Predictors of blood ionized calcium concentration in sick adult cattle.

BACKGROUND: Data on the factors affecting blood ionized calcium concentration (ciCa2+ ) and diagnostic performance of serum total calcium concentration (ctCa) measurements to detect abnormal blood iCa2+ status are lacking in sick adult cattle. OBJECTIVE: Assess the association of ciCa2+ with venous blood pH, plasma concentrations of chloride (cCl), sodium (cNa), and potassium (cK), and ctCa, and total protein, albumin, and globulin concentrations in sick adult cattle. ANIMALS: Two-hundred and sixty-five adult cattle (≥1-year-old) with different diseases. METHODS: Prospective study. Whole blood pH, ciCa2+ , cNa, cK, and cCl were measured using a blood gas and electrolyte analyzer, whereas ctCa, and total protein, and albumin concentrations were determined using an autoanalyzer. The relationship between ciCa2+ and venous blood pH, plasma cCl, cNa, cK, and ctCa, and total protein, albumin, and globulin concentrations was investigated. Sensitivity and specificity were calculated for ctCa for diagnosis of abnormal ciCa2+ . RESULTS: Sensitivity of ctCa measurements to detect abnormal ciCa2+ was 66.0% whereas specificity of ctCa measurements was 72.3%. Serum total calcium concentration measurements accounted for 42% of adjusted blood ionized calcium (iCa2+ 7.40 ) concentration variance. Plasma cCl, and cK had explanatory power of ciCa2+ 7.40 , accounting for an additional 21% and 9% of the variance, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Serum tCa measurements failed to accurately predict blood iCa2+ status in ill adult cattle. Serum tCa concentrations and plasma cCl were the strongest predictors of ciCa2+ in sick adult cattle.

Acid-base imbalances and the association of blood-gas variables, electrolytes, and biochemical analytes with outcome in hospitalized calves undergoing abdominal surgery.

BACKGROUND: Surgical abdominal emergencies in calves are associated with a guarded prognosis and have the potential for complex metabolic derangements including acid-base imbalances. OBJECTIVES: To perform a comprehensive analysis of acid-base status and to assess the prognostic relevance of preoperative clinicopathologic variables in calves undergoing abdominal surgery. ANIMALS: Hospital-based study samples of 535 (dataset 1; DS1) and 83 calves (dataset 2; DS2). METHODS: Retrospective (DS1) and prospective (DS2) case series. RESULTS: In DS1, acidemia (pH <7.33) was present in 49.9%, whereas alkalemia (pH >7.37) was present in 30.7% of calves. Plasma L-lactate, chloride, and serum inorganic phosphorus concentration accounted for 51.9%, 11.6% and 9.4% of the variation of venous blood pH, respectively. Classification tree analysis indicated that a negative outcome (death or euthanasia during hospitalization) was associated with venous pO2 ≤33.6 mm Hg, anion gap >18.3 and >22.9 mEq/L, serum albumin concentration ≤36.5 and ≤29.4 g/L, serum urea concentration >4.4 mmol/L, and plasma ionized calcium concentration ≤1.26 mmol/L. The area under the receiver operating characteristic curve of this model was 0.85 (95% CI: 0.82-0.89, P < .001) and the resulting sensitivity and specificity for the prediction of nonsurvival at the optimal probability cut-point of 0.5 was 89.8% and 65.7%, respectively. In DS2 the model had a similar sensitivity and specificity of 90.5% and 70%, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Clinicopathologic imbalances and associated changes of acid-base status are common in calves with surgical abdominal emergencies and have clinical utility for the prediction of a negative postoperative outcome.

Evaluation of a point-of-care benchtop analyzer for quantitative measurement of C-reactive protein in canine serum and plasma.

