Effect of pre-milking teat dipping on clinical mastitis.
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Biomedical subjects
Publications and source records attributed to J M Booth.
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A study was undertaken to compare the prevalence of dental caries and developmental defects of enamel between 3-year-old children who were lifelong residents of fluoridated areas of Huddersfield (1 ppm F) and non-fluoridated Dewsbury (less than 0.3 ppm F). An interview was also conducted with the parents of the children to provide information regarding previous dental experiences. The study populations were identified using the national child health system. The mean dmft was 0.30 in Huddersfield and 0.74 in Dewsbury. The percentage of children who had experienced dental caries and the percentage with carious teeth were significantly lower in the fluoridated area. The Dewsbury children had suffered more toothache. There was a significantly higher number of children in Huddersfield with diffuse enamel defects on their upper and lower first molars. This study has also demonstrated that the national child health system provides a method for obtaining a random sample of pre-school children from the general population, thus avoiding the problems associated with studies using selected populations. Fluoridation in Huddersfield ceased in October 1989 and it is hoped that this decision will be reversed as soon as possible.
In a trial conducted in the south of England in January to February 1989, blood samples were obtained from nine dairy herds with more than 30 cases of clinical mastitis/100 cows and from nine herds with less than 30 cases/100 cows during the previous 12 months. Whole blood glutathione peroxidase (GSHPx) activity and plasma vitamin E concentration were determined for 12 cows in each herd. The mean (+/-sd) values for the herds with the lower incidence of mastitis were 7.57 +/- 1.86 micrograms/ml plasma vitamin E and 23.8 +/- 22.8 U/ml rbc GSHPx activity, compared with 7.74 +/- 1.69 micrograms/ml plasma vitamin E and 20.61 +/- 8.8 U/ml rbc GSHPx activity for the herds with the higher incidence of the disease. These values indicate that the vitamin E levels were generally adequate but that some animals and herds had low GSHPx activities, suggesting that their diets may have contained inadequate selenium. The activities of GSHPx and the vitamin E levels in plasma were not significantly different in the two groups of herds, and no relationship was found between the two nutrients and the incidence of clinical mastitis. However, there was a significant negative correlation between the activity of GSHPx and the bulk milk cell counts in the herds with a low incidence of mastitis suggesting that there was an association between the incidence of subclinical mastitis or inflammation and the selenium status of these herds.
Two field trials were carried out by five experienced veterinary surgeons to evaluate the milk progesterone test as an aid to the differential diagnosis of cystic ovaries in dairy cows. Of 200 cystic cows, 71 per cent were diagnosed clinically as follicular and 29 per cent as luteal cases; 80 per cent of the cases occurred in the six winter months November to April. The progesterone assay indicated that the diagnosis was correct in 84 per cent of the follicular cases but only 54 per cent of the luteal cases. Seventy-four per cent of the confirmed cystic cases responded to treatment within two weeks according to milk progesterone tests and there were no significant treatment differences. Overall, 80 per cent of the cows became pregnant on average 38 days after treatment having received an average of 1.70 inseminations each. Milk yield data in the first trial indicated that the cystic cows were not significantly higher yielders than their herd-mates.
Mastitis in England and Wales has been controlled over the past 20 years while the average size of dairy herds has doubled to 65 cows. The incidence of clinical mastitis has been reduced from approximately 120 to 150 cases per 100 cows to less than 50 cases. The limited data on the prevalence of subclinical mastitis indicate that it has been reduced from over 50 per cent of cows infected to less than half this level. The application of the major mastitis control measures on the farm has doubled over the period 1973 to 1983 and had reached 66 to 90 per cent for individual measures by 1983. The national mean cell count in milk has been reduced from 573,000 to 352,000 cells/ml between 1971 and 1986, and the proportion of herds having annual mean cell counts below 300,000 cells/ml has increased from 15.7 per cent to 40.7 per cent in the last eight years.
