We had a big drop in temps last night/this morning. I was wondering if big changes can affect the girls output. They're not down a lot .. about a cup or two each. I thought that was a bit odd that both were down at the same time. That's why I was wondering if it is weather related.
Also, I may be rather obsessed about the amount they give. They are each giving a half gallon plus a cup or two every morning. I guess I really don't know how much they should vary in their output. Or, why it varies, except for in the case of mastitis or something.
Weather changes can effect their production, wildflowers blooming in your pasture can effect their production....
Mercury going into retrograde can effect their production.
Unless it is a MAJOR drop, as in, within days, they have dropped more than half, then it is not something to worry about. Down here, especially in summer, a cool front will cause the girls to be more active and play...which will cause their production to drop a little.
Just about anything that burns calories will cause a decrease in production. It's calories they are not putting into making milk. So yes, a cold front, where they are burning more calories to keep warm, does it too.
In my experience photoperiod affects production to a greater degree than weather.
Nearly always the shorter the days the lower they milk and then when the days lengthen they go up.
I find extreme heat depresses production more than extreme cold, but like was said if water consumption dips then production goes down.
Depending on your amount of goats hooking a bucket heater to a bucket and then putting it on a timer and giving them nearly hot water in the winter twice a day will up the production.
Also if you give them fresh water 3x a day and have barn fans in the heat of summer this will help you.
A good goat will go back up if unbred in the spring. I had a doe once that was down to about 10 lbs a day in the dead of winter. In July of the following year I had her on a one day test and she milked over 14 lbs at 418 days fresh.
The heat of summer effects oil efficiency. One uses different oil in winter than in summer. High heat can mean less efficient cooling in a motor. All sorts of seasonal things, right down to the dust of summer clogging air filters, can and do effect how well a car runs.
If it gets too cold, the engine might not even start, because the fuel has gelled. That's why ethanol is added to winter fuels.
Perhaps it is more that we should not expect them to give the same efficiency from season to season without the same sort of tuning and tweaking we would give to a high performance engine from season to season to keep it in top running condition.