Selective dry cow therapy (SDCT) is being used on many farms for the first time this year, following the introduction of new regulations requiring it to be used
Many farms have been using it for a number of years, with most of these farms having reasonable success.
Teagasc has conducted some research to determine what made these farmers successful with SDCT.
Speaking to Agriland, Pablo Silva Bolona, a researcher with Teagasc outlined some recent research conducted on the implementation of SDCT in Irish dairy herds.
SDCT
According to Bolona, international studies show that treating low somatic cell count (SCC) cows (< 200,000 cells/ml) with a teat sealant alone at dry-off was as effective in preventing new dry period infections as using intra-mammary antibiotics combined with teat sealant.
However, Teagasc studies in research and commercial herds show that treating low-SCC cows at dry-off with a teat sealant resulted in a higher average SCC in the following lactation.
This was when compared to treating cows with an antibiotic plus a teat sealant (125,100 cells/ml vs. 75,700 cells/ml, respectively). It also showed a higher probability of having an infection at calving (18.8% vs 3.4%, respectively).
It is important to note that Staphylococcus aureus was causing most of the infections in this study, which is one of the major differences with the international trials.
Boloña explained that a study to understand the factors most associated with SCC was conducted on 21 commercial herds that had implemented SDCT.
In the study, it was determined that cows treated with teat sealant alone had a higher SCC in the following lactation compared to those treated with an antibiotic and a teat sealant (152,000 vs. 120,000 cells/ml, respectively).
The study also determined that cows whose last milk recording SCC from the previous lactation was <150,000 cells/ml had 120,000 cells/ml less SCC compared to cows with >150,000 cells/ml.
SCC levels
Bolona told Agriland that farmers were asked to complete a survey about milking and dry period practices to estimate their association with SCC in the following lactation.
A number of findings were found from this survey, including that farmers that regularly used the California Mastitis Test (CMT) to detect high-SCC cows had lower SCCs compared to farmers that did not use it.
It also determined that farmers that kept records of clinical and subclinical mastitis cases had lower SCC cows compared to farmers that did not keep any records.
During the milking process, it was determined that farmers that always checked and discarded the first strips of milk before milking the cows had lower SCC compared to farmers that did this seasonally or never.
It also determined that farmers that housed their cows in sheds with one or less than one cubicle/cow had higher SCC compared to farmers that housed their cows with more than one cubicle/cow.
The recommended stocking rate of the cubicle sheds is 1.1 cubicles/cow.
Furthermore, cows had lower SCC when their cubicles were cleaned/disinfected twice/day compared to once/day.
Controls
Bolona then outlined a second Teagasc study that analysed what was the best information to predict which cows will have an infection in late lactation.
The analysis included cow SCC throughout lactation, parity and bulk-tank data among others.
The study determined that SCC of cows in the last milk recording was the most significant variable to predict infections in late lactation.
It was therefore determined that if a farmer is not milk recording, they could do one milk recording in late lactation to help guide dry-cow-therapy decisions.
However, it was noted that the benefits of milk recording are best realised when done multiple times throughout the a lactation.
The study also showed that the SCC threshold that maximises correctly classifying infected and uninfected cows was 101,000 cells/ml.
But each farm is different and the SCC threshold for selection of dry cow therapy will depend on the mastitis control situation in each herd and should be tailored accordingly.
Additionally, the SCC in infected first lactation cows was lower than in second and greater lactation cows.
This means that for first lactation cows, a SCC of approximately 61,000 cells/ml had the best results to correctly classify infected and uninfected cows and could be used for selecting dry cow therapy.
Results
The research determined that if SDCT is used on the wrong cows it can lead to an increase SCC in the following lactation.
It also determined that farmers with good mastitis control practices on farms achieved the best results.
Along with the farmers that had good facilities in place such as at least one cubicle/cow and were disinfecting cubicles took place twice/day.
But is also important that the drying-off procedure is done correctly and to a high standard of hygiene.
Which ultimately means that no once factor determined the success of using SDCT on farms, but the culmination of a number of measures.