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23rd February, 2019


Johnes DiseaseThe spring calving season will begin in the majority of dairy farms over the next fortnight.  Many farmers look forward to starting the milking machine again, although the workload associated with calving cows and correct calf management will result in long hours on a daily basis for the next ten weeks.


It is essential that you have done all the preparatory work to optimise both cow and calf health.  Ensure cows placed into calving boxes have an adequate supply of a balanced precalver diet and fresh water in front of them. This is a simple task which is often neglected with a serious negative consequential impact on the metabolic state of the cow.  Feed restriction will impact negatively on post calving uterine involution.  Research has shown clearly that a negative experience in the pre-calving period will increase the calving interval.


The “maternity” ward has to be kept clean between calvings.  This is a high risk environment for the establishment of metritis and endometritis which will increase the calving to pregnancy interval.


The importance of colostrum management has taken an increased impetus with the need to control the risk of Johnes’ disease transmission.  In the first instance it is essential that the new born calf gets sufficient high quality colostrum within the first few hours of life.  Remember, the dry cow transition phase management with mineral and vitamin requirements will dictate colostrum quality.


It is essential to have a stock of colostrum available from older cows in the herd, which have been tested negative to Johnes’ disease.  This will enable you to stomach tube calves where the mother has insufficient or poor quality colostrum or the calf has been compromised following a difficult calving.


The importance of colostrum management cannot be overemphasised.  You have to focus on your calves having a healthy immune system in the first two months of life.  Coccidiosis, cryptosporidium and pneumonia in calves cause too many deaths and debilitation.  There is evidence that these setbacks in early life have an adverse effect on the onset of puberty and reproductive performance in maiden heifers.


With regard to Johnes’ management, it is important to realise that the calving environment is a high risk area for the transmission of the disease from a Johnes’ positive cow to her offspring.  There are risks of transmission associated with faeces, uterine fluids and colostrum.


In the case scenario of a Johnes’ positive cow, it may be prudent to “switch” the calf at birth to reduce the risk of disease transmission.  The importance of a “sterile” calving environment is essential in the prevention of disease transmission.  The day of batch feeding colostrum to new born calves is long gone.  You cannot safely state that your herd is Johnes’ free.  The current tests incorporating milk, faeces and blood will not give 100pc accuracy for a negative status.  The reliability of the test is poor in animals less than two years of age.


Therefore, you need to take preventative measures described above to prevent disease transmission.  Some farmers have resorted to the pasteurisation of both colostrum and whole milk fed to calves.  There are significant effects of the temperature used and its’ duration on the impact of pasteurisation.  Pasteurisation will not eliminate the risk of disease transmission.  However, farmers consider the risk of batch feeding milk to be minimal following pasteurisation.


In reality, the controlled management of feeding colostrum and whole milk to calves will be difficult where large numbers of calves are born over a short period and hired labour is used to manage the young stock.  Pasteurisation of colostrum and whole milk and the use of milk replaced from an early age may be practical alternatives.


The dairy industry needs to place a strong emphasis on management of Johnes’ disease.  Aside from the perceived link to Crohnes’ disease in humans, there is a significant financial loss to the dairy industry.  Johnes’ disease results in significant milk production and reproductive performance impairment prior to the clinical symptoms of the disease.  Indeed, many cows will not present with clinical symptoms with a positive diagnostic test.  The incubation period of the disease prior to presentation of clinical symptoms may be up three years from the time of infection.


Clinical symptoms associated with Johnes’ disease include persistent scour, excessive loss in body condition score, greater risk of secondary diseases associated with impaired immune function and poor reproductive performance.


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