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Milk from dairy farms in England and Wales has been tested regularly for antibiotic residues since 1965. The sensitivity of the test organism was 0.02 iu/ml penicillin or equivalent until the change to 0.01 iu/ml in January 1986. In 1984-85, 99.6 per cent of the 2,000,000 milk samples tested passed the test and there was an average of 695 failures per month. From 7500 on-farm investigations over the two years 1983-85 the most frequent reasons suggested by farmers for their test failures were not withholding milk for the full withdrawal period (19.3 to 16.5 per cent) and accidental transfer of milk (16.3 to 16.7 per cent). Lactating and dry cow intramammary antibiotic preparations were held responsible for rather over 50 per cent and 25 per cent respectively of the failures in both years.
A new and rapid enzyme-amplified immunoassay (AELIA) has been developed for the measurement of progesterone in milk. The AELIA system is a non-isotopic method that gives results within 35 minutes. Milk progesterone concentrations measured in 10 cows sampled daily at various stages of the reproductive cycle were very similar to those recorded by a validated radioimmunoassay. The results show that the speed and sensitivity of the AELIA system would make it possible to diagnose pregnancy rapidly at about 24 days after insemination, to predict the onset of behavioural oestrus from decreasing progesterone values during the third week after a preceding oestrus, and to obtain a daily record of milk progesterone levels in animals treated for infertility of ovarian origin.
The test for antibiotic residues in milk carried out by the Milk Marketing Board (MMB) of England and Wales was increased in sensitivity from 0.02 iu/ml penicillin or equivalent to 0.01 iu/ml on January 1, 1986. The Veterinary Products Committee (VPC) has just completed a review of those intra-mammary antibiotic preparations which had licences of right. When assessing data for product licences the VPC decided that the concentration of antibiotic residues in milk should not exceed the concentrations listed in the 1969 Report of the Joint FAO/WHO Expert Committee on Food Additives. In this publication the level of 0.006 ppm for penicillin corresponds to 0.01 iu/ml which is the level that the MMB will also be using.
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The conductivity of milk from 164 cows in four herds was measured. There were significant differences between the normal and the mastitic quarters in each of the four herds. However, there was a marked difference in conductivity levels between the herds, the mean conductivity of the normal quarters in one herd being higher than that of the mastitic quarters in another herd. In a trial using a hand-held mastitis detector on 123 cows from three herds, 91 per cent of the 106 mastitic quarters were detected. However, 33 per cent of the 315 normal quarters also gave a positive reading.
A survey was undertaken of all isolations of methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MRSA) at a large Australian teaching hospital over a 12 month period. All methicillin-resistant isolations obtained from the Casualty and Outpatient clinics were from staff members or patients with recent hospital contact. Twenty per cent of all methicillin-resistant isolations from in-patients were from specimens taken within 2 days of the patient's admission. Each of these patients had had hospital contact within the previous 4 months and it is assumed that the majority of them reintroduced the organism into the hospital. Such patients may provide an important means by which infection control procedures are bypassed. Patients who were relatively more likely to become infected or colonized with methicillin-resistant than with methicillin-sensitive strains included the elderly and those with postoperative wound infections (especially after orthopaedic or vascular surgery), spinal injuries, peripheral vascular disease, chronic skin ulcers or chronic diseases of the respiratory or urinary tracts. Eleven per cent of MRSA wound isolates and 15 per cent of sputum isolates were associated with serious infections requiring specific treatment, emphasizing the ability of these strains to produce serious illness. A small proportion of staff and asymptomatic patients were found to harbour MRSA and the importance of these individuals in facilitating cross-infection requires further investigation.
A radioimmunoassay for oestrone sulphate in unextracted samples of milk has been developed. The assay was validated by comparison with a method involving hydrolysis and extraction. The direct assay was used to measure oestrone sulphate in milk samples taken at weekly intervals throughout pregnancy in a commercial dairy herd. Concentrations of oestrone sulphate increased approximately 100 days after insemination and were maintained throughout the remainder of pregnancy in the range of 1.85-3.70 nmol/l.
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