BACKGROUND: Canine C-reactive protein (cCRP) is an acute-phase protein that increases dramatically with inflammation and has potential utility in monitoring disease progression and response to treatment. Rapid, automated point-of-care test (POCT) formats could enhance the clinical utility of cCRP measurement. OBJECTIVES: We aimed to evaluate the VetChroma canine-specific POCT assay for the quantitative measurement of cCRP in canine serum or plasma. METHODS: Serum and plasma from discarded canine diagnostic samples were used. Evaluation included intra- and inter-assay coefficients of variation and observed total error (TEobs ), linearity and spike recovery, the effect of interfering substances and sample matrices, and a method comparison study. RESULTS: Intra-assay variation ranged from 2.5%-6.1%, and inter-assay variation ranged from 2.1%-5.4%. The TEobs ranged from 15.1%-19.7%. The assay was linear over the manufacturer's analytical range with no evidence of constant or proportional bias. Recovery of purified cCRP from canine serum ranged from 116.2% to 138.4%. Hemolysis, icterus, and turbidity did not interfere with the assay. The comparison of paired plasma and serum samples revealed constant and proportional bias. Comparison of the VetChroma cCRP assay to a commercial cCRP ELISA revealed significantly different results. CONCLUSIONS: The VetChroma cCRP assay has acceptable test performance to measure serum cCRP concentration. The POCT protocol and test kit are valid for clinical use, although results obtained using other cCRP assays or plasma may not be directly compared.

Comparison of selected serum biochemistry measurements between the Nova Prime Plus VET, Nova pHOx Ultra, and Beckman Coulter AU680 analyzers in dogs.

BACKGROUND: Blood gas chemistry analyzers typically produce results faster and use smaller sample volumes than reference chemistry analyzers. However, results may not be comparable between blood gas chemistry analyzers and reference chemistry analyzers or between different models of blood gas chemistry analyzers. This could suggest the use of separate reference intervals and, thus, has implications when making clinical decisions. OBJECTIVE: We aimed to perform method comparison studies to evaluate selected canine serum biochemical values obtained using the Nova Stat Profile Prime Plus VET (Prime Plus VET), Stat Profile Nova pHOx Ultra (Ultra), and Beckman Coulter AU680 (Beckman) analyzers. We hypothesized that the three analyzers would be identical within inherent imprecision. METHODS: Jugular venous blood samples were collected from 103 endurance-trained sled dogs, and serum was harvested and stored for analysis. Results for serum chloride, potassium, sodium, creatinine, and urea nitrogen concentrations obtained from the Prime Plus VET and Ultra analyzers were compared with results from the Beckman analyzer, which was considered to be a reference method. Results for serum chloride, potassium, sodium, creatinine, urea nitrogen, and L-lactate concentrations obtained from the Prime Plus VET and Ultra analyzers were compared. Passing-Bablok regression and Bland-Altman plots were used for method comparison. RESULTS: Significant (P < 0.05) constant or proportional bias was found for many analytes for all three method comparison studies. CONCLUSIONS: Due to the presence of statistically significant differences between all three analyzers that may be clinically relevant, it is recommended that reference intervals be created for new blood gas analyzers, even when similar methodologies are used.

Effect of antepartum vitamin D3 (cholecalciferol) and postpartum oral calcium administration on serum total calcium concentration in Holstein cows fed an acidogenic diet in late gestation.

Several strategies are available to control periparturient hypocalcaemia in dairy cows. Three complementary strategies were applied in this study: feeding a low DCAD (acidogenic) ration during late gestation, oral vitamin D3 (cholecalciferol) administration in late gestation, and oral Ca administration immediately after parturition. Multiparous Holstein cows (n = 240) were fed an acidogenic ration in late gestation and randomly assigned to one of three treatment groups. Group A (n = 80) were fed the acidogenic diet without supplementary Ca or cholecalciferol. Group Ca + A (n = 80) received 50 g of Ca as an oral bolus at calving and 12 h later. Group D3 + Ca + A (n = 80) were administered 3 mg of cholecalciferol orally each day starting 3 to 5 days before the anticipated calving date and 50 g of Ca as an oral bolus at calving and 12 h later. Blood and urine samples were obtained periodically from a random subset of 20 cows in each group from day 5 antepartum to day 21 postpartum and selected analytes measured. Data was analyzed using mixed models analysis. Serum Ca concentrations in group D3 + Ca + A were higher 12 h before and at parturition, compared to the two other groups. Oral Ca administration transiently increased mean serum Ca concentrations at 6 h after treatment initiation in groups D3 + Ca + A and Ca + A. We conclude that daily oral administration of 3 mg of cholecalciferol for up to 5 days before calving, combined with feeding an acidogenic ration in late gestation and oral Ca immediately after parturition, provided the highest periparturient serum Ca concentrations.

