A GOOD working relationship between farmer and vet is crucial when we want the farmer to take our advice on anything. This is especially the case when dealing with mastitis and fertility and the “magic money” we assure them they are losing but they never see.
What we need as vets is a detailed understanding of the farm, the herd, the staff, the farmer’s skill and enthusiasm to decide what interventions we need to make and then tailor them to the farm so they will actually be carried out!
My example is a North Yorkshire dairy farm milking 100 cows, producing around 8,000l milk/cow/year.
In winter the milking herd is housed in cubicles with dry cows on straw yards, all cows are out in summer. The cows are fed a mixed ration based on grass silage (with Brewer’s grains, caustic wheat, protein bled and liquid molasses) throughout the winter and grass with some big bale hay or silage offered as a buffer in the yards before and after milking. Cake is fed in the parlour all year round depending on yield, but never more than 6kg/cow/day.
The farmer is very keen to treat any signs of mastitis in the cows – and some cows with only mild signs get a course of treatment. Cows are treated (off licence) with up to six tubes per case, often in conjunction with parenteral antibiotics and sometimes NSAIDs. Running a separate high cell count group (over 200,000 cells/ml) was discussed, but with the low number of cows involved the farmer decided it would not be practical. Instead all cows with a cell count over 200,000 cells/ml have yellow tail tape applied and after milking the four claw pieces are dipped separately in a jug of diluted peracetic acid. Nitrile gloves are worn by all staff for milking and cows are pre-dipped and post-dipped effectively. Laminated SOPs produced in conjunction with the practice are displayed for milking routine, mastitis treatment and dry cow treatment.
The farm had always been a high tube user (four tubes per cow per year v. practice average of two) despite running with a cell count around 160,000cells/ml. During their routine herd health plan review in summer 2008, the graph of dry period performance from herd companion was shown to the farmer (see below). A steady climb in the number of cows going low cell count before drying off to high cell count after calving was really disappointing.
There were around 20% of cows picking up infection whilst dry (July 2008). The percentage of chronic cows was steady, but still running around 12%. The farm had a target of 5%, for both parameters.
The apparent cure rate, i.e. high cell count before drying off to low cell count after calving, was disappointing at only 10%. At this time the farm was using a 28day cloxacillinbased dry cow tube (Orbenin DC, Pfizer), despite keeping cows dry for around 60 days.
Previous mastitis bacteriology had confirmed that this herd’s main problem was with environmental mastitis. Some of the Streptococcus uberis mastitis was suspected of being “cow adapted” strains going on to cause chronic intramammary infection and spreading from cow to cow during milking.
We took the opportunity to use the Intervet/Schering-Plough Cobactan bacteriology scheme to ensure that the mastitis pattern hadn’t changed. All of the high cell count samples were individual quarter samples from cows less than 100 days into lactation. The results are summarised in Table 1:
Table 1
High Cell Clinical Total
Count cases
cows
S. aureus 0 0 0
S. uberis 7 2 9
E. coli 5 2 7
No growth 3 2 5
A dry cow tube with the ability to cure existing intramammary infections and offer a better degree of protection against new infections was required. The dry cow tube chosen would need to give a longer period of cover, so the entire dry period was protected.
Cloxacillin, although still considered by many to be first choice for Staphylococcus aureus, is not really effective against Escherichia coli and since we are dealing with both Gram-positive and Gram-negative bacteria a change was required.
An internal teat sealant to further reduce environmental infections in the dry period was to be used in combination with antibiotics. There is good evidence that antibiotics used together with a teat sealant reduce intramammary infections better than an antibiotic alone (Newton et al, 2008).
A discussion was had about targeting high and low cell count cows with different dry cow regimes, but the farmer and myself were reluctant to use a teat sealant alone (risk of iatrogenic coliform mastitis). The farmer raised the issue that by using different antibiotic dry cow tubes in different cows his staff may get confused when the milk was fit for sale after calving.
For the sake of simplicity (and compliance!) all cows regardless of cell count were to be dried off the same, after morning milking, following a standardised aseptic technique (Bradley et al, 2003).
