I think that most everyone agrees that green grass has more nutrition than any of the other colors but there are other important differences that affect cattle health.
Cool-season grasses (C3) generally have less energy and more non-protein nitrogen (NPN) than warm-season grasses (C4). C4 grasses are higher in more complex cell-wall starch and lower in simple sugars than C3 grasses.
Cattle health and production is best on slightly mature C4 grasses, especially when there is a lot of plant diversity. The farther south and the more average the moisture the more this is true.
In the simplest of terms, color coding winter grass based on quality goes from green to red to brown to yellow to white. Green is best, white is worst.
With fall calving, re-breeding, and winter milking, we like to have some green grass and not much white grass or white hay.
Kentucky 31 fescue makes better fall growth than any other C3 grass with which I am acquainted. There are annuals that might beat fescue in the fall if we are experiencing perfect moisture years, but they are expensive and fall moisture is seldom predictable. We stay away from annuals in the beef cattle business.
My experience and quite a bit of research indicate that time, diversity, dry matter, and timing are all important when planning and executing a fall calving program that is highly successful, profitable and sustainable every year.
In the fescue belt, we use generous amounts of fescue, especially after frost and during the winter. The key to success with fescue depends on two factors, in particular:
• Diversity – Cattle grazing large amounts of tall C4 grasses along with lush fescue out-perform straight fescue cattle and do not become as alkalotic or toxified as cattle on near pure pastures (pretty) of fescue. Bluegrass, brome, orchard grass and other C3 plants help dilute the negative fescue affects, but not to the extent of red or yellow standing C4s or dry prairie hay.
• Timing – We do not want cattle consuming over 50% of their dry matter intake from green fescue for over 60 consecutive days. The same pattern is also true with small grains. Performance starts sliding downward after 60 days.
Medium- to high-quality standing diverse dry matter is a huge asset year round. With year-round grazing without hay feeding, this becomes very important.
Good hay is actually near identical to well-mineralized medium to high-quality standing dry grass but it costs a lot more.