In response to industry and consumer calls for more judicious antibiotic use, additional research has gone into selective dry cow treatment (SDCT).
The University of Minnesota College of Veterinary Medicine and Cornell University recently developed two different SDCT protocols, each capable of cutting back antibiotic usage at dry-off by at least 55% while enhancing animal welfare and maintaining herd health.
Blanket dry cow treatment has long been the go-to methodology for most conventional dairies. However, there are certain animals at a significantly lower risk for having subclinical mastitis than their herdmates. If identified and managed, they can be dried off using only a teat sealant and no antibiotics.
Sandra Godden was a lead on the University of Minnesota’s team. For the program to be successful, she says that the untreated animals needed to freshen in as good of health as the treated ones. This was determined by following study cows for 120 days into the next lactation and comparing Dairy Herd Improvement Association (DHIA) SCC, milk production, clinical mastitis risk and culling risk between cows randomly assigned to the SDCT groups versus the blanket treatment group.
The universities developed two different approaches for the program. The University of Minnesota developed a quarter-level culture-based approach using their easy rapid culture system for on-farm use. Candidates for treatment and non-treatment are determined based on the resulting cultures.
Cornell University’s logarithmic method uses cell count histories and records of clinical mastitis. These factors are calculated to sort high- and low-risk animals into separate groups of treatment eligibility.
Observations
All the cows in the study were randomized into one of three groups – selective treatment (culture-guided or algorithm-guided) or blanket treatment (control group). For the algorithm method, groups were broken into high-risk or low-risk, based on somatic cell count (SCC) records and clinical mastitis history.
Each week, technicians sampled the quarters, and animals were either treated with an antibiotic and teat sealant or just teat sealant, based on their treatment assignment.
“The algorithm approach worked equally well to the culture-guided approach,” Godden reports. “Both of them reduced antibiotic use by 55 percent; that was significant.”
Jean Amundson, a veterinarian herself, has been using on-farm cultures in her own SDCT program for a while. She and her family’s 1,000-cow herd in Elk Mound, Wisconsin, was used in the study.
“This validated that what we were doing was a really good choice,” she says, noting that their protocol has allowed them to cut back dry cow antibiotic use by half.
Herd eligibility
As people continued to be interested in how their dairy [products are] ....produced, the industry can expect to have more pressure to continue reducing antibiotic usage. But to be effective without sacrificing animal health, herds need to already have strong dry and fresh cow programs that are reasonably healthy.
According to Godden, they recommend this protocol for herds with bulk SCCs less than 250 cells per milliliter with decent control over very contagious mastitis-causing pathogens.
With those standards, Minnesota DHI ran a list to estimate how many herds would be eligible for these SDCT protocols in April and May 2019.
They found 59% of herds on the report were eligible. Of those herds, they further estimated about 79% of cows would have been listed as low-risk and likely to not need treatment.
“That’s over 10,000 cows that could potentially not have been treated in just April and May in Minnesota alone,” she says. “If we extrapolate that to other dairy states, there’s a huge potential for a lot of herds to be thinking about adopting this. I’m hoping this will catch on, and producers will get excited.”
Financial components
Besides enhancing antibiotic stewardship, SDCT programs are also financially significant.
As part of their research, the University of Minnesota did an economic analysis on both proposed programs.
Godden reports that, on average, herds that adopted the culture method could save $2.14 per cow dried off. Those who were on the logarithm method could save even a bit more.
“On average, we expect you would save 7 dollars and 85 cents per cow dried off,” Godden says. “The major reason they’re saving money is because you’re using less antibiotics.”
The logarithm method saves more because the SCC data needed are essentially free to herds that are already on a routine DHIA testing program. Cost of on-farm culturing is about a $4 investment per cow when you calculate buying the plates and supplies, labor for sampling and plating milk, and cost of maintaining an on-farm culture lab.
The University of Minnesota is closely working with their state Dairy Herd Improvement Association (DHIA), which has come out with the algorithm-based SDCT report that will allow producers to have a list of which animals are high- and low-risk.
Cornell is making similar efforts with the New York DHIA so producers can generate their own reports through DairyComp.
Godden also reports that researchers and extension educators in Ontario are also working with their DHI teams to make their own reports and educate veterinarians and producers. She and Amundson are both optimistic that SDCT will continue to be adopted by many dairy producers.
“A lot of farmers are very aware of consumer concerns,” Amundson says. “It makes sense, and it’s better overall for the environment, for the cows and for us.”
