Bull's fertility

The objectives of the project are to study the contributions of bull spermatozoa (SPZ) and seminal plasma (SP) to dairy cattle fertility.

This project is important to the animal breeding industry, particularly dairy producers, since fertility rates have been declining in dairy cattle (and other species). It has generally been assumed that selection for high milk yield has had a negative effect on female fertility. However, other factors may also be involved, for example, selecting bulls according to their sperm survival during freezing may have inadvertently selected for reduced fertility. A new method developed by the applicants, Single Layer Centrifugation (SLC), will be used to separate bull SPZ and SP. Sperm quality will be assayed and related subsequently to pregnancy rates obtained after AI. Epididymal sperm samples from slaughterhouse material, which have never been exposed to SP, will form an additional treatment group, subjected to the same analyses for sperm quality. SP from bulls of low and higher fertility will be chemically defined in terms of lipidomics and proteomics.

A cross-over study will be conducted in which SP from low fertility bulls is added to SPZ from high fertility bulls and vice versa, and the effects on sperm quality examined. Similarly the effect of both types of SP on the female reproductive tract will be determined. Characterization of the bioactive components of SP may lead to additives for semen extenders that can enhance fertility.

Financier: FORMAS
Co-applicant: Anders Johannisson; Patrice Humblot
Collaborator: Viking Genetics