Ovulation detection and timing of insemination based on hormone concentrations, vaginal cytology and the endoscopic appearance of the vagina in domestic bitches.

The fertilization period, the time when fertilization can occur, can best be determined using a combination of vaginal cytology and morphology of the vaginal mucosa, behaviour and endocrinology. Neither vaginal cytological changes nor standing oestrus are reliable indicators of the fertilization period per se although with natural mating or when using AI with fresh semen there may be enough biological leeway for pregnancy to follow insemination timed using these parameters alone. This is indicated by the well recognized fecundity of bitches mated early or late in oestrus. Precise discrimination of the fertilization period, which is often required and is necessary for AI using frozen semen, can be achieved by using vaginoscopy to detect the onset of shrinkage with angulation of the mucosal folds. Vaginoscopy is also useful to determine the probable end of the fertilization period and the transition to a 'metoestrous' vaginal smear is also useful in this regard. Detection of the LH peak enables the start of the fertilization period to be forecast quite precisely but, in lieu of practical assays with which to measure plasma LH, a rise in plasma progesterone concentration to 6-8 ng/ml may be more practical.