January 2015 Fertility and Breeding Notes

Doreen Corridan MVB MRCVS PhD 

Munster Cattle Breeding



In herds where Johnes is an issue production and fertility are affected; however cows are usually culled for infertility or SCC before they develop the clinical signs of Johne’s-scouring and losing weight.
Herdowner’s need to test their entire milking herd to get a handle on their Johne’s status, using either milk at milk recording or blood at the annual herd test. 

While the test is not as accurate as the test for BVD, combined with a risk assessment on your herd, will help you establish your status and give you a way forward to deal with the disease.
If you are purchasing female replacements try and source them from herds who are testing for Johnes and are low risk, get your vet to contact the vet from the seller to establish the Johne’s status.
Incubation period

While Johnes is typically picked up in the first year of life, it has a long incubation period of 2-10 years. This is the difficulty with the disease as we can have ‘unseen spread’ for a number of years before it becomes an issue.
The aim is to protect the replacements heifer calves each year as they are born. Milk/beestings fed and exposing young replacement calves to dung from positive cows needs to be stopped.

Key point: It is important to establish your Johne’s status-as it can cause significant losses, even if they aren’t visible on farm.  Testing is a crucial part of this and very worthwhile even if the test isn’t quite as accurate as other tests.
The following 9 point plan is working well on high risk farms with positives identified

1. Keep testing and a profile will quickly develop with each test.

2. Cull the positives and suspects once confirmed and the last replacement heifer born from them. The advantage of culling them is that they will be no longer excreting dung, milk and beestings that is positive for Johnes on the farm.

3. Some herd-owners do not like the idea of culling heavily pregnant cows even though they are positive. In these cases they need to calve them in a separate area to avoid contaminating the calving box and feed none of their milk or beestings to any calves.

4. Cows need to be clean at calving, tails clipped and cubicles limed to avoid the new born calf getting infected from dung ingested.

5. Clean calving boxes are a must, they need to be well bedded.

6. The Key is to snatch the heifer calf from the calving box as soon as possible.

7. Each heifer calf then gets the 3 litres of beestings from its own dam in the first 2 hours followed by milk from its own dam until it is put on milk replacer.

8. It is essential that the replacement heifers get milk replacer even in a quota year.  Protect your 2015 replacement heifer crop. In herds that have issues with scour, vaccination with Rotavec Corona 3-8 weeks pre-calving works well

9. The final piece is to graze the calves in clean pasture for the first year of their life i.e. grazing ground that had no slurry spread on it and where no cows have grazed. This piece is very important if herds that are retaining positive cows as they are continually contaminating pastures, housing and the slurry.
Key point: Herds who have embraced all of the above 9 points are having great success. Every step you take in the right direction is helping. The sooner you start, the sooner you will make progress.


Prevention of hypocalcemia and milk fever ensures a healthy cow around calving and a good productive, fertile subsequent lactation. The cow with milk fever is the tip of the iceberg, many others are suffering hypocalcemia. Low calcium can persist from calving up to 10-45 days later. Next year may be a difficult year due to the late introduction of cows to dry cow minerals, higher BCS than normal at calving due to the long dry period.  

Key point: Prevention of milk fever and hypocalcemia is crucial as it is a ‘gateway’ disease which greatly increases the likelihood of other metabolic issues.

1. Magnesium (Mg) supplementation pre-calving is most important in prevention.


Dry cows need 25g+ of Mg daily in the 8 weeks pre calving-begin now. Trace element boluses do not contain any macro elements such as Magnesium, Phosphorus or Sodium and they do not contain any Vitamins.

3. Over conditioned cows are four times more likely to develop milk fever. This is due to reduced appetite pre calving resulting in lower intakes of Mg and Calcium (Ca) also a fatty liver and Vitamin D3 not being activated.  It will be difficult to achieve target BCS 3.03.25 this year with the long dry off period and the intakes of silage. BCS your cows now and feed straw if required. Now is the time to begin reducing intakes as cows will put on a full BCS in three month on ad-lib silage alone.

4. In high Potassium (K) silages hypocalcemia can be difficult to prevent, silages range from 0.6 to 5.6% K. Issues arise above 1.8%. Feed low K silages if available to the dry cows, if not available-dilute with straw or talk to your vet about feeding chloride salts in a DCAD diet 2-3 weeks pre-calving.

5. Ca supplementation at calving for high risk cows (older/high BCS)-At and immediately after calving
Key point: To prevent milk fever target 25g+ Mg per head per day (trace element boluses have zero Mg!), BCS and act on the results to prevent over-conditioned cows calving down and feed low K forage to dry cows.
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