Dependence of the apparent bicarbonate space on initial plasma bicarbonate concentration and carbon dioxide tension in neonatal calves with diarrhea, acidemia, and metabolic acidosis.

BACKGROUND: Marked strong ion (metabolic) acidosis in neonatal diarrheic calves usually is corrected by IV administration of NaHCO3 . The distribution space for IV-administered bicarbonate, called the apparent bicarbonate space (ABS), appears to depend on initial plasma bicarbonate concentration (cHCO3 ) and varies considerably in calves. OBJECTIVE: To determine whether ABS was associated with initial plasma cHCO3 and other acid-base variables. ANIMALS: Twenty-five neonatal diarrheic calves with acidemia and metabolic acidosis. METHODS: Prospective observational study using a convenience sample. Calves received NaHCO3 (10 mmol/kg) and glucose (1.4 mmol/kg) IV in a crystalloid solution at 25 mL/kg over 60 minutes. The ABS (L/kg) was calculated at 4 time points over 2 hours after the end of the infusion. The relationship between ABS and initial acid-base variables was characterized using nonlinear, linear, and stepwise regression. RESULTS: The median value for ABS calculated from the initial plasma cHCO3 increased from 0.53 L/kg (range, 0.40-0.79) at the end of IV infusion to 0.96 L/kg (range, 0.54-1.23) 120 minutes later. Data obtained at the end of infusion provided the best fit to initial plasma cHCO3 and jugular venous blood Pco2 , such that: ABS = 0.41 + 1.06/cHCO3 and ABS = 0.87-0.0082 × Pco2 . CONCLUSIONS AND CLINICAL IMPORTANCE: The observed median value for ABS of 0.53 L/kg in our study was similar to the empirically used value of 0.6. However, ABS values varied widely and were increased in calves with severe metabolic acidosis. We therefore recommend calculating ABS using the initial plasma cHCO3 or venous blood Pco2 , if respective measurements are available.

The effect of age and sex on selected hematologic and serum biochemical analytes in 4,804 elite endurance-trained sled dogs participating in the Iditarod Trail Sled Dog Race pre-race examination program.

Endurance-trained sled dogs provide a unique translational model to characterize changes in hematologic and serum biochemical analytes due to the aging process. The primary objective of this study was to determine the effect of age and sex on specific hematologic and serum biochemical parameters in the endurance trained sled dog. Longitudinal and cross-sectional data were analyzed from 9,746 blood and serum samples from 4,804 dogs collected over 7 years as part of the Iditarod Trail Sled Dog Race pre-race examination program. Mixed models analysis was used for statistical analysis and P < 0.01 was considered significant. Dogs ranged from 1-12 years of age and 39% were female. Serum total calcium and phosphorus concentrations and white blood cell count decreased nonlinearly to asymptotic values by 6.6, 3.1, and 6.9 years of age, respectively, equivalent to estimated physiologic ages in human years of 44, 27, and 46 years. Serum glucose concentrations reached their lowest value at 7.8 years of age, equivalent to an estimated human physiologic age of 50 years, after which time the concentration increased. Serum globulin concentrations increased with age, but nonlinearly for females and linearly for males. Most sex-related differences were <5%; however, females had lower serum urea nitrogen (14.7%) and creatinine (7.3%) concentrations, lower serum alanine aminotransferase activity (16.6%), and higher serum total bilirubin concentration (12.8%) and platelet count (6.0%). The endurance-trained sled dog provides an excellent model to separate the physiologic effects of age from those of a sedentary lifestyle on hematologic and serum biochemical analytes.

