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23rd February, 2019


The month of April brings a new dawn to our primary breeding programme for grass based milk production in Ireland.  Early turnout to grass has not been successful on my farm visits in the South.  Land is saturated because of the persistent rain over the winter months.  It is questionable the practice of where dietary requirements are not met and significant poaching of the grazing platform occurs.


This practice has a negative knock-on effect on heat cycles post calving.  Your primary focus has to be the minimization of negative energy balance period post calving.  Healthy cows resume heat cycles between 2 and 3 weeks post calving.  In excess of 90pc of these first heats are silent.  However, they are an excellent biomarker of previous management.


The management of your cows during the dry cow period and the calving process will dictate the resumption of heat cycles early post calving.

Lameness, mastitis, body weight loss precalving, poor silage quality, mineral imbalances and calving difficulties are all stressors which will be detrimental to return of heat cycles post calving.


Why are these early post calving heats so important?

Research has shown that the calving to pregnancy interval is shorter for cows having heat cycles resume by the time they are three weeks calved.  This all makes sense biologically.  From a farmers perspective there is the financial reward achieved by a lower empty rate at the end of a 14 week breeding period.


As your breeding programmes begin over the next three weeks, it is worth remembering that your heat detection rate will already be partially determined by events during the transition period.  It is essential that cows are fit when the breeding programme begins.  Events such as mastitis, lameness, reduced dietary requirement intakes and golf ball grazing will reduce the heat detection rate.


The heat detection rate is a combination of visual observation time spent watching cows, aids to heat detection, stressors preventing either the resumption of normal heat cycles or the duration and intensity of heat events. A sensible measure of heat detection rate should entail 24 day observation period for cows calving > 40 days at the onset of your breeding programme.  These cows make up the breeding group eligible for breeding and accounts for fact that some cows may have heat cycles of 24 day duration.


Your focus has be an optimal of heat detection rate with in excess of 90pc of cows fit for breeding detected in heat.  Research data from Teagasc, Moorepark has shown that missed heats cost €250 in grass based milk production systems.  Therefore, it is essential that you prepare for this pivotal driver of optimization of future financial returns from your dairy business.


Ensure all freeze brands are clearly visible.  Shave the surrounding build up of hair.  Use emulsion tail-paint applied as a six inch strip to the tail-head of each cow.  Use a bright red or yellow paint initially and apply a blue paint strip to those cows AI’d for the first time.  This enables you to focus more time watching cows not yet detected in heat and monitoring irregular heat cycles in those cows already AI’d.


Some farmers just use tail paint removal at milking times to determine timing of AI.  In my opinion, you should spend 20 minutes watching cows’ activity before bringing cows in for milking in the morning, three hours after both the morning and evening milking.


As herd sizes increase, there are now some excellent aids to heat detection. Farm software packages now offer applications which can be linked to your mobile phone.  These enable you to record heat events on your mobile phone in the field which automatically updates your software package and even draft cows out for AI.  There are now several activity monitoring systems to aid in heat detection.  It is essential to remember that these are aids and will not replace the human eye.


Scanning your cows prior to the breeding season will identify those cows cycling, the stage of the heat cycle and those cows requiring veterinary attention.  Cows can be selected on this basis for the use of sexed semen.  Remember it is futile using hormonal treatments on cows not fit for breeding and a waste of money on expensive semen.  Informed decision making makes economic sense.


Dr. Dan Ryan is a cow fertility expert and can be contacted at


Article written by Dr. Dan Ryan in The Farming Independent April 8th 2014.