An experiment was designed to estimate the optimal interval from the beginning of estrus to artificial insemination (AI). The data were analyzed by means of a mathematical model. The analysis was based on pedometer readings and results of rectal palpation at 42 to 49 d post-AI of 171 breedings in 121 cows. The chance of conception was highest between 6 and 17 h after increased pedometer activity; the estimated optimum was at 11.8 h. In this data file, the effects of disease, inseminator, time of AI (a.m. or p.m.), and bull did not contribute to the improvement of the model. The effects of disease were not significant because of the low incidence of any specific disease. Activity measurements can be used as a tool for AI strategy to improve conception in groups of healthy cows and heifers already showing visual signs of estrus.

The behaviour, growth rate, feed intake, health and slaughter quality of group-housed veal calves fed automatically with milk replacer were compared with those of veal calves kept in individual crates and bucket-fed the same milk replacer. The growth rate and feed intakes of the group-housed calves were lower than those of the calves in individual crates. Their feed conversion rates were similar and there were no significant differences in carcase conformation. The meat of the group-housed calves was paler in colour. The feeding behaviour of the group-housed calves was studied to see whether sick animals could be identified at an early stage but behaviour alone provided an inadequate detection system. Intensive health controls in one of the trials showed that infectious respiratory and digestive diseases may be a greater problem in group-housed veal calves than in veal calves kept in crates.

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A model, based on automatically collected data, was developed for detection of subclinical mastitis. The logistic regression model was based on the following variables: milk electrical conductivity, milk production, parity, and DIM. Subclinical mastitis was defined as a minimal period of 1 wk in which the SCC was > 500 x 10(3) cells/ml. In contrast, periods were defined as healthy if the SCC was < 200 x 10(3) cells/ml. The resulting model had a sensitivity of 55% and specificity of 90% for individual milkings. For periods of 14 milkings, sensitivity was 54% and specificity 92% when the threshold for that period was > 6 electrical conductivity signals for high SCC. Based on these test characteristics, the model could be used as an initial screening tool in a herd with a high incidence of subclinical mastitis. Cows with a signal would have a higher probability of being diseased than the total population. In such herds, separation of milk from the signaled cows might be a possible management strategy to reduce the SCC in the bulk milk tank.

No abstract