Objective—To determine the total number of
Cryptosporidium parvum oocysts and Giardia spp
cysts shed by dairy calves during the period when
they are most at risk after natural infection.
Animals—478 calves naturally infected with C parvum
and 1,016 calves naturally infected with Giardia spp.
Procedure—Oocysts or cysts were enumerated from
fecal specimens. Distribution of number of oocysts or
cysts versus age was used to determine the best fitting
mathematic function. Number of oocysts or cysts
per gram of feces for a given duration of shedding
was computed by determining the area under the
curve. Total number of oocysts or cysts was calculated
by taking the product of the resultant and the
expected mass of feces.
Results—Intensity of C parvum oocyst shedding was
best described by a second-order polynomial function.
Shedding increased from 4 days of age, peaked
at day 12, and then decreased. An infected 6-day-old
calf would produce 3.89 X 1010 oocysts until 12 days
old. Pattern of shedding of Giardia spp cysts was best
described by exponential functions. Intensity of shedding
increased from 4 days of age, peaked at day 14,
and then decreased. An infected calf would produce
3.8 X 107 cysts from day 50 until day 56.
Conclusion and Clinical Relevance—The large
number of oocysts and cysts shed indicates that
shedding by dairy cattle poses a risk for susceptible
calves and people. Estimates reported here may be
useful to aid in designing cost-effective strategies to
manage this risk. (Am J Vet Res 2001;62:1612–1615)
Objective—To determine the apparent prevalence of shedding of Cryptosporidium spp in healthy alpaca crias and their dams on 14 farms in New York and 1 farm in Pennsylvania.
Animals—110 alpaca crias and their 110 dams.
Procedures—Fecal samples were obtained from 220 alpacas at 14 alpaca farms in New York and 1 farm in Pennsylvania. For each animal, age, sex, and health condition were recorded. A fecal score (1 = normally formed; 2 = soft or loose; 3 = diarrhetic) was recorded for each cria. Cryptosporidium oocysts were identified in fecal samples by a direct immunofluorescence assay.
Results—Apparent prevalence of fecal shedding of Cryptosporidium oocysts was 8% (95% confidence interval, 4% to 15%) in dams and was 7% (95% confidence interval, 3% to 13%) in crias. There was no significant difference in age between dams with positive fecal test results for Cryptosporidium oocysts (median age, 4 years; range, 3 to 8 years) and dams with negative results (median age, 4 years; range, 2.5 to 19 years). No significant difference was found in age between crias with positive fecal test results (median age, 20 days; range, 7 to 53 days) and those with negative results (median, 36 days; range, 2 to 111 days). No significant difference in fecal scores was found between crias with positive versus negative fecal test results.
Conclusions and Clinical Relevance—A higher than previously reported apparent prevalence of fecal shedding of Cryptosporidium oocysts in healthy alpacas was found. A zoonotic risk should be considered, especially for Cryptosporidium parvum.
Objective—To evaluate clinical variables assessed during the first 24 hours of hospitalization as prognostic indicators for nonambulatory cattle treated by use of a flotation tank.
Design—Retrospective case series.
Animals—51 nonambulatory cattle that underwent flotation treatment.
Procedures—Signalment, history, serum biochemical analyses, patient behavior during flotation, and outcome data were collected from medical records. Outcome was survival to discharge from the hospital or nonsurvival (death or euthanasia). Data were analyzed by use of Wilcoxon rank sum, Fisher exact, and χ2 tests.
Results—19 of 51 cattle survived. Survivors and nonsurvivors did not differ significantly with regard to median weight; age; stage of lactation; duration of recumbency prior to flotation; serum potassium, ionized calcium, or phosphate concentrations at admission to the hospital; or serum creatine kinase activity (value at admission to the hospital, highest value, and last recorded value). Cattle that were able to walk out of the tank after the first flotation treatment were 4.8 times as likely to survive as those that could not. Cattle that did not eat during flotation treatment were 1.9 times as likely to die as those that ate. Cattle that stood apparently normally on all limbs during the first flotation treatment were 2.9 times as likely to survive as those that had an asymmetric stance or were unable to stand.
Conclusions and Clinical Relevance—Results indicated that objective variables evaluated during the first 24 hours of hospitalization and flotation treatment are associated with outcome among nonambulatory cattle; findings might assist in logical decision making with respect to treatment options.
