FOLLICULAR DYNAMICS, REPEATABILITY AND PREDICTABILITY OF FOLLICULAR RECRUITMENT IN COWS UNDERGOING REPEATED FOLLICULAR PUNCTURE

The aim of our study was to characterize follicular recruitment and gr owth in response to the repeated removal of follicles. All tertiary fo llicles (> 2 mm of diameter) in the ovaries of 10 non-lactating Holste in Friesian cows were punctured at midcycle (Day 0) by means of an ult rasound-guided needle. Puncture sessions were scheduled twice weekly a t 3- or 4-d intervals over 3 mo. In the middle of the experiment, i.e. , Week 7, the effects of 2- and 5-d intervals between follicular punct ures were tested and compared with the previous 3- and 4-d intervals. After this period, 6 animals were slaughtered to study the effect of p uncturing on gross ovarian morphology. The protocol of puncturing foll icles with 3- to 4-d intervals was continued for an additional 3 mo in the remaining 4 animals. Twice-weekly puncturing of all tertiary foll icles abolished estrous cycles and lead to an increase in follicular w ave frequency without apparent negative effects on either the reproduc tive tract or ovaries. After puncture the new follicular wave attained full numerical development within 3 d. Two-day intervals resulted in a lower number of follicles than the 3-d interval (11.0+/-t3.8 vs 15.4 +/-6.1; P< 0.05). In contrast 4- and 5-d intervals between puncture re sulted in an increase in follicle size when compared with that of the 3-d interval. The mean+/-SD number of recruited follicles varied betwe en animals ranging between 7.8 +/-2.5 to 19.2+/-6.0. The mean number o f follicles recruited increased from the first month (March) to the th ird month (May) of sampling (11.8+/-4.7 vs 16.4+/-6.5; P< 0.01), and t hen decreased between the third (May)and the sixth (August) month of s ampling (21.5+/-4.7 vs 16.8+/-5.0; P< 0.01). During the experiment, th e number of recruited follicles Varied cyclically, with waves having a length of 6 puncture session (PS) or 3 wk (i.e., the mean length the bovine estrous cycle). Follicular recruitment after repeated ovum pick -up showed a high repeatability (r=0.576). A model was also developed showing good predictability of the potential of animals to recruit fol licles on the basis of the first 4 to 6 PS. Our results showed that de spite large Variation in follicular recruitment between animals, the h igh repeatability and good predictability of follicle recruitment demo nstrates the possibility of characterizing animals on their potential for follicle growth. (C) 1997 by Elsevier Science Inc.