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Biomedical subjects

S W Martin

Publications and source records attributed to S W Martin.

At least 163 records · Page 9Linked to original sources
PubMed1978

The use of case history studies to differentiate potentially infected from potentially noninfected herds with reactors to Brucella abortus antigens.

Data on farm characteristics and the results of the first herd test for brucellosis were collected for 74 reactor and 74 negative herds in Wellington County, Ontario. Each reactor herd was classified as either probably infected or probably not infected using the occurrence of abortions prior to the first herd test or during the testing period, the total number of cattle removed and/or the spread of reactors within the herd as criteria of infection. Statistical techniques were used to select variables which were good "discriminators" between probably infected and noninfected herds. In general, reactor herds were primarily dairy herds and were somewhat larger than negative herds. The presence of only single suspicious reactors on the first test appeared to be a good predictor of lack of infection with Brucella abortus. Among the 37 farms in this category the single reactor was removed from only eight farms and no evidence o fthe spread of infection was observed. The presence of one or more positive reactors on the first herd test appeared to be a good predictor of the presence of infection. Of the 24 farms in this category, evidence of the spread of infection was present in ten farms and seven of these ten farms were eventually depopulated. The brucella milk ring test appeared to be the most effective means of identifying infected herds under the conditions present in Wellington County.

Abortion, Veterinary↗
PubMed1978

The effects of Brucella strain 19 vaccination on titers in the tube agglutination test: a case control study.

The degree of agglutination in the tube agglutination test of the sera of 373 "reactor" cattle was compared to that of 800 "non-reactor" cattle from multiple reactor herds in southwestern Ontario. Vaccinated cattle had lower titers than did nonvaccinated cattle. Thus, vaccinated cattle were less likely to be classified as positive than nonvaccinated cattle irrespective of the method of interpreting the results of the tube test. When the full allowance for vaccination was used, vaccinated cattle were less likely to be classified as suspicious than nonvaccinated cattle. The extent of herd vaccination did not appear to markedly influence the effects of vaccination or the prevalence of reactors. Thus, it appeared that vaccination with strain 19 produced a small protective effect (inferred from the lower titers in vaccinated animals), but that the magnitude of this effect was markedly dependent on the appropriateness of the vaccine allowance for classifying cattle. Further work is needed on this aspect of vaccination with strain 19.

Agglutination Tests↗
PubMed1978

Age, breed and seasonal patterns in the occurrence of ten dairy cow diseases: a case control study.

A total of 5,990 occurences of the diseases abomasal displacement, cystic graafian follicles, endometritis, hypocalcemia, ketosis, mastitis, metritis, ovarian hypofuction, pyometra and retained placenta were included in a case control study. The study was based on a hospital population of Holstein, Ayrshire, Guernsey and Jersey cows who were at least two years of age. The data were retrieved from computer storage of material abstracted for the Veterinary Medical Data Program. The transcription of data from original case records to these abstracts was examined as a source of error. An attempt was made to define each of the diseases by reference to random samples of the clinical records. Using the log-odds method, trends were noted for the youngest cows to be at increased risk of the reproductive diseases and for the Guernsey cows to be at increased risk of the uterine diseases. There was a tendency for peaks in disease occurrences in the winter (as opposed to summer) months.

Abomasum↗
PubMed1978

A study of the role of genetic factors in the etiology of left abomasal displacement.

The ancestry of 69 cows having left displaced abomasum was compared with that of 69 cows (matched for age, farm and lactation) not having experienced left displaced abomasum. A variety of tests were used to ascertain if certain bulls or families of bulls produced daughters with an increased risk of developing left displaced abomasum. However, there were no significant differences between the pedigrees of the affected and nonaffected cows.

Abomasum↗
PubMed1977

The evaluation of tests.

In order to correctly evaluate a test, at least four attributes should be measured: namely, sensitivity, specificity, accuracy and precision. Sensitivity is the proportion of diseased animals which are correctly identified, whereas specificity is the proportion of healthy animals which are correctly identified. These two attributes are important, not only because of the reasons implied by their definition but because they influence both the apparent prevalence of disease and proportion of test-positive animals which are actually diseased. The ability of a test to give a true measurement of the substance being measured, its accuracy, and its ability to give consistent results on the same sample, its precision, are good measures of quality control. Both these attributes influence the sensitivity and specificity of the test. Inaccuracies and inconsistencies arise from the test itself, the technician and the nature of the sample being tested.

