Large numbers of non-cyclers will prevent you from achieving your target 6-week in-calf rate because they depress the two key drivers - the 3-week submission rate and conception rate to first insemination.
Both drivers are important, but the 3-week submission rate has a bigger impact because it is more readily influenced by your management during that first 3 weeks of the AB programme.
Of course, good heat detection is essential to reach the submission target of 90 percent or more. The cows not inseminated in the first 3 weeks in a herd with good heat detection rates will mostly be 'non-cyclers'.
There are two types of non-cyclers
1. Cows that have ovulated (i.e. ovaries are 'cycling') but not shown any visible signs of heat.
These may have had a 'silent' heat. About 70–80 percent of cows will not have a visible heat at the first ovulation after calving.
2. Cows that have not even started ovulating since calving and cannot have a heat – a true non-cycler.
These are technically described as non-cycling or 'anoestrus'. It is the most common form of infertility in New Zealand herds.
A veterinary examination can distinguish cows in each category. However, the current practice is not necessarily to palpate these cows.
The recommendation is that both types of non-cyclers will benefit from receiving the standard form of treatment.
Doing pre-mating heat detection provides early warning you have non-cyclers, and time to do something if required.
Treating non-cycling cows
Short-term measures to treat non-cycling cows include treating them with hormones. There is no "one size fits all" approach. Each farm needs to assess their non-cycler situation individually and formulate a plan.
Treating cows is more cost-effective than doing nothing. This has been validated in research over a wide range of milk payments and responses to treatment. It confirms that investing in the treatment of non-cycling cows provides worthwhile returns to farmers.
Timing of treatment
Identifying and treating non-cycling cows before mating significantly improves their reproductive performance in seasonally calving dairy herds. This was proven in research that was carried out to assess whether hormone treatment before the start of mating, or leaving treatment until sixteen days after mating began, achieves better results.
Treatment eight days before the planned start of mating increases the number of cows that conceive in the first three weeks. It also reduces the time from the start of mating to conception. The conception rate of cows mated following treatment has been shown to be the same as cows mated at their first spontaneous cycle after calving.
There are many reasons why cows may not cycle. If your herd is experiencing large numbers of non-cycling cows each season, there is likely an underlying issue that needs to be addressed with your vet and adviser.
This gap calculator assesses the likely impact of your non-cycling rate on your herd’s overall reproductive performance.