The advent of ultrasound and its use for the examination of theories in the mare has brought a cruel realization to veterinarians that ovarian palpation was even less accurate in the diagnosis of ovulation than they had already conceded. Although themature follicle is normally readily palpable, asignificant number of instances arise where ovulation is in doubt, even when examinations are made at intervals as short as 24 hours. Particularly confusing is the softening often found in a regressing follicle during the transitional phase in spring when it may resemble an early corpusluteum (CL). When two or more follicles develop within the same ovary but ovulate asynchronously, it is often impossible to ascertain by palpation alone what has happened inthe ovary. When palpations are made at intervals of 48 hours or more, a firm follicle can be replaced by a CL of similar size and consistency. Follicular hemorrhage without ovulation had long been suspected but because the follicle luteinizes causing the mare to become diestrous, it was assumed that ovulation must have occurred at some point.
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