfer (FPT) of immunity in calves,
and assess the effect of refractometric test endpoints
on sensitivity, specificity, and proportion of calves classified
correctly with regard to passive transfer status.
Procedure—Blood samples were obtained from calves
that were < 10 days old. Serum IgG concentration was
determined by use of a radial immunodiffusion assay.
Accuracy of 3 refractometers in the prediction of serum
IgG concentration was determined by use of standard
epidemiologic methods and a linear regression model.
Results—At a serum protein concentration test endpoint
of 5.2 g/dL, sensitivity of each refractometer
was 0.89 or 0.93, and specificity ranged from 0.80 to
0.91. For all refractometers, serum protein concentration
test endpoints of 5.0 or 5.2 g/dL resulted in sensitivity
> 0.80, specificity > 0.80, and proportion of
calves classified correctly > 0.85. Serum protein concentrations
equivalent to 1,000 mg of IgG/dL of serum
were 4.9, 4.8, and 5.1 g/dL for the 3 refractometers.
Conclusions and Clinical Relevance—The refractometers,
including a nontemperature-compensating
instrument, performed similarly in detection of FPT.
Serum protein concentration test endpoints of 5.0
and 5.2 g/dL yielded accurate results in the assessment
of adequacy of passive transfer; lower or higher
test endpoints misclassified larger numbers of
calves. (J Am Vet Med Assoc 2002;221:1605–1608)
Objective—To determine whether serum IgG concentrations
in neonatal calves are adversely affected
by short-term frozen storage of colostrum.
Sample Population—Experiment 1 consisted of 10
pairs of Holstein calves (n = 20) fed matched aliquots
of either fresh (n = 10) or frozen and thawed (10)
colostrum. In experiment 2, 26 Holstein calves were
fed either fresh (n = 13) or frozen and thawed (n = 13)
Procedure—Experiment 1 consisted of calves resulting
from observed parturitions; calves were randomly
assigned to treatment groups (fresh or frozen and
thawed colostrum) in pairs. Calves were fed 4 L
aliquots of colostrum via oroesophageal intubation at
3 hours of age. Serum IgG concentrations at 2 days of
age were compared between the 2 groups by use of
a paired t-test. Experiment 2 consisted of calves
resulting from observed parturitions; calves were randomly
assigned to treatment groups (fresh or frozen
and thawed colostrum). Calves were fed 4 L aliquots
of colostrum via oroesophageal intubation at 3 hours
of age. Regression analysis was used to determine
whether calf serum IgG concentration was a function
of colostral IgG concentration and colostrum storage
Results—Significant differences were not observed
between the 2 groups in experiment 1. No significant
relationship was observed between colostrum storage
group and serum IgG concentration in experiment
2. The model that best predicted serum IgG concentrations
accounted for 20% of the variability in
serum IgG concentration.
Conclusion and Clinical Relevance—Frozen
colostrum is an adequate source of IgG for calves. (J
Am Vet Med Assoc 2001;219:357–359)
Objective—To evaluate diagnostic utility of a commercially
available immunoassay for assessing adequacy
of passive transfer of immunity in neonatal
Procedure—Blood and serum samples were obtained
from the calves prior to 2 weeks of age. The immunoassay
was performed, along with refractometry and an
18% sodium sulfite turbidity test. Serum IgG concentration
was determined with a radial immunodiffusion
assay. Sensitivity and specificity of the immunoassay,
refractometry, and the sodium sulfite test were calculated
by comparing results with results of the radial
Results—Sensitivity and specificity of the blood IgG
immunoassay were 0.93 and 0.88, respectively, compared
with 1.00 and 0.53 for the sodium sulfite test.
For refractometry, sensitivity and specificity were 0.71
and 0.83, respectively, when a serum total solids concentration
of 5.2 g/dl was used as the cutoff between
positive and negative test results.
Conclusions and Clinical Relevance—Results suggest
that the immunoassayperforms well in detecting
calves with inadequate passive transfer of immunity.
(J Am Vet Med Assoc 2002;220:791–793)