Factors associated with the risk of antibiotic residues and intramammary pathogen presence in milk from heifers administered prepartum intramammary antibiotic therapy

Heifers (n=136) from 5 herds were treated with a commercially available beta-lactam intramammary (IMM) antibiotic preparation containing cephapirin sodium at 10-21 d prior to anticipated parturition to evaluate the risk of antibiotic residues occurring in milk postpartum and to determine factors associated with antibiotic residues and IMM pathogen presence in milk postpartum. Mammary secretions collected from quarters before antibiotic administration and during weeks 1, 2 and 3 postpartum were analyzed for mastitis pathogens. Composite milk was collected at milkings 3, 6 and 10 postpartum and analyzed for beta-lactam residues using a microbial inhibition antibiotic residue screening test. Antibiotic residues were confirmed with beta-lactamase treatment and re-tested for residues. Residues were detected in 28.0, 8.82 and 3.68% of milk samples obtained at the third, sixth, and tenth milking postpartum, respectively. Increases in interval between prepartum antibiotic therapy and parturition and an increase in the postpartum interval to sampling were associated with a decrease in risk of antibiotic residues. The presence of antibiotic residues in milk at the third milking was associated with a reduced risk for IMM pathogen prevalence in the first 21 d postpartum. Lower somatic cell counts, an increase in mean milk yield over 200 days in milk and a reduction in IMM pathogen prevalence were associated with the presence of an antibiotic in milk postpartum. Screening milk for antibiotic residues in milk postpartum following prepartum antibiotic therapy in heifers is recommended to reduce the risk for antibiotic residue contamination of milk.     

Approaches to modeling intramammary infections in dairy cattle

In this paper, three approaches (Markov processes, discrete-event simulation, and differential equations) to modeling intramammary infections (IMI; focusing on the dynamic changes between uninfected, subclinical, and clinical udder-health states) are described. The objectives were to describe the various approaches to modeling intramammary infections, determine if simulations of the examples of the three approaches yield stable prevalences, and discuss the approaches' limitations. The literature review showed that there is no agreement on the proportion of animals that change health states. The approach of discrete-event simulation modeling included the most cow-level risk factors and udder-health states (hence, was judged to replicated best the dynamics of the infection process) and yielded stable prevalences for all udder-health states. However, there remain parts of the dynamics that need further research. These include the pathogen-specific probabilities and times of occurrence for: regression of clinical IMI to subclinical IMI, flare-up of subclinical IMI to clinical IMI, and incidence of subclinical IMI. Also, the assumption in all current approaches of homogenous mixing is violated because the primary contact structure for contagious pathogens during milking is either between cows through residual infectious milk in the milking machine or within a cow by vacuum fluctuations or teat-cup liner slips. Better contact structures should be incorporated so that the effects of control strategies can be better-estimated. Moreover, the three modeling approaches discussed assumed that all non-infected quarters are susceptible to infection—which might be denied by work in genetic resistance.     

Antibiotic residues in goats milk following intramammary treatment

Two lactational intramammary antibiotic preparations (cloxacillin and oxytetracycline) were each used to treat eight goats by intramammary infusion in one half. The rate of release of the antibiotics was monitored by a diffusion assay based on the sensitive organism Bacillus stearothermophilus var. calidolactis. Cloxacillin was still detectable 156 hours after the final treatment while oxytetracycline was undetectable 108 hours following treatment. A small but significant amount of antibiotic was translocated between treated and untreated halves of the udder in both cases.     

The relationship between milk yield and cystic ovarian disease in cattle

Studies were conducted to understand the relationship, if any, between the amount and pattern of milk yield and the occurrence of cystic ovarian disease (COD) in dairy cattle. More than 70 cows with cysts were compared with herd mates of similar lactation number. Total milk yield in lactations when cysts occurred and in the preceding lactations were not different from the corresponding lactations in control cows. Patterns of monthly milk yield did not differ between the two groups of cows. However, weekly analysis in early lactation revealed differences. Both groups of cows achieved peak yields at a similar time (5.4 +/- 1.2 vs 5.7 +/- 1.9 weeks post partum in normal vs cows with COD). However, owing to an early decline in yield of cows with COD, their duration of peak yield was significantly shorter (P less than 0.05) than in the control cows (3.2 +/- 2.2 vs 5.6 +/- 2.4 weeks). Both the attainment and the decline of peak yield occurred 5.6 (range = 2-15) weeks before the cysts were diagnosed. It is concluded that COD is not particularly a disease of higher yielding cows and that COD has no discernible effect on the milk yield or its pattern. It is speculated, however, that some cows in early lactation, while trying to meet the requirements of sustained peak milk production, are more susceptible to minor environmental changes (such as new social interactions, or changes in diet). These events may lead to a drop in milk production and disruption of events controlling normal ovulation, resulting in the formation of ovarian cysts.     

