With resistance to antibiotics becoming more and more prominent within the news, farmers and processors are being urged to think more about antibiotic usage on farm to help try and combat the problem. Some milk processors are already stipulating that ‘blanket’ antibiotic treatments cannot be used at drying off; others I’m sure will follow.
Mastitis cases can be a stumbling block within any dairy herd whether they be clinical or sub-clinical, affecting the wellbeing and productivity of any cow infected, which in turn will have a large impact on yield and fertility.
The cost of treating a clinical case of mastitis averages £250-£300, varying from around £60 to treat a mild case of mastitis to the cost of the loss of a cow following a severe case of mastitis (AHDB). Also both clinical and sub-clinical mastitis occurring before AI have been associated with reduced conception (Schrick et al., 2001).
‘Clinical mastitis is characterised by visible abnormalities in the milk or the udder. The most obvious abnormalities in the milk are flakes, clots, and a watery appearance, whereas Subclinical mastitis is inflammation of the mammary gland that does not create visible changes in the milk or the udder. Although the milk appears normal, sub-clinically infected cows will produce less milk, and the quality of the milk will be reduced. In addition, infected cows can be a source of infection to other animals in the herd’ (NMC)
Clinical mastitis is what most farmers refer to as ‘having mastitis’ but far more common on farm is sub-clinical which can be up to 40 times more common than clinical cases of the illness (AHDB). Monitoring SCC’s (Somatic Cell counts) of cows within the herd will help farmers to see which cows are at greater risk from mastitis.
A threshold SCC of 200,000cells/ml would determine whether a cow is infected with Mastitis, cows with a result of >200,000 cells are highly likely to be infected on at least one quarter (AHDB).
Pathogen identification is paramount if an effective treatment is to be taken, knowing whether or not your pathogen is environmental or contagious will help producers to take measures to control pathogens before they present themselves as a case of mastitis.
Cows can become infected with mastitis for two main reasons, one being overwhelming amount of pathogens at the teat end, this, combined with a failure or reduction in the cows immune system causes the cow to suffer from mastitis. Challenges such as hyperkeratosis at the teat end or cracked teats are large influencers in the development of new infections ‘Hyperkeratosis predisposes teats to bacterial colonisation’ (Fox, 1997; Timms, 1998) also, ‘Cracked teats are at 1.8 times higher risk for acquiring new infections during dry period’ (Dingwell et al., 2004). The largest immune challenge on dairy cows is around calving, this teamed with poor hygiene or the presence of bacteria can lead to fresh cases of mastitis.
There are many management techniques which farmers can use to help keep udder health at a maximum and reduce antibiotic usage in the dairy herd.
Screening for SCC
- Bulk Milk Minimum
- All Replacement Raised off-site
- Cows with Clinical Mastitis
- Cows with High SCC Advanced
Source: Royster, 2015
Screening on farm, in some aspect is essential to identify the mastitis status of a herd or through milk recording which can help to identify high risk cows in the herd. Using milk records and herd records, cows can be identified that should be treated with antibiotics at drying off. Those not at high risk, could be treated with just a non-antibiotic teat sealant which should reduce the risk of new infections.
Teat preparation along with milking routine have a great impact on the prevalence of mastitis within a herd. Fore-stripping is essential for identifying clinical cases but
‘~75% of all cases are subclinical.’ (Royster, 2015)
making sure that teats are in the correct condition will reduce the risk of mastitis pathogens being able to enter teats, as
‘…contagious pathogens move through the end of the teat, travel through the teat cistern and eventually end up in the main tissue of the udder; this can take between one and three days’ (David Pettitt, 2009). Using the correct teat dips/teat preparation products will keep teats both healthy and clean. Regular services on milking equipment ensuring that vacuum levels and calibrations are correct will reduce the risk of over milking which also increases the risk of teat end damage.
Management of Sheds and Bedding
The most common examples of environmental bacteria are Escherica coli (E-Coli), Streptococcus uberus and Streptococcus Facecalis (David Pettitt, 2009). These can be picked up from bedding or in the parlour. It is no secret that deep sand bedding is the gold standard for cow comfort and hygiene, this said, any bedding material can be effective at keeping mastitis at bay.
This comes down to management, as long as bedding material is kept fresh, clean and dry this will reduce the amount of pathogens present, therefore reducing the risk to cows.
In general terms, there are two large groups of bacteria, known as either Gram-positive or Gram-negative bacteria, differentiated by their Gram staining characteristics. Gram staining was developed by Hans Christian Gram and is used to differentiate bacterial species based on the physical properties of their cell walls.
Bacterial cell wall structure plays an important role in determining a bacterium’s susceptibility to different antibiotics and thus is an essential factor in selecting the most effective antibiotic for treatment. (AHDB)
In America, producers are reducing their antibiotic usage by using a process called ‘on farm culturing’ developed by the University of Minnesota. This is where samples of infected milk are placed onto culture plates and incubated, then checked for any growths in different sections to identify which type of pathogens are present in the milk. It can either be done on farm or at the vets, but you would need results back within twenty four hours to make sure a quick effective treatment decision can be made. This is a fast, inexpensive way to categorise the cause of Mastitis into treatment categories for example:
- Gram-Negative, No-Growth = No Treat
This refers to culture negative results; these instances of no growth happens to 20-40% of clinical cases and therefore do not deserve antibiotics. The cow will often clear the infection themselves.
- Gram-Positive = Treat
Cleaning of Equipment
A presentation from Dr Erin Royster a few weeks back asked some interesting questions, for example, how old is the pipe in the parlour? I can guess the answer for most is more than a few years. The pipe itself can easily be a haven for bacteria.
Washing the units and the parlour with a dirty pipe would seriously hinder the efforts made elsewhere to prevent any cows within the herd contracting mastitis. It is often the equipment or processes we don’t even think about which could help with keeping the number of mastitis cases down and therefore the cost of treating the mastitis.
Overall the discussions we have been having recently around mastitis have been focussed on better recording and ensuring we are not giving every cow antibiotics for every case of mastitis regardless of severity. It is important to have easily to hand the history of the mastitis cases, which quarter this cow had mastitis in last time and what severity this was. If an animal in the herd has been having mastitis each lactation and on more than one occasion is it worth giving it more antibiotics? Is the cow now costing too much and being a passenger in the herd? With each farm more acutely aware of costs than ever before the prevention and curing of mastitis is certainly an issue dairy farms should focus on in order to prevent ‘blanket’ treatments and save money. Another point to consider is that without any individual cow history or individual milk records you can operate a targeted antibiotic DC policy.