Animals↗
PubMed1975

Dairy calf mortality rate: characteristics of calf mortality rates in Tulare County, California.

Sixteen dairy farm owners in Tulare County, California, provided data on heifer calf births and deaths. Eleven of these dairymen had maintained records on the calves before this study was done, and 5 agreed to maintain them for 6 months. Basic statistical techniques, including time series analyses and life-table methods, were used to examine the data for temporal and demographic characteristics. Overall, the calf mortality rate on the 16 farms averaged 17.3 to 20.2%. The interfarm variation in mortality rate was large, ranging from 3.7 to 32.1%. Time series studies indicated that the extent of death losses increased during midsummer (June, July, August) and midwinter (November, December, January), with mortality rates in winter months being 20% greater than those in summer. Death losses in October and March were highly variable; however, losses in October usually exceeded the yearly average; those in March did not. Also, 80% of the dairymen recorded the same relative change in mortality rate during each of 2 consecutive winters and 2 consecutive summers. The risk of death for calves was greatest in their 1st week of life on most of the farms; of all deaths in calves less than 5 weeks old, 55% occurred during the 1st week of life, and 27% occurred during the 2nd. In general, the death loss in calves between 5 weeks and 3 months old was less than 2%.

Animals↗
PubMed1975

Dairy calf mortality rate: influence of management and housing factors on calf mortality rate in Tulare County, California.

Data on calf mortality, calving site, calf-rearing facilities, and calf-management procedures were collected from 16 dairy farms in Tulare County, California. Discriminant analyses were used to test if any significant differences in these factors existed between farms with higher than average and farms with lower than average death losses. The average mortality rate over a period of at least 2 years on individual farms varied from a low of 3.5 +/- 1.1% to a high of 30.6 +/- 3.1%. Calf management personnel was the only factor significantly related to the mortality rate, with considerably fewer death losses on farms where the owner managed the calves than on farms where employees performed these duties. In general, other factor categories relating to size of the cow herd, calving site, and calf housing were not related significantly to calf deaths. The average number of heifer calves born each year on individual farms was increasing year by year, and on some farms, there seemed to be a concomitant increase in death losses. This, together with the tendency toward greater number of deaths on the larger owner-managed farms, indicated that calf care was diluted under these conditions.

Animals↗
PubMed1975

Dairy calf mortality rate: influence of meteorologic factors on calf mortality rate in Tulare County, California.

Monthly calf mortality data for a period of 5.5 years in Tulare County, California, were compared with monthly summarized weather data for that county, using multivariate statistical techniques. In winter, increases in the calf mortality rate (CMR) were significantly associated with cold, wet, windy weather; in summer, greater death losses were associated with hot, dry weather. In general, the calf losses in winter seemed more closely related to weather phenomenon than those in summer. The CMR during a 6-month period (July to December, 1973) were predicted, using equations containing data on the more important weather variables. The predicted CMR significantly differed from the observed death rate during July through September. During October through December, the predicted and observed CMR did not significantly differ. An increase in mortality rate was not predicted for winter, mainly because of low rainfall, and none occurred.

Animals↗
PubMed1975

Dairy calf mortality rate: the association of daily meteorological factors and calf mortality.

The number of dairy heifer calves born each day, the number of these calves which died prior to 36 days of age and the actual date of death were recorded and analyzed for possible associations with weather factors. The demographic data on dairy calves were supplied by 16 farms in Tulare County, California for the months of July to December 1973. High temperatures in the summer and low temperatures in the winter were associated with an increased risk of death. Calves born during the periods of extreme temperatures had a higher risk of death than those born on more temperate days, while death, when it occurred was temporally related to days of extreme temperatures. Periods of increased risk of death often were associated with large temperature fluctuations irrespective of the absolute temperature. Nonmeteorological factors specific to invidual farms also appeared to influence daily calf mortality rates.

Age Factors↗