ULTRASONIC CHARACTERIZATION OF FOLLICULAR WAVES IN MARES WITHOUT MAINTAINING IDENTITY OF INDIVIDUAL FOLLICLES

A mathematical method was developed for characterizing follicular waves in early pregnant mares. For validation, the results were compared to those derived by a method using day-to-day identification of individual follicles (identity method); the same data set was used for both methods. The following steps were used for each mare: 1) depicting individual diameter profiles over Days 0 to 40 for the 3 largest follicles per ovary without regard to day-to-day follicle identity; 2) separating the follicles into large (>20 to >26 mm) and small categories; 3) using the large category to profile the diameters of individual follicles; and 4) using the small category to detect significant waves of follicular activity on the basis of Tukey's multiple-range test. The identity method detected wave emergence at 15 to 16 mm using the retrospectively identified dominant follicle. The mathematical method detected emergence of waves at a mean diameter of 9.5 +/- 0.5 mm, 2 days earlier than did the identity method. Allowing for the 2 days earlier detection, the 2 methods led to similar conclusions on the characteristics of follicular waves. The mathematical method has the following apparent advantages: 1) data can be collected more quickly and with less skill than for the identify method; 2) bias due to inspecting data of the previous days, as required in the identity method, can be eliminated; and 3) days of emergence of a follicular wave can be identified earlier and with greater objectivity. The first step of the procedure (profiling the diameters of the 3 largest follicles per ovary) should be useful to practitioners and others engaged in clinical research who need a simple method of characterizing follicular waves.