Ovarian hypoplasia in heifers due to germ cell weakness.
Ovarian hypoplasia due to germ cell weakness was found in 18 heifers of the Swedish Red and White breed simultaneously with a sharp increase of the same syndrome in bulls of the same breed. The heifers were examined because they had not shown estrus or had not become pregnant after several months on pasture together with a fertile bull. After palpation of the ovaries per rectum they were classified as normal, partially hypoplastic or totally hypoplastic. The heifers were slaughtered and the numbers of primordial follicles were counted in the serially sectioned ovaries. The average numbers of follicles per ovary in the 3 diagnostic groups were 18716, 6617 and 4761, respectively. The numbers of primordial follicles in hypoplastic ovaries were significantly lower than in normal ovaries but were still within normal limits for heifers. However, the hypoplastic ovaries were very small, and the totally hypoplastic ones weighed only 1 g or less. The growth of the primordial follicles was disturbed and very few developed into Graafian follicles. There were also many empty cortical cords and anovular follicles. The heifers had all been sired by bulls belonging to breeding lines where germ cell weakness had occurred.
Settergren
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Department of Obstetrics and Gynaecology, Faculty of Veterinary Medicine, SLU Uppsala, Sweden.