Heat Detection

Heat Detection
By Katrina Roberts, Herd Health Veterinarian

So, what’s the most important job on your farm for the next six weeks (or more)?

Hopefully everyone reading this has mumbled ‘picking the cows on heat’. But this isn’t something to declare loudly not mumble. InCalf research tells us that this job needs to be done by the most experienced people in your farm team and should not be shared between all staff. I know that doesn’t make for a particularly exciting few weeks ahead, but you all know that the effort you put in now, will repay you next season in more milk and more AB calves. With many of our clients considering all AB in the milking herd this season, heat detection is more important than ever. There is no bull there to fix up the cows you missed!

The herds that are achieving 78% 6 week inCalf rates are achieving more than 90% of their herd submitted by the end of week 3, but we know that the national average submission rate is only 80%. We also know that missed heats is one of the primary reasons for that lower than target submission rate.

The duration that cows are in standing heat varies considerably (range 2-28h but typically 12-18h), therefore those cows with shorter heats really need some dedicated observation to be identified and put up at the right time. The intensity of a cow’s heat can be negatively affected by factors such as poorer body condition score, poor health, low energy intakes, adverse weather conditions and stress.

The heat behaviours exhibited are due to the hormone oestrogen, and therefore the higher the levels of oestrogen, the stronger the signs of heat. A recent published study in the UK clarifies the timing of the varying signs that cows exhibit during a heat event. The first signs of heat that a cow exhibits are sniffing other cows followed by allowing cows to sniff them. These are followed by the on-heat cow resting her chin on other cows and then allowing cows to rest their chins on her. This then follows the on-heat cow mounting other cows and nearby cows attempting to mount her (but her rejecting the mounting), and then finally standing to be mounted. After the cows have finished standing heat, the signs of heat that preceded the standing mount occur in reverse order. The on-heat cows are most active (most walking) during the mounting and being mounted periods. Other signs of heat commonly observed in New Zealanc cows (but not reported in that study) include bellowing, reduced milk production, a change in milking order, mucus around the vulva or on the tail and evidence they have been ridden by other cows (mud on the flanks, saliva on their backs).

Good heat detection is not just about observing the signs of a cow on heat is it also what each of your farm team do with that information. Is everyone on your farm aware of their role in the heat detection system?

There are simple checks that can be undertaken during the pre-mating period to make sure you are all ready for the planned start of mating:
  • Have all your calving dates been entered into Minda/Insite?
  • Are all ear tags clean (check that electronic tags/collars are working for ALL cows)
  • Are the drafting gates all functional?
  • What heat detection aids (tail paint, other detectors) are you using, how are they being applied, do all staff know how to apply them correctly?
  • How often are heat detection aids being reapplied and by who?
  • Do all staff know the signs of a cow on heat?
  • If someone see a cow on heat, where does this information go (whiteboard, Protrack, pass it onto the Manager)?
  • Where are the on-heat cows going to wait for the AB Technician?
  • Who is responsible for returning the mated cows to their appropriate mob after AB?
If you need some help getting your staff motivated for this season’s heat detection, please talk to your vet.


Date Added: Saturday, 1st September 2018


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