Relationship between in-line milk progesterone before and after artificial insemination and fertility outcomes in dairy cows.

The aim of this study was to evaluate the possibility to predict outcomes of artificial insemi- nation (AI) in dairy cows based on in-line milk progesterone (P4) concentration. The research was carried out on the herd of loose housing 245 dairy cows of 2-4 lactations, with average milk yielding 11.000 kg per cow. Milk sampling, measuring, and recording of milk P4 concentration was carried out using the Herd Navigator (HN). The grouping was performed according to the following three indices: the first by reproductive condition - pregnant or not pregnant after AI, the second by P4 concentration from day 20 before AI to day 20 after AI, and the third by P4 concentration at AI time. There was a significant difference in P4 concentration in the group of pregnant cows from day 15 to day 9 before AI, and it was by 18.3% higher com- pared to that in the group of non-pregnant cows in the said period (p⟨0.01). The milk P4 concen- trations began to differ mostly from day 10 after AI. At that time, the average P4 concentration in the group of pregnant dairy cows was by 36.8% higher compared to that in the group of non-pregnant cows (p⟨0.01). A statistically significant difference between the ratio of the cows with high, medium, and low P4 concentration on days 20-16 before AI (p⟨0.01) was determined. The highest number of cows with up to 2-3 ng/ml P4 concentration became pregnant at the AI time. In-line milk P4 records captured on day 10-15 before AI can be used to predict the proper for reproduction period. By P4 concentrations on day10 after AI, the ratio of pregnant cows in herd can be assessed.

Impaction onto a Glass Slide or Agar versus Impingement into a Liquid for the Collection and Recovery of Airborne Microorganisms.

To study impaction versus impingement for the collection and recovery of viable airborne microorganisms, three new bioaerosol samplers have been designed and built. They differ from each other by the medium onto which the bioaerosol particles are collected (glass, agar, and liquid) but have the same inlet and collection geometries and the same sampling flow rate. The bioaerosol concentrations recorded by three different collection techniques have been compared with each other: impaction onto a glass slide, impaction onto an agar medium, and impingement into a liquid. It was found that the particle collection efficiency of agar slide impaction depends on the concentration of agar in the collection medium and on the sampling time, when samples are collected on a nonmoving agar slide. Impingement into a liquid showed anomalous behavior with respect to the sampling flow rate. Optimal sampling conditions in which all three new samplers exhibit the same overall sampling efficiency for nonbiological particles have been established. Inlet and collection efficiencies of about 100% have been achieved for all three devices at a sampling flow rate of 10 liters/min. The new agar slide impactor and the new impinger were then used to study the biological factors affecting the overall sampling efficiency. Laboratory experiments on the total recovery of a typical environmental microorganism, Pseudomonas fluorescens ATCC 13525, showed that both sampling methods, impaction and impingement, provided essentially the same total recovery when relatively nonstressed microorganisms were sampled under optimal sampling conditions. Comparison tests of the newly developed bioaerosol samplers with those commercially available showed that the incorporation of our research findings into the design of the new samplers yields better performance data than data from currently available samplers.

Variation in quantitative respirator fit factors due to fluctuations in leak size during fit testing.

Variation in fit factors during quantitative respirator fit testing was studied for a high degree of fit (aerosol fit factors > 1000) and a low degree of fit (aerosol fit factors < 1000). In a controlled human study, fit factors were determined sequentially for three different exercises by (1) an aerosol fit test (using a portable condensation nuclei counter and room aerosol as the test agent) and (2) the newly developed dichotomous-flow fit test (Dichot). For the higher level of respirator fit, the aerosol fit factors were 30 to 60 times the corresponding flow fit factors, and for the lower level of respirator fit they were 2 to 4 times the flow fit factors. A coefficient of variation (CV) of 84% (GSD 1.6) for the higher respirator fit and 178% (GSD 2.2) for the lower respirator fit data was observed in the human study when aerosol fit factors for the three exercises were pooled. In a similar mannequin study, the center sampling probe gave aerosol fit factors with a CV of 5.4% (GSD 1.05). The flow fit factors for all three exercises pooled had a CV of 36% (GSD 1.3) for the higher respirator fit and 40% (GSD 1.5) for the lower respirator fit data, while the mannequin study gave flow fit factors with a CV of 2.2% (GSD 1.02). Thus, the variation in fit factors obtained in the human study was much higher than that obtained in a mannequin study. However, the variation in the aerosol method relative to the flow method, in the human study, os of the same order of magnitude as in the mannequin study.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting microbiological colony count accuracy for bioaerosol sampling and analysis.

The effects of the following variables on the occurrence of colony masking (the indistinguishable merging or overlap of sufficiently close colonies) were evaluated experimentally using the bacterium Bacillus subtilis: spore density on a collection surface, concentration of nutrients in the culture medium, sample incubation time, and ability of an observation system to distinguish overlapped colonies. Increasing spore surface density and incubation time increased colony masking, whereas lowering nutrient concentration decreased colony diameter and, therefore, masking but also limited spore germination and growth. Overall, full-strength medium was best for accurate counting of early microcolonies examined with the aid of a microscope, whereas half- or quarter-strength medium was better for counting older readily observable macrocolonies. Masking bias was determined for varying spore surface densities and colony diameters and was applied to two widely used slit-to-agar bioaerosol impactors. Appropriate collection times have been determined for these samplers to minimize colony masking for expected bioaerosol concentrations. It was found, for example, that 6-min samples collected from an environment with an air concentration of 10(3) CFU m-3 would result in colony surface densities, for 3-mm colonies, of 1.5 and 3.9 microorganisms cm-2 for the two samplers with respective masking biases of < 10% and < 20%.