Bulk tank SCC at 460,000 with nine cows to dry off

What drives the bulk count. Bulk SCC is a weighted average dominated by a minority of high-cell-count cows. With a herd mean around 460,000, removing or segregating a handful of chronic cows typically moves the tank figure fastest - it is arithmetic, not microbiology.

Next 72 hours

1. Culture every clinical case before treating, and start treatment only on the affected quarter per label. Treating blind wastes money and selects for resistance.
2. Segregate high-SCC milk. CMT-positive cows and the two three-quarter cows should be milked last or into a separate bucket; their milk must not enter the tank. This is the single fastest lever on the bulk figure.
3. Fix the milking routine today: forestrip every quarter, pre-dip and wipe dry, post-dip 100% of cows (currently 60%), and re-check vacuum and liner condition. Fourteen-month-old liners on 1,100 milkings/quarter are close to their 2,500 limit and are a plausible source of new infections and teat-end damage.
4. Bedding and environment: the damp, uncovered sawdust is a classic environmental mastitis reservoir. Change bedding, store it under cover, scrape alleys twice daily, and check cow cleanliness scores.
5. Record everything - cow ID, quarter, date, treatment, withdrawal - because the processor and the vet will want a herd-level picture.

What I do not do

• No blanket intramammary treatment of the whole milking herd. Subclinical infections in lactation cure poorly (often well under 50%), it costs a lot, it creates milk withdrawal losses, and it is exactly the practice antimicrobial stewardship programmes target.
• No culling decisions until cultures and SCC records show which cows are chronic.
• No assumption that the machine is the cause - the calving pattern below points elsewhere first.

Why dry-off matters here. The dry period is when most new intramammary infections are acquired or cured. Blanket dry-cow therapy (DCT) is no longer defensible where it is not needed; selective DCT plus an internal teat sealant gives nearly the same protection for low-risk cows while cutting antibiotic use sharply.

Allocation criteria for the nine cows

• Low risk → sealant alone: no clinical case in the last 3 months, all-quarter CMT negative at dry-off, individual cow SCC below about 200,000 on the last two herd records, and no history of a chronically infected quarter (e.g. no blind quarter, no repeated Staph aureus).
• High risk → antibiotic DCT plus sealant: any clinical case in the last 3 months, CMT positive (especially the two cows with three positive quarters), SCC above 200,000, previous history of chronic mastitis, or a high-yielding cow being dried off abruptly.
• Practical steps: dry off abruptly when yield is below ~15 L/day, milk out fully, aseptic scrub, treat, then seal every quarter; keep the cow standing for 30 minutes; check for strip-cup leakage over the following week; mark and monitor for heat and swelling.
• The two three-quarter cows are the strongest candidates for culling rather than another lactation of treatment.

The five early-lactation cases change the priority. Heifers and cows calving with mastitis have almost certainly been infected during the dry period or in the calving environment, not by the milking machine. That means:

• the dry-cow and calving pens, bedding and drainage need auditing now (sample the sawdust, the water troughs and the calving pen);
• heifers cannot be given DCT at all, so their protection comes from the rearing environment, fly control, teat condition and a clean calving area;
• the teat sealant becomes more, not less, important for the nine cows being dried off, because it is the barrier that stops the environmental infections that are already showing up in first-calf heifers.

Reading the pattern. Infections acquired in the dry period or at calving show up as clinical mastitis in the first 2–4 weeks of lactation. If the machine were the main problem, cases would be spread across all stages of lactation and would cluster in particular milking groups or parlour sides. Here 5 of 7 cases are in fresh cows, including two heifers that have never been through the parlour properly, so the balance of probability is an environmental source in the dry-cow/calving area, not a machine fault.

Confirmation

• Culture the clinical cases and the high-SCC quarters. The result matters: Streptococcus uberis and Escherichia coli point strongly to bedding and calving environment; Staphylococcus aureus or Streptococcus agalactiae point to contagious spread at milking and would change the emphasis back to the parlour.
• Sample the bedding (fresh and used), water troughs, calving pen surfaces and the sawdust store.
• Review drying-off records for the cows that calved: were these cows sealed? Were they leaking milk at dry-off? A leaking teat canal in a dry cow is a direct route for environmental bacteria.
• Check the parlour: liner condition, vacuum level and teat-end condition at the same time - both problems can co-exist.

How I would present it

1. Cause is likely environmental for most of the problem; that is good news because bedding, drainage and calving-area management are cheap fixes compared with a parlour rebuild.
2. Immediate target: get bulk SCC below 400,000 within the next two monthly tests by excluding/handling the high-SCC cows.
3. Medium term: selective dry-cow therapy, sealant, liner replacement at 2,500 milkings, 100% post-dipping, dry bedding.
4. Provide a simple one-page plan with dates and named responsibilities, and set a target SCC of 250,000 by next spring rather than just 'below the threshold' - the threshold is the penalty line, not a healthy herd.