Winning forage entries don’t make winning rations
Winning forage entries don’t make winning rations
by Ev Thomas and Bill Mahanna
Thomas is retired from the William H. Miner Agricultural Research Institute and is the president of Oak Point Agronomics, Hammond, N.Y. Mahanna is with DuPont Pioneer, and an adjunct professor at Iowa State University.
Marshall McCullough was a University of Georgia dairy nutritionist who wrote for Hoard’s Dairyman for many years, including the book Roughages for Dairy Cattle.
One day after looking at some extremely high protein, low-fiber entries at a national hay contest, he commented: “That’s not forage, it’s poultry feed!”
He was making a point: Should hay and silage contests represent what farmers should be striving for in their forage production programs or should they be “beauty contests for forages” with the most immature, lush entry often winning the top prize?
A comment also worth noting from Cornell University forage agronomist Jerry Cherney: “Hay/silage contests are like purebred dog shows. They look nice, but you would probably never want any of those winners as a pet.”
Defining high-quality forages
Most farmers and agronomists know what makes a high-quality forage. According to Steve Fransen, a forage crops specialist at Washington State University, alfalfa should be harvested in the bud stage and orchardgrass should be harvested in the boot stage. Few in the dairy industry would disagree with these guidelines that have served many of us well.
Contrast this, however, with the results of a recent hay contest: We often consider high-quality alfalfa to be “20-30-40”: 20 percent crude protein, 30 percent ADF (acid detergent fiber) and 40 percent NDF (neutral detergent fiber). The winning alfalfa hay entry in this particular contest tested 20 percent, but it was 20 percent NDF, not 20 percent protein! Crude protein (CP) content was actually higher than NDF.
We occasionally hear concerns about butterfat-protein inversions in milk where the true protein is higher than the butterfat content, but this is another type of “inversion” and not one dairy farmers should be trying to achieve.
Hay and silage contests are based on a combination of laboratory analysis and visual evaluation, with lab analysis typically counting for 60 to 70 percent of the score. Some contests (including the World Forage Analysis Super Bowl) base 10 percent of the score for corn silage and haylage on milk per ton.
Visual appearance, usually worth 30 percent of the score, includes color, texture, maturity and leafiness. However, how important are these factors when particle size, kernel damage, fiber and protein levels are measureable parameters that are important in ration balancing?
The appearance of the forage isn’t the key but how it’s consumed and digested by the cow. In other words, appearance is much less important than disappearance (intake and digestibility).
Set an upper limit
Too many of these contests don’t set any limits on the analytical numbers: The higher the Relative Feed Value (RFV) or a more recent measure, Relative Forage Quality (RFQ) which takes digestibility into account, the higher the score. Farmers entering these contests realize that in order to win they may need to harvest the forage for the contest entry much earlier than they would normally for their herds.
What do you think was the harvest interval that produced the 20 percent NDF alfalfa in the previously mentioned entry? What about per-acre yield?
This certainly wasn’t bud-stage alfalfa unless only the top foot of the plant was harvested in the before-mentioned sample. Similarly, in forage contests that include corn silage there isn’t any way to control chop height, so one entry may have been chopped at an 8-inch stubble height while another entry was chopped at 20 inches. This would considerably impact the amount of grain in the sample. A potential improvement for silage entries may be to include a fermentation analysis in addition to the nutrient analysis.
More isn’t necessarily better
Extremely high protein alfalfa may win hay contests but it’s not a winner in most dairy rations. According to dairy nutritionists, the high protein level found in very immature alfalfa is rapidly fermented in the rumen and not used efficiently by dairy cattle. Very high protein alfalfa can actually be a negative because protein fed in excess of animal needs has an energy cost and can potentially reduce milk production. The more of this type of forage that’s fed, the more difficult it is to formulate rations that meet the protein, energy and fiber requirements of the cow.
Two related comments from Cornell’s Cherney are worth noting: “Low-quality forage kills milk yield, but super high quality forage kills cows.” And “Super high quality, low NDF forage has killed more cows in New York than mulch hay forage.”
Several years ago at a California Alfalfa Symposium, a Midwest dairy nutritionist stated that the “ideal” alfalfa for dairy cows has 18 percent crude protein and 40 percent NDF which is very close to the “20-30-40” many consider as ideal quality alfalfa.
While there’s not universal agreement on this — some California extension specialists identify “Extra-premium” alfalfa as 24 percent CP and 33 percent NDF — nobody we know of is recommending alfalfa with less than 30 percent NDF.
A key question that should be asked by the organizers and judges of hay and silage contests: How close does this forage come to the very best that a farmer would want to grow, harvest and feed?
Yield is important
One big thing missing from hay and silage contests, though not one that’s practical (or more likely, not even possible) to include, is yield. One reason farmers seldom harvest alfalfa in the prebud stage is because this type of forage doesn’t work well in most rations. However, a more economic and practical reason is that there simply isn’t enough yield at that early stage to justify harvest.
Furthermore, these contests don’t look at the agronomic view in many instances. Continued harvest of alfalfa and other perennial legumes at such an immature stage doesn’t allow the plant to accumulate enough carbohydrates for the next crop. The result: Lower yields of the current and subsequent harvests and potentially reduced stand life. Proper forage management is an effort to harvest at the ideal combination of yield and quality, and both bud-stage alfalfa and boot-stage grass meet this goal.
This Hoard's Dairyman article appears on page 3 of the January 10, 2013 issue.