Intravenous and Oral Fluid Therapy in Neonatal Calves With Diarrhea or Sepsis and in Adult Cattle.

Optimal fluid therapy protocols in neonatal calves and adult cattle are based on consideration of signalment, history, and physical examination findings, and individually tailored whenever laboratory analysis is available. Measurement of the magnitude of eye recession, duration of skin tenting in the lateral neck region, and urine specific gravity by refractometry provide the best estimates of hydration status in calves and cattle. Intravenous and oral electrolyte solutions (OES) are frequently administered to critically ill calves and adult cattle. Application of physicochemical principles indicates that 0.9% NaCl, Ringer's solution, and 5% dextrose are equally acidifying, lactated Ringer's and acetated Ringer's solution are neutral to mildly acidifying, and 1.3-1.4% sodium bicarbonate solutions are strongly alkalinizing in cattle. Four different crystalloid solutions are recommended for intravenous fluid therapy in dehydrated or septic calves and dehydrated adult cattle: (1) lactated Ringer's solution and acetated Ringer's solution for dehydrated calves, although neither solution is optimized for administration to neonatal calves or adult cattle; (2) isotonic (1.3%) or hypertonic (5.0 or 8.4%) solutions of sodium bicarbonate for the treatment of calves with diarrhea and severe strong ion (metabolic) acidosis and hyponatremia, and adult cattle with acute ruminal acidosis; (3) Ringer's solution for the treatment of metabolic alkalosis in dehydrated adult cattle, particularly lactating dairy cattle; and (4) hypertonic NaCl solutions (7.2%) and an oral electrolyte solution or water load for the rapid resuscitation of dehydrated neonatal calves and adult cattle. Much progress has been made since the 1970's in identifying important attributes of an OES for diarrheic calves. Important components of an OES for neonatal calves are osmolality, sodium concentration, the effective SID that reflects the concentration of alkalinizing agents, and the energy content. The last three factors are intimately tied to the OES osmolality and the abomasal emptying rate, and therefore the rate of sodium delivery to the small intestine and ultimately the rate of resuscitation. An important need in fluid and electrolyte therapy for adult ruminants is formulation of a practical, effective, and inexpensive OES.

Echocardiographic assessment of left ventricular systolic function in neonatal calves with naturally occurring sepsis or septic shock due to diarrhea.

Sepsis is associated with clinically relevant cardiovascular changes. The objectives of this study were to evaluate the clinical value of echocardiography for monitoring left ventricular (LV) systolic function in septic calves. A prospective longitudinal study was performed using a convenience sample. Twenty septic calves and 10 healthy calves were enrolled in the study. Arterial blood pressure (BP) was measured and M-mode echocardiography performed to characterize LV systolic function; the latter included measurement of ejection fraction, EF; stroke volume, SVI and cardiac output indexed to body weight, CI; E-point of septal separation, EPSS; pre-ejection period, PEP; ejection time, LVET; ratio of PEP to LVET; velocity of circumferential shortening, Vcf, LV end-diastolic volume index (LVEDVI) and LV end-systolic volume index (LVESVI) on admission and 6, 24, 48 and 72 h later in septic calves and once in healthy calves. Admission data were compared using the Mann-Whitney U test and P < .05 was considered significant. Decreased preload and afterload were present in septic calves, as indicated by marked decreases in BP, LVEDVI, LVESVI, SVI, CI, EPSS when compared to healthy calves. Systolic function appeared adequate in septic calves, based on EF and FS compared to control calves. There was no difference in heart rate, LVET, PEP:LVET, or Vcf between septic and health calves. We conclude that circulatory dysfunction, rather than systolic dysfunction predominates in septic calves. Positive associations on admission between CI and LVEDVI, LVESVI, and SVI support this conclusion. Echocardiographic determination of LVEDVI and CI appears useful in directing treatment in septic calves.

