{HEAD ~ Milk} and other animal products are important as {TAIL ~ a food source} contributing more than a third of the calories, and between a third and all of the major nutrients in the U.S. food supply 
important as
{ HEAD ~ Milk } and other animal products are important as { TAIL ~ a food source } contributing more than a third of the calories , and between a third and all of the major nutrients in the U.S. food supply
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH