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23rd February, 2019


Grass based spring calving programmes are nearing an end. Cows remaining to calve are in my opinion high risk pregnancies.  These cows cause the greatest health issues in the dry cow and fresh cow transition periods.  The late calving group is associated with a previous history of impaired reproductive performance linked to a combination of genetic and environmental stressors.

The late calving cow has to experience a positive dry and fresh transition period. This entails ensuring there is a significant lying and feed space and top quality silage supplemented with minerals and vitamins.  High potassium silage will cause significant metritis in freshly calved cows.  As temperatures increase and rate at which the feed face of silage pits are used decreases, there is a greater risk of mycotoxin contamination of silage.  Mycotoxins will cause severe adverse effects on cow health.

Less attention is given to our late calving cows. Fresh silage and water has to be kept in front of cows at all time.  There is a temptation to turn out late calving cows to grass.  This can cause severe metabolic problems with an increased incidence of milk fever, ketosis and displaced stomachs.  In my opinion, the late calvers should be kept on a constant dry cow diet balanced for minerals and vitamins.  The late calving group will tend to have a higher incidence of over conditioned cows and cows carrying twins.  Restricting feed intake and the suggestion by some advisors to reduce confinement are a definite no go solution.

Research has shown that administration of a bolus containing monensin 4 to 5 weeks precalving to have a positive effect on metabolic status with a reduced incidence of ketosis in over conditioned cows. This bolus also reduces the risk of rapid weight loss in the period precalving among cows carrying twins.

Breeding programmes for spring calving in 2018 will begin on most farms over the next four weeks. There is significant frustration among farmers regarding the recent debate concerning EBI figures for AI sires to be used this year.  This should not have happened so close to the onset of breeding programmes when decisions have been made regarding AI sires for 2018.

Your primary challenge will be the identification of cows with reproductive problems. This needs to be done now and not 4 to 6 weeks into your breeding programme.  With an emphasis placed on a 90% calving rate in a 6 week period, the problematic breeders need attention now.

Booster vaccinations for BVD, Leptosprosis and IBR need to be complete now. Some farmers have excluded vaccination programmes in an attempt to reduce costs.  This will have a detrimental effect on reproductive performance if the herd is stressed at any time, forcing persistently infected animals to shed either bacterial or viral infections.

Tail paint and teaser bulls with chin-ball markers are still the best aids in heat detection for grass based milk production systems. Focus on cows with poor body condition and lame cows.  Supplemental feeding with concentrates to this subgroup will benefit future reproductive health.  Lameness issues have to be addressed and rectified now if these cows are to survive with a calving opportunity in 2018.

If you plan using sexed semen in your breeding programme, consider an earlier start date to allow for a poorer pregnancy rate. There is tremendous variation achieved using sexed semen when compared to non-sexed semen.  When using sexed semen in dairy farms it is advisable to use a prebreed scan to access suitability of the cow.  A pregnancy rate of 50% should be considered acceptable with sexed semen.

In conclusion, the success of this year’s breeding programme will depend on management of your late calvers, identification and treatment of problematic cows and your ability to achieve an accurate 90% heat detection rate during the first 24 days of the breeding season.


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