Photosynthetic cells contain chlorophyll and other light-sensitive pigments that capture solar energy. In the presence of carbon dioxide, such cells are able to convert this solar energy into energy-rich organic molecules, such as glucose.
Yes, you can add a little lemon juice or vinegar to the goat's milk to make it into a buttermilk or kefir. This will lower the pH of the milk, and allow it to release the CO2 stored in the sodium bicarbonate (baking soda), causing the bread to rise. Goat's milk generally has less fat and more vitamins.
I don't think the milk will make you sick. Lots of things have buttermilk in them and if you don't have buttermilk you can substitute fresh milk to which you have added vinegar--that results in sour milk. The flavor might be different, but ... How to make SOUR MILK. http://www.ehow.com/how_4907490_make-sour-milk.html.