Evaluation of a Neck Mounted 2‐Hourly Activity Meter System for Detecting Cows About to Ovulate in Two Paddock‐Based Australian Dairy Herds

Two studies were conducted to assess the performance of a commercially available neck‐mounted activity meter to detect cows about to ovulate in two paddock‐based Holstein‐Friesian dairy herds. The activity monitoring system recorded cow activity count in 2‐hourly periods. Study I investigated the ability of the system to detect cow ovulatory periods in dairy herds managed in two different Australian environments and breeding systems using five activity alert algorithms. Herd 1 consisted of approximately 130 milking cows calving year‐round in a sub‐tropical environment and kept in a single dry lot paddock. Herd 2 consisted of approximately 400 milking cows calving seasonally in a temperate climate and fed pasture by rotation through multiple grazing paddocks. Ovulatory periods and non‐ovulatory days were identified using milk progesterone monitoring alone or in combination with ovarian ultrasonography; using these ‘gold standards’ 141 and 135 ovulatory periods were identified in 64 and 135 cows in Herds 1 and 2 respectively. Sensitivity of the activity monitoring system for detecting cow ovulatory periods ranged from 79.4% to 94.1%, specificity from 90.0% to 98.2% and positive predictive value from 35.8% to 75.8%. Study II investigated the ability of the activity meter system to predict the timing of ovulations in paddock‐based pasture‐fed dairy cattle (Herd 2). The time of ovulation was estimated by repeat trans‐rectal ovarian ultrasonography at approximately 0, 12, 24 and 36 h after artificial insemination (AI). The mean times (±SD) from onset and end of increased activity to ovulation were 33.4 ± 12.4 and 17.3 ± 12.8 h respectively (n = 94). Fifty per cent of cows (n = 47) ovulated within the 8‐h period between 30 to 38 hs after the onset of increased activity, 76.6% (n = 72) within the 16 h between 24 to 40 h, 85.1% (n = 80) within the 24 h between 18 and 42 h and 90.4% (n = 85) within the 32 h from 19 to 51 h after the onset of increased activity. Results from these studies show that in paddock‐based dairy cows in two diverse management systems, this neck‐mounted activity meter system detects high proportions of cows that are about to ovulate and provides a useful indication of when ovulation is likely to occur. However, the specificities and positive predictive values using the algorithms assessed may be lower than desirable.     

Tetravalent uranium in calcite

X-ray absorption spectroscopy and x-ray fluorescence microprobe studies of 35-million-year-old calcite from a Mississippi Valley-type zinc ore deposit indicate substitution of tetravalent uranium for divalent calcium. Thus, tetravalent uranium has a stable location in calcite deposited under reducing conditions. This result validates uranium-series dating methods (including uranium/lead dating) for ancient calcite and shows that calcite provides a sink for uranium in deep groundwater aquifers and anoxic lacustrine and marine basins.     

A review of laboratory techniques and their use in the diagnosis of Leptospira interrogans serovar hardjo infection in cattle

SUMMARY This paper reviews the laboratory diagnosis of Leptospira hardjo infection in cattle. Two genotypes of L hardjo, Hardjoprajitno and Hardjobovis, have been identified in cattle, but only Hardjobovis has been isolated in Australia. There are problems with diagnosis and control of bovine leptospirosis. Infection is usually subclinical and the serological titres vary greatly in peak and duration. Leptospires may be excreted in urine for up to 18 months. Low microscopic agglutination test titres may be significant in unvaccinated herds as indicators of endemic infection. Vaccines differ in their composition, and their efficacy is difficult to evaluate. The serological response after vaccination is difficult to differentiate from the response after infection. Pregnant cows that become infected may abort, but this is usually after the serological response has peaked. Therefore, paired serum samples are of little use in diagnosing abortion caused by L hardjo. Fluorescent antibody techniques are more sensitive than dark field microscopy for detection of leptospires in urine and tissue samples. Techniques for culture have improved but are still difficult to perform and take 3 months or longer for results to be known. DNA probes and polymerase chain reaction tests are very sensitive and specific, quick to perform, and can be used on fluid and tissue samples.     

Flood basalt volcanism during the past 250 million years

A chronology of the initiation dates of major continental flood basalt volcanism is established from published potassium-argon (K-Ar) and argon-argon (Ar-Ar) ages of basaltic rocks and related basic intrusions. The dating is therefore independent of the biostratigraphic and paleomagnetic time scales. Estimated errors of the initation dates of the volcanic episodes determined from the distributions of the radiometric ages are, approximately, plus or minus 4 percent. There were 11 distinct episodes during the past 250 million years. Sometimes appearing in pairs, the episodes have occurred quasi-periodically with a mean cycle time of 32 +/- 1 (estimated, error of the mean) million years. The initiation dates of the episodes are close to the estimated dates of mass extinctions of marine organisms. Showers of impacting comets may be the cause.     

Can rapid climatic change cause volcanic eruptions?

Many major volcanic eruptions coincide with cooling trends of decadal or longer duration that began significantly before the eruptions. Dust veils provide positive feedback for short-term (less than 10 year) global cooling, but seem unlikely to trigger glaciations or even minor climate fluctuations in the 10-to 100-year range. On the contrary, variations in climate lead to stress changes on the earth's crust-for instance, by loading and unloading of ice and water masses and by axial and spin-rate changes that might augment volcanic (and seismic) potential.