At the 2018 Western Canadian Dairy Seminar, Tine van Werven shared two new treatments tried in the European market, as well as her experience over the past few years implementing selective dry cow treatments in the Netherlands.
“We see a shift more and more from cure to prevention,” said van Werven, an associate professor at Utrecht University.
In order to prevent mastitis, it is helpful to know when cows are at the highest risk for new intramammary infections. One high-risk time is at dry-off, which is a very critical period for the cow, she said. A second risky time is when colostrum genesis occurs.
Four factors have been identified that have an effect on new infection rates.
1. Milk production – The higher the milk production, the more chance of milk leakage. It also decreases teat-end closure.
2. Cracked teat ends – The more callouses on the teat ends, the easier it is for micro-organisms to enter the teat canal.
3. Exposure to bacteria – If the mammary gland is sterile at dry-off, the only thing left to do is prevent bacteria from the outside from entering the udder.
4. Impaired immune response – Aggression and stress can weaken a cow’s immune system and impair its response to infectious bacteria.
With today’s cows producing 65 to 85 pounds of milk at dry-off, it makes ending a lactation to prepare for the next one more challenging.
“If you can use antibiotics, that makes this much easier, but if you want to dry them off without antibiotics, you have to be sure you decrease milk production before you dry them off,” van Werven said.
If a cow’s mammary gland is using a lot of energy trying to absorb 65 or 75 pounds of milk, it doesn’t have much energy left to defend against micro-organisms.
In addition, teat-end closure is jeopardized. Through research, there was a 50 percent difference in the amount of teat ends closed between cows producing more than 46 pounds of milk at dry-off compared to cows producing less than 46 pounds of milk.
In the Netherlands, it is recommended to decrease milk production before drying off to 26 pounds of milk per day.
“That’s a difficult thing,” she said, noting 35 pounds is a little more achievable.
One way to lower milk production is to feed only hay, but doing so can result in a negative energy balance. Therefore, some pharmacological studies have looked into ways to inhibit prolactin synthesis to impair milk production.
A single injection of a prolactin inhibitor was shown to lower milk production as well as a hay-only diet but without affecting the energy status of the cow.
By reducing milk production, it reduces milk leakage and open teat ends, and therefore is a way to reduce new intramammary infection as well.
However, van Werven said the prolactin inhibitor was also shown to influence the calcium status of the cow. If cows are not fed properly through the dry period, its use might cause an increase in hypocalcemia cases.
Another prevention method developed in the last few years is immunomodulation. Used in human medicine to boost the immune system of people undergoing chemotherapy, a colony-stimulating factor encourages bone marrow to produce more white blood cells.
When a subcutaneous injection of recombinant bovine granulocyte stimulating factor was given in comparison to a saline injection, the result was fewer cases of mastitis and, for cows that did get mastitis, the duration was shorter and the severity was less.
“This is another treatment tool you could use to improve udder health during or just before the dry period,” van Werven said.
Selective dry cow treatment
They started using selective dry cow treatment in the Netherlands in 2014. Van Werven shared what they have learned as an industry over the past few years of putting it into practice.
The idea was to find a balance in reducing dry cow treatments without increasing the incidence of mastitis.
“If you get more mastitis back, then you are losing your benefit,” she said. “You have to find a way that you dry them off with less without getting a lot of extra mastitis back.”
First, they developed a simple guideline to base treatment decisions on the last DHI report as long as it was prepared in the last six weeks. A threshold was set to allow dry treatment with antibiotics of heifers with a somatic cell count (SCC) of more than 150,000 and multiparous cows with an SCC more than 250,000.
“We also decided to [select] on the cow level [instead of the quarter level] because we think all four quarters are not independent,” she said.
Changes to farm management were also encouraged.
“It’s not that easy to say we used dry treatment for 30 years and now let’s do something else, to just quit and expect life goes on as it was before,” van Werven said. “If you don’t improve your management, selective dry cow treatment could be a disaster.”
Dairy producers were told to treat dry cows like princesses and give them plenty of attention. Create an environment with less stress, which means no overstocking, enough space to eat and a place to lie down for every cow. Maintain good body condition scores to reduce problems after parturition. Feed a well-balanced dry cow ration with a good ratio of fat, protein and all the necessary vitamins and minerals.
