4. Improved Farm Management Test and Cull Case Studies

The Milne Family at Carcary Holsteins
Recording is key at the Milne's

Recording is key at the Milne's

Following one of the six strategies from the National Johne’s Management Plan is helping to deliver control of this challenging disease to farmers across the country.  

Strategy 4: Improved farm management, test and cull

The Milne family; Sandy with Emma, and parents Ian and Dawn alongside their dedicated staff have been dealing with Johne’s disease on their Scottish dairy farm since the mid to late 1990's. Although the definitive source of the disease isn't known, Ian believes it is likely to have come from a few black and white cattle which were bought in to enhance the traditionally red and white herd. Today, they have 400 milking cows on the 1250 acre landmass situated at Brechin, between Dundee and Aberdeen.

In the late 1990's, when Johne’s disease is thought to have started to become a problem on the farm, there is thought to have been an element of ignorance. Cows were being culled due to poor condition and scour, without any knowledge of the underlying cause. At the time, it was common practice at the East Pitforthie and for many others, to pool colostrum for the calves and vaccination was the mainstay control measure for tackling Johne’s disease.

In the early 2000's the farm began testing cattle for Johne’s disease. It became apparent at this stage that the vaccination programme was leading to a number of false positive results, and by February 2008 the vaccination programme was stopped.

In 2003 a new unit was built on the current site at East Pitforthie, which saw the two 120 cow herds run by the Milne's combined onto the one site. The ongoing intention was to push cow numbers up to the 400 mark. By then the family was very aware of the Johne’s disease problem on the farm and planned to cull hard on test results, whilst aiming to expand at the same time.

Strategy four from the six strategies identified by the National Johne’s Control Group has been implemented within the Carcary herd to help control and prevent Johne’s disease. Without a doubt, improvements in farm management and recording have made the biggest inroad. The Milne family in conjunction with their vet, Graeme Richardson of Thrums Vet Group, Kirriemuir, are under the belief that they may be able to eradicate the disease completely in the medium to long term, but this is only made possible by the layout of buildings on farm which facilitate segregation of different groups.

Johne’s disease management protocols on farm now are very regimented, and although it initially took time to get the entire team on board, they now understand the importance and relevance in managing and controlling Johne’s disease. A three coloured tag system is practised on farm. A white tag indicates an animal classed as clear, a blue tag shows the grand-dam tested positive for Johne’s disease and finally a yellow tag shows the animal was snatch calved. Furthermore, all cows and heifers are blood tested at drying off. The unit allows a split in the calving accommodation, with one side designated 'clean' while the other is classed 'dirty'. The young stock and dry cow shed is also solely kept for 'clean' animals.

The farm has also introduced many more set procedures around the time of calving that all aim to minimise and break the cycle of Johne’s disease transmission. These include;
  • Segregation: any calf born to a dam that has had a positive blood test for Johne’s disease is either snatch calved or if a heifer calf is not snatched it is identified straight away as being only for beef rather than as a replacement.
  • Any calf born from a blue tagged dam is not fed its mother's colostrum or milk. In the office a list of ‘clean’ animals is displayed- extra colostrum is collected from these animals and is pasteurised, bagged and frozen.
  • Any milk from Johne’s disease positive dams is only fed to bull calves that are not kept as breeding animals.
  • Cows with positive blood tests are culled once they are dried off or if they deteriorate and show clinical signs of the disease, indicating they are likely to be shedding, they are culled a soon as possible.
  • All calves, even those born to a ‘clean’ dam, are moved to individual calf housing as soon as possible after birth.
They have also improved their ongoing testing/monitoring and are now doing regular milk testing. From these results, the Johne’s disease status of every cows is recorded annually on the farms computer to improve the detail with which the herds Johne’s disease status is monitored.

