Mastitis is the only disease that dairy cattle farmers face that has direct impact on the daily bottom line. Every farmer will be familiar with that prickle of irritation when you first notice clots in the milk of that new calved heifer or favourite older cow, knowing the wastage and extra effort required for treatment that will inevitably follow. All that almost pales into insignificance though when you consider that for every clinical case, there are likely a good number of sub-clinical cases in a herd. Sub-clinical cases not only push up bulk tank cell count, sometimes meaning lost bonus or even milk contract penalties, but impact on lifetime production of the affected animals.
Using individual somatic cell counts can help identify these sub-clinical cows. Whilst vets, processors and some retailers advise using milk records on a monthly basis to select problem animals now many farms have ceased monthly recordings. Identifying persistent or repeatedly high cell count cows over time allows appropriate treatment or removal of these animals from the herd. The trick to long term control though is to reduce the incidence of mastitis in the first place, be it clinical or sub-clinical and that can be achieved almost exclusively through good management practices.
Cow vs. Bacteria vs. Environment
There are a number of bacterial species commonly involved in mastitis that are either spread from cow to cow, in the milking parlour (hands or milking process), or picked up from the environment. Most bacteria enter the udder through the teat canal, to colonise the quarter, causing hot and painful swelling in acute clinical cases. Cows can become systemically ill in severe cases and mastitis then could require treatment with licensed antibiotics. Not that the udder isn’t defenceless; with natural anti-microbial compounds and immune cells found in milk, a robust teat canal sphincter and the formation of a keratin teat plug during dry periods, the cow doesn’t submit to a case of clinical mastitis without a fight.
Problems arise when management systems don’t allow a cow’s defences to fully protect her. Inadequacies in milking parlour hygiene practices, certain management factors and selective breeding can all offer bacteria an unwelcome helping hand.
Time to Close Down
After milking, the teat sphincter takes approximately 30 minutes to close fully and in that period, a cow is vulnerable to infection by environmental bacteria such as Streptococcus uberis and E.coli. Some breeding traits have selected for mastitis; animals bred to have shorter, wider teat canals to facilitate faster milking seem particularly prone to mastitis.
Adequate post-milking loafing time in a dry, clean environment is vital to prevent bacteria taking advantage of this easy way in. If cows return to housing directly after milking, many will be found in their cubicles within this 30 minutes, so passageways and housing should be clean and offer a low risk to the udder. Inert substrates such as sand can really help with this, along with cubicles that are functionally appropriate to ensure that they are used correctly by cows.
Drying Off so Bacteria can Shove Off
The dry period is another time of potential risk. The keratin plug, seals the teat end through the dry period, takes some time to develop and in some instances may not even form before calving. The remaining milk ‘sitting’ in the udder provides the perfect habitat for bacteria to multiply. It is the period directly after drying off when many environmental infections occur, often festering unnoticed until clinical disease flares up at calving. This is because a cow’s immunity temporarily dips at calving, allowing these bacteria to overwhelm udder defences leading to mastitis.
Drying off should be considered the start of the next lactation – and as such given all the care that the next lactation’s income deserves! To administer dry-cow, be it antibiotic and teat sealant or a sealant alone, must be seen as a technical job needing all due care and attention to protect against any new infection such as E.coli entering the quarter.
Dry cow tubes containing antibiotics can be used – with many farmers still “treating” all cows in the same way. Others have adopted a strategic approach with selective therapy using sometimes varying antibiotics depending on the milk and mastitis records for each individual to make decisions including many that have no history or signs of problems that may have teat sealant alone.
Treating only those with a history of clinical mastitis or a cell count (over 200,000 cells/ml) at dry-off should save money and could reduce selection pressure for anti-bacterial resistance.
Keep it Clean with a Good Routine
Parlour hygiene is the other main area where mastitis control is played out. Contagious infectious bacteria such as Staph aureus, Strep dysgalactiae and Strep agalactiae are the ones that are often implicated here. A milking routine addressing both environmental and contagious bacterial challenge should be considered:
- Washing hands through milking and wearing disposable gloves will help reduce the spread due to the farmer.
- Foremilking can help remove teat canal contamination with environmental bacteria, cleans teat ends and can help with finding mastitis.
- Good pre-milking teat preparation prevents contamination of milk and clusters with environmental bacteria.
- Effective post-milking teat disinfection kills any infectious bacteria picked up from the previous cow.
- A parlour wash-up routine that includes at least one hot wash (greater than 85 degrees centigrade) with at least 10-12 litres per unit will ensure no infectious agents remain in the system. It is also important to make sure that all chemicals are used at the correct concentration.
Milking machine function should also be checked regularly as inappropriately high vacuums or delayed cluster removal can cause damage to teat ends, interfering with natural teat defences.
Taking a Leaf out of the History Book
European Union legislation (EU 92/46) dictates the minimum standard for the sale of milk on our farms. The original programme to improve bulk milk SCC started though back in the 1960s and 70s when the ‘five point plan’ was implemented to reduce clinical cases due to Staph aureus followed by penalties for poor milk quality. The plan worked well, herd average BMSCC dropped from around 600,000 in the 1970s to 200,000 cells/ml now. The same five point plan still forms the core of mastitis control advice today, with additions for environmental bacteria control as outlined.
Is it really that simple? No – only hard work and a dedicated milk quality programme can see best udder health on the majority of farms. Mastitis rates of 10 cases per 100 cows each year or even below are still rare whilst farms seeing more than 100 cases per 100 cows are common: at £218 per average clinical case¹ that would be a difference of £19,620 between some of the best and some of the worst herds, in terms of udder health, for every 100 cows. Surely for that kind of difference it is worth investing in udder health?
Note – this article was brought to you by Farmacy.co.uk and edited by Rob Drysdale MRCVS on behalf of Elanco Animal Health, makers of Tylan 200 Injection.
- Hillerton, J.E., and E.A. Berry, 2005. Treating Mastitis in the cow. Journal of Applied Microbiology vol.98 pp1250-1255