Evaluation of hand-held sodium, potassium, calcium, and electrical conductivity meters for diagnosing subclinical mastitis and intramammary infection in dairy cattle.

BACKGROUND: Subclinical mastitis (SCM) and intramammary infection (IMI) increase the sodium (Na) concentration and electrical conductivity (EC) and decrease the potassium (K) and calcium (Ca) concentrations in glandular secretions of lactating dairy cattle. HYPOTHESIS: Low-cost portable Na, K, Ca, and EC meters are clinically useful cow-side tests for diagnosing SCM and IMI. ANIMALS: One hundred fifteen dairy cows at dry off and 92 cows within 4-7 days postcalving. METHODS: Quarter foremilk samples were obtained and the somatic cell count (SCC) was measured using a DeLaval cell counter with SCM defined as SCC ≥ 200 000 cells/mL. Microbiological culture of foremilk samples was used to diagnose IMI. Cisternal milk Na, K, and Ca concentrations and EC were measured using portable ion-selective meters. Logistic regression was used to determine the area under the receiver operating characteristic curve (AUC) and the optimal cut point was determined using Youden's index. Diagnostic test performance was evaluated by comparing the AUC and calculating the sensitivity, specificity, and positive likelihood ratio (+LR) at the optimal cut point for SCM and IMI. RESULTS: Diagnostic test performance was much better when the meters were used to diagnose SCM as compared to IMI. Cisternal milk Na concentration provided the most accurate method for identifying quarters with SCM or IMI. However, AUC was <0.90 and +LR was <10 for all diagnostic test evaluations. CONCLUSIONS AND CLINICAL IMPORTANCE: Cisternal milk Na, K, and Ca concentrations and EC were not sufficiently predictive of SCM or IMI to be recommended as clinically useful diagnostic tests.

Pharmacokinetics and pharmacodynamics of intramammary cefquinome in lactating goats with and without experimentally induced Staphylococcus aureus mastitis.

Values for pharmacokinetic variables are usually obtained in healthy animals, whereas drugs are frequently administered to diseased animals. This study investigated cefquinome pharmacokinetics in healthy goats and goats with experimentally induced mastitis. Five adult lactating goats received 75 mg of cefquinome intramammary infusion using a commercially available product into one udder half in healthy goats and goats with clinical mastitis that was induced by intracisternal infusion of 100 cfu of Staphylococcus aureus ATCC 29213 suspended in 5 ml of sterile culture broth. Cefquinome concentrations were determined in plasma and skimmed milk samples using high-performance liquid chromatography (HPLC). Pharmacodynamics was investigated using the California Mastitis Test and pH of milk. Experimentally induced mastitis significantly increased the California Mastitis Test score and pH, and decreased the maximal cefquinome concentration and shortened the half-life in milk when compared to healthy goats. In conclusion, mastitis facilitated the absorption of cefquinome from the mammary gland of lactating goats and induced marked changes in milk pH, emphasizing the importance of performing pharmacokinetic studies of antimicrobial agents in infected animals.

Clinical utility of urine specific gravity, electrical conductivity, and color as on-farm methods for evaluating urine concentration in dairy cattle.

