Acaricidal Efficacy of Thirty-Five Egyptian Plants Against the Camel Tick, Hyalomma Dromedarii

PURPOSE

Alternative and affordable tick control strategies are crucial to control and prevent tick bites and tick-borne diseases.

METHODS

In this study, we evaluated the acaricidal efficacy of 35 aqueous plant extracts (17%) against the camel tick, Hyalomma dromedarii.

RESULTS

The phytochemical profile indicated the presence of various secondary substances. Plants were classified into three groups according to their mortality percentage 15 days post-treatment with 17%. This highly effective group (91%-95%) comprised Ocimum basilicum, Mespilus germanica, and Viola alpine followed by Carum carvi, Cucurbita pepo (peel), and Peganum harmala. A moderately effective group (80%-90%) included Acacia nilotica, Apium graveolens, Capsicum annuum, Ceratonia siliqua, Cucurbita pepo (seeds), Equisetum arvense, Eruca sativa, Ginkgo biloba, Plantago psyllium, Phyllanthus emblica, Punica granatum, and Ziziphus spinachristi. The 20 remaining plants were assigned to the less effective group (< 80%). Viscum album (58.3%), which was the least effective reference plant. The high potency of six plant extracts as acaricides may be attributed to the high content of active principles, e.g., phenols, flavonoids, and tannins.

CONCLUSION

All of these highly effective plants are recommended for use as an acaricide, in case of facing acaricidal resistance or limited options for tick control.

Effect of drilling process parameters on bearing strength of glass fiber/aluminum mesh reinforced epoxy composites

The current study attempted to evaluate the impact of drilling parameters and delamination on the bearing strength of both neat GFRP (NG) and hybrid GFRP/aluminum (Al)-wire mesh with two various configurations, first with Al-mesh in the outer surface of specimen (AG) and the other with Al-mesh in the core of specimen (GA). Drilling procedure is carried out using [Formula: see text] 6 mm carbide twist drill with three different tip angles (90°, 120° and 135°), as well as Three different speeds and feeds (1000, 2000, and 3000 rpm) and (20, 40, and 60 mm/min), respectively. Taguchi and ANOVA analyses are used to analyze the influence of processing parameters. The findings showed that AG specimen experienced the least delamination damage. The maximum bearing strength refers to NG specimen, which is 9.6% and 8.7% more than AG and GA specimens, respectively. Drill point angle has the major effect on bearing strength for both AG and GA specimens, while for NG feed rate is of the major effect. The developed regression model displayed a high level of fitness with an average prediction error of less than 3%.

Evaluation of the stress-reducing effect of trace mineral injection in beef calves

BACKGROUND

Little is known about the effects of trace mineral supplementation on the stress response in beef calves.

OBJECTIVES

To investigate the effect of injectable trace mineral supplementation (ITM) on the stress response in beef calves exposed to different types of stress.

ANIMALS

Thirty weaned Angus and Angus crossbred calves.

METHODS

The enrolled calves were randomly assigned to 2 groups: ITM, 15 calves received modified-live virus vaccine (MLV) and ITM SC and 15 calves received MLV and saline SC (CONT). The calves were exposed to 3 types of stress: the stress of MLV vaccination (d0), nasal aerosol with bovine viral diarrhea virus-2 (BVDV-2) challenge (d5), and liver biopsy (d26). The calves' body weights and health status were monitored. Leukocyte counts, serum cortisol concentration ([cort]), BVDV-2 serum neutralizing antibodies (SNA), and percentages of CD4⁺ , CD8⁺ , WC1⁺ _, and CD25⁺ T-lymphocytes were measured.

