Re: What would be the effects on the offspring of a chocolate milk cow?

Dear Josh

You’re not actually making the cow, right? You’re writing about making one?

I assume you have worked out a way to get all the chocolate-making genes from a cocoa tree into your cows. Now you want to increase the sugar levels in the cow’s milk. The first point to note is that cows milk already contains sugar. This is in the form of lactose, which is similar to sucrose (table sugar). Sucrose tastes sweet. You might want to try and find some pure lactose and see what it tastes like.

Chocolate milk contains between 2 and 4 extra teaspoons of sugar per cup. How much lactose is there in cow’s milk? This page says 4.0 grams per deciliter, which is about 2 teaspoons per cup. You need to double or triple the amount of lactose in cow’s milk.

You clearly don’t want to just add sugar, like the factories that make chocolate milk. A genetic engineer faced with this sort of challenge might try to see whether there is some other species that makes more lactose in its milk, and then transfer the genes from that species into cows. It turns out that humans (and donkeys and mink) have the highest level of lactose in their milk, about 7.0 grams per deciliter. (You might want to think about why that should be so.) I suppose you could use the lactose- making genes from a person or a donkey and put them in a cow. But it would probably be much simpler and cheaper to add a couple of spoons of ordinary sugar to the chocolate milk from your cow.

As for the effects of chocolate milk on the cow’s calves, that is impossible to say. The extra sugar might cause problems, but don’t forget that calves only drink milk for a little while, a few months at most. In any case, if your cow’s chocolate milk was any good it would be too valuable to give to her calves.

I hope that helps.

Jeremy Cherfas
Science Writer
International Plant Genetic Resources Institute