Inhibin acts as a negative feedback regulator of follicle stimulating
hormone (FSH), therefore, attenuation of its biological activity throu
gh immunisation should lead to an increase in the circulating concentr
ations of FSH. In turn, this should result in increased ovulation rate
s and a consequent increase in litter size. In this article, we review
work on the structure and function of inhibin which ultimately led to
the development of inhibin-based fecundity vaccines. These vaccines h
ave been shown to cause increases in ovulation rate and litter size in
sheep and increases in ovulation rate in cattle and pigs. The data es
tablish a basis for using inhibin vaccines to increase fecundity in an
imals of economic importance.