How do your forages rate nutritionally? Mike Hutjens, University of Illinois extension dairy nutritionist, has developed a simple scoring system to help you grade your crops.
“The scoring system is almost like a relative feed value or relative forage quality index. It gives you a target or ideal number that you can compare across a set of numbers. And it reinforces what some of the key parameters are when you look at a forage test result,” he says.
The grading system, in other words, shows where growers need to hold or improve the quality of their forage crops.
For corn silage from a bunker, for example, Hutjens lists six nutrient content parameters growers could consider: NDF, NDFD, crude protein, starch, lactic acid and dry matter.
In the example below, Hutjens offers target numbers to shoot for. Your nutrition consultant or extension educator familiar with your operation may want to help determine your target numbers, he adds.
Compare those numbers with your own forage test results. Then grade the forage by entering a score for each quality parameter. If your forage tests better than the target for each parameter, score one point for each percentage point that beats the target number. In some cases, Hutjens points out, a lower test number will result in a positive score.
If your test number is below the target number, subtract or add one point for each differing percentage point. In the corn silage example, an NDF target score of 42 brings a -6 point score if your test result is 48. A starch target of 32 with a forage test result of 34 offers a +2 point score.
Then add the individual scores for the grand total.
“If you're a +10, you've got great forage. If you're a minus, ask yourself, where did I lose the points?” Hutjens says. Those areas need work, he adds.
|Quality Parameters||Target||Your Forage||Score|
|NDFD (% in 30 hrs)||57||55||-2|
|Crude Protein (%)||8||7||-1|
|Lactic Acid (%)||5||4||-1|
|Dry Matter (%)||33||36||-3|
To rate your alfalfa haylage, consider nutrient and storage factors. They are: crude protein, NDF, NDFD, ADF and lignin, plus dry matter, lactic acid, inoculation and particle size. The example below, of alfalfa haylage stored in a bag, was rated not with target numbers, but with ranges, for the most part. Plug in your numbers from your forage test results and then determine point scores by comparing your numbers to the point basis numbers.
In the example, the quality of the haylage was excellent, Hutjens says, but it was chopped too short and too dry. Although the +8 score was good, dry matter content and chop length needed improvement at ensiling. The scoring system is the same as the one for corn silage: +10 is considered excellent; any minus totals show that definite improvements are needed.
In looking at the haylage parameters, Hutjens notes crude protein's 20+ to under 26 range. “I would argue that when you get over 26, you are looking at too much soluble and degradable nitrogen. It's actually going to put a load on the liver, converting excess rumen ammonia urea that requires and takes energy from the cow. The added nitrogen has to be converted to microbial protein to be effective, and the cow's rumen can't handle haylage over 26% crude protein. Therefore, it's going to be a waste product and a cow will excrete that as urea. And that will take energy away from milk yield or pregnancy.”
|Nutrient Content||Your Forage||Score||Point Basis|
|Crude protein (%)||23%||+3 points||+1 for each percent over 20%; -1 for over 26% and below 20%|
|NDF (%)||37%||0 points||-1 for each percent out of the range (30-40%)|
|NDFD (%)||53||+3 points||+1 for each percent over 50%; -1 for each point under 50%|
|ADF (%)||29||0 points||-1 for each percent out of range (28-35%)|
|Lignin||6%||+1 point||+1 for each percent below 7%; -1 for each percent above 7%|
|Storage Factors||Your Forage||Score||Point Basis|
|Dry Matter (%)||47%||-1 point||-1 for each 2% out of range (35-45% for bagged haylage)|
|pH||4.1||0 points||+1 for each pH unit over 4.5|
|Lactic Acid||5%||+1 point||+1 for each percent over 4%; -1 for each percent below 4%|
|Inoculated||Yes||+2 points||+2 for using a research-proven silage inoculant|
|Particle Size*||70%||-1 point||-1 for each 10% below 80% on the top two screens|
|*Sum of top two boxes of a Penn State forage particle separator|
For NDF, if the fiber gets below 30%, it may not function as an effective forage by stimulating cud chewing and impacting the rate of passage, he says. When it's over 40%, “I'll argue that it's lower-quality forage.”
Similar charts can be made for grasses or small-grain forages stored in varying forms and storage units. To get target or value numbers, consult with a nutritionist or extension educator.