A comparison of three methods of oestrus synchronization for fixed time insemination in dairy heifers

Abstract

Proc. Aust. Soc. Anim. Prod. 1996 Vol. 21 A COMPARISON OF THREE METHODS OF OESTRUS SYNCHRONISATION FOR FIXED TIME INSEMINATION IN DAIRY HEIFERS M.R. PERICHA, R.C. MULLEYB, I.J. LEANC and R. REINBERGER * * ' D D Leppington Pastoral Company, Pty Ltd, Bringelly, N.S.W. 2 17 1 School of Agriculture, University of Western Sydney-Hawkesbury, Richmond, N.S.W. 2753 Dept of Animal Science, University of Sydney, Camden, N.S.W. 2570 Dept of Animal Health, University of Sydney, Camden, N.S.W. 2570 We sought to evaluate 3 commonly used methods for synchronisation of oestrus for fixed-time insemination; the controlled release intra-vaginal device (Eazi-breed CIDR - Carter-Holt Harvey Plastics, New Zealand) (CIDR); prostaglandins (Prosolvin - Intervet Pty Ltd) (PG); and a norgestomet/oestradiol valerate aural implant (Crestar - Intervet Pty Ltd) (CSTAR). Effective means of synchronisation of oestrus, which will allow successful use of fixed-time insemination, will encourage greater use of artificial insemination in heifers. Heifers (n = 327) were aged between 20-24 months and were well grown, estimated to be greater than 350 kg and randomly assigned within blocks of 3 to the 3 treatments. Treatment 1 (n = 108) consisted of the intra-vaginal implantation of a CIDR for 10 days. These cattle were given a 10 mg oestradiol benzoate capsule at device insertion and 2 ml of PG at day 6 following device insertion. Treatment 2 (n = 110) consisted of 2 injections of 1 ml of PG given 10 days apart. Treatment 3 (n = 109) consisted of the aural insertion of a norgestomet 3 mg pellet and injection of 3 mg of norgestomet and 5 mg oestradiol valerate at pellet insertion. The pellet was removed from the ear on day 10. Heifers were inseminated 48 hours after device removal for CIDR and CSTAR groups, and 72 and 96 hours after treatment for the PG group. The heifers were tail painted and reported as in oestrus if most of the tail-paint was removed. Two outcomes were examined: display of oestrus and pregnancy. The heifers were mated in 4 batches over a 6-month period. Six weeks following mating, the heifers were tested to determine pregnancy. The operators detecting oestrus and diagnosing pregnancy were blinded to group allocations. Only 4 bulls were used in the trial and were randomly and evenly distributed across treatments. 384