Determination of oestrus in the female tammar, Macropus eugenii, by analysis of cellular composition of smears from the reproductive tract

Abstract

Oestrus in the tammar, Macropus eugenii, was diagnosed from observed changes in the proportion of partly cornified epithelial cells in smears taken from the anterior urogenital sinus throughout oestrous cycles in both pregnant and nonpregnant females. Intra- and inter-animal variability in counts of cells necessitated smoothing of the data, which were also rescaled to a cycle length of 30 days. A simple non-sinusoidal periodic model was fitted to the proportions of partly cornified cells in each cycle. The analysis confirmed a common structure across cycles. A marked and consistent feature of this structure was a decrease from about 80 to 20% in partly cornified cells commencing just before oestrus, a feature tested as a detector of oestrus. The procedure proved to be reliable, but to invoke a rule developed for this purpose, a run of daily smears was needed. The maintenance of a routine record for individual animals over 10-1 1 days, including oestrus, may seem onerous but in practice has proved to be more dependable than reliance on chance observations of matings or a retained seminal plug. With experience, an empirical diagnosis of oestrus can be achieved with a shorter run of smears.