RESULTS

Serum cortisol concentration ([cort]) showed strong associations with the percentage of CD8⁺ (r_s  = .50), BVDV2-SNA (r_s  = -.43), and WC1CD25⁺ (r_s  = .41) cells, and rectal temperature (r_s  = .40). The highest [cort] was reported 3 days after aerosol BVDV-2 challenge. Serum [cort] was decreased in ITM-treated calves 3 days post-BVDV-2 challenge, compared with CONT calves, with an average decrease of 18.5 ng/μL (95% confidence interval [CI], -6.07 to -31.3). The ITM-treated calves were heavier and healthier (P < .01) than the CONT calves.

CONCLUSIONS AND CLINICAL IMPORTANCE

Trace mineral supplementation appears to have stress mitigation effects in beef cattle that may reflect positively on growth and health performance. Viral exposure is associated with a high degree of stress, which is considered a major welfare concern.

Validation of a fully automated chemiluminescent immunoassay for cattle serum and plasma progesterone measurement

Introduction

Monitoring circulating progesterone concentration ([P4]) is an important component of basic and applied reproduction research and clinical settings. IMMULITE^® 2000 XPi (Siemens Healthineers, Cary, NC) is a newly upgraded fully automated immunoassay system marketed for human use to measure concentrations of different measurands including P4.

Objectives

Our objective was therefore to characterize the analytical performance of the IMMULITE^® 2000 XPi P4 immunoassay (IPI) across the reportable range in serum and plasma of cattle.

Methods

The IPI validation protocols included characterization of the method linearity, within-run, and between-run precision through calculation of the coefficient of variation (CV). The method accuracy was assessed through the calculation of the spiking-recovery (SR) bias across the reportable range (0.2-40.0 ng/mL). Passing-Bablok regression and Bland-Altman plots were used to determine the interlaboratory bias for two laboratories. Three types of observed total error (TEo) were calculated based on the considered type of bias, TEo_SR (spiking-recovery), TEo_RB (range-based bias), and TEo_AB (average-based bias).

Results

The IPI was linearly related to the true value (R ² = 0.997) across the reportable range. The within-run and between-run precision (CV%) of the IPI for both serum and plasma [P4] of clinical relevance (1, 2, 5, and 10 ng/mL) were <5 and <10%, respectively. The TEo reported here for serum and plasma at [P4] of 1 and 5 ng/mL was ~20 and 25%, respectively. Of interest, the three types of TEo were relatively similar regardless of the considered bias.

Conclusions

We concluded that the automated IPI provides a precise, accurate, reliable, and safe method for measuring [P4] in both serum and plasma of cattle. Consistent with the manufacturer's recommendations, the serum matrix is more accurate than plasma.

Comparison between bearing strengths of molded-in and machined holes of GFR/PP composites

This study is an investigation of weight fraction (wt%) and fiber feedstock length (FFSL) effects on the bearing strength (BS) of bolted joints in glass-fiber-reinforced (GFR) polypropylene (PP) composites manufactured by an injection molding technique. The investigation was made for holes produced either by molding or machining. For machined holes, the effect of drilling parameters (feed and speed) on BS was discussed. It is observed that BS decreased as FFSL increased. BS of both molded-in and drilled specimens was enhanced by increasing wt% of glass fiber. While slightly better BS was observed for molded-in specimens than drilled ones for all specimens. The drilling conditions’ effect on BS was found to be insignificant for drilled holes in long fibers reinforced PP, where the most significant factor was wt%. However, for short fibers reinforced PP, the spindle speed was the most significant factor followed by feed, while wt% has the lowest effect. Failure morphology mode for specimens indicates that for molded-in specimens, neat PP specimens failed under pure bearing mode while GFR/PP specimens failed under the mixed-mode failure (bearing and net tension). For machined specimens, all specimens failed under mixed-mode failure except for the highest wt% specimens which failed under net tension.

