The value of the biomarkers cathelicidin, milk amyloid A, and haptoglobin to diagnose and classify clinical and subclinical mastitis

Timely and objective diagnosis and classification of mastitis is crucial to ensure adequate management and therapeutic decisions. Analyzing specific biomarkers in milk could be advantageous compared with subjective or semiquantitative criteria, such as palpation of the udder in clinical mastitis cases or evaluation of somatic cell count using cow side tests (e.g., California Mastitis Test) in subclinical mastitis quarters. The objective of this study was to investigate the diagnostic value of 3 biomarkers; cathelicidin, milk amyloid A, and haptoglobin for the diagnosis of subclinical and clinical mastitis. Furthermore, the suitability of these biomarkers to differentiate between mild, moderate, and severe clinical mastitis and the influence of different pathogens on biomarker levels was tested. A total of 67 healthy cows, 119 cows with subclinical mastitis, and 212 cows with clinical mastitis were enrolled in the study. Although cathelicidin, haptoglobin, and milk amyloid A were measured in all samples from healthy cows and those with subclinical mastitis, haptoglobin, and cathelicidin results were only available from 121 out of 212 cows with clinical mastitis. Milk amyloid A was measured in all samples. In cows with clinical mastitis, the mastitic quarter and a second healthy quarter serving as a healthy in-cow control quarter were sampled. It was possible to differentiate between healthy quarters, quarters with subclinical mastitis, and quarters with clinical mastitis using all 3 biomarkers. Concerning cathelicidin, thresholds were 0.000 [sensitivity (Se) = 0.83, specificity (Sp) = 0.97] and 0.053 (Se = 0.98, Sp = 0.99) for normalized optical density at 450 nm (NOD450) for differentiating between healthy quarters and quarters with subclinical or clinical mastitis, respectively. Thresholds of 1.28 µg/mL (Se = 0.65, Sp = 0.76) and 1.81 µg/mL (Se = 0.77, Sp = 0.83) for milk amyloid A and 3.65 µg/mL (Se = 0.92, Sp = 0.94) and 5.40 µg/mL mL (Se = 0.96, Sp = 0.99) for haptoglobin were calculated, respectively. Healthy in-cow control quarters from cows with CM showed elevated milk amyloid A and haptoglobin levels compared with healthy quarters from healthy cows. Only the level of milk amyloid A was higher in severe clinical mastitis cases compared with mild ones. In contrast to clinical mastitis, cathelicidin and haptoglobin in subclinical mastitis quarters were significantly influenced by different bacteriological results. The measurement of cathelicidin, milk amyloid A, and haptoglobin in milk proved to be a reliable method to detect quarters with subclinical or clinical mastitis.

Short communication: Diagnosis and classification of clinical and subclinical mastitis utilizing a dynamometer and a handheld infrared thermometer

In times of ongoing automatization of dairy cow husbandry, objective and reliable tools for mastitis diagnostic are highly in demand. The objective of this study was to investigate the diagnostic value of a handheld dynamometer and an infrared thermometer to diagnose and score clinical and subclinical mastitis and to compare those values with results from palpation of the udder tissue. Overall, 218 cows with clinical mastitis (i.e., 46 mild, 106 moderate, and 66 severe cases), 142 with subclinical mastitis, and 68 healthy cows were enrolled. Our data provide evidence that the dynamometer is an accurate diagnostic tool to differentiate between healthy udder quarters, and those with subclinical and clinical mastitis. Furthermore, the severity score of clinical mastitis can be estimated by dynamometer. The firmness threshold for the detection of clinical mastitis was 1.002 kg. Using a threshold of 1.175 kg in clinical mastitis quarters, it was possible to differentiate between negative and positive bacteriological results. A differentiation between healthy and clinical mastitis quarters with the infrared thermometer was possible, albeit udder surface temperatures were highly influenced by ambient temperature. Udder surface temperature increased by 0.15 to 0.18°C for each degree of ambient temperature. In conclusion, the utility of an infrared thermometer to estimate the udder health status of dairy cows is limited, whereas the handheld dynamometer appeared to be an accurate and objective method.

Quantitative analysis of cefquinome considering different matrix compositions of bovine colostrum and raw milk

A robust liquid chromatography-tandem mass spectrometry method was developed and comprehensively validated for the quantification of cefquinome considering the changing matrix composition from bovine colostrum to raw milk. Sample preparation consisted of addition of isotopically labeled cefquinome internal standard prior to protein precipitation of 2 g colostrum or milk followed by solid-phase extraction. A wide concentration range from 1 to 5000 ng cefquinome per gram of colostrum or milk was quantified using a 3200 QTRAP tandem mass spectrometer in positive ionization mode with electrospray ionization. Validation was performed according to the European Commission Decision 2002/657/EC guidelines. Matrix-comprehensive in-house validation included analytical limits CC_α and CC_β, recovery, precision and calibration curves with prediction intervals, storage conditions, and evaluation of robustness based on factorial effect analysis. The detection limit was 0.2 ng cefquinome per gram of colostrum or milk. Recovery was between 98.4 and 99.4% for cefquinome concentrations from 4 to 240 ng/g. None of the investigated validation factors (matrix, storage of extracts, lot of SPE cartridges, and operators) exerted an influence higher than ± 3.2%, indicating that these factors make relatively low contributions to the respective combined measurement uncertainties. The comprehensively validated method enables routine residue control purposes and to monitor the pharmacokinetics of cefquinome in bovine colostrum and raw milk. In particular, residue depletion curves of cefquinome from high concentrations in first milking after treatment to concentrations far below the maximum residue limit can be measured.

