Synchronisation programs form an integral component of successful reproductive management in the modern dairy herd. Synchronisation involves the management of the cow oestrus cycle so that a cow may be bred in a controlled and planned manner.
Gonadotropin-releasing hormone, or GnRH, is one of the key hormones used in successful synchrony programs today. GnRH is a hormone made in a part of the cow brain that acts to release more hormones (FSH and LH) that are vital for successful follicular development and ovulation in the ovary. Just like other hormones we use to synchronise cows (e.g. Prostaglandin or PG), a synthetic version of GnRH is part of a hormonal program to induce the cows natural cycle and is efficient and safe to use.
GnRH based programs were developed in the mid 90s and had traditionally been used in fixed-time synchrony programs. Specific use of GnRH based programs for the treatment of post-partum anoestrus (non-cycling or no visible oestrus), a common condition found in the modern dairy cow, became a valuable method of treatment by the dairy industry in Australia when oestradiol benzoate (ODB) became unavailable.
Due to the wider exposure and familiarity with GnRH based programs in non-cycling cows, a greater interest in whole herd synchrony by Australian herd owners has evolved. Warrnambool Veterinary have identified this trend, and since 2009 have been actively involved in many on-farm comparisons using GnRH based programs, in both cycling and non-cycling cows.
Warrnambool Veterinary is convinced that when used in conjunction with other hormones, GnRH is an essential part of a whole herd synchrony or a non-cycling cow treatment program that is successfully used to get more cows in calf.
Our commitment to our dairy farmers is to use evidence based research and results to guide reproductive recommendations that will result in positive benefits for their herds.
An example of the successful use of GnRH, in combination with other hormones, is in a synchrony program aimed at treating post-partum anoestrus cows. In 2011 Warrnambool Veterinary showed that an equivalent 1st insemination conception rate (CR1) and 6 week in-calf-rate (6 wk ICR) could be achieved in non- cycling cows when compared to their cycling herd mates (40% CR1 and 57% 6wk ICR). This is an outstanding result for the most difficult cows in a herd to get in calf!
However the use of GnRH in an attempt to “enhance” fertility at the time of AI, which is referred to in a recent article “No value in blanket treatment with GnRH at AI” (The Australian Dairy farmer May-June 2014, pg33) should clearly be differentiated from synchrony programs using GnRH.
This study from Gippsland found a benefit in a small group of cows when GnRH was used at the time of insemination. In these cows the conception rate was increased slightly, but overall there was no benefit from treatment.
These findings reinforce our current recommendation that the blanket use of GnRH at the time of AI is not an economically worthwhile practice to increase conception rates.