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Biomedical subjects

D B Harker

Publications and source records attributed to D B Harker.

14 recordsLinked to original sources
PubMed1984

Induction of parturition in cattle using dexamethasone and cloprostenol: economic performance and disease incidence after treatment.

Details are given of clinical management and disease problems associated with the routine induction of parturition on a herd basis, as well as the veterinary costs involved. A review of the economic performance of cows calved by this method is made and some guidelines laid down as to the conditions under which such a technique could be used as a management tool.

Animals↗
PubMed1983

Evaluation of tail paste as an oestrus detection aid using serial progesterone analysis.

Serial progesterone assay of 127 commercial dairy cows over several months identified 363 possible oestrous events. Of these, tail paste correctly identified 81.5 per cent, while the stockmen unaided recorded only 70.2 per cent (national average 55 to 60 per cent). The significance of such a degree of improvement, the factors restricting oestrus detection efficiency and the difficulties in creating the appropriate mental attitude to oestrus detection improvements are discussed.

Animals↗
PubMed1982

Induction of parturition in a commercial dairy herd: clinical management and treatment.

Twenty-six dairy cattle were treated with dexamethasone during medium to late pregnancy to induce premature calving. Thirteen produced calves within an average of 5-6 days of treatment. The remainder were given a subsequent injection of cloprostenol 10 days after the steroid treatment and, with one exception, all calved within the following two days. A high incidence of retained placenta was experienced, in common with other methods of inducing parturition, but this was not generally found to be associated with detrimental effects on health or fertility.

Animals↗
PubMed1981

Use of cloprostenol with dexamethasone in the termination of advanced pregnancy in heifers.

The difficulty of devising a standard treatment regime for cattle which would predictably terminate pregnancies in the 200 to 250 day range is described. Eight 15-month-old heifers which had been accidentally mated when approximately eight months old were examined by rectal palpation and condition scored. To induce abortion an intramuscular injection of 20 mg dexamethasone phenylpropionate was given followed 11 days later by an intramuscular injection of 500 microgram cloprostenol. A record was made of the time of calving along with calving and post calving details. Two of the heifers aborted before the injection of cloprostenol. The other six aborted within 48 hours of receiving this injection. The practical problems associated with aborting immature cattle are discussed as well as the financial aspects.

Abortion, Induced↗
PubMed1978

Evaluation of the optical refractometer for lamb serum immunoglobulin estimation.

Resistance of lambs to neonatal diseases has been shown to be related to their serum immunoglobulin levels. These may be estimated in the laboratory by the zinc sulphate turbidity test (ZSTT). An experiment was designed to evaluate the optical refractometer, a relatively simple and inexpensive piece of equipment which measures the refractive index of a serum sample and thus provides an estimate of its total protein content. Refractometer readings of neonatal lamb sera were found to be closely correlated to their ZSTT readings (r = 0.89). The refractometer appears eminently suited to farm use avoiding elaborate and time consuming laboratory procedures. The limitations of the tests are discussed.

Animals↗
PubMed1978

A simple estimation of the immunoglobulin content of ewe colostrum.

Use of the optical refractometer in performing a rapid assessment of the immunoglobulin content of ovine colostrum under farm conditions was investigated. Refractometer readings were compared with total protein levels and with gamma-globulin levels, determined by the ZSTT, to assess the validity of the technique. In both cases correlation coefficients were high (0.98 and 0.79 respectively). Refractometry was shown to be a valid substitute for the ZSTT in studies on colostrum gamma-globulin levels.

Animals↗
PubMed1976

Mycoplasmas and ovine keratoconjunctivitis.

The clinical course of an outbreak of keratoconjunctivitis in housed lambs and their dams was followed. Signs were transient generally and became severe in only a small proportion of lambs. The outbreak became most obvious when the lambs were 46 to 55 days old, when 46.9 per cent were affected. Mycoplasma conjunctivae isolations, confirmed by comparison with the type strain by biochemical and serological reactions, increased to 62.1 per cent of all eyes swabbed, but no correlation could be demonstrated between presence of the organism and clinical status. The reasons for this are discussed. Mycoplasma ovipneumoniae was also recovered from the eyes of a small number of lambs. Instillation of a broth culture of M conjunctivae into the conjunctival sacs of four hoggs produced a transient keratoconjunctivitis similar to that observed in the field, but no effect was observed in animals inoculated intravenously. M conjunctivae may therefore be the aetiological agent of non-follicular infectious ovine keratoconjunctivitis, although further work in gnotobiotic or specific pathogen free lambs is required to establish the fact beyond doubt.

Animals↗
PubMed1976

The use of molybdenum for the prevention of nutritional copper poisoning in housed sheep.

An experiment was designed to investigate the practical possibility of incorporating small quantities of molybdenum salts into the high copper diets of intensively fattening lambs to prevent or reduce the gradual accumulation of copper from feed. At slaughter (14 weeks of age) lambs which had received Mo supplement (7.7 ppm Mo) showed liver copper levels which were 40.1 per cent lower than those in the control group which, in turn, presented a mean liver copper concentration near the upper limit of the normal range for adult sheep. Changes in blood ceruloplasmin and SGOT levels and in the comparative rate of accumulation of liver copper indicated that the addition of ammonium molybdate to the concentrate diet might be a useful method of reducing the risk of nutritional copper poisoning in housed sheep.

Animals↗