Their farm vet, Graeme Richardson, from Thrums Veterinary Practice, said: “Vaccination was introduced as a control strategy when the level was relatively low, whilst vaccination was being practised the level of infection rose, peaking at about 35%. Since stringent management practices were enforced by the farmer alongside a carefully crafted test and cull policy the level has dropped to around 2% and is still dropping.

“The key to successful Johne's control is to establish what actions need to be prioritised on each individual farm. Each one has different circumstances and resources and trying to shoe horn all farms into a tick box exercise does not work. Without doubt, where we have had greatest success is where the farmer buys into the programme of change and we as vets can guide him/her with a bespoke programme of control and risk management.”

Summing up the effect of Johne’s disease and its subsequent control the Milne family say it has led to improved attention to detail on farm which has in addition helped the whole business grow.

Ian tells a poignant story that he felt brought the message home some years ago - a tested clean, prize winning cow within the pedigree Carcary herd calved a strong heifer calf in a clean bedded and isolated area. However, the calf managed to move off the clean area and into an area potentially contaminated with infected muck. Without hesitation Ian instructed the calf to be classed as dirty/infected and to be tagged accordingly as not to be bred from in the future. If you are serious about tackling Johne’s disease there is no room for sentimentality - the disease is ruthless in nature and so must everyone else be in dealing with it.  

West Hayes Farm
Case Study Strategy 4: Improved Farm Management Test and Cull
David Hiscox, West Hayes Farm
Rachel Hayton, Synergy Farm Health

West Hayes Farm in Sherbourne, Dorset is a 300 dairy herd in an extensive grazing system, utilising Friesian and crossbred genetics.

Vet Rachel Hayton from Synergy Farm Health introduced their Johne’s management strategy in 2011. The strategy has been overseen by Dave ever since, organising the testing regime, culling decisions and calving and youngstock management as well as making sure the farm staff carry out the necessary practices (including snatch calving) when he isn't there.

In 2011 Johne’s disease was considered one of the major threats to the farm due to the levels of clinical disease seen.

The dairy herd is split into two cohorts (a) the dairy herd producing replacements and (b) the dairy herd producing beef animals. The two cohorts calf at distinct times of year with the former calving between February and May.

The whole herd is milk sampled for Johne’s serology on individual milk samples prior to dry off. Any animals in the “Dairy producing dairy” block identified as amber or red on the milk test are excluded from the calving box and calved in an isolation unit. All calves from this unit are snatched prior to colostral transfer and if this cannot be achieved, they are tagged as “Johne’s suspect” animals and not retained as replacements.

The “Johne’s free calving box” is not used for mastitis, lame of sick cows during this period, as these animals are possibly candidates for Johne’s shedding. Any replacement heifers born to a suspect mother are snatched and fed either colostrum from low risk cows identified on milk testing, or artificial colostrum.  Milk for sick cows under milk withdrawal is NOT fed to replacement calves. There is separate equipment for dairy and beef calves. Dairy replacements are then converted to milk replacer.

This strategy was chosen because the farm had a very high Johne’s prevalence, reflected in a high proportion of test positive cows and a steady trickle of clinical cases. It was felt that improved farm management alone would not lead to a sufficiently rapid reduction in disease prevalence and there was a need to remove animals before they became heavy shedders. However culling all test positive cows in the early days would have led to an unacceptably high culling rate. Therefore a compromise was reached whereby test positive cows are culled as soon as they develop any other problem, or simply look "plain". As a result cows have not demonstrated overt clinical disease for some time. At the same time the intensive management required to calve in replacement heifers is only required during a 3 month period.

Disease prevalence based on serology results has been dropping steadily in the last few years (4/30 positive in the last 30 cow screen) with the result that very low prevalence/eradication is now seen as an achievable option.

For eradication to be a realistic goal the control plan would have to be tightened up further, in ways that could not even have been considered 5 years ago.

Next steps might be:
  1. Closed herd. Currently bought in animals calve in to the beef bred cohort
  2. Sexed semen to further reduce the number of highly supervised calvings
  3. Not retaining offspring born to high risk cows