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Appraise forage for higher profitability

Robert Charley and Renato Schmidt Published on 03 February 2010

In modern dairy operations, forages are typically the major component of the ration fed.

However, there is still a broad belief that the best crops are those that look good and/or give the highest production of forage mass. The recent economic downturn and lower milk prices, however, makes producing high-quality forages even more important, and so the focus needs to be on producing the highest quantity of the best-quality forages possible. By shifting the focus in this way, the producer can make considerable savings on the supplemental feed bill and increase the return of investment over feed costs. A key factor in ensuring that a dairy operates as profitably as possible is to produce low-cost, high-quality forages.

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Sensory appraisal is useful in evaluating forages: What does not smell very nice to us is also not going to appeal to dairy cows and so an “off” or unpleasant aroma will foretell of likely intake problems. Visual inspection can also help identify critical parameters not readily determined by chemical analysis such as stage of maturity, leafiness, texture and presence of weeds. Although these sensorial evaluations are valuable, the only way to measure nutritive value is through appropriate laboratorial analyses on samples representative of the feed being fed, which requires forage be analyzed regularly throughout feeding to pick up any important variations.

Normally, as forage crops mature, yield increases but so does the fibrous portion. Compared to other components like proteins, starch and simple carbohydrates, fiber is less digestible; additionally, fiber digestibility and protein concentration decrease as the plant matures. Thus, high forage mass can be produced at the expense of valuable nutrients and nutrient availability. It is estimated delaying harvest of a forage crop by two or three days reduces digestibility by one percentage point.

Digestibility is the most important variable related to forage quality, since it is the key impactor of the kinetics of digestion and passage. The overall rate of digestion of a material is dictated by the fiber digestibility, and a low rate of digestion posts a bottleneck for increasing intake.

Although corn is somewhat different because its quality improves as the plant reaches maturity due to starch accumulation in the kernel, the comparison between brown mid-rib (BMR) and conventional hybrids is a good example of the importance of fiber digestibility. BMR hybrids have significantly higher NDF digestibility (c. 10 percent) than conventional hybrids, reducing gut fill and leading to significantly higher milk production per ton of silage fed and potential reductions in the amount of grain fed per hundredweight of milk produced. However, the generally lower yields per acre with BMR hybrids can present producers with an interesting choice between yield and quality. BMR hybrids can also be less resistant to pests and diseases, and more prone to drought effects and have poorer standability than conventional varieties, although modern BMR varieties have improved significantly over earlier generations incorporating the technology.

Another alternative studied to enhance fiber digestibility of corn is to high-cut conventional hybrids, but again the yield is lower. Research has shown that the expected results are not as consistent or guaranteed as those obtained when feeding BMR. The reduction in yield will not be acceptable to all, though high cutting does also decrease the nitrate levels in the silage, which could be important, especially in drought conditions. Each producer has to study his/her specific scenario and decide which options fit best in their operation.

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The University of Wisconsin – Extension website offers an online tool to evaluate corn and alfalfa/grass silages. MILK2006 is a useful spreadsheet that calculates milk per ton and milk per acre for silage hybrids. In this updated version of previous UW spreadsheets a more detailed analysis can be done by using data for in vitro starch and fiber digestibilities, and kernel processing score.

Relative feed value (RFV) has been used to rank and compare forages, but it is based on NDF and acid detergent fiber (ADF) contents to predict animal intake and energy (digestible DM), respectively, and was really developed as an assessment tool for dry hay. The assumption that ADF has a constant relationship to digestibility is not accurate. Relative forage quality (RFQ) incorporates fiber digestibility (NDF-D) into the calculations. The use of NDF-D to estimate RFQ allows for a more accurate prediction of animal performance and consequently better feed value for hay and/or silage than RFV. For example, although the range of RFV and RFQ values is virtually the same, samples with RFV of 140 may have RFQ values from 110 to 170. This is particularly important for grasses because they have elevated fiber concentrations, but that fiber is highly digestible.

Keep in mind that it all starts with good management of soil fertility, choosing the adequate cultivar for the specific area and production goals and monitoring the fields. Then harvest the crops at the right stage of maturity, wilt to the desired target if necessary, use a research-tested microbial inoculant, fill quickly, pack tightly and cover rapidly to ensure a good fermentation in the silo. During the season it is important to keep one eye on the stage of maturity of your crops and another on advice from extension advisers about the rate of progress of maturity in the local area for the given season. It is recommended that for the best balance of yield and quality, corn for silage is harvested at 1/2 to 1/3 milk line (32 to 38 percent DM); for alfalfa it is recommended to start at the bud stage and be complete by 1/10 bloom with a DM of 35 to 45 percent (wilt if necessary); for grasses, harvest at the boot stage, with a DM of 35 to 45 percent for ensiling.

Before feeding, sample your forages and have a dependable laboratory test them before balancing your ration. Remember that each crop and harvest has its own characteristics – specific field, stage of maturity, cultivar and time of cutting – and that there may be considerable variation within a mass of silage, even though produced from one crop harvest. Analyzing each silage, and frequently analyzing the material as it is fed, never forgetting to test the dry matter level, will result in a more accurate and better-balanced ration, production levels closer to expected and less variability in production, given proper use of accurate analytical data. Using theoretical values based on averages to balance the nutrients can lead to waste nutrients lost in the slurry or reduced production due to sub-optimal overall nutrition. Either way, it is money left on the table, or on the barn and parlor floor.

For producers using a custom grower or chopper, it is important to agree and clearly and consistently communicate the targets/objectives for each crop and harvest. It is recommended to have all targets and objectives written down, possibly even integrated into a contract. It may not be possible to control every single aspect, such as cutting haylage in the afternoon to maximize the concentration of sugars. However, the forage should be tested before chopping to check the nutritive value and key parameters like chop length, processing (if applicable) and packing density/time should be reviewed one more time. PD

Bob Charley
  • Bob Charley

  • Forage Products Manager
  • Lallemand
  • Email Bob Charley

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