Dairy farmer using tablet

First Service Conception Rates vs Heat Numbers

Caroline Reid

Written by Caroline Reid

A production animal veterinarian
based in Vetlife Wanaka, Caroline
is also on our CowSmart team.

With an increasing number of cows in New Zealand wearing cow monitoring devices, we have an ever-growing number of animals available for data assessment.  

The 24/7 data from cow monitoring devices provides a massive data pool. All this data gives us information for evaluating ways to fine-tune our established farming systems and veterinary advice in order to maximise our production without compromising animal health.  

One of the many interesting data sets that we have scrutinised from last year’s mating, is the conception rate to a cow’s first insemination relative to how many heats she had had prior to AI. The graph below combines data from over 3,000 matings across six farms in Canterbury and Central Otago – all first matings on these farms are included.  

Graph showing first service conception rates vs heat numbers

The graph clearly shows the increase in conception rate as the number of heats the cow has had prior to first service increases. Conception rate increases from 50% conception in the cow’s first heat to a 57% conception rate at the second heat. The conception rate increases again if the cow’s first service is at her third or fourth heat.  

This data really shows the benefits of getting cows cycling early after calving. Your approach to getting cows cycling early should be multifaceted; it should include focussing on maximising your six-week in-calf rates in order to have an early calving herd. Cow monitoring data should be used to ensure cows recover swiftly after calving, and those that do not should be assessed and treated appropriately. Consideration should also be given to treating non-cycling cows early, so that they have their first heat after a non-cycler programme prior to the mating period, making use of the increased conception rate to second heats over first. 

To optimise your conception rates, have a discussion with your local Vetlife veterinarian to find out how we can help to get your cows cycling earlier and ready for mating. If you already have cow monitoring on your herd, ask about how Vetlife and CowSmart can help you get the most out of your monitoring, including health alert triages, custom reports and farm performance reviews.