Dairy production provides high-quality, healthful nutrients to people on a planet soon to be inhabited by over 9 billion people. In doing so, it is ever more important to continuously improve the care of dairy animals, safeguard the environment we all share, and reliably produce nutritious food while maintaining the economic viability of the people working in dairy agriculture. In this paper, we review some associations between dairy consumption and human health along with the many interconnections between people, dairy animals, plants, and our shared environment. Understanding these relationships is an example of one health at work. In the US, total dairy consumption is at its highest point in the last 50 years, while many objective measures of cow health (eg, subclinical mastitis) have never been better since they have been recorded. Further, indications of food safety such as violative antibiotic residues in milk have never been lower. Dairy foods provide essential nutrients such as protein, vitamin B12, and calcium, while there is also evidence that they are protective against chronic conditions such as cardiovascular disease. Finally, the environmental footprint of dairy production in the US, as measured by metrics such as carbon dioxide–equivalent emissions intensity per unit of dairy nutrient, is the lowest it has ever been. The companion Currents in One Health by Nguyen et al, AJVR, January 2023, discusses some additional animal welfare and environmental impact implications of modern dairy production management in detail.
Objective—To determine the risk posed by
Cryptosporidium parvum and Cryptosporidium
hominis from dairy cattle in the New York City watershed
Sample Population—Samples from cattle at risk for
shedding Cryptosporidium organisms on randomly
selected dairy farms in the NYCW.
Procedure—Feces were collected for 4 years from
calves at risk for infection on 37 dairies. Oocysts were
detected by use of centrifugation concentration-flotation
microscopy. The DNA was directly isolated from
fecal samples and used to amplify fragments of the
small subunit ribosomal RNA and thrombospondinrelated
adhesion protein C-2 genes by use of nested
polymerase chain reaction assays. Small subunit ribosomal
RNA fragments were restriction digested by
the enzyme VspI and thrombospondin-related adhesion
protein C-2 fragments were digested by Eco91I
to distinguish between C hominis (formerly known as
genotype 1) and C parvum (formerly known as genotype
Results—Of 437 fecal samples examined, 214 contained
oocysts. Amplicons were generated for 200
samples. We can be certain, with 95% confidence,
that cattle in the NYCW did not harbor C hominis.
Conclusions and Clinical Relevance—Cryptosporidium
infections in cattle are under examination
because of the potential contamination of public waters
by manure. Although cattle may be the source of
zoonotic infection via C parvum, they pose little risk for
C hominis (the strain commonly isolated from humans
in waterborne outbreaks of disease). Other sources of
oocysts should be considered when investigating outbreaks
attributable to contaminated urban drinking
water because cattle pose only a small risk via shedding
of C hominis. (Am J Vet Res 2005;66:413–417).
Objective—To perform respiratory chain enzymatic
activity assays on canine skeletal muscle biopsy specimens
and establish reference range values of skeletal
muscle enzyme activities for dogs.
Sample Population—Biopsy specimens from the
vastus lateralis muscle were obtained from 24 dogs
(8 sexually intact males and 14 sexually intact
females) ranging from 15 months to 6 years of age.
Procedure—Mean values of citrate synthase,
cytochrome-c oxidase, succinate dehydrogenase,
succinate dehydrogenase-cytochrome-c reductase,
nicotinamide adenine dinucleotide (NADH) dehydrogenase,
and NADH dehydrogenase-cytochrome-c
reductase activities were established by use of 6
standard spectrophotometric assays for respiratory
chain enzyme analysis.
Results—Compared with published data for skeletal
muscle enzyme activities in humans, skeletal muscle
enzyme activities in dogs were 2- to 4-fold higher.
Additionally, citrate synthase activity, a marker for
mitochondrial volume, was positively correlated with
age in dogs, suggesting that mitochondrial volume
increases with age, although no apparent change in
respiratory chain enzymatic activity with an increase
in age was found.
Conclusions and Clinical Relevance—Reference
range values for skeletal muscle enzyme activities of
dogs are needed to accurately interpret results of respiratory
chain enzymatic activity assays. During investigation
of metabolic myopathies, if skeletal muscle
biopsy specimens are evaluated for respiratory chain
enzyme kinetics, they should be performed and evaluated
in concert with skeletal muscle biopsy specimens
from clinically normal animals of the same
species. (Am J Vet Res 2004;65:480–484)
Objective—To elucidate the ecology of Listeria monocytogenes on dairy cattle farms by determining the prevalence of the organism in various samples.
Sample Population—Dairy cattle operations in central New York State.
Procedures—A repeated cross-sectional study design was used. Various samples were obtained from cattle (feces, composite udder milk, and udders), their environment (silage, feed bunks, water troughs, and floor bedding), inline milk filters, and bulk tank milk from 50 dairy farms. Samples were tested for L monocytogenes by use of a PCR assay with 2 steps of bacterial enrichment. Data were analyzed with mixed-effect logistic regression to control for the potential clustering of L monocytogenes on particular farms.
Results—L monocytogenes was detected in composite milk, udder swab samples, and fecal samples at prevalences of 13%, 19%, and 43%, respectively. There was no significant clustering of the pathogen by farm. Listeria monocytogenes was more common in samples obtained from cattle and the environment during winter and summer versus the fall. The prevalence of L monocytogenes was twice as high in samples obtained from feed bunks, water troughs, and bedding, compared with that in samples obtained from silage (65%, 66%, 55%, and 30%, respectively).