Technical note: Evaluation of a colorimetric point-of-care test for measuring urine ammonium concentration in periparturient dairy cattle

Urine ammonium concentration ([NH₄⁺]) provides a clinically useful indicator of the magnitude of nutritionally induced systemic acidification in dairy cattle when urine pH < 6.1. The objective of this study was to evaluate the analytical performance of a low-cost point-of-care colorimetric test in measuring urine [NH₄⁺] in dairy cattle consuming an acidogenic ration. A method comparison study was performed using 154 urine samples from 43 periparturient Holstein-Friesian cows. We compared urine [NH₄⁺] measured by an indophenol blue colorimetric test (MColortest, Merck KGaA, Billerica, MA; test method) with levels measured by formaldehyde titration (reference method). Diagnostic performance was evaluated using Pearson correlation coefficient (r), Passing-Bablok regression, Bland-Altman plot, and binary logistic regression. Urine [NH₄⁺] measured by the colorimetric test was strongly correlated (r = 0.98) with urine [NH₄⁺] measured by formaldehyde titration. Method comparison studies indicated that the colorimetric test provided acceptable test performance when urine [NH₄⁺] < 80 mmol/L. Logistic regression analysis indicated that the area under the receiver operating characteristic curve for the colorimetric ammonium test was high at 0.985 when used to identify formaldehyde titration [NH₄⁺] > 10 mmol/L, equivalent to urine pH <6.1. At the optimal cut point ([NH₄⁺] > 11 mmol/L) for the colorimetric test, sensitivity = 0.94, specificity = 0.97, positive likelihood ratio = 27.6, and κ = 0.89, indicating excellent test performance. We conclude that the indophenol blue colorimetric test provided an accurate, low-cost, and practical on-farm test for measuring urine [NH₄⁺] in diluted urine samples from dairy cattle consuming an acidogenic ration.

Risk factor analysis of bovine leukemia virus infection in dairy cattle in Egypt

Identification of the risk factors associated with Enzootic bovine leukosis (EBL) is essential for the adoption of potentially prevention strategies. Accordingly, our objectives were to determine the geographic distribution of Bovine Leukemia Virus (BLV) infection and identify the risk factors associated with cow-level BLV infection in the Egyptian dairy cattle. A cross-sectional study was conducted on 1299 mixed breed cows distributed over four provinces in the Nile Delta of Egypt in 2018. The randomly selected cows on each farm were serologically tested for BLV, and the cow's information was obtained from the farm records. Four variables (geographic location, herd size, number of parities, and age) were used for risk analysis. A total of 230 serum samples (17.7 %) were serologically positive for BLV. The highest prevalence of BLV infection was associated with parity (OR = 3.4, 95 %CI 2.4-4.9) with 80 % probability of being BLV-positive at parity ≥5, followed by herd size (OR = 1.8, 95 %CI 1.4-2.2). However, geographic location seems to have no impact on the prevalence of BLV infection in Egypt. Our findings strongly indicate that the intensive surveillance and effective prevention strategies against BLV infection in Egypt should be provided to multiparous cows with ≥5 parities and live in large farm with more than 200 cows.

Clinical utility of plasma progesterone and blood and plasma glucose concentrations in predicting parturition in Holstein cows

An accurate, practical, and low-cost method for predicting parturition is urgently needed in the dairy industry. The objective of this study was to evaluate changes in plasma progesterone concentration ([prog]) and glucose concentration in whole blood ([gluc]_b) and plasma ([gluc]_p) as predictors of parturition within 6, 12, and 24 h in primiparous and multiparous Holstein cows. Blood samples were obtained daily at approximately 0900 h from 34 primiparous and 72 multiparous Holstein cows in late gestation and the time of calving recorded to the nearest hour. Plasma [prog] was measured using an ELISA, and [gluc]_b and [gluc]_p using a low-cost point-of-care glucose meter. The optimal cut-point for predicting parturition was determined using binomial logistic regression with general estimating equations, because the data set consisted of repeated measures for each cow. Diagnostic test performance was evaluated by comparing the area under the receiver operating characteristic curve (AUC) and calculating the sensitivity, specificity, and κ at the optimal cut-point for predicting parturition. Plasma [prog] was the most accurate predictor of parturition within 24 h (AUC = 0.96) and 12 h (AUC = 0.93), whereas [gluc]_b was the most accurate predictor of parturition within 6 h (primiparous, AUC = 0.96; multiparous, AUC = 0.86). We conclude that a decrease in plasma [prog] is currently the most accurate test for predicting calving within 24 h. Measurement of [gluc]_b is a promising new test for the cow-side prediction of parturition in dairy cows due to its accuracy, practicality, and low cost.