BACKGROUND: Urine concentration (UC) provides clinically useful information concerning hydration status and renal function of animals. OBJECTIVES: To characterize the clinical performance of urine specific gravity measured by optical refractometry (USG-R ) or Multistix-SG urine reagent dipstick (USG-D ), urine electrical conductivity using an OAKTON Con 6 conductivity handheld meter (UEC ), urine color (UColor ) using a custom-designed 8-point color chart, and urine creatinine concentration (UCreat ) for assessing UC in dairy cattle. ANIMALS: 20 periparturient Holstein-Friesian cows. METHODS: Urine was obtained by perineal stimulation or urethral catheterization and urine osmolality (UOsm , reference method), USG-R , USG-D , UEC , UColor , and UCreat determined. Diagnostic test performance was evaluated using Spearman's rho and logistic regression to determine the area under the receiver operating curve (AUC) and optimal cut point for diagnosing hypohydration (UOsm ≥800 mOsm/kg). P < .05 was considered significant. RESULTS: The best performing test for diagnosing hypohydration was USG-R (AUC = 0.90) at an optimal cut point ≥1.030. The second-best performing test was UEC (AUC = 0.82) at a cut point of ≥23.7 mS/cm, followed by UCreat (AUC = 0.76) at a cut point of ≥95.3 mg/dL, and UColor (AUC = 0.74) at a cut point of ≥4 on an 8-point scale. Urine specific gravity measured by dipstick performed poorly (AUC = 0.63). CONCLUSIONS AND CLINICAL IMPORTANCE: USG-R and UEC provide practical and sufficiently accurate methods for measuring UC in dairy cattle. Urine color had moderate clinical utility as a no-cost cow-side method for assessing UC, whereas dipstick refractometry is not recommended for assessing UC.

Electrocardiographic findings in 130 hospitalized neonatal calves with diarrhea and associated potassium balance disorders.

BACKGROUND: Hyperkalemia in neonatal diarrheic calves can potentially result in serious cardiac conduction abnormalities and arrhythmias. OBJECTIVES: To document electrocardiographic (ECG) findings and the sequence of ECG changes that are associated with increasing plasma potassium concentrations (cK+ ) in a large population of neonatal diarrheic calves. ANIMALS: One hundred and thirty neonatal diarrheic calves (age ≤21 days). METHODS: Prospective observational study involving calves admitted to a veterinary teaching hospital. RESULTS: Hyperkalemic calves (cK+ : 5.8-10.2, blood pH: 6.55-7.47) had significantly (P < .05) longer QRS durations as well as deeper S wave, higher T wave, and higher ST segment amplitudes in lead II than calves, which had both venous blood pH and cK+ within the reference range. The first ECG changes in response to an increase in cK+ were an increase in voltages of P, Ta, S, and T wave amplitudes. Segmented linear regression indicated that P wave amplitude decreased when cK+ >6.5 mmol/L, S wave amplitude voltage decreased when cK+ >7.4 mmol/L, QRS duration increased when cK+ >7.8 mmol/L, J point amplitude increased when cK+ >7.9 mmol/L, and ST segment angle increased when cK+ >9.1 mmol/L. P wave amplitude was characterized by a second common break point at cK+ = 8.2 mmol/L, above which value the amplitude was 0. CONCLUSIONS AND CLINICAL IMPORTANCE: Hyperkalemia in neonatal diarrheic calves is associated with serious cardiac conduction abnormalities. In addition to increased S and T wave amplitude voltages, alterations of P and Ta wave amplitudes are early signs of hyperkalemia, which is consistent with the known sensitivity of atrial myocytes to increased cK+ .

Evaluation of 5 methods for diagnosing failure of passive transfer in 160 Holstein calves.

