Sunday 25 September 2016

The heat is on as the breeding season kicks in

Dan Ryan

Published 20/05/2015 | 02:30

Jim Irwin and Tomas Cooney from Lely at the live milking demonstration using the Lely Astronaut robotic milker at this week's Balmoral Show. Photo: Chris McCullough
Jim Irwin and Tomas Cooney from Lely at the live milking demonstration using the Lely Astronaut robotic milker at this week's Balmoral Show. Photo: Chris McCullough

We are now between three and six weeks into our spring calving breeding programme and the challenges of heat detection and AI are indeed immense.

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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.

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 10 stock bulls will be either subfertile or infertile. Have you had your stock bull fertility tested? It is also essential that you can identify problem 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 costs 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 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 40 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 10-15pc of your cows with a minimum opportunity cost of €5,000 for reproductive failure in a 100 cow dairy herd.

Economic benefits

There are also the economic benefits from 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 nine weeks after breeding.

The inclement weather experienced during the first two weeks of May has really 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 one day when cows were in heat between day 1 and day 6 of their cycle. It can also predict to within one day cows coming into heat over the next three 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.

Despite the targeted 90pc submission rates, the reality is that averages are closer to 70pc on more than 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 of 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 www.cowsdna.com

dryan@ independent.ie

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