Manipulation of the Estrous Cycle in Sheep and Goats

Manipulation of the estrous cycle is an important tool for out-of-season breeding and for implementing fixed-time artificial insemination and embryo transfer technologies. This chapter covers non-hormonal and hormonal methods used to synchronize estrus in sheep and goats. Non-hormonal methods are increasing in demand by the organic farming industry. The male effect is the oldest technique for the induction and synchronization of cyclicity. It can be used alone or in combination with photoperiodic stimulation or melatonin administration. The response to the male effect and factors influencing it are discussed. During the breeding season, estrous synchronization can be achieved with prostaglandin F2α administration or progestogen treatment. Out-of-season estrous synchronization protocols rely on progestogen use. The various estrous synchronization protocols are described and presented in a simple graphical illustration. The chapter concludes with a discussion of ovulation synchronization protocols.