The objective of this study was to determine the diagnostic performance of an electronic beta-hydroxybutyrate (BHBA) hand-held meter (Precision Xtra) for use in dairy cattle. Specific objectives were to compare the electronic BHBA meter with serum BHBA concentrations determined photometrically and 2 commonly used chemical cowside tests (Ketostix, Ketolac) and to evaluate accuracy in a field study employing 35 investigators. Of the 196 blood samples collected in experiment 1, 17 (8.7%) contained > or =1,200 micromol of BHBA/L of blood and 10 (5.1%) contained > or =1,400 micromol of BHBA/L of blood. Pearson correlation coefficients were highly significant for all tests. The highest correlation coefficient (0.95) was found between measurements of whole blood BHBA determined with the Precision Xtra test and the serum BHBA concentrations determined photometrically. Correlation coefficients between serum BHBA and BHBA in urine using Precision Xtra and Ketostix, and milk using Ketolac were lower. The Precision Xtra test was both 100% sensitive and specific at > or =1,400 micromol of BHBA/L of whole blood. Using milk and urine, positive and negative predictive values were considerably lower for both chemical tests as well as for the electronic meter. In the second study undertaken with 35 bovine veterinary practices, 926 blood samples were collected. In this study, the Precision Xtra test had sensitivities of 88 and 96% at 1,200 and 1,400 micromol of BHBA/L of whole blood, respectively. Specificities were 96 and 97%, respectively. Level of agreement was lower in the second study employing multiple investigators. Considerable differences in variance occurred among investigators. We conclude that the electronic hand-held BHBA measuring system using whole blood is a useful and practical tool to diagnose subclinical ketosis. Sensitivity and specificity are excellent for a cowside test and higher than 2 commonly used chemical dipsticks (Ketostix and Ketolac).

The prevalence of dystocia is high in many dairy herds and is associated with stillbirth and negative effects for the cow. An accurate predictor of calving would enable supervision of cows more precisely to a relevant time interval so that obstetrical assistance can be provided in a timely manner. This might help to decrease calf mortality rate. Evidence exists that cows exhibit a decrease in body temperature before the onset of calving. The performance of a decrease in body temperature as a test to predict the onset of calving in dairy cows has not been investigated. The objective was to investigate test criteria of a decrease in vaginal and rectal temperature as predictors of calving in dairy cows. In 3 experiments, temperature loggers (Minilog 8, Vemco Ltd., Halifax, Canada) were inserted into the vagina of cows before calving (n = 85), and rectal temperatures were measured twice daily in 55 of these cows. Vaginal temperatures were 0.2 to 0.3 °C and 0.6 to 0.7 °C lower on the day of calving compared with 24 and 48 h before calving, respectively. Rectal temperatures were 0.3 to 0.5 °C and 0.4 to 0.6 °C lower on the day of calving compared with 24 and 48 h before calving, respectively. Vaginal temperatures exhibited a diurnal rhythm during the 120 h before calving, which continued on a lower level during the 48 h preceding parturition. In the 3 experiments, a decrease in vaginal temperature of ≥ 0.3 °C over 24h could predict calving within 24h, with sensitivity ranging from 62 to 71% and specificity ranging from 81 to 87%. Similarly, a decrease in rectal temperature measured at 0730 h of ≥ 0.3 °C could predict calving within 24h, with sensitivity from 44 to 69% and specificity from 86 to 88%. Although dairy cows exhibit a distinctive decrease in vaginal and rectal temperatures commencing approximately 48 h before calving, detecting this decrease does not determine the onset of calving precisely. Nevertheless, it can provide valuable information in addition to the traditional signs (i.e., relaxation of the sacrosciatic ligament) that calving is imminent.

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In this prospective observational study rectal and vaginal temperature of 82 (26 primiparous, 56 multiparous) early post-partum healthy dairy cows that calved without intervention within 3 months and did not show clinical signs of infectious and metabolic diseases were continuously measured and evaluated for associations with plausible factors during the first 10 days in milk (DIM). During May, June and July mean (±SD) temperature humidity index (THI) was 60·1±5; 66·8±5·6 and 74·2±4·3, respectively. Environmental conditions had a negligible effect on body temperature (BT) during May (P<0·05). During June and July, however, the ambient temperature and THI influenced BT (P<0·05). Furthermore, plausible factors like parity, DIM, months and time of day had an effect on BT (P<0·05). Overall, primiparous cows demonstrated 0·2°C greater BT during the first 10 DIM than multiparous cows. The effect of parity, however, on BT varied between DIM according to month (P<0·001). During this 3-month study period all cows demonstrated BT rhythms; however, the amplitude of BT increased from May to July (0·3 to 0·7°C). A greater proportion of the vaginal temperature measurements exceeded a threshold tested (≥39·5°C) during July (46·8%) than in June (33·9%) and May (19·3%). Overall the percentage of BT values above a threshold of ≥39·5°C was lower during the period 6.00-10.00 compared with the remaining 20 h (P<0·05). Therefore this study concluded that the BT of healthy post-partum dairy cows during the period 1-10 DIM post partum is greater compared with the reference range of 38·6 to 39·5°C reported by others and is influenced by parity, DIM, time of day and THI. When the association between BT and THI increased the reliability of threshold levels of BT (≥39·5°C) decreased.

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