Measurement of urine pH and net acid excretion and their association with urine calcium excretion in periparturient dairy cows

Urine pH (U_pH) and net acid excretion (NAE) are used to monitor the degree of systemic acidification and predict the magnitude of resultant hypercalciuria when feeding an acidogenic ration to control periparturient hypocalcemia in dairy cattle. The objectives of this study were to evaluate the diagnostic performance of urine dipstick and pH paper for measuring U_pH, and to characterize the U_pH-NAE relationship and the association of urine Ca concentration ([Ca]) with U_pH and NAE. Urine samples (n = 1,116) were collected daily from 106 periparturient Holstein-Friesian cows fed an acidogenic ration during late gestation. Net acid excretion was measured by titration, and U_pH was measured by a glass-electrode pH meter (reference method), Multistix-SG urine dipsticks (Siemens Medical Solutions Inc., Ann Arbor, MI), and Hydrion pH paper (Micro Essential Laboratory Inc., Brooklyn, NY). Diagnostic performance was evaluated using Spearman correlation coefficient (r_s), Bland-Altman plots, and logistic regression. Urine pH measured by urine dipstick (r_s = 0.94) and pH paper (r_s = 0.96) were strongly associated with U_pH. Method-comparison studies indicated that the urine dipstick measured an average of 0.28 pH units higher, and pH paper 0.10 pH units lower, than U_pH. Urine [Ca] was more strongly associated with U_pH (r_s = -0.65) than NAE (r_s = 0.52). Goals for controlling periparturient hypocalcemia under the study conditions were U_pH <6.22 and <6.11, based on achieving urine [Ca] ≥5 mmol/L and estimated urinary Ca excretion ≥4 g/d, respectively. Urine pH was as accurate at predicting urine [Ca] as NAE when U_pH >6.11. We conclude that pH paper is an accurate, practical, and low-cost cow-side test for measuring U_pH and provides a clinically useful estimate of urine [Ca].

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.

Evaluation of the analytical performance of a portable ion-selective electrode meter for measuring whole-blood, plasma, milk, abomasal-fluid, and urine sodium concentrations in cattle

A portable ion-selective electrode (ISE) meter (LAQUAtwin B-722; Horiba Instruments Inc., Irvine, CA) is available for measuring the sodium ion concentration ([Na]) in biological fluids. The objective of this study was to characterize the analytical performance of the ISE meter in measuring [Na] in whole-blood, plasma, milk, abomasal fluid, and urine samples from cattle. Method comparison studies were performed using whole-blood and plasma samples from 106 sick calves and 11 sick cows admitted to a veterinary teaching hospital, 80 milk and 206 urine samples from 16 lactating Holstein-Friesian cows with experimentally induced free water, electrolyte, and acid-base imbalances, and 67 abomasal fluid samples from 7 healthy male Holstein-Friesian calves fed fresh milk with or without an oral electrolyte solution. Deming regression and Bland-Altman plots were used to determine the accuracy of the meter against reference methods. The meter used in direct mode on undiluted samples measured whole-blood [Na] 9.7 mmol/L (7.3%) lower than a direct ISE reference method and plasma [Na] 16.7 mmol/L (12.7%) lower than an indirect ISE reference method. The meter run in direct mode measured milk [Na] 3.1 mmol/L lower and abomasal fluid [Na] 9.0% lower than indirect ISE reference methods. The meter run in indirect mode on diluted samples accurately measured urine [Na] compared with an indirect ISE reference method. We conclude that, after adjustment for the bias determined from Bland-Altman plots, the LAQUAtwin ISE meter provides a clinically useful and low-cost cow-side instrument for measuring [Na] in whole blood, plasma, milk, and abomasal fluid.

