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Study of Follicular Development and Heredity of Morphological Types of Ovaries in Prepuberal Gilts^1,2

Agriculture Canada Research Station, Lennoxville, Quebec, J1M 1Z3

Abstract

Two different morphological types of ovaries ("grape" and "other" types) previously described by microscopic examination were studied on 107 live gilts. The ovarian type and distribution of macroscopic follicles during the prepuberal period were determined at 140, 160 and 180 d of age by laparoscopic examination. The incidence of grape-type (GT) ovaries was higher (P < .05) at 140 d of age (50.5%) than at 160 d (38.3%) or 180 d (35.5%). At maturity (d 19 of the first postweaning estrus), 37.7% of the ovaries were classified as GT. The proportion of gilts that maintained their initial type (at 140 d of age) at 160 d, 180 d and at maturity was higher (P < .05) for the gilts having the other-type (OT) ovaries (49% and 25% for OT and GT, respectively). The mean number of small follicles (1 to 3 mm in diameter) was higher (P < .05) for the OT ovaries at 140 d (71.5 vs 18.0) , at 160 d (79.3 vs 26.2) and at 180 d (77.0 vs 32.8). The number of follicles of 4 to 5 mm was higher (P < .05) for GT ovaries at 140 d (16.4 vs 4.8), at 160 d (20.9 vs 4.8) and at 180 d of age (21.4 vs 5.7). The large follicles ( 6 mm) were more numerous for the GT at 140 d (7.0 vs .3), at 160 d (5.7 vs .5) and at 180 d (4.4 vs .6). No statistical difference was observed at maturity in the distribution of follicles between the two types. The prepuberal ovarian type did not influence the age at puberty, whereas the ovulation rate at the first postweaning estrus was higher for gilts that maintained the GT at the three prepuberal laparoscopies (16.5 vs 12.7). The study of the relation between dams' and daughters' ovarian morphology indicates that the character does not seem to be determined by heredity. The different ovarian types could be the morphological manifestation of a cyclic phenomenon taking place in the ovary during the prepuberal period.

¹ Contribution no. 199.

² The authors wish to thank A. Bouchard for the histology and R. Noel for care of the animals.

³ Dept. de Biologie, Faculté des Sciences, Universite de Sherbrooke, Sherbrooke, Québec, J1K 2R1.

⁴ Dept. de Zootechnie, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, Québec, G1K 7P4.

⁵ Send reprint requests to this author.