title: The use of DNA index and karyotype analyses as adjuncts to the estimation of fertility in stallions.
abstract: A total of 174 stallions were subjected to a standard fertility examination and classified as fertile, subfertile or sterile. All stallions were phenotypical males involved in breeding programmes with no detectable abnormalities in their reproductive organs. Fertile stallions had no history of any breeding problem. Subfertile stallions were referred with a history of a breeding problem that was subsequently determined not to be attributable to the mares or infectious diseases. They were divided into chromosomally normal and abnormal groups on the basis of karyotype. The relative DNA content of lymphocytes (DI) was estimated by flow cytometry to relate this parameter with chromosome status. Of 62 completed karyotypes, 44 were normal diploid stallions and 18 had chromosomal defects, including mosaics with sex or autosomal deletions or duplications. The seasonal pregnancy rates for the subfertile chromosomally defective and subfertile chromosomally normal stallions were similar but were less than half of those of the fertile stallions. With the present limited data, no association was noted between DI and pregnancy rate. The mean DI for the subfertile stallions with chromosome defects was not different from those of the fertile and the subfertile chromosomally normal stallions. However, the DI for a mosaic stallion with sex chromosome deletion was lower than the DI for the fertile stallions. Extremely high and low values of the DI may be useful for flagging potential subjects for detailed chromosome investigation. The DI also was correlated negatively (P less than 0.002) with progressive sperm motility.
authors.affiliation: Hofmann Fertility Clinic, Section of Reproductive Studies, New Bolton Center, Kennett Square, Pennsylvania 19348.
authors.forename: R M
authors.initials: RM
authors.lastname: Kenney
authors.forename: M G
authors.initials: MG
authors.lastname: Kent
authors.forename: M C
authors.initials: MC
authors.lastname: Garcia
authors.forename: J P
authors.initials: JP
authors.lastname: Hurtgen
mesh_terms: D000818:Animals; D002875:Chromosomes; D004247:DNA / Q000032:analysis*; D005298:Fertility / Q000235:genetics* / Q000502:physiology; D006736:Horses / Q000235:genetics / Q000502:physiology*; D007621:Karyotyping; D008297:Male; D012621:Seasons; D012661:Semen / Q000502:physiology
chemical_list: D004247:DNA