I learned an interesting fact many years ago in an herb class. Which was, that probably many people in MI, as high as 75%,
were deficient in Vitamin D. Why? Well, it seems during the winter months from October through March, , the sun rays, due to the angle to the earth,
are not sufficient enough to stimulate the production of Vitamin D in the skin. This is not just the states in the far North, but all states
above 37th parallel north. This is roughly half the US!
Vitamin D is a very important vitamin. It helps to metabolize essential minerals like calcium, magnesium, phosphorus and zine.
This is important for poultry because without Vitamin D, your flock will not be able to absorb the calcium they eat and then it will steal calcium from the bones.
Although the sunny, clear days in winter are welcome to break up our cold and cloudy days, people and birds alike are not gaining any Vitamin D from it.
So it is essential your flock get an excellent main diet feed that is fresh with balanced vitamins and minerals. I think the winter is not the time of year to upset that
balance too much with a lot of food outside the main formulated diet. Your birds will be utilizing a lot of energy from food to stay warm, and it is even more critical
their food is nutrient dense and balanced for maximum vitamin utilization.
If you do feel a need to supplement some Vitamin D occasionally, I created a recipe for a winter oil, with which you can add a little optional cod
liver oil. Cod liver oil is a natural fish oil which can add both Vitamin A and D, which is especially good to supplement these vitamin deficiencies. If you are feeding
your flock a good diet, you should not have to supplement that much, if at all.
Winter Oil 