The antibiotic tube chosen was the cefalonium-based tube Cepravin Dry Cow (Intervet/Schering-Plough). It was chosen because of its broad spectrum of activity,adata sheet claim of 10 week Gram-positive activity and its good ability to cure existing infections. The antibiotic was used in conjunction with Orbeseal (Pfizer). This is to provide a physical barrier to new infection during the dry period. Much of the mastitis in the first 100 days of lactation is picked up in the dry period (Bradley and Green, 2001).
At the next routine visit the calving environment was examined. Since it was summer time, only cows likely to calve imminently were kept in. The calving accommodation was clean, well-bedded with straw and passed the squelch test! Cows were calving in decent body condition (2.0-2.5) and losing no more than half a condition score point in early lactation. Milk fever was not really a problem, farm records had only 10 cows given calcium in the preceding 12 months – most of these were given as a precaution in perceived “high risk” cows. The farm did suffer from some toxic “E. coli”-type mastitis and the practice had treated three cows aggressively in the year July 2007-July 2008 (one of the three cows died). Other than the toxic mastitis this was an area we were generally happy with (Figure 1).
Since summer of 2008 there has been a decrease in new infections during the dry period dropping from a maximum of 20% down to a mere 3% (see graph above). This is well below the 5% target and a result that exceeded both my own and the farmer’s expectations! There is a drop in chronic infections during the dry period, roughly from 12% down to 7%, much closer to the 5% target. This is likely be from a combination of two factors: better cure rate of the new antibiotic therapy and some of the high cell count cows were curing in the early dry period and then becoming re-infected!
The apparent cure rate during the dry period for cows drying off with a high cell count climbed from 10% up to 23%. This means many more cows starting off in a new lactation as uninfected –a huge improvement!
Since July 2008 the practice has not had to treat a single cow with toxic mastitis and the incidence of mastitis in the herd during the first 100 days of lactation has approximately halved. Long-hand paper calculations are summarised in the table below (mastitis is not recorded on this herd through Interherd!) – Table 2:
If we take the cost of a mild case of mastitis at £84.60 and a severe case of coliform mastitis at £468.63 (£1,709.35 – if the cow dies) then we have a saving of £3,023.98, giving a net benefit to the farm of over £2,000 once the additional drying off costs are allowed for (Esslemont and Kossaibati, 2002).
This doesn’t even take into account other benefits such as a reduction in cell count and a reduced risk to other cows of catching S. uberis from an infected cow. In the last year his bulk milk cell count has fallen from 160,000 to 130,000 cells/ml. Having all the required information available lets us make informed, evidence-based decisions about the dry cow management of the dairy herds in our care. Furthermore it allows us to demonstrate the effects we are having on the situation and (hopefully) builds confidence in the vet and strengthens the vet/farmer relationship.
References
Bradley, A. J. and Green, M. J. (2001) An Investigation of the Impact of Intramammary Antibiotic Dry-cow Therapy on Clinical Coliform Mastitis. Journal of Dairy Science 84: 1,632-1,639.
Bradley, A. J., Huxley, J. and Green, M. J. (2003) A Rational Approach to Dry Cow Therapy 2. Product Selection. In Practice January: 12-17.
Esslemont, D. and Kossaibati, M. (2002) The Costs of Poor Fertility and Disease in UK Dairy Herds. DAISY Research Report No. 5, Intervet (publisher).
Milne, M. H., Biggs, A. M., Barrett, D. C., Young, F. J., Doherty, S., Innocent, G. T. and Fitzpatrick, J. L. (2005) Treatment of Persistent Intramammary Infections with Streptococcus uberis in Dairy Cows. The Veterinary Record 157: 245-250.
Newton, H. T., Green, M. J., Benchaoui, H., Cracknell, V., Rowan, T. and Bradley, A. J. (2008) Comparison of the Efficacy of Cloxacillin Alone and Cloxacillin Combined with an Internal Teat Sealant for Dry-cow Therapy. The Veterinary Record 162: 678-684
