The earlier non-cycling cows are treated, the better the return on investment.

Economic analysis has shown that it is more profitable to treat non-cycling cows as soon as possible, regardless of your calving pattern. 

Reasons for non-cycling cows: 

  • Pregnancy: a surprisingly frequent cause for apparent non-cycling cows. All non-cyclers should be vet-checked prior to any treatment to avoid loss of a potential pregnancy. 
  • Poorly grown heifers: failure to reach target weight at first joining and calving. Onset of puberty is influenced more by body weight than age.
  • Cows in poor body condition: aim to have cows calve at BCS 4.5 (1-8 scale).
  • Reproductive problems: cysts, infections or other issues with the reproductive tract can lead to non-cycling.
  • Other health problems such as lameness, can influence apparent cyclicity.
  • Late calving cows are less likely to cycle in the first month of joining. Speak with your veterinarian about how to effectively manage late-calving cows prior to the start of joining.
  • Cows are cycling but heats were missed.

When should non-cycling cows be identified?

  1. Prior to the start of mating: using tail paint and pre-mating heat detection. Cows not showing any signs of oestrous should be treated 10 days prior to mating start date. They should then have their first heat at the start of mating.
  2. All cows which have not cycled in the first 21 days of mating: these cows should be vet-checked as waiting for these cows to cycle on their own will cost you money. 

Treatment for non-cyclers
The main treatment for non-cycling cows is the Ovsynch program of which there are various different modifications.

Modified Ovsynch Shown to Improve Fertility
A trial conducted in SW Victoria involving 1703 dairy cows selected from five split-calving herds, showed the potential benefits of using a Modified Ovsynch program. Lactating cows were divided into two equal groups:

1. Original Ovsynch program:
Day 1: GnRH
Day 7: PG
Day 10: GnRH.
~13 to 16 hours after Day 10
GnRH: Fixed time AI for all cows.

2. Modified Ovsynch program:

Same treatments as Original Ovsynch group, with an additional PG on day 8. 

Results
After adjusting for the effect of herd, conception rates were 7.0% greater in cows in the Modified Ovsynch group. 

Conclusion
Using the Modified Ovsynch Program in Holstein and Holstein-Friesian dairy cows in a pasture-based system may increase the conception rate using a fixed time artificial insemination protocol.

To decide the exact program and timing to treat non-cycling cowsit is important you talk to your vet prior to the start of mating. Call the Farm Desk on 5561 7666