Histopathological alterations in the antral ovarian follicles in dairy cows with a tendency to emaciation

The aim of the study was to define interrelationships between histopathological alterations in ovarian antral follicles and body condition in dairy cows with a tendency to emaciation (BCS 1 and 2) compared with dairy cows with normal body condition (BCS 3). The ovaries were recovered from slaughtered cyclic dairy cows (at the luteal phase of the cycle) of Czech Fleckvieh and Holstein breeds at different times of the post-partum period. The animals were estimated as belonging to certain grade of body condition score (BCS) according to a 5-point scale. Only dairy cows with BCS1 (emaciation; n=6), BCS2 (tendency to emaciation; n=5) and BCS3 (optimal body condition status; n=6) were available for the experiment. The ovarian samples were embedded into Technovit 7100 resin; the tissue sections were stained with buffered basic fuchsine with toluidine blue. For acidic mucopolysaccharides (aMPS) a combination of PAS-technique with Alcian blue was used. Histological analysis showed that emaciation was associated with an increased occurrence of late (cystic) and luteinization-related atresia in granulosa and theca cells and increased levels of aMPS in small atretic follicles. Our observations indicate that dairy cows with a tendency to emaciation (BCS 2) or emaciated (BCS 1) have elevated occurrence of late atresia and atresia with luteinization, while initial atresia is less. This expands our basic knowledge of ovarian histopathology providing new insight into the association of antral follicle atresia and body condition status in dairy cows.