Biomedical subjects
D A Whitaker
Publications and source records attributed to D A Whitaker.
Milk production, weight changes and blood biochemical measurements in dairy cattle receiving recombinant bovine somatotropin.
Fortnightly injections with 500 mg (1.4 ml) of recombinant bovine somatotrophin in 20 dairy cows and heifers at 80 +/- 7 days after calving resulted in increasing milk yields, compared with paired control cows, for three to four days. The advantage was maintained for a further seven to eight days with a decline occurring during the last two to three days before the next injection. The milk yield did not return to the level of the control cows, and the gap between the lactation curves widened as treatment continued, until two to three weeks after the last injection. The cows' response to treatment was greater than the response to heifers. Blood beta-hydroxybutyrate concentrations reflected the higher energy requirements of the treated animals and the weight loss of the treated heifers. Urea-nitrogen concentrations were significantly lower in the treated animals, suggesting that they utilised protein more efficiently. Treated animals had higher inorganic phosphate concentrations, although they remained within the normal ranges. Differences in calcium, magnesium, albumin and globulin concentrations were either statistically or practically not significant.
Health, welfare and fertility implications of the use of bovine somatotropin in dairy cattle.
Twenty-two Friesian and Friesian cross Ayrshire cows and 16 first lactation heifers were paired. Twenty were injected subcutaneously with 500 mg recombinant bovine somatotropin (sometribove) and 18 with a placebo at fortnightly intervals, starting 80 (+/- 7) days after calving, through the winter of 1986-87. The cows' weights and changes in condition, milk yields, milk solids, health and fertility were recorded regularly. Compound cake was fed at a fixed stepped rate according to the number of days since the cow calved. Silage was available on an easy-feed basis. Ten cows had their daily silage intake measured. Sometribove treated cows produced on average 27.7 kg of milk per day, 4.5 kg more than the controls. Treated heifers produced 23.5 kg per day, 2.5 kg more than the controls. Milk quality was unchanged. Treated cows gained weight during the trial, but not by as much as the controls. Control heifers also gained weight but the treated heifers lost, on average, 3 kg. Local reactions at the injection site were not felt to be of welfare concern, nor was the general effect of the extra milk production. A small number of treated animals experienced mastitis and had poorer fertility but the differences were mostly not statistically significant. If bovine somatotropin should become licensed for use in Britain it is recommended that clear guidelines should be issued on the management practices necessary for economic success and for the welfare of the treated animals.
Blood composition and liver fat in dairy cows.
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Incidence of lameness in dairy cows.
A survey of the number of treatments for lameness in 21,000 dairy cows from 185 herds in the University of Edinburgh/Dalgety Spillers dairy herd health and productivity service in England and Wales showed an average incidence of cases of 25 per cent. Veterinary surgeons treated 6.3 per cent and farmers 18.7 per cent and 1.4 per cent of cows were culled because of lameness. Monthly and regional variations were recorded. An assessment of the economic effects suggested that the average annual cost in a 100 cow herd was 1175 pounds with an overall cost to British farmers of more than 35 million pounds. The economic importance is such that research into specific factors affecting foot health should be carried out. Meanwhile, a broad approach to prevention and control of lameness on farms is recommended under the general headings of management/environment, nutrition and breeding.
Incidence of clinical and subclinical hypomagnesaemia in dairy cows in England and Wales.
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Purgeable organic compounds in mother's milk.
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Financing preventive medicine.
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A dairy herd health and productivity service.
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Subclinical ketosis and serum beta-hydroxybutyrate levels in dairy cattle.
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A field trial to assess the effect of copper glycinate injections on fertility in dairy cows.
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A device for sampling of human alveolar breath for the measurement of expired volatile organic compounds.
This report describes the development of a portable spirometer capable of collecting primarily alveolar breath into 1.8-L canisters for subsequent gas chromatographic/mass spectrometric (GC/MS) analysis. Based on CO2 measurements, greater than 97% of the breath collected is alveolar in origin. Sample collection takes place in approximately two minutes. Clean air for inhalation is provided by two organic vapor respirator cartridges. Studies of the breakthrough volume of test compounds at both the 5- and 50-micrograms/m3 levels indicate that each cartridge filter can be used to sample over 300 L of air and that this volume is not altered by intermittent use and storage of the filter for up to five days. In experiments designed to mimic human breathing, recoveries of test compounds through the device at the 5-mu/m3 level ranged from 87 to 112%. Essentially no volatile organic compound (VOC) memory (i.e., adsorption carryover by the device) was measured at the 50-micrograms/m3 level. The data suggest that the device can be used successfully for organic compounds with volatilities greater than that of p-dichlorobenzene.
Development and testing of a whole-air sampler for measurement of personal exposure to volatile organic compounds.
A small and relatively lightweight (3.35 kg) whole-air (canister) sampler that can be worn to monitor personal exposures to volatile organic compounds was developed and evaluated. The prototype personal whole-air sampler (PWAS) consists of a 1-l canister, a mass flow controller, two 1.3 amp hour batteries, a DC/DC converter, and an electronics module with a digital display for the sampling set point, actual flow rate, and battery voltage. The sampler (25.5 x 22.5 x 7.5 cm) fits into a laptop computer carrying case and is able to collect a 900 ml sample at a linear flow rate over 12-16 hours. Laboratory tests demonstrated that the sample flow rate was not affected by temperature or the activity of the person wearing the sampler. Recoveries of methylene chloride, chloroform, 1,1,1-trichloroethane, benzene, n-octane, o-xylene, n-decane, and p-dichlorobenzene averaged 89% or better for three final prototype samplers. Recoveries were slightly lower for vinyl chloride (74%) and n-dodecane (82%). The precision for the three prototypes was excellent during laboratory tests with the coefficient of variation (CV) < 10% for all the test compounds. Although the unit was designed for use as a personal whole-air sampling system, it can also be used as an extremely compact microenvironmental whole-air sampler.
Particle Total Exposure Assessment Methodology (PTEAM) 1990 study: method performance and data quality for personal, indoor, and outdoor monitoring.
The Particle Total Exposure Assessment Methodology (PTEAM) study provided the opportunity to test methodologies for measuring personal and microenvironmental PM10 and PM2.5 concentrations in a full-scale probability-based sample of 178 persons and homes in Riverside, California during the fall of 1990. The purpose of the study was to estimate frequency distributions of exposure to PM10, PM2.5, and selected elements in an urban population. Quality control samples and analyses were used to evaluate method performance. These included collocated sample collection, field and lab blank filters, sampler and balance field audits, and intra- and interlaboratory replicate elemental analyses. A portion of the study was also designed to include side-by-side operation of the personal and microenvironmental samplers with reference method (high-volume and dichotomous) samplers to provide an evaluation of method comparability. Over 95% of the approximately 2,900 scheduled samples were collected and analyzed, with very few losses due to equipment failure. The method limit of detection for the personal and microenvironmental monitor PM10 sampling was 8 micrograms/m3. Mean relative standard deviations (RSDs) of 2% to 8% were obtained for collocated personal and microenvironmental samples. Sampler flow rates were within the +/- 10% accuracy criterion during two field audits. Balances operated in a specially designed mobile laboratory were within specified tolerances for precision (+/- 4 micrograms) and accuracy (+/- 50 micrograms). Elemental analysis accuracy was measured with standard reference materials with biases ranging from 2% to 7%. Measurement precision for most elements ranged from 2.5% to 25% mean RSD. Personal and microenvironmental samplers gave median PM10 concentrations that were approximately 9% higher than the dichotomous sampler and 16% higher than the high-volume sampler across 96 monitoring periods at a fixed outdoor location.