You might think that in this world of “bigger” and “better,” a well-managed forage system is one that maximizes yields with maximum feed quality. While that sounds good, you need to realize that achieving both extremes is not possible. Rather, to reach maximum tonnage, you will lose quality to the maturity of the crop.
Likewise, to achieve maximum quality, you’ll lose tonnage if a crop is harvested when it is too immature. Therefore, the goal should be to optimize forage quantity and quality by careful selection of seed varieties, proper soil fertility, sound pest management and timely planting and harvesting.
Producing high-quantity and -quality alfalfa is largely dependent on harvesting at the optimum maturity. Alfalfa producers face several challenges in deciding on the optimum time to begin harvesting the first cutting. The evidence is well-documented that alfalfa nutrient quality decreases as the plant matures from the bud stage to full flower. At the same time, the pounds of plant material harvested per acre increase as the plant matures. Thus, the optimum harvest date is a compromise between the feed quality and the feed quantity produced.
The predictive equation for alfalfa quality (PEAQ) is an excellent tool to help determine the first harvest date in the spring. PEAQ is an in-field predictor of forage quality by monitoring plant height and maturity. The plant height and maturity provide a close estimate of the relative feed value (RFV) in the field. By determining the RFV of standing alfalfa, producers can more accurately gauge when to begin the first-crop harvest.
First-cutting alfalfa needs to be harvested as soon as the RFV in the field reaches 170 to achieve high quality and to set the cutting schedule for the rest of the growing season. Subsequent cuttings should be taken every 26 to 30 days. Keep in mind that the PEAQ analysis in the field does not include harvesting and storing losses. Various research trials have shown field and storage losses account for 15 to 20 points of RFV.
Therefore, to strive for premium quality alfalfa of 150 RFV, harvesting the first cutting would be necessary when the PEAQ hits 170 RFV. While the RFV index is recommended to determine the PEAQ stage, the relative forage quality (RFQ) is the preferred index for balancing the dairy cow ration.
Relative forage quality is based on in vitro neutral detergent fiber digestibility and summative equations. RFQ provides a better linkage between the forage quality and the actual cow response because it is a direct measure of the forage fiber degradation, and it can more accurately predict what goes on in the cow’s digestive system.
RFQ will have a similar mean range as RFV. However, when evaluating whether to purchase or feed forages based on RFQ and RFV, today’s recommendation is always to use the RFQ index. However, the RFQ equation is not used in evaluating corn silage.
Producing high-quantity and -quality corn silage is dependent on hybrid selection, plant population, harvest maturity and harvest and storage management. Plant population can impact dry-matter yield per acre. Research suggests plant populations for corn silage be increased by 10 percent to 15 percent above the recommendation for grain production. Corn silage hybrid selection should be made on the quantity and quality of corn silage produced. PD
—From North Dakota State University Dairy Focus
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