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23rd February, 2019


We are now between 3 and 6 weeks into our spring calving breeding programmes. The challenges of heat detection and AI are indeed immense. As herd size increases, the cost of accurate heat detection is a job in itself. Note, the descriptor ‘accurate’. Many farmers in their pursuit of high admission rates and the €250 cost of a missed heat, are submitting cows for AI which are not in heat.

A comment frequently made when Scan Man Vet technology identifies mistiming of AI “I use a relatively cheap Gene Ireland straw when the signs of heat are questionable”. This approach needs to be avoided as you run the risk of uterine infection by AI of cows which are not in heat. In addition, you will increase the incidence of embryonic death in cows previously inseminated.

As you complete your first three weeks of breeding, it is essential to identify those cows which have not been bred. These should be presented for veterinary attention as there is a €250 reward for every breeding opportunity accurately detected. The same rule applies when using a stock bull. One in ten 10 stock bulls will be either subfertile or infertile. Have you had your stock bull fertility tested? It is essential that you can identify those cows using tail paint, which is topped up at least twice a week.

There is a temptation to ‘blindly’ administrator prostaglandins to those cows not detected in heat. This will only work if cows are reproductively sound and in the middle of their cycle. Some cows may respond to prostaglandins but the heats will be infertile as there is a uterine infection preventing the normal expression of heat. The sensible approach is to seek veterinary attention bearing in mind the €250 cost associated with failure to successfully breed the cow at the right time.

When stock bulls are run with the herd, there is a significantly greater financial risk that cows with reproductive problems will not be identified. Stock bulls will address poor heat detection if the cows are fit and cycling. As stressors in the herd increase, reproductive dysfunction increases with poorer manifestation of heats. It is important to have sufficient bull power when using stock bulls. You need one fit bull for every forty eligible cows.

It makes economic sense to scan your herd, when running stock bulls six weeks into the breeding programme. This will enable veterinary attention for cows with reproductive problems. This will account for 10 to15pc of your cows with a minimum opportunity cost of €5,000 for reproductive failure in a 100 cow dairy herd.

There are also the economic benefits of assessing bull fertility based on early pregnancy diagnosis for the first three weeks of the breeding season for those cows eligible to establish pregnancy. Early embryonic death can also be accurately identified from in-depth diagnostic scanning. Early embryo death between 20 and 34 days after breeding will prevent cows returning to heat for periods up to 9 weeks after breeding.

The inclement weather experienced during the first two weeks of May has indeed reduced the expression of heats. ScanMan Vet technology has identified many cows not visually detected in heat where tail paint or scratch cards were used as aids as having undergone ‘silent heats’. This technology can accurately identify to within 1 day when cows were in heat between day 1 and 6 of cycle. It can also predict to within 1 day cows coming into heat over the next 3 days after scanning.

As the stress load on the herd increases, associated with a combination of either poor grazing conditions, dietary imbalance for minerals, energy requirements, lameness or mastitis, the expression, intensity and duration of heats decreases.

You cannot afford to miss heats in a year when profit margins from milk production are tight. You need to continuously bear in mind the opportunity cost of €250 per missed heat in grass based spring milk production systems. Dr. Stephen Butler in Moorepark has conducted excellent research work associated with synchronisation of heats. This technology will deliver significant financial gains where heat detection is poor on a farm. The targeted 90pc submission rates in reality average closer to 70pc on excess of 70pc of farms analysed from our database.

Heat detection in maiden heifers is primarily concerned with having heifers achieve targeted weights at the onset of the breeding season. Previous events such as calf scour and pneumonia will delay the onset the puberty independent of bodyweight when heifers are 14 to 16 months of age.

Dr. Dan Ryan is a bovine reproductive physiologist and can be contacted at


Article written by Dr. Dan Ryan in The Farming Independent May 19th 2015.