Publication Database

Investigation of cefquinome residues in milk after antibiotic dry cow treatment and risk factors for milk leakage in dairy cows (2019)

Art

Hochschulschrift

Autor

Bachmann, Joana (WE 19)

Quelle

Berlin, 2019 — 81 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/24469

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Abstract / Zusammenfassung

The overall objective of this thesis was to examine the effect of the milk fraction and short dry periods on the residue concentration of cefquinome in milk after antibiotic dry cow treatment and to investigate risk factors for milk leakage in dairy cows before and after dry-off. The first study investigated the residue concentration of an antibiotic dry cow treatment containing cefquinome considering the milk composition in two different milk fractions and evaluated the test characteristic of two commercially available screening tests in relationship to the analyzed milk fraction and the milk composition. Thirteen dry dairy cows were enrolled in this study. One quarter each per cow was treated with an intramammary (IMM) dry cow antibiotic containing cefquinome on day 21, 14 and 7 before calculated calving date. Milk samples were collected from each quarter before (foremilk samples) and after milking (stripping samples) twice daily during the first 10 d postpartum. All samples were tested for antibiotic residues with the lateral flow test Milchtest BL and the microbial inhibitor test Delvotest BR Brilliant Plates and were analyzed for milk composition. The residue concentration of cefquinome was determined using high performance liquid chromatography-tandem mass spectrometry. The logarithm of cefquinome concentration was higher in foremilk (1.495 ± 0.080) compared to stripping samples (1.377 ± 0.078; P = 0.001). Foremilk samples had 38.4 times higher odds to be evaluable in the Milchtest BL than tests of stripping samples. High protein content increased and high logarithm of SCC tended to increase the odds of not evaluable results in the Milchtest BL. Milk samples with higher protein content were more likely and with a lower urea content tended to be more likely to have a false positive result in the Delvotest BR Brilliant Plates. Overall, the results of this study indicate that foremilk should be the recommended milk fraction to be tested for residues of cefquinome and to be used in lateral flow tests to avoid test failure. Furthermore, high protein content should be considered as a cause of test failure and false positive results when milk during the first 10 d postpartum is tested for antibiotic residues using lateral flow or microbial inhibitor tests. The optimum dry period length is still an active field of research. Several studies in the last years have detected advantages of short dry periods on milk production, reproductive performance and energy balance during early lactation. The impact of short dry periods on the residue concentration of dry cow antibiotics in milk after calving has not yet been investigated. The objective of the second study was to investigate the residue concentration of a dry cow antibiotic containing cefquinome during the colostrum period and early lactation in quarter foremilk samples after short dry periods. Overall, 19 dry dairy cows were enrolled in the study. In order to achieve antibiotic concentrations representative for short dry periods three quarters of each cow were treated with an IMM dry cow antibiotic containing 150 mg of cefquinome on day 21, 14 and 7 before calculated calving date (treated quarters). One quarter of each cow was not treated (control quarter). Foremilk samples from each quarter were collected twice daily until 21 days and once daily until 36 days after IMM dry cow treatment (end of withdrawal period), respectively. Treated quarters were allocated to 1 out of 3 groups based on the dry period length after the dry cow treatment (dry period group 1: 1 to 7 days, dry period group 2: 8 to 14 days, dry period group 3: more than 14 days). The cefquinome concentration up to the 37th milking was higher in dry period group 1 (581.40 ± 90.71 ng/g) than in dry period group 2 (115.41 ± 15.38 ng/g; P = 0.001) and 3 (21.28 ± 6.00 ng/g; P < 0.001), respectively. On average 31.3 ± 1.2, 19.0 ± 1.1 and 6.7 ± 0.8 milkings (P < 0.001) and 19.4 ± 0.4, 20.6 ± 0.5 and 24.1 ± 0.7 days (P < 0.05) after treatment were necessary for the concentration of cefquinome to fall below the maximum residue level (MRL) in dry period group 1, 2 and 3. The results of this study indicate that shorter dry periods lead initially to higher cefquinome residues in milk after calving, but due to the more rapid depletion of cefquinome after calving fewer days after treatment are necessary for the cefquinome concentration to fall below the MRL. The residue concentration after short dry periods still fell below the MRL within the recommended withdrawal period for milk of 36 days 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 to a considerable number of milkings that have to be discarded, due to long withdrawal periods after calving. The occurrence of milk leakage has been reported in approximately 30% of cows after dry-off, with the highest likelihood of the occurrence 2 days after dry-off and in approximately 5.3% of lactating cows while entering the milking parlor. Risk factors for milk leakage on cow level have rarely been investigated. A laboratory model was developed to determine risk factors for milk leakage under controlled conditions. The laboratory model, composed of two capillary viscometers, was used to measure the efflux time and calculate the dynamic viscosity of milk samples. Parameters which lead to a decreased efflux time and dynamic viscosity of the milk samples were considered to increase the likelihood of milk leakage in the field. Overall, the objective of the third, in vitro study was to determine the effects of the teat canal diameter, IMM pressure, milk temperature, milk composition, dry-off and IMM dry cow therapy on efflux time and dynamic viscosity of quarter foremilk samples and thereby evaluate plausible risk factors for milk leakage in dairy cows before and after dry-off. Quarter foremilk samples from 6 dairy cows were collected each on the day of dry-off and 2 days after dry-off with and without antibiotic dry cow therapy. The efflux time decreased as the hydrostatic pressure and milk sample temperature increased (P < 0.001). The dynamic viscosity slightly increased as the hydrostatic pressure increased, but decreased as the milk sample temperature increased (P < 0.001). The efflux time and dynamic viscosity increased as the fat and protein content increased (P < 0.001). In samples collected after dry-off, the efflux time and dynamic viscosity were higher than in samples before dry-off (P < 0.001). Antibiotic dry cow therapy had no effect on the efflux time (P = 0.485). Considering decreased efflux time and decreased dynamic viscosity as a measure for higher likelihood of the occurrence of milk leakage, wider teat canal diameter, higher IMM pressure, higher milk temperature and lower concentrations of fat and protein could be reported as plausible risk factors for milk leakage in dairy cows.