Scott McDougall sorting milk samples during herd testing for mastitis.
After hearing reports of clinical mastitis cases developing over the dry period, industry experts have been digging to uncover what could be causing the problem. They were keen to identify factors to help advise veterinarians and farmers on how they could reduce the risk.
“It’s frustrating to deal with mastitis at the best of times, but it’s a real hassle when it develops in the dry period,” Cognosco managing director and lead researcher Scott McDougall says.
“We were trying to understand why this was happening, what it was about individual farms or individual cows that was leading to this apparent increase in the risk of mastitis.
“Particularly because it appeared to be happening more frequently in herds that have been using selective dry cow therapy and farmers and vets who may have had a problem in the past needed to have the confidence to try again.”
McDougall worked with researchers from DairyNZ and Bayer New Zealand. Together they uncovered when cows only received internal teat sealant (ITS) their risk of clinical mastitis developing in the dry period was associated with their age, milk yield before drying-off and timing of drying-off.
And the cows that developed clinical mastitis over the dry period had a higher risk of clinical mastitis and an elevated somatic cell count (SCC) in the following lactation.
“Traditionally, candidates for dry cow therapy are selected on their somatic cell count or whether they have had clinical mastitis during the season,” McDougall says.
“But for herds who have had problems in the past or are at risk of experiencing dry period clinical mastitis, they should also consider the age and production volume of the cow regardless of her cell count.
“We found if an animal is more than four years old and is producing more than 10 litres of milk at that last herd test, the risk roughly doubles.”
The research also highlighted that management of cows around drying-off and the level of hygiene during the process needs to be vigilant. Steps need to be taken to reduce milk yield prior to drying off cows as well as their physical management after dry-off,” he says.
“Those basics need a bit more care and thought when using selective dry cow therapy and teat sealants.
“When antimicrobials are on board there is a bit more flex as they act as a backstop to protect the cow if they acquire a new infection, but when we are being selective we need to be a little bit more diligent.
“For example, if a cow runs down the race with an udder half-full of milk she might leak and expose the teat canal to bugs and possibly lose the teat sealant that was inserted.”
And one of the most important factors is hygiene when performing the procedure.
“We regularly hear farmers say the infection was already there, they must’ve missed that cow when choosing their dry cow therapy group for whatever reason, but all our data shows even when a truly infected cow is given teat sealant alone, the majority of them self-cure and don’t develop clinical mastitis anyway,” he says.
“We didn’t see any of those cows develop clinical mastitis over the dry period in our research, but the ones that did have had a new infection introduced.
“The mammary gland hasn’t seen the bugs, the immune system is in idle and if we accidentally put a bunch of bugs in there the immune system can’t react fast enough and those are the ones that develop clinical mastitis usually quite quickly after drying-off.”
The recommendations from the industry support programme SmartSAMM are still valid and were reinforced with the research findings. They stress the importance of ensuring the team has had sufficient training and helping them understand the reasons behind doing things.
“There needs to be an emphasis on training, doing some cows before the dry-off date to practice and having a clear process of one person per cow, responsible for cleaning the teat, inserting the tube and marking the cow to remove the chance of error,” he says.
“When individuals focus on a specific task, for example, one person running ahead cleaning teats, there are more chances for problems. They might get too far ahead and bugs could contaminate the teat before the tube has been inserted or there could be confusion which teats have been prepared.
“It can be a tricky conversation for vets to have with farmers, but it’s really important to have a competent team to reduce the risks.”
Timeframes are also important. McDougall explains a well-trained person can treat around 20 cows per hour effectively.
“Sometimes bringing in a team of trained techs can be a good option but whatever method they choose, we can’t stress enough how important it is to get right,” he says.
“A bit of planning and training will go a long way for a successful dry-off.”