BACKGROUND: Inadequate absorption of colostral IgG1 is termed failure of transfer of passive immunity (FTPI). Dairy calves with FTPI have increased mortality and morbidity in their first 6 months of life. OBJECTIVES: This study compared the clinical performance of 5 methods for diagnosing FTPI in Holstein calves. METHODS: An observational study was performed using 160 Holstein heifer calves. Serum was harvested at 48 hours of age, and FTPI was assessed using a digital Brix refractometer for total solids measurements, and digital refractometry and the biuret method to measure serum total protein (STP) concentrations. Serum gamma-glutamyltransferase activity was measured with an automated analyzer, and serum IgG was measured with the zinc sulfate turbidity test and an enzyme-linked immunosorbent assay. Diagnostic test performance was compared with that of the reference method (FTPI defined as a serum total IgG concentration <10 g/L). Test performance was evaluated using the area under the receiver operating characteristic curve, the sensitivity, the specificity, and the positive likelihood ratio at the optimal test cut point, and by calculating the kappa coefficient. RESULTS: A serum digital Brix percentage of <7.8% and an STP concentration of <52 g/L measured using digital refractometry were the best methods to identify calves with FTPI. The STP concentration measured with digital refractometry was 0.1 g/L lower than that measured with the biuret method. CONCLUSIONS: The digital Brix refractometer and the digital refractometer provide accurate and clinically useful methods for identifying dairy calves with FTPI. In this study, the excellent performance of the Brix refractometer was likely due to the use of a fixed sample volume (200 µL) and a uniform sample temperature at the time of measurement.

Clinical signs and outcomes of beef cattle undergoing cesarean section because of dystocia.

OBJECTIVE To characterize signalment, clinical signs, reproductive history, surgical management, and outcomes of beef cattle undergoing cesarean section because of dystocia at a veterinary teaching hospital. DESIGN Retrospective case series with nested cohort study. ANIMALS 173 beef cattle admitted to a veterinary teaching hospital from 2001 through 2010 that underwent cesarean section because of dystocia. PROCEDURES Medical records were reviewed and information collected on cattle signalment; reproductive history; cause of dystocia; anesthetic protocol; surgical management; number, sex, and body weight of calves delivered (alive or dead); perioperative treatment; duration of hospitalization; and discharge status. A questionnaire regarding postoperative fertility was mailed to all owners, and owners who did not respond were contacted via telephone. RESULTS Overall mortality rate for calves was high, with 37.6% (62/165) of calves delivered dead or dying ≤ 24 hours after cesarean section. Mortality rate was higher for female versus male calves and for calves from dams with signs of labor for ≥ 3 hours versus < 3 hours before hospital admission. Overall mortality rate for dams was low, with only 10 of 161 (6.2%) dams failing to survive for ≥ 21 days after hospital discharge. Postoperative fertility rate was acceptable, with 75% (44/59) of dams that were rebred after cesarean section giving birth to ≥ 1 live calf. CONCLUSIONS AND CLINICAL RELEVANCE Cesarean section was a clinically useful method for resolving dystocia in beef cattle, providing a high dam survival rate and an acceptable postoperative fertility rate. Beef cattle producers should seek veterinary assistance whenever clinical signs of dystocia are noticed, preferably within 6 hours after onset of parturition.

Plasma calcium concentrations are decreased at least 9 hours before parturition in multiparous Holstein-Friesian cattle in a herd fed an acidogenic diet during late gestation.

Calcium homeostatic mechanisms are challenged in periparturient multiparous dairy cattle due to the rapid transport of large amounts of calcium into the mammary gland associated with colostrogenesis, resulting in decreased plasma total calcium concentration ([Ca]). An unresolved issue is the timing of the decrease in plasma [Ca] relative to the time of parturition, with the consensus view being that plasma [Ca] does not decrease until after parturition. The objective of this study, therefore, was to characterize the change in plasma [Ca] over time in periparturient dairy cattle. Plasma and mid-stream urine samples were collected daily starting 3 d before calving from 104 periparturient Holstein-Friesian dairy cows in a herd fed an acidogenic total mixed ration during the late dry period. Mixed-models ANOVA and linear and multivariable regression analyses were conducted. Plasma [Ca] decreased in periparturient multiparous cattle (n = 70) but not in primiparous cattle (n = 34). Compared with mean values approximately 72 h before parturition ([Ca] = 2.32 mmol/L), mean plasma [Ca] in multiparous cattle first decreased at 9 h before parturition (2.13 mmol/L) and remained decreased for up to 48 h after parturition, with the lowest mean value (1.87 mmol/L) occurring at 28 h after parturition. Mean 24-h urine Ca excretion was calculated to decrease by 3.5 to 3.8 g in periparturient multiparous cattle. Regression analysis indicated that plasma [Ca] in the 12-h period before and 24-h period after parturition was strongly and negatively associated with age but was also negatively associated with milk production indices. We conclude that plasma [Ca] was decreased at least 9 h before parturition in multiparous dairy cattle fed an acidogenic diet in late gestation, and that calcium homeostasis was disrupted for 2 to 3 d around parturition.