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 (U_SG‐R) or Multistix‐SG urine reagent dipstick (U_SG‐D), urine electrical conductivity using an OAKTON Con 6 conductivity handheld meter (U_EC), urine color (U_Color) using a custom‐designed 8‐point color chart, and urine creatinine concentration (U_Creat) 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 (U_Osm, reference method), U_SG‐R, U_SG‐D, U_EC, U_Color, and U_Creat 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 (U_Osm ≥800 mOsm/kg). P < .05 was considered significant.

Results

The best performing test for diagnosing hypohydration was U_SG‐R (AUC = 0.90) at an optimal cut point ≥1.030. The second‐best performing test was U_EC (AUC = 0.82) at a cut point of ≥23.7 mS/cm, followed by U_Creat (AUC = 0.76) at a cut point of ≥95.3 mg/dL, and U_Color (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

U_SG‐R and U_EC 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.

Changes in skeletal muscle thickness and echogenicity and plasma creatinine concentration as indicators of protein and intramuscular fat mobilization in periparturient dairy cows

High-producing dairy cows experience a state of negative energy balance in the periparturient period that is partially addressed by increasing the rate of fat and protein mobilization. Previous studies have focused on the rate of fat mobilization, and consequently the rate of protein mobilization has not been well characterized. The objective of this study was therefore to determine the change in indicators of muscle mass during early lactation using ultrasonographic measurement of muscle thickness and changes in plasma creatinine concentration. The maximum thickness of the gluteus medius and longissimus dorsi muscles of 106 Holstein cows (34 primiparous, 72 multiparous) was determined ultrasonographically on d -3, 0, 3, 7, 14, 21, and 28 relative to the day of parturition. Plasma creatinine concentration was measured periodically during the same period. Mixed models analysis and Passing-Bablok regression were used to analyze the data. Gluteus medius thickness, longissimus dorsi loin thickness (LDLT), and longissimus dorsi thoracic thickness (LDTT) were decreased at 28 d postpartum compared with d 3 antepartum. Plasma creatinine concentration was weakly associated with gluteus medius thickness, LDLT, and LDTT (Spearman's rho = 0.31, 0.39, and 0.32, respectively). Plasma creatinine concentration in primiparous and multiparous cows at 28 d postpartum decreased by 0.24 and 0.30 mg/dL, respectively, compared with values 3 d antepartum. We concluded that ultrasonographic measurement of LDLT and LDTT and change in plasma creatinine concentration may provide practical methods for monitoring the rate of protein mobilization in periparturient dairy cows. Ultrasonographic examination of LDLT and LDTT therefore complements ultrasonographic measurement of backfat thickness and may be useful in the evaluation of energy reserve mobilization in periparturient dairy cows.

Ability of milk pH to predict subclinical mastitis and intramammary infection in quarters from lactating dairy cattle

Milk pH is increased in lactating dairy cattle with subclinical mastitis (SCM) and intramammary infection (IMI). We hypothesized that milk pH testing provides an accurate, low-cost, and practical on-farm method for diagnosing SCM and IMI. The main objective was to evaluate the clinical utility of measuring milk pH using 3 tests of increasing pH resolution: Multistix 10 SG Reagent Strips for Urinalysis (Multistix strips, Bayer HealthCare Inc., Elkhart, IN), pH Hydrion paper (Microessential Laboratory, Brooklyn, NY), and Piccolo plus pH meter (Hanna Instruments, Woonsocket, RI), for diagnosing SCM and IMI in dairy cattle. Quarter foremilk samples were collected from 115 dairy cows at dry off and 92 fresh cows within 4 to 7 d postcalving. Quarter somatic cell count (SCC) was measured using a DeLaval cell counter (DeLaval, Tumba, Sweden), with SCM defined as SCC >200,000 cells/mL and IMI defined as SCC >100,000 cells/mL and the presence of microorganisms at ≥10 cfu/mL of milk. Milk pH was measured at 37°C using the 3 test methods. The Hydrion pH paper performed poorly in diagnosing SCM and IMI. Receiver operating curve analysis provided optimal pH cutpoints for diagnosing SCM for the pH meter (dry off, ≥6.67; freshening, ≥6.52) and Multistix strips (dry off and freshening, ≥7.0). Test performance of the pH meter and Multistix strips was poor to fair based on area under the receiver operating curve, sensitivity, specificity, positive likelihood ratio, and kappa coefficient. The pH meter and Multistix strips performed poorly in diagnosing IMI at dry off and freshening. We concluded that milk pH does not provide a clinically useful method for diagnosing SCM or IMI in dairy cattle.