Antibiotic residues in goats milk following intramammary treatment

Two lactational intramammary antibiotic preparations (cloxacillin and oxytetracycline) were each used to treat eight goatsby intramammary infusion in one half. The rate of release of the antibiotics was monitored by a diffusion assay based on the sensitive organism Bacillus stearothermophilus var. calidolactis. Cloxacillin was still detectable 156 hours afterthe final treatment while oxytetracycline was undetectable 108 hours following treatment. A small but significant amount of antibiotic was translocated between treated and untreated halves of the udder in both cases.     

硫酸头孢喹肟乳房注入剂在牛奶中的药代动力学研究

选取8头健康黑白花奶牛,每头牛随机选择两个乳区,以每个乳区1支(8g:75mg/支)的剂量进行单次乳房灌注给予硫酸头孢喹肟乳房注入剂。采用超高效液相色谱-串联质谱(UPLC-MS/MS)方法检测乳中头孢喹肟的浓度。结果表明,该制剂采用单次乳房灌注给药后,乳中药物能发挥较好抑菌效果的时间约为24～30小时,因此建议该制剂治疗奶牛临床型乳房炎的用药方案为：1支(8g:75mg)/(乳区.次),每天给药1次。     

Disposition kinetics of lactoferrin in milk after intramammary administration

Disposition kinetics of lactoferrin (Lf) purified from cheese whey was studied in the milk of Finnish Ayrshire cows after intramammary administration of 1 g of Lf into one udder quarter. Intramammary administration of 1 g of Lf increased Lf concentration in milk for several hours. Mean elimination half-life of Lf was 2.2 h and a mean maximum concentration of 6.3 g/L was reached between 1 and 4 h. After 8 h of administration, Lf concentrations in milk decreased to almost the same level as before the infusion. Forty-eight hours postinfusion, the mean Lf concentration was again higher than in the milk samples taken before the infusion of Lf, being on average 1.5 g/L. Lactoferrin caused some local tissue irritation in the udder quarter. Severity of the irritation reactions varied between cows. The udder quarters of primiparous cows reacted faster than those of multiparous cows, but irritation reactions decreased more rapidly in the older cows than in primiparous cows. The cows had no general signs such as fever or anorexia. The somatic cell count returned to baseline level 4 days after the administration.     

Efficacy of using an internal teat sealer to prevent new intramammary infections in nonlactating dairy cattle

OBJECTIVE: To determine whether insertion of an internal teat sealer (ITS) at the end of lactation would prevent development of new intramammary infections (IMIs) during the nonlactating period. DESIGN: Controlled clinical trial. ANIMALS: 939 Holstein-Friesian dairy cows from 16 herds. PROCEDURES: Results of bacteriologic culture of milk samples collected 14 days prior to the end of lactation were used to assign cows to groups (group 1 = negative results for all quarters; group 2 = positive results for > or = 1 quarter). Quarters of cows in group 1 were treated with an ITS or a single intramammary dose of cloxacillin; quarters of cows in group 2 were treated with cloxacillin in conjunction with an ITS or with cloxacillin alone. Milk samples were collected at the end of lactation and within 8 days after calving. RESULTS: Regardless of whether the outcome of interest was new IMIs caused by any pathogens, major pathogens, environmental pathogens, or streptococci other than Streptococcus agalactiae, quarters in group 2 treated with both cloxacillin and an ITS were less likely to develop a new IMI than were quarters treated with cloxacillin alone. For cows in group 1, no significant difference in risk of new IMIs was found between treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that for dairy cattle with an IMI late in the lactation period, intramammary administration of cloxacillin at the end of lactation followed by insertion of an ITS enhanced protection against development of new IMIs, compared with use of cloxacillin alone.     

