[Hormonal disruptors and farm animals]. / Hormoonontregelaars en landbouwhuisdieren.

A number of man made environmental contaminants displays a weak hormonal, usually oestrogenic, activity. Currently such contaminants are termed hormone disruptors, a terminology that also includes natural compounds with hormonal activity, such as phyto and fungal oestrogens. Fertility and morphological defects in wildlife are related to high exposure to man made hormone disruptors. The potential threat of such exposure for human reproductive health is widely discussed. A possible decline in sperm counts in men is one of the subjects related to such environmental factors. There are no firm indications for this threat. Additional research is needed, however, for a more complete assessment. Farm animals so far played a minor role in the discussion. Therefore, in a study published elsewhere, long term trends in sperm counts of Dutch Dairy Bulls have been evaluated (27). No decline was found in 75,238 ejaculates collected between 1977 and 1996 from 2,314 bulls of the centre for artificial insemination (AI) NOORDWEST. Results of this study, published elsewhere, formed the reason to broader go into the relation between hormone disruptors and farm animals, observed effects of phyto-oestrogens in such animal and the role these animals could play in further research.

Long-term trends in sperm counts of dairy bulls.

A possible decline in sperm counts in men and its potential relation to exposure to environmental contaminants are subjects of a broad discussion. Whereas data for human research in this area are limited, records over prolonged periods on sperm counts in dairy bulls are amply available and provide useful information. Therefore, 75,238 ejaculates collected between 1977 and 1996 from 2,314 bulls at Noordwest, a center for artificial insemination (AI) in the Netherlands, were used to evaluate long-term trends in sperm output. Data were adjusted for known effects, of which age was the most important, followed by interval between semen collections, breed and season of collection. Mean sperm output per year of collection from 1978 through 1996 varied between 6.2 x 10(9) and 9.5 x 10(9) without any long-term decline. Mean sperm output per year of birth from 1970 through 1995 showed less variation, between 6.7 x 10(9) and 9.0 x 10(9), also without any long-term decline. Earlier published data of 22,120 ejaculates of 3,030 bulls of the same region, tested between 1962 and 1977, showed a corresponding sperm output, confirming the absence of any decline. The unaffected sperm output in bulls in the Netherlands during the last decades in spite of exposure to pesticides and other polychlorinated organic compounds, the type of environmental contaminants under discussion, is a positive signal, although a complete extrapolation to the human situation remains difficult.

Oestrus control and the incidence of mammary nodules in bitches, a clinical study with two progestogens.

The incidence, size and location of mammary nodules were established in 10 practices in The Netherlands by the clinical examination of bitches in which oestrus was controlled with proligestone (P), 331 animals, or medroxyprogesterone acetate (MAP), 341 animals and in 339 animals never medicated with such compounds. In comparison with the unmedicated control and the P-medicated animals of comparable age the incidence of mammary nodules of all sizes was significantly increased in the MAP-medicated animals. There was no significant difference in nodule incidence between the P-medicated animals and the control animals. Based on the assumption that nodules above a certain size are most likely tumours, these results indicate that oestrus control with MAP stimulates tumour development even in animals medicated for less than four years. The practical value of the reported differences, especially in relation to the subsequent requirement for surgical removal of tumours in bitches, medicated for oestrus control, is discussed.

[Veterinarians and computers (author's transl)]. / Dierenartsen en computers.

Because of the fact that the use of computers depends both on the user and on the apparatus, some characteristics of veterinarians and computers are discussed. Although veterinarians probably are not pre-eminently computer-minded in view of their choice of profession and training, they will be increasingly confronted with disciplines tending to employ data-processing systems as an item of training and field of interest. The extent to which computers can be used, will depend on their accessibility, reliability in operation, accuracy, flexibility and cost price. A discussion of these features shows that the fear of computers usually is greater than that warranted by the technology currently available. Their use commences at the point at which large numbers of data have to be processed and automation offers advantages from the point of view of economy or organization (systems of administration and payment). Moreover, data which has already been available for a certain period, is rendered accessible for the first time by automatic processing (meat inspection). Finally, a demand will be created by the supply of data. A number of uses in the various veterinary disciplines are discussed. Part of a computer teaching programme of a faculty of veterinary medicine is described as a practical instance.

A Multitest System for Detection of Antibiotics in Milk.

