Purdue University: Dairy Facts average milk cow Purdue's website 7,000 gallons of milk Cow produced Purdue University Cow http://www.ansc.purdue.edu/faen/dairy%20facts.html Purdue University 21 billion ansc.purdue.edu average milk cow Purdue University ansc.purdue.edu Purdue University tells us 876,000 glasses of milk http://www.ansc.purdue.edu/faen/dairy%20facts.html six gallons average milk cow 50 pounds thousands 130 cows,