Residue concentration of cefquinome after intramammary dry cow therapy and short dry periods

Short dry periods and their effects on milk production, reproductive performance, as well as cow and udder health have been widely studied. A dearth of information is available about the consequences of short dry periods on the residue concentrations of dry cow antibiotics in milk after calving. The objective of our study was to determine the residue concentration of a dry cow antibiotic in milk after short dry periods during the colostrum period and early lactation. Quarters of 19 dry cows were treated with an intramammary (IMM) dry cow antibiotic containing 150 mg of cefquinome on d 21, 14, and 7 before calculated calving date. One quarter of each cow did not receive treatment and served as negative control. After calving, quarter foremilk samples were collected twice daily until 21 d and once daily until 36 d after IMM dry cow treatment (i.e., end of withdrawal period). A total of 588 foremilk samples from odd milking numbers were chosen for the determination of the residue concentration of cefquinome using HPLC-tandem mass spectrometry until the residue concentration fell below the limit of quantification (1 ng/g), which occurred at the latest in milking number 37. The dry period length of the treated quarters was categorized in 3 dry period groups ranging from 1 to 7 d (4.8 ± 2.4), 8 to 14 d (11.5 ± 2.3), and 15 to 26 d (19.5 ± 3.3; ±SEM), in dry period group 1, 2, and 3, respectively. In dry period group 1, the cefquinome concentration increased after calving until the third milking and decreased considerably until the fifth milking. In dry period group 2, the cefquinome concentration peaked at the second milking and decreased considerably until the fifth milking as well. There was no increase in cefquinome after calving in dry period group 3. Up to the 37th milking, the cefquinome concentration was higher in dry period group 1 than in dry period group 2 and 3. On average, 31.3 ± 1.2, 19.0 ± 1.1, and 6.7 ± 0.8 milkings and 19.4 ± 0.4, 20.6 ± 0.5, and 24.1 ± 0.7 d after treatment were necessary for the concentration of cefquinome to fall below the maximum residue limit (MRL) in dry period group 1, 2, and 3, respectively. These results indicate that shorter dry periods lead initially to higher cefquinome residues in milk. The residue concentration after experimental short dry periods still falls below the MRL within the recommended withdrawal period for milk of 36 d after IMM dry cow treatment. For the sake of food safety and economics, these short dry periods should not be used in the dry cow management, as they lead up to a maximum of 31.3 ± 1.2 milkings and 19.4 ± 0.4 d after treatment with cefquinome residues above the MRL. Therefore, a considerable number of milkings have to be discarded due to long withdrawal periods after calving.

A survey of drying-off practices on commercial dairy farms in northern Germany and a comparison to science-based recommendations

While dry cow management is important for health, milk production and fertility information on drying-off procedures implemented on commercial dairy farms is lacking. Current drying-off management procedures on commercial dairy farms were evaluated using a questionnaire and results compared with recommendations given in the current literature. Ninety-one participants from a farmer education event completed the survey. On average, cows were dried off seven weeks before calving. Only 9.9 per cent of the farms had a dry period length of five weeks or less. A continuous milking regime without dry period was not established on any farm participating in the survey. Most farmers performed an abrupt drying-off (73.0 per cent). Only 11.8 and 15.0 per cent attempted to lower milk yield prior to drying-off by reducing milking frequencies and adjusting feed rations, respectively. While a blanket antibiotic dry cow treatment was carried out on 79.6 per cent of the farms, selective dry cow treatment was not mentioned by any farmer. Although 77.4 per cent preponed the drying-off date in low-yielding cows, an altered drying-off procedure in high-yielding dairy cows was rare (9.7 per cent). This survey provides an insight into drying-off procedures currently applied on commercial dairy farms in northern Germany.

Measurement of fecal glucocorticoid metabolites and evaluation of udder characteristics to estimate stress after sudden dry-off in dairy cows with different milk yields

Sudden dry-off is an established management practice in the dairy industry. But milk yield has been increasing continuously during the last decades. There is no information whether the dry-off procedure, which often results in swollen and firm udders, causes stress, particularly in high-producing dairy cows. Therefore, we evaluated the effect of a sudden dry-off on extramammary udder pressure and the concentration of fecal glucocorticoid metabolites (i.e., 11,17-dioxoandrostane, 11,17-DOA) as an indirect stress parameter. Measurements were carried out within the last week before dry-off and until 9d after dry-off considering 3 groups of milk yield (i.e., low: <15 kg/d, medium: 15-20 kg/d, and high: >20 kg/d). Udder pressure increased in all yield groups after dry-off, peaked at d 2 after dry-off and decreased afterwards. Pressures were highest in high-yielding cows and lowest in low-yielding cows. But only in high-yielding cows was udder pressure after dry-off higher than before dry-off. Baseline 11,17-DOA concentrations depended on milk yield. They were highest in low-yielding (121.7 ± 33.3 ng/g) and lowest in high-yielding cows (71.1 ± 30.0 ng/g). After dry-off, 11,17-DOA increased in all yield groups and peaked at d 3. Whereas in medium- and high-yielding cows 11,17-DOA levels differed significantly from their respective baseline during the whole 9-d measuring period, low-yielding cows showed elevated 11,17-DOA levels only on d 3 after dry-off. However, especially the increase in 11,17-DOA after dry-off between the 3 yield groups was considerably different. Mean 11,17-DOA increase from baseline to d 3 was highest in high-yielding cows (129.1%) and considerably lower in low-yielding cows (40.1%). The highest fecal 11,17-DOA concentrations were measured on d 3 after dry-off, indicating that the stress was most intense on d 2, which is due to an 18-h time lag; at about the same time, udder pressure peaked. Our results showed a negligible effect of a sudden dry-off on low-yielding cows. High-yielding cows, however, faced high extramammary pressures and increased glucocorticoid production. Considering animal welfare aspects, a review of the current dry-off strategies might be warranted.