Reproduction, Fertility and Development Reproduction, Fertility and Development Society
Vertebrate reproductive science and technology

Use of equine chorionic gonadotrophin in synchronised AI of seasonal-breeding, pasture-based, anoestrous dairy cattle

M. A. Bryan A E , G. A. Bó B , C. Heuer C and F. R. Emslie D
+ Author Affiliations
- Author Affiliations

A VetSouth Ltd, PO Box 12, Winton, Southland, New Zealand.

B Instituto de Reproducción Animal Córdoba (IRAC), 2 Univ. Católica de Córdoba, 3UNICEN, 4Ag. Cba. Ciencia, Córdoba, Argentina.

C Epicentre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand.

D Bomac Laboratories Ltd, PO Box 76-369, Manakau City, Auckland, New Zealand.

E Corresponding author. Email:

Reproduction, Fertility and Development 22(1) 126-131
Published: 8 December 2009


In seasonally calving dairy areas, a critical index of efficiency and profitability is the ability to maintain a short annual calving spread. In essence, this means that all cows need to conceive within 90 days of calving. Anovulatory anoestrus (AA) is a major barrier to reproductive performance under these conditions and the successful treatment of AA is an important aspect of reproductive intervention. The present paper reviews regimens used to treat AA in New Zealand and reports on a large-scale field trial investigating the effects of equine chorionic gonadotrophin (eCG) within a proven efficacious treatment protocol. The administration of eCG at the time of removal of a progesterone-releasing device in an 8-day, oestradiol benzoate (EB)-based treatment protocol increased the percentage of cows in calf after 7 and 28 days of breeding. The interaction between cow age and treatment with eCG was significant, with cows over 5 years of age having higher conception rates (P = 0.002) and 7 day in-calf rates (P = 0.002) than cows on a standard 8-day treatment protocol without eCG. The addition of eCG to a standard 8-day EB/progesterone protocol can improve reproductive success in seasonally calving AA dairy cows.

Additional keywords: anovulatory anoestrus, oestradiol benzoate, progesterone.


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