This is a very well known Swedish proverb. Well, in Sweden at least.
It means "There's nothing to worry about ... yet." No need to panic yet, we still have (some time).
The proverb above is actually just a short version of:
"There is no cow on the ice as long as it´s behind is still ashore"
which maybe makes more sense. No need to panic, yet, the whole cow is not on the ice yet. We still have time.
Having a cow on ice can be a rather interesting adventure I guess. So, as long as the cow is only halfway on the ice there is no need to panic. But as soon as the all of the cow is on ice you need to worry... Cows are not well designed to walk on ice.
Why should there be cows on the ice anyway? Well, Sweden have lots of lakes and large archipelago. And there is also ice on these lakes and water in the winter of course. So, relocating cows using iced lakes and waters was not uncommon. Might be a lot easier as well than using small ferries to transport cows in summer.
"There is no cow on the ice."
One of the best Swedish proverb around. And when using it you should never ever use the long version.
(In Swedish: "Det är ingen ko på isen" - and a long version: "Det är ingen ko på isen så länge rompan är på land.")