It's that time of year again.  The new feed composition table is out.  Here's the article from BeefMagazine that will sum of the info quite nicely. 

Remember that the nutritional composition of feedstuffs varies widely, especially hay.  The soils can have a large impact on micronutrient content and time of harvest will impact protein and lignin content.  You do not want to short change livestock, especially during late gestation of pregnancy.