Clinical signs, profound acidemia, hypoglycemia, and hypernatremia are predictive of mortality in 1,400 critically ill neonatal calves with diarrhea.

Profound acidemia impairs cellular and organ function and consequently should be associated with an increased risk of mortality in critically ill humans and animals. Neonatal diarrhea in calves can result in potentially serious metabolic derangements including profound acidemia due to strong ion (metabolic) acidosis, hyper-D-lactatemia, hyper-L-lactatemia, azotemia, hypoglycemia, hyperkalemia and hyponatremia. The aim of this retrospective study was to assess the prognostic relevance of clinical and laboratory findings in 1,400 critically ill neonatal calves with diarrhea admitted to a veterinary teaching hospital. The mortality rate was 22%. Classification tree analysis indicated that mortality was associated with clinical signs of neurologic disease, abdominal emergencies, cachexia, orthopedic problems such as septic arthritis, and profound acidemia (jugular venous blood pH < 6.85). When exclusively considering laboratory parameters, classification tree analysis identified plasma glucose concentrations < 3.2 mmol/L, plasma sodium concentrations ≥ 151 mmol/L, serum GGT activity < 31 U/L and a thrombocyte count < 535 G/L as predictors of mortality. However, multivariable logistic regression models based on these laboratory parameters did not have a sufficiently high enough sensitivity (59%) and specificity (79%) to reliably predict treatment outcome. The sensitivity and specificity of jugular venous blood pH < 6.85 were 11% and 97%, respectively, for predicting non-survival in this study population. We conclude that laboratory values (except jugular venous blood pH < 6.85) are of limited value for predicting outcome in critically ill neonatal calves with diarrhea. In contrast, the presence of specific clinical abnormalities provides valuable prognostic information.

Evaluation of learning curves for ovariohysterectomy of dogs and cats and castration of dogs.

OBJECTIVE To define learning curves for fourth-year veterinary students performing ovariohysterectomy procedures in dogs and cats and castration in dogs. DESIGN Retrospective study. SAMPLE 3,196 ovariohysterectomies or castrations performed in dogs and cats by 88 veterinary students during a spay-neuter surgery and animal shelter rotation (n = 3,056) or by 1 experienced general practitioner (n = 140). PROCEDURES Data collected from medical records included patient signalment, type and duration of procedure, and sequence (by date and time) of the procedure within a list of procedures of the same type generated for each student. For each procedure type, geometric mean surgery time and 95% confidence intervals were determined for each number of surgeries completed by ≥ 10 students. Median surgery times for the same procedure types were determined for the experienced practitioner. The learning curve for each procedure was modeled with nonlinear (3-factor exponential equation with a nonzero asymptote) and linear regression. For each procedure, the asymptote (optimal surgery time) for students was compared with the experienced practitioner's median surgery time. RESULTS 2,945 surgeries (mean, 33/student) performed by ≥ 10 students were analyzed. Surgery time decreased in a nonlinear manner as student experience increased for castration of adult or pediatric dogs and ovariohysterectomy of pediatric dogs and adult or pediatric cats. Surgery time decreased in a linear manner as experience increased for ovariohysterectomy of adult dogs. CONCLUSIONS AND CLINICAL RELEVANCE To the authors' knowledge, this was the first study to map surgery times for common surgical procedures consecutively performed by veterinary students. Results clearly indicated the value of repetition to improve surgical skills (as measured by surgery time) during a 3-week period.