The author is a professor emeritus of animal sciences at the University of Illinois, Urbana.
The 2021 forage year was a challenge for some due to drought and wildfires. Yet, it bore good news for others with favorable growing conditions and yields.
Every year, forage quality comes with challenges as illustrated in the figure. Consider several key points:
• Each crop has variation due to growing conditions, maturity, and storage conditions.
• Corn silage has a tighter range in variation, leading to more uniform and predictable quality.
• Low-lignin corn silage (BMR) shifts the curve to the right, resulting in higher fiber digestibility due to lower lignin content and higher neutral detergent fiber digestibility (NDFD).
• Alfalfa has lower NDFD-30 (neutral detergent fiber digestibility at 30 hours) compared to corn silage with more variation (flatter and wider curve). This curve could improve in the future as reduced-lignin alfalfa varieties are used.
• Grasses and small grain forage crops have a flatter curve with wider variation. Grass forages could be similar to corn silage in NDFD (good news) while other samples are more straw-like (bad news).
Four U.S. forage testing labs shared summaries of their 2021 forage testing results (Cumberland Valley Analytics, Dairyland Labs, Dairy One, and Rock River Labs). Tables 1 and 2 reflect one lab’s results. The results from the other three labs can be seen in the November Hoard’s Dairyman webinar, “A feed and forage outlook for the year ahead,” found at on.hoards.com/WB_110821.
Table 1 summarizes 2021 alfalfa haylage characteristics compared to an average of the last three years. The good news is that the 2021 alfalfa crop reflects high quality. Crude protein remains high at 21% if your dairy cattle can capture the soluble protein as microbial protein. Dry matter or moisture levels are optimal at 56.9% moisture or 41.5% dry matter. Neutral detergent fiber is optimal at 36.6%, but NDFD-30 is low at 48.5%. Our guideline for legume forage is over 50% NDFD-30 hours.
Producers should monitor ash content, which reflects soil contamination, fermentation risks, and negative impacts on cow health. Relative forage quality index (RFQ) is optimal at 160; that is slightly higher than the three-year average of 158. Our RFQ alfalfa goal for inclusion in lactating cow diets is a value over 150.
Corn silage results
Corn silage quality is summarized in Table 2. Overall, the crop has optimal results compared to the three-year average. Dry matter (34.9%) or moisture (65.1%) are optimal for packing, fermentation profile, and palatability. Raising dry matter one percentage point (from 34.9% to 35.9%, for example) can raise starch levels one percentage point (from 34.7% to 35.7%, for example). Starch levels are optimal at 34.7%, reducing the need for $5.80-bushel corn.
Table 2 also compares BMR (low lignin corn silage) to traditional corn silage, reflecting higher NDFD-30 digestibility from 60.6% for traditional corn silage while BMR is 67.7% (this difference is expected and optimal). Lower undigestible NDF (uNDF) reflects lower levels of lignin in these hybrids. Starch levels tend to be lower and wetter compared to traditional corn silage (Table 2).
Seven forage strategies
1. Compare your forage test results on your farm to the average values in Table 1 and 2. Watch the previously mentioned webinar and compare regional data along with Canadian grass forage values. Where does your 2021 forage quality fit in Figure 1? Will you need to purchase more corn or protein supplement? Will your forage quality reduce your feed bill?
2. Calculate the amount of forage uNFD in your current diet. Forage uNDF is important for two reasons. If the amount of uNDF is too high, dry matter intake can be limiting as rate of feed passage is slowed (high fill factor) along with additional eating time at the feed manager or bunk. If ration uNDF is too low, rumen function and microbial efficiency can be reduced. Miner Institute suggests 0.3% to 0.4% of the cow’s body weight, which is 5.2 to 5.6 pounds of forage uNDF for Holstein cows (1,400 pound cows times 0.3 or 0.4). Some examples are illustrated below:
Farm A: 30 pounds of alfalfa dry matter containing 16.8% uNDF = 5.04 pounds of uNDF
Farm B: 30 pounds of alfalfa dry matter containing 18.5% uNDF = 5.55 pounds of uNDF
Farm C: 30 pounds of corn silage dry matter containing 9.6% uNDF = 2.88 pounds of uNDF
Research from Miner Institute reported if uNDF forage levels are high, reducing forage particle size may improve dry matter intake and animal performance.
3. Conduct a forage inventory to determine if you have enough forages on your farm to meet all dairy cattle needs until your next forage harvest in 2022. Ideally, if corn silage inventory allows extended fermentation, research indicates that the starch is more digestible and available after three to six months of storage. The term “Christmas corn silage” reflects the desired three to five months of storage and fermentation time before feeding.
4. If you are limited in forage amount, make your diet adjustments now. One strategy is to reduce the amount of forage fed. Table 3 lists guidelines if forage NDF levels are reduced with added NDF from by-product feeds (such as corn gluten feed or soy hulls) and less starch. Two considerations are listed below when using Table 3.
Defining forage NDF — add the top three boxes of the Penn State Particle Separator with the third box having 4 millimeter (mm) openings for silage — as particle size is a factor in determining forage NDF. A corn silage example illustrates this calculation. If the top box or 19 mm sieve has 8%, the second box or 8 mm sieve has 65%, and third box or 4 mm sieve has 15%, the result is 88% fNDF.
Starch availability and rumen fermentation rates differ. For example, high-moisture corn is different than dry corn, and it is different when compared to barley or wheat.
5. Check with your seed salesperson to determine if you are planting optimal hybrids and forage crops for 2022. With lower-lignin forage hybrids and varieties available, this strategy could be a recommended decision.
6. Cover crops continue to be important to reduce soil loss, retain soil moisture, and reduce nutrient losses. Winter triticale and rye can make excellent quality forage early in the 2022 growing season, allowing a full-season corn silage crop to follow the winter annual cover crop. Maturity is critical to determine if the forage quality is adequate for lactating cows versus dry cows or heifers.
7. Due to wet harvest conditions, mold development can be a concern. Check if this could be a potential problem, if a mycotoxin binder should be considered, and if corn distillers grain could be at risk.