If cows are not treated with antibiotics at dry-off, extra emphasis should be placed on hygiene.
Keep udders healthy during the lactation. The lower the SCC is when a cow enters the dry period, there is less chance for a new infection to develop.
Poor teat-end quality with a lot of hyperkeratosis makes it easy for micro-organisms to enter the teat end. In the teat-end closure study mentioned earlier, it was found there is always a percentage of cows that will not experience teat-end closure during the dry period. “That forces us to keep up the hygiene of the dry cow pen as well as possible,” she said.
Van Werven encouraged dairy producers to conduct a hygiene score on the farm, either on their own or with the help of a veterinarian or nutritionist. “You should do it once,” she said. “Just use your eyes and check your cows because you can get used to the hygiene of your own cows.”
Results of selective therapy
Prior to the ban on the preventative use of antimicrobials in 2012, and the introduction of selective dry cow treatment in 2014, it was known 70 percent of antibiotics used went into the mammary gland. In 2017, that ratio remains relatively the same, with two-thirds of antibiotics used in the mammary gland; however, the amount of intramammary tubes used for dry cow treatment decreased, van Werven said.
In addition, fewer antibiotics were used to treat mastitis, partly due to increased use of alternative treatments. “Less treatment does not mean less mastitis, but at least we didn’t see an increase,” she said.
This is evident in the national SCC, which was at its lowest rate ever in 2017. By looking at the combined SCC of approximately 18,000 herds, she said, “We don’t see any detrimental effect of selective dry cow treatment on our udder health figures.”
In the Netherlands, a new intramammary infection is defined as a change in SCC from below the threshold of 150,000 cells per milliliter for primiparous and 250,000 for multiparous cows at the last DHI recording before calving to an SCC of equal to or greater than the threshold at the first milk recording after calving.
Using data collected from the 280 herds belonging to the University Farm Animal Practice in the Netherlands, there was an average of 16 percent new intramammary infections in the dry period before selective dry cow treatment was introduced.
From 2014 to 2016, there was a slight increase in the percent of new infections. Van Werven said she observed two groups of farmers those first few years – the early adopters and the followers. Some farmers were eager to start and attempted to dry off all cows without any treatments. The followers waited to see some results before deciding to adopt the practice.
“I think we have proof of balance now, not only in our practice but also in the Netherlands,” she said.
In 2017, there was the same amount of new intramammary infections as what occurred before the selective dry cow treatment was implemented.
When she analyzed the use of different classes of antibiotics by the herds in the practice, van Werven said she was surprised to find 17 percent of the farmers used zero dry cow treatments in the last year. While some may be organic farms, it was a larger amount than she had expected to see.
She also noticed the farms that used less dry cow treatment also used less mastitis treatments. “This figure doesn’t give us the idea that if you use less dry cow treatment, you have to use more mastitis tubes,” she said.
“It seems very clear it’s just a management effect – the farms that have low somatic cell counts and well-established management use less dry cow treatment and also less mastitis treatment,” van Werven continued.
When she looked for a correlation between new intramammary infections during the dry period in farms with zero dry cow treatment and all other farms, she didn’t find one. The range of new infections was the same.
“It looks like there is no correlation between the percentage of new intramammary infection and the use of dry cow treatment,” she said. “Management and the profession of the farmer plays a much larger role.”
After a few years of putting it into practice in the Netherlands, it appears selective dry cow treatment has no detrimental effects on udder health figures.
The bottom line
Even though there are new developments being made in mastitis prevention to improve udder health, they don’t replace good farm management.
“The technical improvements should only be used on top of optimal management and not instead of,” van Werven said. “I don’t believe a solution is in a vial or syringe. You have to do your management in a very good way.”
The dry period is the start of a new lactation and not the end of the previous one. When you do all you can to reduce stress, provide an optimized ration and keep a clean environment, it is possible to reduce the amount of antibiotics used at dry-off. 
-
Karen Lee
- Editor
- Progressive Dairyman
- Email Karen Lee