Clinical Utility of Plasma Fructosamine Concentration as a Hypoglycemic Biomarker during Early Lactation in Dairy Cattle

Background

Plasma fructosamine concentration ([FRA]) is a widely used long term hyperglycemic biomarker in humans and dogs, but its clinical usefulness as a hypoglycemic biomarker in dairy cattle is uncertain.

Objectives

To evaluate the relationship between plasma [FRA] and glucose concentration ([gluc]) as well as indices of energy balance during early lactation in dairy cattle, and to characterize the influence of plasma total protein concentration ([TP]) and albumin concentration ([albumin]) on [FRA].

Animals

Convenience sample comprising 103 periparturient Holstein–Friesian cattle.

Methods

Plasma [gluc], [TP], [albumin], and other clinicopathologic indices of energy status were determined periodically from Day 4 postpartum. Body condition score (BCS) was assessed, and backfat thickness (BFT) and longissimus dorsi muscle thickness (LDT) were measured ultrasonographically. Plasma [FRA] was measured at approximately 28 days postpartum. Associations between plasma [FRA] and study variables were evaluated using Spearman's rho and stepwise forward linear regression. Statistical significance was declared at P < 0.05.

Results

A positive association was detected between plasma [FRA] and mean plasma [gluc] from Days 4–28 postpartum (r_s = +0.36, P < 0.001), and between plasma [FRA] and LDT (r_s = +0.28, P = 0.007), BCS (r_s = +0.23, P = 0.029), and BFT (r_s = +0.21, P = 0.043). Multivariable regression identified a positive association between plasma [FRA] and mean plasma [gluc] and [albumin] from Days 4–28 postpartum. Correcting plasma [FRA] for [albumin] improved the association (r_s = +0.46, P < 0.001) between plasma [FRA] and mean plasma [gluc].

Conclusions and Clinical Importance

Plasma [FRA] does not provide a clinically useful method for quantifying the magnitude of hypoglycemia or negative energy balance in dairy cows during early lactation.

Evaluation and Comparison of 2 On-Farm Tests for Estimating Somatic Cell Count in Quarter Milk Samples from Lactating Dairy Cattle

Background

The somatic cell count (SCC) is commonly used to monitor udder health and diagnose subclinical intramammary infection (IMI) in dairy cattle.

Hypothesis

The Somaticell test (ST)2 and California mastitis test (CMT) are clinically useful cow‐side tests for diagnosing subclinical IMI.

Animals

One hundred and eleven dairy cows at dry‐off and 92 cows within 4–7 days postcalving.

Methods

Quarter foremilk samples were obtained and analyzed with a DeLaval cell counter (DCC, reference method),1ST, and CMT. The ST was run in a simulated cow‐side manner using milk at 37°C instead of 0–8°C as recommended by the manufacturer. Test performance for diagnosing IMI (DCC SCC >200,000 cells/mL) was evaluated by calculating the area under the receiver operating characteristic curve (AUC) and the kappa coefficient (κ) at the optimal cut‐point for each test. The effect of milk/reagent temperature also was evaluated.

