Progesterone or progestogens can be administered either intravaginally or via ear implants. The ear implant Synchromate B (SMB) has been used widely in the USA and Europe. SMB (Ceva laboratories) utilises a 6mg norgestomet ear implant with an intramuscular injection of 5mg oestradiol valerate and 3mg norgestomet. Crestar (Intervet, UK) is a similar regime but the ear implant contains 3mg norgestomet. The objective of this experiment was to evaluate the effectiveness of Crestar as a synchronising agent for potential recipients in an embryo transfer programme.
A total of 334 Hereford x British Friesian maiden heifers, housed in straw bedded pens were allocated at random to be synchronised using either a PRID (Sanofi) plus prostaglandin; or a Crestar (Intervet, UK) regime. Equal numbers of heifers received each treatment.