BIOLOGICAL PRINCIPLES OF FERTILITY IN FEM ALE CATTLE

Fertility is the capacity of individuals to reproduce. Birth of progen ies in mammals is the final point of a cascade of biological events an d processes which develop in a determinate time hierarchy but function ally in a close linkage. All events and processes together form the bi ological bases of fertility. Main biological principles of fertility a re as follows: - oogenesis, follicular genesis - puberty - follicular growth and maturation, ovulation - fertilization - embryonic developme nt - implantation - fetal development - parturition Sexual reproductio n in mammals is characterized by the alternation of haploid and diploi d cell generations and by their manifold interactions. Both the altern ation of cell generations and the interactions between germinative, em bryonic and somatic cells are induced and controlled by a great and th eir products. Studies in the fields of protein biochemistry immunology ,cytophysiology and molecular biology contribute to understand the str ucture and function of genes and their products. Paracrine and autocri ne regulation mechanisms give rise to the fine regulation of all repro ductive processes on a cellular level. However, current knowledge of t he individual biological principles of fertility is clearly different. This contribution tries to illustrate the current state of knowledge of selected biological principles of fertility.