Results

Compared to the reference method, the ST run in a simulated cow‐side manner had an AUC = 0.68 and κ = 0.24 at dry‐off, and AUC = 0.74 and κ = 0.40 in fresh cows. The CMT performed much better than the ST in diagnosing subclinical IMI with AUC = 0.88 and κ = 0.77 at dry‐off, and AUC = 0.87 and κ = 0.76 in fresh cows. The measured ST value decreased with increasing temperature of the milk/reagent mixture.

Conclusions/Clinical Importance

The ST is optimized for use on milk at 0–8°C and is therefore designed for on‐farm use on refrigerated milk samples. The ST is not suited for use as a cow‐side screening test for IMI because the milk temperature exceeds the recommended range for the test.

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.

Evaluation of an Electrochemical Point-of-Care Meter for Measuring Glucose Concentration in Blood from Periparturient Dairy Cattle

BACKGROUND

The Precision Xtra(®) meter is a promising low cost electrochemical point-of-care unit for measuring blood glucose concentration ([gluc]) in cattle blood. The meter uses an algorithm that assumes the intra-erythrocyte [gluc] equals the plasma [gluc] on a molal basis, and that the hematocrit is similar in humans and cattle.

OBJECTIVES

The primary objective was to determine the accuracy of the meter for measuring plasma [gluc] in dairy cattle. Secondary objectives were to characterize the influence of hematocrit and sample temperature on the measured value for [gluc].

ANIMALS

A total of 106 periparturient Holstein-Friesian cattle.

METHODS

Blood and plasma samples (1,109) were obtained and Deming regression and Bland-Altman plots were used to determine the accuracy of the meter against the reference method (plasma hexokinase assay). Multivariable regression and linear regression were used to determine the effect of hematocrit and sample temperature on the plasma [gluc] measured by the meter.

RESULTS

Intra-erythrocyte [gluc] was 18% of plasma [gluc] on a molar basis. Sample temperature had a significant linear effect on plasma [gluc] as measured by the meter for 3/5 plasma samples when measured [gluc] > 160 mg/dL.

CONCLUSIONS AND CLINICAL IMPORTANCE

The meter utilizes an algorithm that is optimized for human blood and is inaccurate when applied to bovine blood. Until a cattle-specific algorithm is developed, we recommend using plasma as the analyte instead of blood and calculating plasma [gluc] using the equation: [gluc] = 0.66 × [gluc]p-meter + 15, where [gluc]p-meter is the value reported by the meter. If blood is measured, then we recommend using the equation: [gluc] = 0.90 × [gluc]b-meter + 15.

Induction of resistance in tomato plants against tomato mosaic tobamovirus using beneficial microbial isolates

The possibility of making use of the phenome non of Systemic Acquired Resistance (SAR) to control viruses achieved by the soaking treatment of tomato seeds cv. Castl Rock with three growth forms to Bacillus circulans, Pseudomonas fluorescens 2 and Trichoderma harzianum against Tomato mosaic tobamovirus (ToMV) infection. All the application forms of beneficial biotic inducers were reduced the mean number of ToMV local lesions on Datura metel. P. fluorescens 2 was found to be the best treatment in three forms on reduction of local lesion number 42.2, 32.7 and 38.1 of microbial liquid culture, microbial cells or spores and microbial culture filtrate forms, respectively, while the highest mean numbers of local lesions were 51.5, 61.7 and 73.5 of microbial liquid culture, microbial cells or spores and microbial culture filtrate, respectively for T. harzianum. The microbial culture filtrate form was more effective than other microbial forms to reduce mean number of ToMV local lesions to B. circulans, P. fluorescens 2 and T. harzianum isolates, 40.7, 32.1 and 51.5, respectively. The individual microbial isolates on all three microbial forms able to vary ToMV local lesions similarity (homologous or heterologous) and morphology (size center and surrounded with halo or without halo) compared with TMV mother strain.