Somatic cell count in milk of selenium-supplemented dairy cows after an intramammary challenge with Staphylococcus aureus

The objective of this study was to evaluate the effect of selenium (Se) supplementation on milk somatic cell count (SCC) in dairy cows. Twelve multiparous Holstein-Friesian cows were fed a diet containing a suboptimal Se concentration (<0.05 ppm, dry basis) starting 2 months before calving. Supplemented cows (n=6) received a single s.c. injection of barium selenate (1 ml/50 kg BW) 45 days prior to calving, whereas control group was kept unsupplemented. Twenty weeks after calving, two mammary quarters (right side) of each cow were challenged with 205,000 cfu/ml of Staphylococcus aureus (strain Newbould 305). Blood was collected bi-weekly until day 150 of lactation for the analysis of blood glutathione peroxidase (GPx1; EC 1.11.1.9) activity. To re-isolate the challenging pathogen and to evaluate SCC, aseptic milk samples were collected daily starting on the day of challenge, and finishing 7 days after inoculation. Unsupplemented cows had a lower activity of GPx1 through the experiment (P<0.001). Natural log SCC (lnSCC) was higher in unsupplemented than Se-supplemented cows (P=0.04), showing evidence of significance after 5 days. Selenium supplementation of dairy cows fed a diet containing a suboptimal Se concentration, resulted in higher blood activity of GPx1, and lower mean lnSCC after an intramammary challenge with Staph. aureus.     

Kappa-casein in milk. An immunochemical investigation of the kappa-casein content in milk from Danish cattle breeds

The ϰ-casein content in milk from the Danish cattle breeds SDM, RDM and Jersey was investigated by means of immunoquantitation in antibody containing agarose gels. The method, which determines the total ϰ-casein complex, is suitable for routine work. The reproducibility of the method was found to be ± 4.1 %.The ϰ-casein concentration, expressed as percentage of the total protein content in milk, was significantly lower in milk from SDM (21.5%) and RDM (21.3%) than in Jersey (23.9%). The investigation showed that the ϰ-casein constitutes a greater part of the protein in milk than previously assumed.The amount of ϰ-casein was positively correlated with the protein content in milk, but there was no relation between the relative ϰ-casein content and the percentage of fat, milk yield and the time after calving.Keyword: kappa-casein, milk, cattle, immunoquantitation     

The mechanism of excretion of drugs into milk from untreated glands after intramammary application

It is often maintained that after intramammary application of penicillin the excretion of penicillin via the untreated glands takes place by direct diffusion from treated to untreated glands (vide Hawkins et al. 1962, Jacobs & Pennings 1969, Rollins et al. 1970). Blobel (1960) mentions the possibilities of both direct diffusion from gland to gland and the excretion via the blood.     

Pharmacokinetics of albendazole administered by an intraruminal pulse release electronic device in cattle

Albendazole was administered to 12 young Charolais cattle, 300 kg bodyweight, using an intraruminal pulse release electronic device. The device released 2 g albendazole three times at 31 day intervals. The kinetic study of two main metabolites of albendazole in all animals at the time of each release showed that on 36 occasions the devices worked at the expected time; the mean kinetic profiles were nearly identical at first, second and third release. A good repeatability was generally also noticed for each animal individually; the bioavailability of the drug did not seem to be different from that obtained after administration of albendazole as an oral drench.     

Pharmacokinetics in sheep and cattle of albendazole administered by an intraruminal slow release capsule

Forty sheep and 40 heifers were dosed with an intraruminal slow release capsule (IRSRC) constructed to deliver albendazole (ABZ) at a low daily dosage for three months. Blood samples were collected at standardised intervals for 110 days and analysed by high performance liquid chromatography for the quantification of the two main metabolites sulphoxide (SO.ABZ) and sulphone (SO2ABZ). The plasma profiles show sustained concentrations of the active metabolite SO.ABZ for 105 days in sheep (m = 0.06 +/- 0.032 micrograms ml-1) and 85 days in cattle (m = 0.10 +/- 0.019 micrograms ml-1). In both species, the proportions of the metabolites were inverted compared to that observed after a single dosage. The bioavailability of ABZ after the administration of the IRSRC compared with a drench was reduced in sheep but increased in cattle. The IRSRC exhibited a preventive and therapeutic effect for at least three months.