Conclusions and Clinical Relevance—L monocytogenes was more prevalent in samples obtained from dairy cattle and their environment than in milk samples. Strategies to control the pathogen in dairy operations should focus on cow hygiene and sanitary milk harvesting on the farm.
Longevity and herd turnover rate are becoming common topics of discussion as the dairy industry strives for continuous improvement in efficiency, profitability, animal welfare, and environmental sustainability. Having the most productive animal fill each slot on a dairy makes strategic replacement and the resulting herd turnover an important tool for producers. Dairy operations can be considered to have slots available to be occupied by cows. The number of slots available is governed by dairy characteristics including parlor size and facility design. With sustainability and profitability goals, producers should aim to fill each slot with the most productive animal. The advantages of a modest surplus of replacement heifers allowing for a higher herd turnover rate are examined and shown to improve herd profitability, enhance welfare, and reduce environmental impact. A model assuming constant demand for dairy foods is presented with increased herd turnover rate leading to more milk production per cow and reduced enteric methane emissions. This analysis demonstrates that all else being equal, raising more replacements (having a relatively higher herd turnover rate and decreased herd-level longevity) improves sustainability compared to management aimed at lower herd turnover rates. Understanding the drivers of herd turnover in dairy production has important implications for the components of one health: animal well-being, food production, and environmental stewardship. The present work examines one tool toward this goal, while the companion Currents in One Health by Nguyen et al, JAVMA, January 2023, takes a broader view of many aspects of dairy sustainability.
Objective—To evaluate the effect of nutritional plane on health and performance of dairy calves after infection with Cryptosporidium parvum.
Design—Randomized, controlled trial.
Animals—20 Holstein bull calves.
Procedures—Calves were assigned to a higher plane of nutrition (HPN; 0.30 Mcal intake energy/kg of metabolic body weight using a 28% protein-20% fat milk replacer) or conventional nutrition (CN; 0.13 Mcal intake energy/kg of metabolic body weight using a 20% protein-20% fat milk replacer). Calves were inoculated with C parvum oocysts at 3 days old. Fecal and health scores, oocyst counts, weight gain, dry matter intake, and hematologic variables were measured for 21 days. Data were analyzed with nonparametric and regression methods.
Results—Body weight (day 1), serum total protein concentration (day 3), and PCV (day 3) were not different between groups. Oocyst shedding was not different between groups. The PCV was higher in the CN group (40%), compared with the HPN group (32%) at the end of the study. Fecal scores (FS) improved faster in the HPN group (median, −0.1 FS/feeding), compared with the CN group (median, −0.06 FS/feeding). The HPN calves had better average daily gain (ADG) than did CN calves (median, 433 g/d vs −48 g/d, respectively). Feed efficiency (ADG:dry matter intake ratio) was better for HPN calves than CN calves (median, 131.9 g/kg vs −31.4 g/kg).
Conclusions and Clinical Relevance—After a pathogen challenge, calves maintained hydration, had faster resolution of diarrhea, grew faster, and converted feed with greater efficiency when fed a higher plane of nutrition.
Objective—To estimate the sensitivity, specificity, likelihood ratios, and predictive values of blood β-hydroxybutyrate (BHB) concentrations in dairy cows immediately prior to surgical correction of left-displaced abomasum (LDA) for determining associations between BHB concentration and removal from the herd ≤ 30 days after surgery and to evaluate postsurgical risk of removal for cows with the BHB concentration that had highest sensitivity and specificity for predicting this outcome.
Design—Prospective cohort study.
Animals—136 dairy cows with LDA diagnosed between 5 and 30 days in lactation (ie, days in milk).
Procedures—Blood BHB concentration was measured immediately prior to surgery. All cows underwent surgical correction of LDA while standing. Follow-up information was obtained ≥ 30 days after surgery. Receiver operating characteristic curves were used to estimate a critical threshold value for BHB concentration that was associated with removal from the herd, and this value was used in Poisson regression to estimate risk ratio for the same outcome.
Results—While controlling for parity in the model, cows with a BHB concentration < 1.2 mmol/L at the time of LDA surgery were 2.5 times as likely (95% confidence interval, 1.3 to 5.0) to be removed from the herd ≤ 30 days after surgery, compared with cows that had a BHB concentration ≥ 1.2 mmol/L.
Conclusions and Clinical Relevance—Results indicated that blood BHB concentration in dairy cows undergoing surgical correction of LDA may potentially be a useful prognostic indicator for the likelihood of removal from the herd ≤ 30 days after surgery. Further research is needed to evaluate other risk factors that may be associated with this outcome.