SUMMARYFertility indices, such as non-return rate and number of services per conception, have worsened significantly over the past few years. Because oestrus detection is one of the major factors influencing these indices, this study was performed to determine whether, how long, and at what time dairy cows show signs of oestrus in their behaviour. Two high producing herds with about 40 open cows were observed for 30 minutes every 2 hours for 6 weeks. The various signs of oestrus were recorded. The milk progesterone concentration was monitored daily to detect ovulation. A scale (Table 2) was composed according to the frequency of these symptoms during and between oestrous periods. This scale was used in order to determine which cows were in oestrus. Each oestrous symptom was given a score and the scores were summed for a 24-hour period. If a score of >100 points was reached within a 24-h period, the cow was considered to be in oestrus.As used, the oestrus detection scale proved to be very convenient. Because standing oestrus was observed in only 37% of the oestri, this criterion had a very low sensitivity for oestrus detection. With the use of this scale and 12 observations per day, we reached a detection rate of 100%. If a more practical observation scheme would have been used (e.g. observing the herd twice daily, for 30 min) lower threshold values would have been obtained. This observation scheme resulted in a detection rate of 74% with no incorrect assessments.

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The average size and shape of a polymer coil confined in a slit between two parallel plates depends on the distance L between the plates. On the basis of numerical results, four different regimes can be distinguished. For large values of L the coil is essentially unconfined. For intermediate values the coil orientates without being squeezed considerably. For still smaller values the coil is squeezed with a corresponding decrease in the value of the radius of gyration. A further reduction in slit width is accompanied by a sharp increase in the value of the radius of gyration, signaling the onset of the transition from threeto two-dimensional behavior. ¿-Dependent scaling relations are supposed to be valid in the latter regime. Using Monte Carlo results for self-avoiding walks on a cubic lattice, scaling predictions for the parallel component of the radius of gyration and the end-to-end point distance as well as for the osmotic pressure and the number of segments at the wall are presented and verified.

The shape and orientation of a polymer in a good solvent confined between two parallel plates is investigated by Monte Carlo simulations of self-avoiding random walks on a simple cubic lattice. Decreasing the width of the slit, the coil starts, due to its anisotropic shape, to orient long before its shape changes. Only after the longest principal axis is aligned considerably parallel to the plates, the coil is squeezed. Using a scaled distance between the plates, a corresponding state behavior as a function of chain length is found. The results are in good agreement with predictions based on an analytical rigid ellipsoid model with principal axes’ lengths set equal to the span lengths along the principal axes of inertia of the self-avoiding random walk.

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