Most cheesemakers think about heat as a cave problem. It's also a herd problem, and it starts well before the milk ever reaches your vat. With a wide stretch of the country under an extended heat event this month — severe enough in some regions that livestock operations have reported outright heat-related losses — this is a good week to talk about what heat stress actually does to milk, not just to cows.
When a cow's core temperature climbs, her body redirects energy toward staying cool and away from milk synthesis. The visible effect is lower yield, which everyone budgets for. The less visible effect is a shift in composition: butterfat and protein percentages both tend to drop under sustained heat stress, and somatic cell counts often climb as the animal's immune system comes under strain. None of that shows up as an obvious red flag at intake. It shows up two days later as a vat that won't set the way it should, or a yield that's off from what your make sheet predicts.
Reading milk before you commit a vat to it
If you buy milk rather than milk your own herd, ask your supplier what they're doing to manage heat stress this month — shade, fans, sprinklers, water access, ration adjustments — and ask whether they've seen composition drift on recent loads. A supplier who can answer specifically is one worth sticking with. If you're both farmer and cheesemaker, the same questions apply to your own operation, and the stakes are higher because you can't source around a bad week.
Practical adjustments worth considering when milk is running lean on fat and protein:
- Expect lower yield per hundredweight and plan your batch sizes accordingly rather than discovering the shortfall mid-make.
- Watch your culture and rennet timing more closely than usual. Milk with altered composition can behave differently at set, and a recipe that's dialed in for normal-season milk may need small adjustments.
- If somatic cell counts are elevated, treat it as a signal worth investigating with your supplier, not just a number to note and move past.
This is exactly the territory our Milk Quality & Herd Health course covers — not the veterinary side of treating a heat-stressed animal, but the practical side of understanding what's happening to your raw material and adjusting your operation around it. It runs periodically through the Education Committee and is one of the more directly useful credentials for anyone managing both a herd and a cave. If you've been meaning to take it, a summer like this one is as good a reason as any.
We'll say the obvious part plainly: none of this is a substitute for a veterinarian's judgment about animal welfare during a heat event. It's about what to expect on the cheesemaking side once the immediate crisis is managed.
What "normal" looks like right now
One thing worth flagging for newer members: if this is your first hot season running a make schedule, don't assume the slower sets and lower yields you might be seeing are a mistake on your end. Composition drift from heat stress is genuinely different from a bad batch, and the two can look similar if you're not tracking milk intake numbers alongside your make notes. Members who keep even a simple log — fat and protein percentage at intake, set time, final yield — tend to catch the pattern faster and stop second-guessing their technique when the real culprit is what's happening in the pasture, not the vat.
It's also worth talking to your peers. A short note to the Education Committee, or a question posed in a course alumni thread, can save you from re-solving a problem someone two states over already worked through this season. That's a lot of what membership is for in a summer like this one: fewer people figuring out the same heat-driven surprise alone.
If you take one thing from this post, let it be this: watch your composition numbers as closely as your thermometer this month. The thermometer tells you what's coming. The composition numbers tell you what already happened, and what to adjust before your next vat.
The International Cheese Federation (ICF) and More Cheese are entirely fictional. This post is demonstration content created for MemberJunction. All people, organizations, events, courses, certifications, figures, and quotations in it are invented, and nothing here represents a real association, a real business, a real person, or real professional advice.