A description is given of the Delvotest® P multi, a test system for detection of antibiotics in milk to be used when large numbers of samples have to be investigated. By using a special delivery pipet, one person can handle 400 samples per hour. Sensitivity and test duration are similar to those of the Delvotest® ampoule test. The sensitivity may be decreased, if wanted, simply by using a smaller sample size: a sample of 0.03 ml instead of 0.1 ml decreases the sensitivity for penicillin from 0.003 to 0.01 IU per ml.

[Veterinarians and computers (author's transl)]. / Dierenartsen en computers.

Uses of the computer in veterinary medicine are reviewed. The fact that the constantly increasing volume of the literature continues to be accessible is mainly due to the use of computers. In scientific research, the results of measurements and studies are being increasingly recorded and processed automatically. Diagnosis and epidemiology are promoted by more adequate processing and analysis of centrally collected data, as are herd management and disease control programmes in farm animals. In veterinary education, the computer is used as an aid in instruction. Administrations of practices are eminently suited for automation. Future developments in these fields are also discussed.

[Penicillin residues in yearlings following preventive treatment of summer mastitis with a preparation containing high doses of penicillin for use of dry cows (author's transl)]. / Penicilline residuen bij pinken na preventieve behandeling tegen wrang met een droogzetpreparaat.

In view of questions arising in the field, regarding the periode for which treatment with a preparation containing high doses of penicillin for use of dry cows to prevent summer mastitis may result in a positive kidney test, the urinary concentrations of penicillin in these animals were determined. The study of these levels, in conjunction with previous experience in cattle, showed that kidney tests are only likely to be positive during the first two days.

Antibiotic Residues in Milk: Dye Marking Versus Direct Control.

Advantages and disadvantages of control for antibiotic residues in milk by compulsory dye marking of anti-mastitis preparations or by direct tests utilizing microbiological methods are reviewed. It appears feasible to construct a very strict direct control system utilizing highly sensitive microorganisms in laboratory methods or incorporated in industrially-made test kits. Useful methods whereby a dramatic decrease in both the incidence and amount of antibiotic residues can be attained are described. Compared to these systems, the compulsory addition of dye-markers to anti-mastitis preparations is unnecessary and even undesirable.

[The use of a dry cow preparation for the prevention of summer mastitis in maiden heifers (author's transl)]. / Preventie van zomermastitis (wrang) bij pinken door toediening van een droogzetpreparaat

An investigation was made of the preventive value of topical application to juvenile udders of a dry cow preparation containing 300,000 IU of procaine penicillin G (Penzal N 300). Penicillin concentrations in udder secretions of 30 young cows were examined. In calves up to 10 weeks and in maiden heifers up to 7 weeks after application an average concentration of 0.05 ml IU per ml of secretion was found. In the same groups, 12 and 9 weeks respectively after application, the concentration was 0.01 IU per ml of secretion. Experiences in practice in an area with a high infection rate have shown an obvious protection in 700 maiden heifers. Some cases of infection did occur both shortly (1.0%) and from 5 weeks after application (1.9%). The clinical character of the latter was much milder than is usual for summer mastitis. When administered in time and in the correct manner the dry cow preparation examined showed reasonable protection against summer mastitis.

Comparative in vitro studies of a number of anti-mastitis antibiotics.

In vitro activities of penicillin, ampicillin, dihydrostreptomycin, nafcillin, cloxacillin and commercially available combinations of these antibiotics against a variety of Gram-positive mastitis-causing micro-organisms were examined. As a rule, penicillin proved to be more active against penicillin-sensitive strains of micro-organisms than ampicillin and nafcillin and far more so than cloxacillin. In combination with di-hydrostreptomycin, which in itself showed hardly any activiy, the activity of penicillin against streptococci was enhanced considerably. This confirms the synergistic effect of this combination. No clear synergism was noted in the activity against staphylococci. Against strains which were less sensitive to penicillin, there was not much difference in activity between penicillin, ampicillin, nafcillin and cloxacillin. Nafcillin was found to be much more active against streptococci than cloxacillin. The anti-staphylococcal activities of these two antibiotics however were identical. The activity of the combination of penicillin, dihydrostreptomycin and nafcillin against most micro-organisms was mainly due to the penicillin in the combination. Against Streptococcus agalactiae and the most penicillin-resistant staphylococci, nafcillin contributed clearly to the activity. The activity of the combination ampicillin + cloxacillin against Streptococcus agalactiae was mainly based on the activity of the ampicillin in the combination. Against penicillin-resistant staphylococci, the activity of the combination was mainly due to the activity of cloxacillin. Against the other micro-organisms, both compounds contributed to the activity of the combination.